Tuning the space and charge in molecular delocalization of highly efficient blue TADF emitters based on a 3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione acceptor
Anandan M., Nasiri S., Managutti P.B., Mohamed S., Padgurskas J., Rukuiza R., Nunzi J.M., Nutalapati V., Li Y.
Article, Journal of Materials Chemistry C, 2026, DOI Link
View abstract ⏷
Development of stable and efficient blue thermally activated delayed fluorescence (TADF) emitters remains challenging due to intrinsic trade-offs among high excited-state energy, small singlet–triplet energy splitting (ΔEST), suppressed nonradiative decay, and solid-state morphological stability. A major limitation lies in the scarcity of acceptor units that simultaneously enable deep-blue emission, conformational rigidity, and resistance to aggregation-induced quenching. Here, we introduce saturated 3,4,6,7,9,10-hexahydroacridine-1,8-dione (HHAD) as an unconventional acceptor for blue TADF emitters. Unlike conventional planar acceptors, HHAD combines strong electron-withdrawing carbonyl groups with an intrinsically nonplanar and rigid framework. Two phenyl-bridged donor–π–acceptor emitters incorporating carbazole donors were designed to regulate intramolecular motion through linkage topology. Single-crystal X-ray diffraction reveals twisted donor–acceptor geometries with suppressed π–π stacking. Consequently, both emitters exhibit aggregation-induced emission, solid-state photoluminescence quantum yields exceeding 80%, and small ΔEST values down to 0.06 eV, enabling efficient reverse intersystem crossing. The neat emitter device exhibits pure blue emission with CIE coordinates of (0.179, 0.183). Upon optimization in a DPEPO host matrix, the device achieves an external quantum efficiency of 19.71%, a peak brightness of 48 859 cd m−2, and a turn-on voltage below 3.06 V. These results demonstrate that the conformationally engineered HHAD acceptor offers an effective platform for high-performance blue TADF emitters.
Synergistic molecular design-triggered hybridized local and charge-transfer emission for efficient (>6%) deep-blue electroluminescence
Keerthika P., Moon J., Kumar A., Khan D., Gudipati S., Nutalapati V., Maruthapillai A., Lee J.Y., Konidena R.K.
Article, Journal of Materials Chemistry C, 2026, DOI Link
View abstract ⏷
Rational molecular design coupled with strategic structure–property optimization is crucial for surpassing the theoretical EQE limit (>5%) of deep-blue fluorescent organic emitters in OLEDs. In this work, we present a series of phenanthro[9,10-d]imidazole (PI)-based deep-blue emitters, systematically modified at the N1- and C2-positions with carbazole, phenyl, or cyano functionalities. This molecular library enabled precise control over π-conjugation, excited state dynamics and charge-transfer (CT) characteristics, effectively confining emission within the deep-blue region (<420 nm) with narrow full width at half-maximum (FWHM < 60 nm). Cyano-substituted derivatives displayed red-shifted emission and pronounced positive solvatochromism in emission, attributed to photoinduced intramolecular charge transfer in the excited state. Combined experimental and computational studies confirmed hybridized local and charge-transfer (HLCT) behavior in compounds, PICz-BP, PICz-CN, PIP-CN and PIP-BP, ascribed to the regulation of high-lying excited states by virtue of functional group alteration. The carbazole-functionalized emitters exhibited low oxidation potential and enhanced thermal stability. In the series, PIP-BP demonstrated the best OLED performance, achieving an EQEmax of 6.7%, a current efficiency of 3.5 cd A−1, and a CIEy of ∼0.06. Importantly, PICz-CN, PICz-BP, PIP-CN and PIP-BP exceeded the EQE limit (5%) of conventional fluorescent emitters, underscoring the critical role of structure–function tailoring in regulating HLCT emission for realizing efficient deep-blue OLEDs.
Electrical impedance and dipolar phenomena in Lu2O3-modified fluoro-silicate glass for electrolyte applications
Sekhar A.V., Kostrzewa M., Kumar V.R., Ingram A., Kut T.V.N.K., Zarska S., Bragiel P., Venkatramaiah N., Veeraiah N.
Article, Journal of Alloys and Compounds, 2026, DOI Link
View abstract ⏷
The structural, dielectric, and electrical transport properties of 30Na2O–20CaF2–(50–x)SiO2–xLu2O3 (x = 0–10 mol%) glasses were investigated for solid electrolyte applications. XRD confirmed the amorphous nature, while DSC, Raman, and PAL studies revealed enhanced network polymerization and rigidity of the glass network with increasing Lu2O3 due to Lu3 +–O–Si linkages. Dielectric permittivity, a.c. conductivity, were studied over 4 Hz–8 MHz and 306–633 K. Conductivity (both a.c and d.c.) decreased with increasing Lu2O3 concentration because of reduced ionic mobility. Electrical modulus and Cole–Cole analyses indicated dipolar relaxation associated with Ca2+–NBO complexes and Lu3+-induced structural distortions. Na+ ion hopping was identified as the dominant conduction mechanism with negligible polaronic contribution. Among all compositions, the glass containing 2.5 mol% Lu₂O₃ exhibited the highest ionic conductivity, indicating its potential as a solid electrolyte, with electrical transport predominantly governed by Na⁺ ion hopping and negligible polaronic contribution.
Sodium silicate-CuSiO3 nanocrystal glass-ceramics for multifunctional and efficient electrical energy storage
Arun Kumar P., Kostrzewa M., Ingram A., Sahaya Baskaran G., Venkatramaiah N., Kapusniak P., Bragiel P., Piasecki M., Venkatramu V., Ravi Kumar V., Veeraiah N.
Article, Ceramics International, 2026, DOI Link
View abstract ⏷
The influence of CuO incorporation on the structural, dielectric, and electrical properties of Na2O-SiO2-P2O5-Y2O3 glass-ceramics was investigated to assess their potential as solid-state electrolytes. Glasses containing 0-0.5 mol% CuO were synthesized and thermally treated to promote controlled crystallization. XRD and SEM confirmed the presence of CuSiO3 crystallites within an amorphous matrix. XPS, ESR, and optical absorption revealed the coexistence of Cu+ and Cu2+ ions, while Raman, IR, and PAL spectra indicated that Cu + ions occupy tetrahedral network sites and Cu2+ ions act as modifiers. The fraction of Cu+ ions increased with total CuO content. Dielectric and a.c. conductivity studies (frequency range: 4 Hz-8 MHz; temperature range: 310-633 K) indicated that higher CuO concentrations reduced both the dielectric constant and conductivity. This decrease is attributed to enhanced polaronic hopping and lower ionic mobility. While lower CuO compositions favored ionic conductivity and stability—making them suitable for electrolyte layers—higher CuO content promoted polaronic conduction, suggesting these glass-ceramics could also serve as electrodes in solid-state batteries.
Oxygen sensing properties of room temperature phosphorescent halogenated hexahydroxanthene derivatives
Anandan M., Nasiri S., Managutti P.B., Mohamed S., Nunzi J.M., Nutalapati V., Li Y.
Article, Materials Science and Engineering: B, 2026, DOI Link
View abstract ⏷
A series of halogenated hexahydroxanthene (XAN) derivatives, XAN-F, XAN-Cl, XAN-Br, XAN-I, and XAN-5F, were synthesized to investigate their room-temperature phosphorescence (RTP) and optical oxygen-sensing performance. Single-crystal X-ray diffraction revealed that heavier halogens (Br and I) induce nearly orthogonal dihedral angles between the xanthene and phenyl rings (84.87° for XAN-Br and 86.18° for XAN-I), enhancing molecular rigidity and spin–orbit coupling (SOC). This structural configuration promotes efficient intersystem crossing (ISC) and suppresses nonradiative decay, enabling pronounced RTP. In contrast, XAN-Ph without halogen substitution displayed fluorescence, while derivatives bearing lighter halogens (F, Cl, and 5F) exhibited only low-temperature phosphorescence. Thin films of XAN-Br and XAN-I containing 1 wt% Zeonex displayed strong RTP with lifetimes up to 4.48 ms. They also showed exceptional ISC quantum yields (93.02 % for XAN-Br and 93.51 % for XAN-I) and large vacuum-to-air photoluminescence intensity ratios (14.67 and 15.33, respectively). These features translated to excellent oxygen sensitivity, with Stern-Volmer quenching constants (Ksv) of 6.08 × 10−5 and 1.11 × 10−4 ppm−1 for XAN-Br and XAN-I, respectively. This high oxygen sensitivity arises from efficient triplet–triplet energy transfer from the XAN's triplet excited state to ground-state triplet oxygen, leading to nonradiative quenching. With their metal-free composition, efficient RTP, excellent oxygen responsiveness, and good solution-processability into thin films, XAN-Br and XAN-I represent promising candidates for use in optical oxygen sensors for biomedical diagnostics, food preservation, and environmental monitoring.
Phenanthroimidazole-based fluorescent nanofibers with 2-thiohydantoin for mercury detection and plant tissue bioimaging
Goswami B.G., Selvaganesan A., Datta K.K.R., Nutalapati V.
Article, Food Chemistry, 2026, DOI Link
View abstract ⏷
Herein, we have designed a novel fluorescent probe, Phen-2TH , using a one pot Knoevenagel reaction between Phen-CHO and 2-thiohydantoin with 84 % yield, and is characterized by various spectroscopic techniques like FTIR, 1H{13C} NMR and LC-MS. Phen-2TH exhibited a strong absorption band at ∼419 nm with a green fluorescence at λmax = 525 nm in pure THF and show an excellent solvatochromic properties with a large bathochromic shift by varying the solvent polarities. Phen-2TH form a distinct self-assembled structures like needles, nanofibers and nano-aggregates with variations in the hydrophilic and hydrophobic media (THF: H2O). Particularly, the emission behaviour significantly alters from green to orange with variation in the hydrophobic environment. At f w = 70 %, the emission maxima exhibited a red shift towards orange emission at ∼640 nm. Phen-2TH shows a unique turn-OFF fluorescence response behaviour towards the detection of Hg2+ ions in aqueous media a LOD of ∼55 pM with K sv of 6.3 × 104 M−1. Job's plot analysis and 1H NMR mechanistic investigations reveal the formation of 2:1 stoichiometry between Phen-2TH and Hg 2+ . Mercury binds to the thiohydantoin unit and weakens the ICT process due to its diamagnetic nature. Furthermore, the potential of the probe for real-time monitoring of Hg2+ in various environments, including deionized water, milk, fish, and sprouted pea roots were analyzed through fluorescence imaging. A smartphone-assisted RGB-based color recognition array approach is implemented for the qualitative and quantitative analysis of Hg2+ ions with an LOD of ∼77 μM. The study demonstrated herein provides a promising approach for the real-time monitoring of contaminations in the food and other toxic pollutants.
Imidazole-2-thiohydantoin conjugates for trace water detection in organic solvents and visual colour recognition for real-time monitoring
Goswami B.G., Selvaganesan A., Kalyani K., Datta K.K.R., Nutalapati V.
Article, RSC Advances, 2026, DOI Link
View abstract ⏷
Trace water is a detrimental impurity present in organic solvents that negatively impacts various organic reactions, necessitating the development of new sensitive and selective methods for its detection. In this study, we develop two novel donor–acceptor molecules, Im-2TH and Di-OMeIm-2TH, using a Knoevenagel condensation reaction between imidazole-based aldehydes and 2-thiohydantoin. Im-2TH and Di-OMeIm-2TH show intramolecular charge transfer (ICT) bands at 414 and 425 nm, along with strong green and yellow emissions at 550 and 585 nm in THF, respectively. Both compounds exhibit strong solvatochromic behaviour with changes in the polarity of the solvent and show aggregation-induced emission (AIE) characteristics with distinct variations in their surface morphology (spheres, fibers, and needle-shaped flakes) as the fraction of water varies in THF, ACN and DMSO mixtures. Consequently, tuning their surface morphology and change in their emission behaviour offer potential for trace water detection in organic solvents. Di-OMeIm-2TH exhibits superior sensitivity compared with Im-2TH, as evident from its higher Ksv values of 1.3945, 3.117, and 0.6787 M−1 with limit of detection (LOD) of 0.060, 0.034 and 0.124 ppm in THF, ACN, and DMSO, respectively. Furthermore, Im-2TH and Di-OMeIm-2TH were employed for trace water detection in real samples such as cement, sand, sugar, salt and detergent powder. A smart phone-based fluorometric assay is developed for the recognition of colour variation and RGB array profiles to facilitate the detection of water content in organic solvents for real-time monitoring.
UVB Luminescence and Structural Insights of Gd3+-Activated Na2O–Ga2O3–B2O3–Y2O3 Glasses for Applications in Phototherapy Devices
Elizabeth M., Sekhar A., Purnachand N., Nutalapati V., Prasad P., Raju G., Kumar V., Veeraiah N.
Article, Luminescence, 2026, DOI Link
View abstract ⏷
In this work, the UVB emission of Gd3+ ions incorporated into the Na2O–Ga2O3–B2O3–Y2O3 glass matrix was thoroughly investigated by varying the concentration of Gd2O3. Photoluminescence measurements revealed a strong and well-defined emission peak at 312 nm, related to the 6P7/2 → 8S7/2 transition of Gd3+ ions under 273 nm excitation. Notably, the emission intensity increased nearly threefold as the Gd2O3 concentration rose from 0.2 to 0.8 mol%. The results were examined using Judd–Ofelt analysis and supported by decay kinetics, infrared spectra, ESR spectra, and DSC studies. The enhancement of luminescence was mainly attributed to reduced phonon losses associated with Ga2O3. However, a decline in emission intensity at 1.0 mol% Gd2O3 was observed, which was ascribed to ion clustering and cross-relaxation processes. Overall, this study demonstrates that tailoring the Gd2O3 concentration provides an effective approach to enhance UVB output in alkali–yttria–gallium–borate glasses. The composition containing 0.8 mol% of Gd2O3 is identified as a promising luminescent material for phototherapeutic applications, particularly in the treatment of skin disorders such as psoriasis and vitiligo, and for use in the fabrication of phototherapy devices.
Photoinduced birefringence studies in CuO doped Pb3O4-Bi2O3-B2O3 glass ceramics using femtosecond laser
Bhadrarao D., Rakus P., Venkata Sekhar A., Chitti Babu V., Dana Rao Y., Ravi Kumar V., Naga Raju G., Purnachand N., Venkatramaiah N., Veeraiah N.
Article, Optik, 2026, DOI Link
View abstract ⏷
In this investigation, photo-induced birefringence of Pb3O4-Bi2O3-B2O3 glass ceramics doped with varying content of CuO (ranging from 0.2 to 1.0 mol%) is presented. The photo-induced birefringence (PIB) exhibited a delayed relaxation process lasting few seconds and indicated that the anisotropic photorefractive (PR) effect significantly exceeded the fast Kerr effect. Photorefractive birefringence reached a maximum at a CuO concentration of 0.2 mol%, likely due to enhanced depolymerization of the glass ceramic network that reduces the phonon losses. This is ascribed to the predominant fraction of Cu2 + ions occupying octahedral ( O h ) sites and acting as modifiers. Increasing the CuO content further, up to nearly 0.8 mol%, the magnitude of photorefractive birefringence is observed to reduce. Phonon losses increase because a higher proportion of Cu+ ions occupy tetrahedral ( T d ) positions within the glass ceramic in this concentration range, resulting in stronger interactions between different structural groups in the material. Electrical conductivity and ultrasonic measurements corroborate this finding. Additionally, these glass ceramics were found to be composed of anisotropic CuBi2O4 crystal phases, which enhance their photorefractive (PR) properties. Notably, compositions containing approximately 0.2 mol% CuO demonstrate optimal PR efficiency and are promising candidates for practical applications.
Orthogonal and antenna effects on the chemosensing behaviour of porphyrins towards 2,4,6-trinitrophenol: Colour recognition and portable photodiode device
Article, Journal of Luminescence, 2025, DOI Link
View abstract ⏷
In this work, we have developed two modular freebase porphyrins containing triphenylamine (H2TPAP) and pyrene (H2PyP) units at meso position to understand the role of antenna and orthogonal effects on photophysical and chemosensing behaviour with different nitroaromatic compounds (NACs). The fluorescence studies demonstrate that H2TPAP exhibit strong electronic coupling over H2PyP to induce energy transfer process from peripheral units to porphyrin π-system and behave like strong donor materials. The sequential energy and electron transfer process upon addition of different NACs reveals that H2TPAP show unprecedented selectivity towards the detection of 2,4,6-Trinitrophenol (TNP) with a limit of detection (LODs) of ∼2.3 and ∼6.8 ppm for H2PyP. The mechanistic investigations through NMR and other spectroscopic methods evident that the strong donor-acceptor interactions, protonation at the central core of H2TPAP show both colorimetric and fluorimetric changes with the order of quenching efficiency as TNP>4-NP>2,4-DNP > DUN>4-NBA. A handheld portable photodetector was developed to monitor the dynamic change in photocurrent response. Further, a smartphone interfaced portable fluorimetric method was developed by recognizing colour variations in terms of RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentrations levels will have a significant impact on the development of new handheld chemosensor devices for real time detection of explosive compounds.
Structural and optical properties of Sr3Gd(PO4)3: xHo3 + single phased phosphors for photonic applications
Jamalaiah B.C., Khan P.S., Madhu N., Anandan M., Nutalapati V., Jakka S.K.
Article, Materials Today Communications, 2025, DOI Link
View abstract ⏷
The present investigation explores the structural and optical properties of Sr3Gd(1-x)(PO4)3: xHo3+ phosphors synthesized through modified citrate sol-gel combustion process. The structural analysis through powder X-ray diffraction technique confirms the body centered cubic structure and it was confirmed by Rietveld analysis. The FESEM analysis explores the uniform distribution of agglomerated spherical particles. The elemental mapping reveals the uniformly distributed elements across the analyzed area and the energy dispersive spectroscopic study clarifies the presence of all the elements with proper weight percentage. The Fourier Transform infrared spectroscopic analysis reveals the presence of various structural bonds. The emission spectra revealed 5F3 → 5I8 (524 nm, pale green), 5F4+5S2 → 5I8 (548 nm, bright green) and 5F5 → 5I8 (646 nm, red) transitions upon suitable excitation. The optimal concentration of Ho3+ ions was obtained as x = 1.0 mol% for intense green emission. The temperature dependent emission investigations support exceptional thermal stability with an activation energy of 0.34 eV. The Sr3Gd(PO4)3: Ho3+ (1.0 mol%) phosphor is well suited for lighting and display devices and also for white LEDs applications.
Photocatalyst-free synthesis of quinazolinones from o-aminobenzamides and rongalite under visible light
Arumugam A., Nokku S., Selvaganesan A., Nutalapati V., Senadi G.C.
Article, Organic and Biomolecular Chemistry, 2025, DOI Link
View abstract ⏷
A photocatalyst-free method has been developed for the synthesis of quinazolinones from o-aminobenzamides and rongalite as a C1 synthon under visible light for the first time. This transformation proceeds using atmospheric oxygen as the oxidant, involving the in situ generation of a superoxide radical anion (O2˙−), as supported by EPR analysis. Additionally, the formation of H2O2 was confirmed by UV–Vis spectrophotometric analysis. Key features of this method include broad functional group tolerance, moderate to good yields, gram-scale applicability, and a proof-of-concept demonstration of N-formylation using p-anisidine.
The highly efficient visible-light-induced photoactivity of novel Cu2CdSnS4/Pt/g-C3N5 ternary heterojunction with enhanced photocatalytic methylene blue degradation and hydrogen production
Kamalakannan S., Balasubramaniyan N., Neppolian B., Nutalapati V.
Article, Fuel, 2025, DOI Link
View abstract ⏷
We have synthesized a novel Z-scheme Cu2CdSnS4/Pt/g-C3N5 ternary heterojunction with different amounts of Pt by the photo-deposition-hydrothermal method for photocatalytic performance. As a result of the fast electron-hole recombination and the insufficient absorption of solar light, Cu2CdSnS4/Pt/g-C3N5 retains its best photocatalytic activities. It has been possible to characterize Cu2CdSnS4/Pt/g-C3N5 heterojunction photocatalysts, which are composed of Cu2CdSnS4 and Pt/g-C3N5 nanosheets, using different techniques. It was found that the final composite Cu2CdSnS4/Pt/g-C3N5 heterojunction produced 6482μmol g−1 hydrogen 3 h under visible light irradiation, which was 54 times higher than the pristine g-C3N5 heterojunction and 11 times higher than the pristine Cu2CdSnS4 heterojunction. The sacrificial electron donors triethanolamine (TEOA) and methanol produced higher hydrogen evolution rates than glycerol 3958μmol g− 1 while exhibiting longer photostability of 6482μmol g− 1 and 5684μmol g− 1, respectively. It was found that the final sample Cu2CdSnS4/Pt/g-C3N5 heterojunction photocatalysts displayed excellent photocatalytic activity for the degradation of methylene blue (MB) to pristine g-C3N5. There is an increase in degradation rate over pristine g-C3N5 (R2 = 0.916) with composite Cu2CdSnS4/Pt/g-C3N5. In this study, heterojunction photocatalysts have been demonstrated to have excellent photocatalytic MB degradation and hydrogen production.
A guide to mastering multi-resonance thermally activated delayed fluorescence: from challenges to strategies for high-performance OLEDs
Keerthika P., Nutalapati V., Konidena R.K.
Review, Journal of Materials Chemistry C, 2025, DOI Link
View abstract ⏷
Over the last decade, there has been a considerable upsurge in the development of organic emitters that produce narrowband emission and can utilize triplet excitons without relying on metal-containing components, thereby significantly advancing OLED technology. In particular, boron (B)- and heteroatom-doped polycyclic nanographenes with multi-resonance thermally activated delayed fluorescence (MR-TADF) have emerged as promising emitters. Compared with conventional donor-acceptor (D-A) TADF emitters, MR-TADF materials offer several advantages, including sharp emission spectra (a full width at half maximum of ≤40 nm), high photoluminescence efficiency, and small singlet-triplet energy gaps, making them strong contenders for next-generation OLEDs. Recently, MR-TADF emitters have demonstrated device efficiencies that surpass those of traditional TADF and phosphorescent emitters. However, several interconnected challenges persist, such as limited color tunability, sluggish exciton up-conversion rates, aggregation-induced quenching, efficiency degradation at high brightness, and limited operational lifetimes. These obstacles are often intertwined owing to fundamental “trade-offs” in material properties. Overcoming them requires precise molecular engineering and mastering material design. This review systematically examines the progress in B-based MR-TADF emitters, with a particular focus on molecular design strategies tailored to address these limitations. This study categorizes by emission color to aid the development of high-performance, full-color MR-OLEDs and concludes by outlining the current challenges and potential directions for future research on MR-TADF emitter development.
A double interlocking strategy for narrowband ultra-violet emitters (CIEy ≈ 0.029) with dual functionality for efficient OLEDs
Keerthika P., Han S.W., Kumar A., Nutalapati V., Naveen K.R., Lee J.Y., Konidena R.K.
Article, Chemical Communications, 2025, DOI Link
View abstract ⏷
We unveiled a double interlocking strategy to construct a narrowband ultraviolet (UV) emitter based on indolo[3,2,1-jk]carbazole. The emitter exhibited pure UV emission (λem ∼ 398 nm) with a narrow FWHM of 24 nm. As an OLED emitter, it demonstrated an EQEmax of 4.2% and CIEy of 0.024. Used as a host for green PhOLEDs, it delivered EQEmax of 18.5% with an extremely low roll-off of 1% at 3000 cd m−2.
Functional Engineering Iron Single-Atom Sites on MOF Supports for Enhanced Electrochemical Water Splitting
Marimuthu S., Shankar A., Gawas P., Kannan P., Nutalapati V., Maduraiveeran G., Alnaser A.S.
Article, Small, 2025, DOI Link
View abstract ⏷
The precise control of the local environment, electronic configuration, and electrocatalytic performance of transition metal single-atom sites on nitrogen-carbon supports (MSA-N-C) is essential for electrolytic hydrogen production due to the inherent rigidity of the catalytic active centers. A highly catalytically active and durable bifunctional metal single-atom site on nitrogen-carbon supports (MSA-N─C; M═Fe, Co, and Cu) is demonstrated using a porphyrin-based metal-organic framework (MOF) strategy. Engineered iron single-atom sites on nitrogen-carbon support (FeSA-N─C) demonstrate remarkable electrocatalytic performance for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in an alkaline electrolyte. This is achieved through the optimization of the coordination structure and a large volume of active sites, which advance the intrinsic catalytic activity. The FeSA-N─C catalyst exhibits low overpotentials of ≈288.0 mV for the OER and 206.0 mV for the HER at roughly ≈10 mA cm−2 in 1.0 m KOH. This improved catalytic performance is due to enhanced Fe─N─C coordination, which promotes the formation and activation of the vital O═Fe═O intermediate. This, in turn, improves the electrocatalytic properties by reducing the energy barriers of the intermediates and products involved. This strategy demonstrates the enrichment of the micro-environment Fe-N4 with tunable flexibility, aiding in the rational design of durable electrocatalysts at the atomic scale.
Tert-Butylcarbazole and Methoxycarbazole Substituted on the Phenazine Group Exhibit Mechano and Thermoresponsivity for TADF LEECs
Rabiei M., Hosseinnezhad M., Ghahary R., Nutalapati V., Nasiri S., Nunzi J.-M., Padgurskas J., Rukuiza R.
Article, ACS Applied Optical Materials, 2025, DOI Link
View abstract ⏷
Two new well-defined donor–acceptor–donor (D–A–D′) thermally activated delayed fluorescence (TADF) molecules with mechanochromic and thermochromic architectures were designed and synthesized based on tert-butylcarbazole and methoxycarbazole substituents attached to a phenazine derivative. Density functional theory (DFT) studies revealed molecular structures with extended π-conjugation and low singlet–triplet energy gaps (ΔEST), which enhance reverse intersystem crossing (RISC) for efficient TADF. Single-crystal X-ray diffraction confirms differences in molecular packing. The dye composed of tert-butylcarbazole exhibits lower aggregation and higher photoluminescence quantum yield (PLQY) upon spin-coating in a solid film, owing to its bulkier structure. Thermal stability studies demonstrated high decomposition temperatures (Td> 300 °C) and improved rigidity of the dye consisting of tert-butylcarbazole. Photophysical investigations revealed that the dyes dispersed in a tetrahydrofuran (THF):water mixture showed aggregation-induced emission enhancement (AIEE). Incorporation of the complex organometallic [Ir(buoppy)2(dmapzpy)]PF6as a host in LEECs favors the energy transfer and yields single emission peaks at 588 and 587 nm with 60 wt % host content. The improved device attains maximum current (28.97 cd A–1), power (22.11 lm W–1), and external quantum efficiency (4.02%). These findings underline the significance of substituent design and host:guest interactions in improving TADF LEEC performance and provide new insights for high-efficiency optoelectronic devices.
Recent advances in the molecular designs of near ultraviolet emitters for efficient organic light emitting diodes
Keerthika P., Kumar A., Maruthapillai A., Nutalapati V., Konidena R.K.
Review, Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2025, DOI Link
View abstract ⏷
The exploration of pure organic violet emitters (λem < 420 nm) has garnered significant attention within the scientific community due to their widespread applications in various research domains, including organic light-emitting diodes (OLEDs), biomedical applications, and photolithography, etc. Despite the availability of several near-ultraviolet (NUV) sources, organic emitters have stood out due to their cost-effectiveness, flexibility, and extensive potential for functional tunability. However, the development of highly efficient NUV emitters for OLEDs faces substantial challenges and lags behind their red, green and blue counterparts, primarily due to stringent molecular requirements. Over the past decade, substantial efforts have been dedicated to devising new molecular designs aimed at striking a balance between conjugation length, donor-acceptor interactions, photoluminescence quantum yield, charge transporting properties, and color purity of violet emitters. However, a limited number of reviews were reported on different design strategies for producing violet (< 420 nm) emitters to date. Addressing this gap, this review provides an overview of recent design advances in constructing violet emitters. It delves into their structure-function relationship focusing on photophysical properties and OLED performance. Further, the current status and future prospectus of violet organic emitters are presented.
Investigation of using amine and acetylamine functional units on naphthalimide dyes for photovoltaic devices
Hosseinnezhad M., Nasiri S., Nutalapati V., Gharanjig K., Arabi A.
Article, Pigment and Resin Technology, 2025, DOI Link
View abstract ⏷
Purpose: The purpose of this paper is to introduce four new organic dyes based on naphthalimide for dye-sensitized solar cells (DSSCs). Design/methodology/approach: Four new dyes based on naphthalimide with substitutions of amine and acetylamine in position C4 were designed in conjugation with substituted carbazole as donor–acceptor (D-A) architecture. The absorption and emission characteristics of the prepared dyes were evaluated in H2O, DMF and their mixture (DMF:H2O = 1:1). The feasibility of electron transfer in the DSSCs structure and energy levels were evaluated using electrochemical and density functional theory, which confirm the use of dyes in the DSSCs structure. The DSSCs were prepared using an individual strategy and their optical properties were investigated under the light of AM 1.5. Findings: The prepared dyes exhibit orange color with strong emission at λem = 530–570 nm due to charge transfer with a positive solvatochromic effect. The efficiency of DSSCs based on Dye1-4 1 is: 3.69%, 3.71%, 4.69% and 4.76%. Therefore, the power efficiency increases by about 29 % in the presence of acetylamine group. Practical implications: The design of new structures of organic dyes should be accompanied by the development of optical and electrical properties. In other words, in addition to the continuous production of electrons, efficient dyes must also be resistant to light to increase the life of the device. Social implications: Organic dyes play a key role in the production of electrons in the DSSCs structure. The engineering of these structures and the introduction of widely used but low cost types can play an important role in the development of clean energy production. Originality/value: The application of organic dyes based on naphthalimide was evaluated in the DSSCs structure and its photovoltaic properties were investigated.
Dual Fluorometric and Colorimetric Chemosensor Based on Poly(Arylene Ether Nitrile)s Functionalized Zn(II)Porphyrins for Selective Detection of Cyanide
Sivakumar G., Babu A., Ghanti B., Swathi J., Silambarasan R., Nutalapati V., Banerjee S., Maji S.
Article, Advanced Functional Materials, 2025, DOI Link
View abstract ⏷
Poly(arylene ether nitrile)s (PAENs) appended with Zn(II)-porphyrin in varied molar percentages (5% and 10%) are developed as dual colorimetric and fluorometric sensors for highly sensitive and selective cyanide (CN−) detection. The materials, DP-5%PAEN@Zn and DP-10%PAEN@Zn, exhibit significant Soret band shifts at 420 ± 2 nm, accompanied by the appearance of a new absorption band at 436 ± 2 nm, indicating strong CN− binding with high association constants of 1.3 × 10⁴ M−¹ and 2.3 × 10⁴ M−¹, respectively. A prominent color change from purple to green allowed for naked eye detection. Spectrofluorimetric studies revealed turn-off fluorescence with Stern-Volmer constants (Ksv) of 99.85 × 103 M−¹ for DP-5%PAEN@Zn and 121.08 × 103 M−¹ for DP-10%PAEN@Zn, achieving limit of detection (LOD) of 0.177 and 0.099 ppb, respectively. DP-10%PAEN@Zn demonstrated excellent sensitivity and selectivity toward CN−, and also reusability, as it remained functional after ten TFA treatment cycles. The mechanistic investigation, supported by photophysical, electrochemical, and DFT analyses, revealed a photoinduced electron transfer process via static quenching. Material stability is confirmed through photodegradability, prolonged time, temperature, and humidity testing. Prototype test kits are developed for real-time visual CN− detection in remote and environmental samples (tap, lake, sewage, and soil). Additionally, a smartphone-based color recognition assay is implemented for qualitative and quantitative analysis.
Tuning Mn-MOF by Incorporating a Phthalocyanine Derivative as an Enzyme Mimic for Efficient EGFET-based Ascorbic Acid Detection
Shabanur Matada M.S., Nutalapati V., Jayaraman S.V., Sivalingam Y.
Article, ACS Applied Materials and Interfaces, 2025, DOI Link
View abstract ⏷
In this study, we present the effect of catalytic performance in Mn-MOF upon incorporating varied concentrations of phthalocyanine derivative (H2PcP8OH16) for ascorbic acid detection in an extended gate field-effect transistor (EGFET) configuration. The fabricated Mn-OM-MOF-2/CP electrode demonstrated notable selectivity toward ascorbic acid in physiological conditions of sweat, with a sensitivity of 71.375 μA·mM−1·cm−2, a response time of less than 6 s, and a linear range from 5 to 240 μM. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.26 and 0.78 μM, respectively. Remarkably, the prepared electrodes followed the Michaelis−Menten kinetics. Among them, the Mn-OM-MOF-2/CP electrode demonstrated the highest affinity for ascorbic acid, with a Km value of 0.142 mM. To gain deeper insights into the charge transfer mechanism during ascorbic acid interaction with Mn-OM-MOF-2/CP, we employed the scanning Kelvin probe (SKP) technique and conducted post-FTIR analysis to understand the sensing mechanism. Additionally, post-UV−visible (UV−vis) measurements were performed to explore how the incorporation of the phthalocyanine derivative enhances affinity. Additional studies using standard artificial sweat have confirmed the Mn-OM-MOF-2/CP electrode’s good recovery. Overall, the results of the EGFET method demonstrated the suitability of the Mn-OM-MOF-2/CP electrode for rapid, noninvasive, single-use ascorbic acid detection in 1× phosphate buffer saline (1× PBS).
Impact of Ag₂O doping on the structural and conductive features of Na₂O-SiO₂-P₂O₅-Y₂O₃ glass ceramics embedded with Na₂AgY(Si₂O₅)₃ crystallites for applications as solid-state electrolytes
Kumar P.A., Kostrzewa M., Ingram A., Baskaran G.S., Venkatramaiah N., Venkatramu V., Kumar V.R., Veeraiah N.
Article, Journal of Alloys and Compounds, 2025, DOI Link
View abstract ⏷
This study examines the impact of Ag2O doping in small quantities on the structural, dielectric, and conductivity features of Na₂O-SiO₂-P₂O₅-Y₂O₃ glass ceramics, aiming to enhance their application potential as solid-state electrolytes. Glass samples containing 0–0.04 mol% Ag₂O were synthesized and subjected to heat treatment to promote crystallization. Structural characteristics using XRD, SEM and spectroscopic techniques confirmed the formation of Na₂AgY(Si₂O₅)₃ crystallites that are entrenched in the remnant amorphous phase. Dielectric and a.c. conductivity measurements were conducted across a wide frequency (4 Hz to 8 MHz) and in the range of temperature (310–633 K). Results indicated that increased Ag₂O content enhances the dielectric constant and conductivity, attributed to polaronic hopping and ionic mobility. The findings highlight the potential of Ag₂O doped Na₂O-SiO₂-P₂O₅-Y₂O₃ glass ceramics in energy storage devices, particularly as solid electrolytes in batteries, due to their improved ionic conductivity and stability.
Structural and optoelectronic potential of Ag₂BiO₃-embedded red lead silver-bismuth borate glass-ceramics
Bhadrarao D., Brik M.G., Pavic L., Bafti A., Pisk J., Sekhar A.V., Venkatramaiah N., Kumar V.R., Raju G.N., Veeraiah N.
Article, Journal of Molecular Structure, 2025, DOI Link
View abstract ⏷
This study comprehensively examined the structural, optical, and dielectric properties of Pb3O4-Bi2O3-B2O3 glass-ceramics, doped with varying Ag2O concentrations. XRD and SEM analyses revealed the embedding of non-centrosymmetric Ag2BiO3 ferroelectric crystals (0.6–1.0 μm), whose properties are modeled using GGA and LDA approximations within the Pnn2 space group, aligning with experimental data. XPS highlights the presence of Ag⁺/Ag⁰ and Bi³⁺/Bi⁵⁺ states, while FTIR spectroscopy indicates increasing structural disorder with up to 0.2 mol% Ag2O. Optical absorption identifies Ag⁺-Ag⁰ pairs, and dielectric measurements show an increase in permittivity and a.c. conductivity, with impedance decreasing up to 0.2 mol% Ag2O. Notably, 0.2 mol% Ag2O optimizes structural reorganization and dielectric performance, enhancing the material's suitability for spin-orbitronics, optoelectronics, and solid-state batteries. The findings establish these glass-ceramics as next-generation materials for advanced technological applications.
Alginate-aminoclay/CuO nanocomposite beads: A sustainable and green approach for catalytic reduction of toxic nitroaromatic compounds
Sanakal S.I., Das A., Babu A., Kar P., Nutalapati V., Datta K.K.R., Banerjee S., Maji S.
Article, Journal of Environmental Chemical Engineering, 2025, DOI Link
View abstract ⏷
Nitroaromatic compounds (NACs) are growing worldwide concern for their toxicity, driving a search for efficient removal methods. In the present investigation, we have described the sustainable development of recyclable polymer-based clay metal-oxide nanocomposite beads. First, the copper oxide nanoparticles (CuO NPs) are immobilized on the surface of aminoclay (AC), and then the stabilized CuO NPs are deposited on sodium alginate (Alg). In order to test the broad applicability of the produced AC@CuO-Alg beads, toxic 4-nitrophenol (4-NP) was reduced to 4-aminophenol (4-AP) using the reducing agent NaBH4 in less than 24 minutes with 96 % conversion in water with a rate constant (k) of 0.128 min-1. The catalyst displayed superior stability and good catalytic activity. The catalyst showed strong recyclability, recovering 76% of the catalyst and converting 4-NP to 4-AP with constant activity across four cycles. Furthermore, the reduction of various toxic nitroaromatic compounds such as 4-nitroaniline (4-NA) and nitrobenzene (NB) was investigated in an array of organic solvents including water by varying the temperature. The catalyst demonstrated excellent stability and good catalytic activity in water which is a green solvent in comparison to the organic solvents viz. methanol, ethanol and acetonitrile. The catalyst's properties offer new opportunities for heterogeneous catalysis research.
Triphenylamine-porphyrin conjugates as antenna modular systems towards the detection of 1-hexanol through surface photovoltage under UV and visible light illumination using the scanning Kelvin probe
Palanisamy P., Anandan M., Sasi S., Bora A., Reji R.P., Chedharla Balaji S.K., Kawazoe Y., Raman G., Jayaraman S.V., Sivalingam Y., Nutalapati V.
Article, Sustainable Materials and Technologies, 2025, DOI Link
View abstract ⏷
Two modular porphyrin systems containing triphenylamine (TPA) unit at meso position of freebase porphyrin (H2TPAP) and its metalation with Zn(II) as ZnTPAP is developed to ascertain the role of antenna effect on the photo induced energy transfer process. H2TPAP and ZnTPAP exhibited a significant electronic overlap between peripheral TPA and porphyrin π-system to demonstrate its strong donor behaviour in solid-state thin films. Porphyrin ensembles change their surface photovoltages towards recognition of various VOCs (like ethanol, acetone, 1-hexanol, triethylamine, nonanal, and acetonitrile) as observed through photophysical and excited-state gas-phase interaction studies using Scanning Kelvin Probe (SKP). The chemical sensitivity towards the surface potential is monitored under dark, UV and visible light illuminations. Both H2TPAP and ZnTPAP exhibited to show different behaviour with high selectivity towards 1-hexanol vapours. Under UV light illumination at 365 nm, ZnTPAP exhibited a rapid response (99 %) within 1 s and good recovery (54 %) within 96 s. Under visible light (QTH), the response and recovery decreased due to sequential photo-induced energy and electron transfer processes. Further, density functional theory results confirm that both H2TPAP and ZnTPAP show more affinity towards alcohol vapours compared to other VOCs. Molecular interactions including donor-donor and hydrogen bonding interactions in tandem contribute to the intriguing response to 1-hexanol and enhance the photo response of ZnTPAP over H2TPAP.
Orthogonal effect of pyrene-porphyrin conjugates on the detection of volatile organic compounds under UV and visible light illumination through surface photovoltage
Palanisamy P., Anandan M., Sasi S., Bora A., Balaji S.K.C., Reji R.P., Kawazoe Y., Kalyani K., Jayaraman S.V., Sivalingam Y., Nutalapati V.
Article, Materials Advances, 2025, DOI Link
View abstract ⏷
In this work, we have developed two modular compounds featuring pyrene at the meso position of the freebase porphyrin (H2PyP) and its complex with Zn (ZnPyP). Both compounds exhibited a unique energy transfer process due to the orthogonal pyrene units, demonstrating that appreciable electronic interactions existed between the peripheral units and the porphyrin π-system. These compounds were found to behave as strong donor materials in solid-state thin films. Detailed photophysical properties and excited-state interactions in the gas phase were modulated through surface photovoltage measurements using the scanning Kelvin probe (SKP) technique. These interactions were explored towards the detection of different volatile organic compounds (VOCs) (ethanol, acetone, 1-hexanol, triethylamine, nonanal, and acetonitrile) under dark, UV and visible light illuminations. H2PyP and ZnPyP showed n-type behaviour with high selectivity towards 1-hexanol under UV light illumination, while under visible light illumination, ZnPyP exhibited n-type behaviour and H2PyP showed p-type behaviour. The response and recovery studies demonstrated that H2PyP and ZnPyP showed unprecedented selectivity towards 1-hexanol by altering their p- and n-type behaviour. H2PyP exhibited a high photovoltage response of 93% for an exposure of 17 s with a recovery rate of 23% in 5 s, while ZnPyP showed 97% in 2 s with a recovery rate of 55% in 116 s under UV light. The unique response of H2PyP and ZnPyP to 1-hexanol could be attributed to donor-donor interactions and intermolecular hydrogen bonding at the central core, as well as the variations in the energy transfer process. Furthermore, density functional theory studies revealed that the binding interactions of H2PyP and ZnPyP with VOCs showed a greater affinity for alcohol vapours compared to other compounds.
Biosensors for disease biomarker detections
Book chapter, Applications of Biosensors in Healthcare: Volume 3, 2025, DOI Link
View abstract ⏷
Biomarkers are indicator systems that help to understand the state of health of the patients with high accuracy and help to prevent the disease spread by control measures. Incorporating a biorecognition unit into the molecular ensemble provides quick and powerful ways to detect and distinguish target analytes from diverse samples. It is crucial to identify suitable biomarkers for better clinical intervention and treatment at the early stages of a disease. Optical sensors with image-based technologies have extra advantages such as high sensitivity, reliability, robustness, and potential to be combined on optoelectronic devices. Optical fluorescence imaging provides cellular and subcellular resolutions and image enhancement in 3D and real-time. Fluorescence-based imaging is used in a broad variety of preclinical investigations, and there is great interest in finding further ways to translate the principle into clinical applications. This chapter focuses on the current progress in the use of different fluorescent indicators for the different types of cancer biomarker detection and provides a comprehensive overview of their principles, methodologies, and applications. In addition, we discuss ongoing issues and limitations of the existing systems and methods. Further, we present the key requirements of portable biosensors and the perspective of optical biosensors for cancer biomarker detection.
Antenna effect on Zn(II) porphyrin–based molecular ensembles for the detection of 2,4-dinitrophenol through energy and electron transfer process
Palanisamy P., Anandan M., Raman G., Nutalapati V.
Article, Microchimica Acta, 2025, DOI Link
View abstract ⏷
Two modular systems were synthesized composed of triphenylamine (ZnTPAP) and pyrene (ZnPyP) covalently linked at meso position of the Zn(II) porphyrins. Both compounds behaved as energy transfer antenna and orthogonal units to enhance the electron donating ability of Zn(II) porphyrins. Detailed photophysical and aggregation studies reveal that an appreciable electronic interaction exists between peripheral units to the porphyrin π-system so that they behave like strong donor materials. The electrochemical and computational studies demonstrate delocalization of the frontier highest occupied molecular orbital (−5.08 eV) over the triphenylamine entities (ZnTPAP) in addition to the porphyrin macrocycle. Fluorescence experiments with ZnTPAP and ZnPyP in the presence of different nitro analytes at various concentrations show turn-off fluorescence behaviour and exhibit superior selectivity towards 2,4-dinitrophenol (DNP) with limit of detection (LOD) of ~ 2.3 and 9.2 ppm for ZnTPAP and ZnPyP. Photoinduced electron transfer process is involved in the static and dynamic fluorescence quenching process. A Stern–Volmer quenching association constant (Ksv) determination revealed that ZnTPAP is more sensitive than the ZnPyP. This is attributed to the strong donating behaviour of TPA units caused by intermolecular interaction through metal center and strong π–π interactions with nitro analytes. The present study provides new insights into the ability to tune the affinity and selectivity of porphyrin-based sensors utilising electronic factors associated with the central Zn(II) ion. Furthermore, a smartphone-interfaced portable fluorimetric method by recognising colour variations in RGB and the luminance (L) values facilitate sensitive and real-time sensing at low concentration levels will have a significant impact on development of a new class of chemosensors. Graphical Abstract: (Figure presented.).
Investigation of the Combination of Indoline and Naphthalimide in the Preparation of Photosensitizers for Photovoltaic Devices
Hosseinnezhad M., Nasiri S., Nutalapati V., Gharanjig K., Arabi A.
Article, Journal of Electronic Materials, 2025, DOI Link
View abstract ⏷
Four dyes with substitutions of carbazole and phenothiazine in position C4 of naphthalimide were designed in conjugation as a donor–acceptor architecture (D–A). The absorption and emission characteristics of the prepared dyes were investigated in H2O, dimethylformamide (DMF), and their mixture (DMF:H2O = 1:1). The prepared dyes exhibited a pink and yellow color, with strong emission at λem = 526–590 nm due to charge transfer, with a positive solvatochromic effect. The feasibility of electron transfer in the dye-sensitized solar cell (DSSC) structure and energy levels were evaluated using electrochemical and density functional theory (DFT), which confirmed the use of dyes in the DSSC structure. The DSSCs were prepared using an individual strategy, and their optical properties were investigated under light of AM 1.5. The DSSCs based on dyes 1–4 achieved efficiency of 4.37%, 4.59%, 4.11%, and 4.27%, respectively. Therefore, the power efficiency increased by about 39% in the presence of the phenothiazine group.
Heart Engineering of Photovoltaic Devices: Preparation of New Ru Dyes Using Thioindigo and Phenothiazine
Hosseinnezhad M., Nasiri S., Nutalapati V., Gharanjig K., Nunzi J.
Article, Applied Organometallic Chemistry, 2025, DOI Link
View abstract ⏷
Phenothiazine and thioindigo were used as substitutes to make new Ru dyes for DSSCs. The thioindigo unit is a notable molecule with strong technical qualities in these photosensitizers. As a result, research was done on the cyano substituent as an electron-donating group. Both theoretical and experimental methods were used to assess the complexes' optical response. A better photovoltaic response is achieved by the cyano groups' efficient bonding with the semiconductor layer. Additionally, the complexes that were formed contain two different kinds of electron accepter substituents: cyanoacrylic acid and carboxylic acid, with efficiencies of 7.42% and 4.17%, respectively. Additionally, cosensitization was investigated and analyzed utilizing N719 and two generated complexes. DSSCs made with Complex 1 and 2 and N719 have corresponding efficiency percentages of 8.86% and 9.74%.
Overcoming the 5% EQE ceiling in deep-blue fluorescent OLEDs with hybridized local and charge transfer featured phenanthroimidazole-carbazole emitters
Keerthika P., Kumar A., Selvaganesan A., Moon J., Nutalapati V., Lee J.Y., Konidena R.K.
Article, Journal of Materials Chemistry C, 2025, DOI Link
View abstract ⏷
The design and development of deep-blue fluorescent organic emitters with Commission Internationale de l’Eclairage (CIEy) < 0.06 and external quantum efficiency (EQE) over ∼5.0% remains an enduring focus in organic light-emitting diodes (OLEDs). Herein, we report two new deep-blue organic emitters based on phenanthroimidazole (PI) frameworks, functionalized at the N1 and C2 positions. Specifically, carbazole was introduced at the N1 position via its C3 site to enhance its hole-transporting ability and thermal stability, while either biphenyl (PICz-BP) or cyanophenyl (PICz-CN) was attached at the C2 position to extend π-conjugation and finely tune the photophysical properties. Photophysical studies revealed that both emitters exhibit deep-blue emission, with emission maxima (λ em) of ∼409 nm for PICz-BP and 419 nm for PICz-CN. The slightly red-shifted emission observed for PICz-CN is attributed to enhanced charge-transfer character induced by the electron-withdrawing cyano group. Furthermore, solvatochromic studies and computational analysis revealed that both compounds exhibit hybridized local and charge-transfer (HLCT) excited states, a feature known to enhance radiative decay while maintaining high color purity. Both emitters displayed high photoluminescence quantum yields (PLQYs) and good thermal stability, making them promising candidates for organic light emitting diodes (OLEDs). Their performance was evaluated in both doped and non-doped OLED devices. Notably, the doped device employing PICz-BP achieved excellent performance, delivering a maximum EQE of 6.1% with deep-blue emission (CIEy ≈ 0.06). Remarkably, the non-doped device based on PICz-BP also retained comparable color purity and exhibited an EQE of 4.4%, underscoring the intrinsic emissive strength and stability of the material without the need for a host matrix. Overall, the successful design strategy leveraging HLCT character enabled both emitters to exhibit high EQE > 5%, highlighting their potential for high-performance deep-blue OLEDs.
High triplet hexahydroacridine derivatives as a host prevent exciton diffusion to adjacent layers in solution processed OLEDs
Anandan M., Kment S., Zboril R., Kalytchuk S., Janusas G., Managutti P.B., Mohamed S., Mazloumihaghghi R., Hosseinnezhad M., Nunzi J.M., Nutalapati V., Nasiri S.
Article, Organic Electronics, 2025, DOI Link
View abstract ⏷
One important key to improve OLEDs technology is the development and synthesis of high triplet energy host materials, which play a crucial role in improving the efficiency and lifetime. The present approach shows that it is possible to control the properties of the host materials by carefully selecting the units. Therefore, a hexahydroacridine derivative was chosen to increase the ET value due to lower conjugation. In this study, three hosts with high triplet energy (>3 eV) were designed and investigated based on hexahydroacridine (ACD) as a constant unit and branches of triphenylamine (TPA), pyrene and pyridine derivatives as different groups. Density functional theory (DFT) calculations showed the agreement of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) values with the experimental results, with the highest HOMO from DFT calculation at 5.95 eV and cyclic voltammetry (CV) at 6.09 eV for the ACD-PYRIDINE. The photophysical properties were fully discussed and revealed the fluorescence mechanism of the hosts, so that with the addition of 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-N3, N3, N6, N6-tetraphenyl-9H-carbazole-3,6-diamine (DACT-II), thermally activated delayed fluorescence (TADF) was achieved in the emitter layer with different concentrations of the hosts of 50, 70 and 90 wt%. The promising synthesized hosts were used for the fabrication of green TADF OLEDs. The fabricated OLED based on 90 % wt. ACD-TPA had CIE coordinates X = 0.26385 and Y = 0.55236, with turn on voltage 3.5 V, as well as current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 40 cd A−1, 26 lm.W−1 and 13 %, respectively. Furthermore, the extracted brightness (52508 cd m−2) exceeded the values from previous studies based on acridine as an emitter layer in doped OLEDs.
Assessing the dual toxicity of HfO2 nanoparticles and quinalphos on Pila virens
Chagantipati S., Palanisamy P., Burri G., Jalleda R.L., Shaik N., Nadakuditi V.R., Nasani N., Reddy R.C., Srikanth K., Nutalapati V.
Article, Science of the Total Environment, 2024, DOI Link
View abstract ⏷
Pila virens (P. virens) is an edible freshwater snail, widely distributed in Asia and Africa. P. virens is used as one of the most promising model organisms for monitoring environmental contamination in aquatic ecosystems. The physiological responses to the contaminants such as pesticides and nanomaterials are inadequate, especially in relation to the effects of co-exposure. In this work, we have investigated on the noxious effects of co-exposure between an organophosphorus pesticide, quinalphos and hafnium oxide nanoparticles (HfO2NPs) on the antioxidant responses of P. virens. Phase pure forms of HfO2NPs (monoclinic, P21/c) were obtained by sol-gel method. The crystallinity, structure and surface morphology were analysed with various spectroscopic methods like powder X-ray, Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), High Resolution Scanning Electron Microscope (HR-SEM) and Transmission Electron Microscope (TEM). P. virens after exposure for 96 h to the different concentrations of quinalphos (0.25–2.25 mg/mL) and HfO2NPs (10–50 mg/mL), the median lethal concentration (LC50) was determined to be 1.159 mg/mL and 11.47 mg/mL, respectively and show a significant fatal effect against the snail. The P. virens were exposed to sub-lethal concentrations of LC25 (0.57 mg/mL quinalphos and 5.73 mg/mL HfO2NPs) individually and in combination as a binary toxicity (quinalphos + HfO2NPs), (0.57 mg/mL + 5.73 mg/mL) for 24 and 48 h. Further, the antioxidant responses were assessed which included catalase (CAT), glutathione sulfo-transferase (GST), and malonaldehyde (MDA) activity in the group exposed to quinalphos and HfO2NPs exhibited to show an enhancement in their activity in comparison to controls after 24 and 48 h and revealed that 48 h exposure has significant impact. These results provide a valuable insight towards increased awareness of the physiological defences of P. virens after co-exposure to quinalphos and HfO2NPs in aquatic ecosystem.
Unraveling the role of non-planarity of free base porphyrins in intermolecular hydrogen bonding interactions with phenols
Palanisamy P., G A.J., Varathan E., Nutalapati V.
Article, Journal of Molecular Structure, 2024, DOI Link
View abstract ⏷
Three different types of meso‑substituted freebase porphyrins (H2TTP, H2TMP and H2DDMP) with varied number and nature of electron donating groups (-CH3 and –OCH3) were synthesized. The molecular interactions of the porphyrins with different phenol derivative were explored using single crystal X-ray, NMR and their affinity by varied spectroscopic techniques. All three freebase porphyrins undergo strong intermolecular interactions with 2,4,6-trinitrophenol (TNP) and crystallized in a triclinic crystal system with iso-structural behaviour. The crystal lattices are stabilized through intermolecular hydrogen bonding interactions (N–H∙∙∙O and C–H∙∙∙O) and electrostatic interactions. Increases in the non-planarity of freebase porphyrins enhance the reactivity which results in the formation of picrate anions with 1:2 adduct formation by proton transfer process. The role of weak intermolecular interactions was analysed and quantified through Hirshfeld surface and finger print analysis. DFT studies revealed that the electron-donating effect of the methoxy group plays a major role in decreasing HOMO-LUMO gap and in-plane co-operation through the decrease in the dihedral angles. The electron density at bond critical points follows the order H2TTP.2TNP>H2TMP.2TNP>H2DDMP.2TNP. Absorption and emission studies showed that dramatic changes in the Soret and Q-band pattern and the binding constants were altered with different phenols of varied pKa. The stabilization of molecular adducts were analyzed in correlation with 1H- NMR study to reveal the involvement of the hydrogen bonding.
Porphyrinoid-Functionalized ZnO Nanoflowers for Visible Light-Enhanced and Selective Benzylamine Detection at Room Temperature
Sasi S., Palanisamy P., Reji R.P., Nutalapati V., Velappa Jayaraman S., Kawazoe Y., Sivalingam Y.
Article, ACS Applied Materials and Interfaces, 2024, DOI Link
View abstract ⏷
Functionalization of hybrid organic molecules as layers on ZnO nanoflowers (NFs) gives an excellent combination of sensing toward visible light and vapors of various volatile organic compounds (VOCs). In this work, hybrid organic molecules functionalized ZnO NFs were utilized for the photoinduced detection of benzylamine at room temperature. The ZnO NFs were synthesized via a facile solution route and functionalized with four different porphyrin-conjugated molecules namely (i) pyrene-porphyrin (PP), (ii) pyrene- porphyrinato zinc (ZnPP), (iii) triphenylamine- porphyrin (TP) and (iv) triphenylamine- porphyrinato zinc (ZnTP). The diameter of the flower-like structure was found to be ∼3.2 μm with the thickness of petals being ∼24.1 nm. The gas adsorption performance of the functionalized ZnO NFs on light activation at room temperature was studied by using a scanning Kelvin probe (SKP) system. The improved adsorption properties of the samples can be attributed to the heterojunctions and light activation. In particular, an enhanced response of ZnTP functionalized ZnO (ZnTPZ) toward benzylamine was observed. Further, static gas sensing experiments using ZnTPZ under various concentrations (1, 3, 5, 10, 15, and 25 ppm) of benzylamine vapors both in dark and visible light conditions have exhibited a linear increase in the response. The selectively enhanced response of ZnTPZ compared to that of pristine ZnO was thus confirmed at 1 ppm of benzylamine. The sensitivity and limit of detection of the ZnTPZ sensor were calculated to be 0.0292 ppm-1 and 197 ppb, respectively. The coordination metal (Zn) has helped in effective charge transfer between benzylamine and ZnTPZ by providing additional active sites for interactions. Also, density functional theory calculations demonstrated the role of the hybrid organic molecules on the sensor surface in improving gas adsorption. Further, fresh cabbage was utilized for real sample analysis with the proposed sensor under visible light illumination conditions, and a linear response was obtained for low ppm evaluation at room temperature. Overall, the obtained results suggest the development of novel ZnTPZ-based light-activated gas sensors for low ppm benzylamine detection at room temperature. These kinds of sensors can be used to track the freshness of vegetables as they are transported from farms to commercial outlets.
Role of intermolecular charge transfer towards fluorometric detection of fluoride ions with anthrapyrazolone derivatives
Sivakumar G., Babu A., Das A., Anandhan M., Nutalapati V., Maji S.
Article, Materials Advances, 2024, DOI Link
View abstract ⏷
Anion detection using small molecules as chemosensors holds significant importance in the biological and environmental fields, offering several advantages over conventional methods. In this report, we have developed three anthrapyrazolone derivatives, namely 2,7-dihydrobenzo[1,2,3-cd:4,5,6-c′d′]bis(indazole) (DHBBI), 2-(benzo[1,2,3-cd:4,5,6-c′]bis(indazole)-2(7H)-yl)ethanol (DHBBI-OH), and 2,2′-(benzo[1,2,3-cd:4,5,6-c′d′]bis(indazole)-2,7-diyl)diethanol (DHBBI-2-OH), utilizing straightforward chemical reactions. These compounds were investigated for the fluorometric detection of a series of anions viz. F−, Cl−, Br−, I−, OH−, CN−, ClO4−, SO42−, NO3− and SCN− in the form of tetrabutylammonium salts. Detailed photophysical and mechanistic investigations were conducted to understand the interactions of three fluorophores with different anions. Fluorescence analysis showed considerable changes in the emission intensity of the three fluorophores in the presence of a series of anions as mentioned earlier. Among the synthesized molecules, DHBBI (Ksv = 11.6 × 104 M−1) exhibited the highest selectivity with ∼1.30 and 1.80 fold higher association rate constants and sensitivity with a limit of detection of ∼10.3 mM towards F− ions compared to DHBBI-OH and DHBBI-2-OH. The selectivity and sensitivity towards F− ions were demonstrated in light of hydrogen-bonding interactions between DHBBI and F− ions. Additionally, DFT and TDDFT studies were employed for DHBBI and its derivatives to investigate their structural insights and electronic properties comprehensively.
Laser Driven In Situ Growth of Metal Nanoparticles on Graphene Oxide Nanosheets for Plasmon-Enhanced Optoelectronic Responses
Beniwal R., Biswasray D., Gawas P., Aswathy S., Shadak Alee K., Petoukhoff C.E., Nutalapati V., Mariserla B.M.K.
Article, ACS Applied Nano Materials, 2024, DOI Link
View abstract ⏷
Graphene’s exceptional efficacies for optoelectronic and photonic applications have captivated the world toward technological advancements. However, its atomic-scale thickness impedes light-matter interactions and limits device performances. Recently, graphene adorned with metallic nanoparticles has gained huge attention for its potential to improve the optical absorption in a broad spectral range. Herein, we have enhanced the optical absorption by in situ grown silver and gold nanoparticles on simultaneously reduced graphene oxide nanosheets using nanosecond laser pulses. Plasmon field distributions and interfacial interactions were simulated through finite difference time domain calculations for hybrids, as well as individual metal nanoparticles. Also, extinction cross sections of nanoparticles and reduced graphene oxide nanosheets along with hybrids were simulated to compare with the experimental results, and we found an enriched optical response due to the interaction of the localized plasmon resonance band of metal nanoparticles with broad absorption of reduced graphene oxide nanosheets. We explored the I-V characteristics, particularly at surface plasmon resonance wavelengths, to capture the plasmon effect on device performance and found an enhanced photocurrent for hybrids. The charge transfer and free carrier absorption in these hybrids have shown a giant nonlinear optical absorption in the nanosecond regime. The observed optoelectronic responses of these hybrid materials are well-suited for light sensing and optical safety devices.
Enhanced UVB 311 emission in Sb2O3–SiO2 glasses doped with Gd2O3 and tailored Pb3O4 content for potential phototherapy
Dana Rao Y., Ravi Kumar V., Purnachand N., Venkata Sekhar A., Venkatramaiah N., Sahaya Baskaran G., Veeraiah N.
Article, Optical Materials, 2024, DOI Link
View abstract ⏷
This study investigates the enhancement of the sharp 311 nm UVB emission from Gd3+ ions in antimony silicate glass system doped with a fixed concentration of Gd2O3 (1.0 mol%) and varying amounts of red lead (40–10 mol%). The emission spectra revealed an intense sharp UVB band at 311 nm, originating from the 6P7/2 → 8S7/2 transition of gadolinium ions upon excitation at 273 nm. Interestingly, the intensity of this band nearly doubles as the Pb3O4 content decreases from 40 to 10 mol%. Such improvement was attributed to the decomposition of Pb3O4 into various phases that include α-PbO2, β-PbO2 polymorphs, and PbO. Out of these decomposition products, PbO acted as modifiers, reduced phonon losses and consequently enhanced the emission intensity. The decrease in Pb3O4 content is also hypothesized to promote de-clustering of Gd3+ ions within the glass matrix. This de-clustering reduced cross-relaxation losses, further contributed to the observed emission enhancement. In summary, this study demonstrated a successful strategy for boosting the UVB emission from Gd3+ ions in antimony silicate glasses by manipulating the content of Pb3O4.
Anthrapyrazolone functionalized Oligo(ethylene glycol)methyl ether methacrylates based fluorescent polymeric hydrogel for selective detection of Tetracycline drug
Sivakumar G., Babu A., Anandhan M., Nutalapati V., Maji S.
Article, European Polymer Journal, 2024, DOI Link
View abstract ⏷
Tetracycline (TC) antibiotics are essential for treating bacterial infections; however, overuse and improper disposal place the environment in danger and promote the growth of drug-resistant microorganisms. Monitoring their impact on living organisms is vital. Polymeric-based hydrogels offer promise in antibiotic detection due to their versatility and biocompatibility, despite their uncommon use for this purpose. In this study, we have synthesized a fluorescent polymeric hydrogel, P(OEGMA-co-DIMA) utilizing oligo(ethylene glycol)methyl ether methacrylates (OEGMA) and laboratory-synthesized fluorescent anthrapyrazolone containing monomer, 2-(benzo[1,2,3-cd:4,5,6-c'd]bis(indazole)-2(7H)-yl)ethyl methacrylate (DIMA) for the fluorometric detection of TC in the aqueous medium. The P(OEGMA-co-DIMA) hydrogel exhibited exceptional affinity towards TC while exhibiting high selectivity. The chemosensing behavior of the hydrogel was also compared with the DIMA monomer. Upon adding TC, emission analysis revealed a notable quenching in the emission intensity of the P(OEGMA-co-DIMA) hydrogel as well as the DIMA monomer. The Stern Volmer rate constants (Ksv) of the hydrogel (Ksv = 9.99 x 103 M−1) in water and DIMA (Ksv = 25.63 x 103 M−1) in acetonitrile showed a higher quenching rate constant with a limit of detections (LODs) of 1.3 nM and 0.11 nM. Turn-off fluorescence behavior occurs via a static quenching mechanism through a photoinduced electron transfer process and intermolecular hydrogen bonding. To validate the selectivity, the interference analyses in an aqueous medium with different antibiotics are provided. To rationalize the real-time applicability of the hydrogel, studies were extended to water samples obtained from deionized water, tap water, lake water, and also in milk samples. The recovery rate and LOD for real samples ranged from 83.8% to 111% and 0.83 to 3.6 nM, respectively.
Pyrene Derivative Incorporated Ni MOF as an Enzyme Mimic for Noninvasive Salivary Glucose Detection Toward Diagnosis of Diabetes Mellitus
Shabanur Matada M.S., Kuppuswamy G.P., Sasi S., Velappa Jayaraman S., Nutalapati V., Senthil Kumar S., Sivalingam Y.
Article, ACS Applied Materials and Interfaces, 2024, DOI Link
View abstract ⏷
Herein, we demonstrate the detection of glucose in a noninvasive and nonenzymatic manner by utilizing an extended gate field-effect transistor (EGFET) based on the organic molecule pyrene phosphonic acid (PyP4OH8) incorporated nickel metal-organic framework (NiOM-MOF). The prepared electrode responds selectively to glucose instead of sucrose, fructose, maltose, ascorbic acid, and uric acid in a 1× phosphate buffer saline solution. Also, utilizing the scanning Kelvin probe system, the sensing electrode’s work function (Φ) is measured to validate the glucose-sensing mechanism. The sensitivity, detection range, response time, limit of detection, and limit of quantification of the electrode are determined to be 24.5 μA mM-1 cm-2, 20 μM to 10 mM, less than 5 s, 2.73 μM, and 8.27 μM, respectively. Most interestingly, the developed electrode follows the Michaelis-Menten kinetics, and the calculated rate constant (km) 0.07 mM indicates a higher affinity of NiOM-MOF toward glucose. The real-time analysis has revealed that the prepared electrode is sensitive to detect glucose in real human saliva, and it can be an alternative device for the noninvasive detection of glucose. Overall, the outcomes of the EGFET studies demonstrate that the prepared electrodes are well-suited for expeditious detection of glucose levels in saliva.
Introduction thioindigo as new high stability unit in Ru-complex for DSSCs: Theoretical and photovoltaic investigation
Hosseinnezhad M., Nasiri S., Nutalapati V., Gharanjig K., Nunzi J.M.
Article, Optical Materials, 2024, DOI Link
View abstract ⏷
New Ru-dyes were designed with indoline and thioindigo groups for dye-sensitized solar cells (DSSCs). Thioindigo was used as an effective substitute for improving fastness properties, and the synthesis efficiency of dyes 1 and 2 was 78 and 82 %, respectively. Cyanoacrylic acid is a suitable electron-withdrawing group in the preparation of photosensitizers, which improved the conversion efficiency by about 88 % in this research. The optical response of the complexes was evaluated theoretically and experimentally. The presence of cyano groups effectively bonds with the semiconductor layer, resulting in a better photovoltaic response. Furthermore, the prepared complexes have two types of electron withdrawing groups, carboxylic acid and cyanoacrylic acid, which yield 3.29 % and 6.23 % efficiency, respectively. In addition, co-sensitization using two prepared complexes and N719 was studied and analyzed. The efficiency of DSSCs prepared with N719 and complexes 1 and 2 was 8.10 and 9.49 %, respectively.
Highly sensitive fluorescence turn-OFF and reversible chemical sensor for Hg2+ ion based on pyrene appended 2-thiohydantoin
Gawas P.P., Selvaraj K., Pamanji R., Selvin J., Nutalapati V.
Article, Chemosphere, 2024, DOI Link
View abstract ⏷
A novel fluorometric chemical sensor (PY-2TH) based on 2-thiohydantoin (2TH) in conjugation with pyrene (PY) was designed by facile one-pot Knoevenagel condensation reaction and explored for the sensitive and selective detection of Hg2+ ion in solution and solid state methods. Different analytical techniques like NMR and LC-MS concomitantly confirmed the structure of PY-2TH. Absorption and emission studies demonstrate positive solvatochromic effects indicating intramolecular charge transfer in polar solvents. PY-2TH exhibits unprecedented selectivity for detecting Hg2+ ions in tetrahydrofuran (THF) through turn-OFF fluorescence with 90% decrease in the emission intensity with a limit of detection (LOD) of ∼4.4 ppb. The mechanistic investigation through NMR and optical studies confirm the formation of a 2:1 complex between PY-2TH and Hg2+. Thin films of PY-2TH exhibits the J-aggregate formation in the solid state leading to a shift in the emission towards the near-infrared region. Further, we have demonstrated the applicability of PY-2TH for detection of Hg2+ ions and fluorescence imaging in live Zebrafish larvae and the toxicological effects are explored. Cytotoxic evaluation on Zebrafish larval cells revealed that PY-2TH is found to be non-toxic. Detailed analysis demonstrate the potential of PY-2TH for ultra-sensitive Hg2+ ion detection and removal in aqueous environments, highlighting its applicability for identification of metal contamination in live organisms and environmental toxicity.
Solution-Processed OLEDs Based on a Bipolar AIE Terpyridine Derivative as a Host
Palanisamy P., Rabiei M., Hosseinnezhad M., Palevicius A., Janusas G., Managutti P.B., Mohamed S., de Sousa L.E., de Thieulloy L., de Silva P., Vilkauskas A., Nasiri S., Nunzi J.-M., Nutalapati V.
Article, ACS Applied Optical Materials, 2024, DOI Link
View abstract ⏷
The efficiency of organic light-emitting diodes (OLEDs) with multiple functional components is still limited owing to their complicated design and fabrication process. A postfunctionalization strategy was exploited to develop devices derived from terpyridine derivative bipolar host 4′-(3′,4′,5′-triphenyl-[1,1′:2′,1″-terphenyl]-4-yl)-2,2′:6′,2″-terpyridine to overcome this limitation. The glass transition temperature was up to 176 °C, and the host was favorable for practical OLED devices. The crystallite size of the powder calculated by the modified Scherrer’s method was 102 nm. Furthermore, the ionization potential (IPPE) of the spin-coated host on the fluorine tin oxide (FTO), which is related to the highest occupied molecular orbital (HOMO), was calculated to be 5.98 eV. Both hole and electron mobilities measured by space charge limit current (SCLC) reveal bipolar transport in the host, with a hole mobility of 1.87 × 10-4 cm2 V-1 s-1 and an electron mobility of 6.69 × 10-5 cm2 V-1 s-1. Aggregation-induced emission (AIE) phenomena were discussed in detail with field emission scanning electron microscopy (FESEM). In addition, a thermally activated delayed fluorescence (TADF) emitter consisting of 10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9,9-dimethyl-9,10-dihydroacridine (DMAC-TRZ) was considered in a host-guest system. Taking into account the role of the designed and synthesized host, using poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) as a hole injection layer (HIL) for cyan OLED solution processing, the maximum luminescence, current, power, and external quantum efficiency (EQE) reached 19,986 cd m-2, 45.15 cd A-1, 32.95 lm W-1, and 22.35%, respectively, for host (70 wt %):DMAC-TRZ as an emitting layer.
What is TADF (thermally activated delayed fluorescence) compared to the mechanisms of FL (fluorescence), PH (phosphorescence), and TTA (triplet–triplet annihilation) based on a novel naphthalimide sulfonylphenyl derivative as a host?
Nasiri S., Rabiei M., Shaki H., Hosseinnezhad M., Kalyani K., Palevicius A., Vilkauskas A., Janusas G., Nutalapati V., Kment S., Michel Nunzi J.
Article, Journal of Photochemistry and Photobiology A: Chemistry, 2024, DOI Link
View abstract ⏷
One of the biggest challenges in the field of optoelectronics is to easily identify the mechanisms involved in light-emitting materials. There are several different mechanisms of emission, and the best known are fluorescence (FL), phosphorescence (PH), thermally activated delayed fluorescence (TADF), and triplet–triplet annihilation (TTA). In this study, simple ways to diagnose these mechanisms are presented with an example. N,N-di(benzenesulfonylphenyl)-N-(N-2-aminomethylpyridine-1,8-naphthalimide)amine is synthesized as a host compound due to its high HOMO-LUMO and ionization potential (IP) values and three emitters consisting of 50 wt% Bis (1phenylisoquinoline))(acetylacetonate)iridium(III) (Ir(piq)2(acac)), 10-(4-(4,6-Diphenyl-1,3,5-triazin-2-yl)phenyl)-9,9-dimethyl-9,10-dihydroacridine (DMAC-TRZ) and 1,1′-(2,5-Dimethyl-1,4-phenylene)dipyrene (DMPPP) were considered. Overall, the host compound, doped Ir(piq)2(acac) and doped DMPPP follow the mechanisms of FL, the combination of FL and PH, and the combination of FL and TTA, as the photoluminescence (PL) decay life time and the PL intensity increased with decreasing temperature. However, DMAC-TRZ doped with the host compound showed the TADF mechanism, as the PL decay lifetime and the PL intensity increase simultaneously with increasing temperature. In addition, the difference between the singlet excited state (S1) and the triplet excited state T1 (ΔEST) from the PL and PH spectra at 77 K for the spin-coated DMAC-TRZ-doped host show the lowest value in between the samples at 0.02 eV, and the reverse intersystem crossing (rISC) effect is activated. Moreover, the linear slopes of the power dependence analysis of the DMPPP-doped host were calculated to be 2.04 and 0.91, indicating that there are two components (photons) for this sample which is strong evidence for the TTA mechanism. Taking into account the synthesized host compound, (Ir(piq)2(acac):host), (DMAC-TRZ:host) and (DMPPP:host) as emitter layers, the organic light emitting diodes (OLEDs) were fabricated via solution processing, and the TADF OLED exhibited the highest efficiency among the other OLEDs.
A Review of the Application of Organic Dyes Based on Naphthalimide in Optical and Electrical Devices
Hosseinnezhad M., Nasiri S., Nutalapati V., Gharanjig K., Arabi A.M.
Review, Progress in Color, Colorants and Coatings, 2024, DOI Link
View abstract ⏷
The two technologies of dye-sensitized solar cells (DSSCs) and organic light-emitting devices (OLEDs) are emerging in the development of new sources of energy and lighting, respectively. The exceptional features of these technologies, including their color, insensitivity to temperature, and high response angle, have caused their attention and development. Organic compounds play a key role in these two technologies and cause the effective response and stability of the device, so high stability, longevity, and the possibility of simple application in the structure of the structure are of great importance. Molecular engineering and the application of various substitutions to the naphthalimide core can produce promising results for the preparation of stable organic materials with diversity in properties. In this review, naphthalimides are introduced as an effective core in the preparation of lightand electricity-sensitive dyes. Its application in two technologies, DSSCs and OLED, is explained, and the different components of these technologies are briefly introduced. One of the highest efficiencies reported for dye-sensitized solar cells based on naphthalimide as photosensitizers is 10.8 %. This sensitizer has alkyl and indoline groups. Different structures of arrangement of electron donor and electron acceptor groups will be investigated and the performance efficiency of these devices will also be investigated. Studies show that the amino group is an important substitution in the preparation of naphthalamide fluorescent dyes. The presence of this group will increase the efficiency of the amplifier by up to 10 %.
Influence of Au0 metallic particles on NIR laser emission of Yb3+ ions in Li2O-HfO2-SiO2 glass ceramic
Pavani Koteswari Devi P., Venkata Sekhar A., Ravi Kumar V., Venkatramaiah N., Ravi Kumar V., Veeraiah N.
Article, EPJ Applied Physics, 2024, DOI Link
View abstract ⏷
This study consists of the synthesis, characterization, and analysis of photoluminescence (PL) spectra for Li2O-HfO2-SiO2-Yb2O3 glass ceramics sensitized with small amounts of Au2O3. Using the results of XRD and X-ray photoelectron spectroscopy (XPS) studies indicated a progressive reduction of Au3+ ions into Au0 metallic particles (MPs) with increase of Au2O3 content. Investigations into the infrared spectra highlighted a growing concentration of induced defects in the samples due to the increased proportion of Au0 MPs. Optical absorption (OA) spectra exhibited a distinct band attributed to the 2F7/2 → 2F5/2 transition of Yb3+ within wavelength range of 800-980 nm. Furthermore, a wide absorption band linked to the surface plasmon resonance (SPR) of Au0 MPs was identified in the visible region. PL spectra, recorded at λexc=450 nm, revealed a band between 980 to 1025 nm, associated with the 2F5/2 → 2F7/2 transition of Yb3+ ions. Another emission band was observed due to the sp→d transition of Au0 MPs within the visible region. Observed enhanced PL emission from Yb3+ ions in the NIR range was ascribed to the energy transfer from Au0 MPs to Yb3+ ions. Ultimately, it was deduced that Au0 MPs played a pivotal role in enhancing the PL output of Yb3+ ions in the Li2O-HfO2-SiO2 glass ceramic. Thus, glass ceramics incorporating an optimal concentration of Au2O3 hold significant potential as materials for NIR lasers.
Luminescence features of Ho3+, Er3+ and Tm3+ ions in red lead added non-conventional antimony oxide glass system
Rao Y.D., Sekhar A.V., Kumar V.R., Kumar V.R., Venkatramaiah N., Purnachand N., Gandhi Y., Veeraiah N.
Article, Luminescence, 2024, DOI Link
View abstract ⏷
In this study, a glass system based on heavy metal oxides, namely Pb3O4–Sb2O3–SiO2, was prepared with Ho2O3, Er2O3, and Tm2O3 as dopants. The prepared glass were characterized using X-ray diffraction (XRD) and infrared (IR) studies. The luminescence efficiencies of the three rare earth ions viz., Ho3+, Er3+, and Tm3+ in the glass system were investigated, specifically focusing on green (Ho3+, Er3+), blue (Tm3+), and near-infrared (NIR) emissions. The optical absorption (OA) and photoluminescence (PL) spectra of RE mixed glass displayed strong bands in the visible and NIR regions, which were analyzed using the Judd–Ofelt (J–O) theory. The J–O coefficients (Ωλ) were found to be in the order of Ω2 > Ω4 > Ω6 for all the three glass. Notably, the Tm3+-doped glass exhibited the lowest Ω2 value, which was attributed to a larger degree of disorder in the glass network due to lower fractions of Sb5+ and Pb4+ ions that take part in the glass network forming. This conclusion was arrived based on the IR studies. Furthermore, the quantitative analysis of PL spectra and decay curves indicated that SbHo and SbEr glass were suitable for efficient green emission, while SbTm glass is a promising choice for blue laser emission.
New Insights into Improving the Photovoltaic Performance of Dye-Sensitized Solar Cells by Removing Platinum from the Counter Electrode Using a Graphene-MoS2 Composite or Hybrid
Hosseinnezhad M., Ghahari M., Mobarhan G., Fathi M., Palevicius A., Nutalapati V., Janusas G., Nasiri S.
Article, Micromachines, 2023, DOI Link
View abstract ⏷
Photovoltaic systems, such as dye-sensitized solar cells (DSSCs), are one of the useful tools for generating renewable and green energy. To develop this technology, obstacles such as cost and the use of expensive compounds must be overcome. Here, we employed a new MoS2/graphene hybrid or composite instead of platinum in the DSSCs. Furthermore, the correctness of the preparation of the MoS2/graphene hybrid or composite was evaluated by field emission scanning electron microscope (FESEM), and the results showed that the desired compound was synthesized correctly. Inexpensive organic dyes were used to prepare the DSSCs, and their chemical structure was investigated by density functional theory (DFT) and cyclic voltammetry (CV). Finally, the DSSCs were fabricated using MoS2/graphene composite or hybrid, and to compare the results, the DSSCs were also prepared using platinum. Under the same conditions, the DSSCs with MoS2/graphene composite illustrated better efficiency than MoS2/graphene hybrid or/and graphene.
A novel triphenylamine based push-pull fluorophore bearing a 2-thiohydantoin unit for toxic Hg2+ ion detection: exploring its potential for live cell imaging
Gawas P.P., Ramakrishna B., Pamanji R., Selvin J., Nutalapati V.
Article, Materials Advances, 2023, DOI Link
View abstract ⏷
A novel fluorescent chemosensor (TPA-2TH) containing triphenylamine (TPA) appended in conjugation with 2-thiohydantoin (2TH) is developed and confirmed by various analytical techniques like FT-IR spectroscopy, NMR spectroscopy, HR-MS and single crystal X-ray diffraction (SC-XRD). The crystal structure analysis revealed a propeller-shaped TPA unit and a co-facial herringbone packing arrangement stabilized by N-H⋯S, N-H⋯O and C-H⋯O in the crystal lattice. TPA-2TH exhibited a strong absorption band at ∼431 nm and emitted a yellow-green fluorescence at λmax = 522 nm in THF, attributed to an efficient charge-separated state resulting from ICT between TPA and 2TH. A solvatochromic effect was observed with a red shift in the emission wavelength as the polarity of the solvent increased. TPA-2TH showed unprecedented selectivity with turn-off fluorescence upon complexation with diamagnetic Hg2+ ions, attributed to an increase in the spin-orbit coupling and a weakened ICT effect caused by Hg2+ binding. The addition of Hg2+ to TPA-2TH resulted in the formation of a 2 : 1 complex (TPA-2TH-Hg2+), confirmed by the coordination of a sulphur atom of TPA-2TH with Hg2+ ions, as evidenced by 1H NMR spectroscopy and Job's plot analysis. A linear relationship between the fluorescence intensity of TPA-2TH and the concentration of Hg2+ ions is observed with a LOD of 3.3 pM. Furthermore, the toxicological effect of TPA-2TH is explored in zebrafish larvae and embryos to provide a sensitive bio-indicator for metal ion contamination and fluorescence imaging. This comprehensive approach combining fluorescence quenching and behavioural toxicity assessment offers a practical method for evaluating metal ion contamination and its potential toxic effects on aquatic organisms with acute behavioural toxicity end points using adult zebrafish.
Design of smart polymeric sensor based on poly(N-isopropylacrylamide) and anthrapyrazolone derived fluorescent crosslinker for the detection of nitroaromatics in aqueous medium
Babu A., Sivakumar G., Anandan M., Adhya P., Akash T., Mondal T., Nutalapati V., Maji S.
Article, European Polymer Journal, 2023, DOI Link
View abstract ⏷
Explosive detection in aqueous medium using fluorometric titrations is of paramount importance for security and safety, as it offers a susceptible and rapid method to identify potential threats in water sources or aqueous environments, ensuring the protection of critical infrastructure and public safety. Previously, we have investigated fluorescence-based explosive detection via π-electron-rich anthrapyrazolone-derived fluorophore moiety (dye) as an effective sensor in an organic medium. However, the dye's solubility in water makes it difficult to identify nitroaromatics (NACs) in aqueous media. In the current study, thermoresponsive crosslinked polymer (TCP) with dye [DHBBI(MA)2] added as a crosslinker between the polymer chains is synthesised by straightforward and easy free radical polymerization. The emission intensity of TCP is significantly reduced with interaction with NACs like TNP, ATNP, DNP, and PNP, primarily through static quenching attributed to a photoinduced electron transfer (PET) process. TNP exhibited the most efficient quenching, with a Ksv value of 10.7 × 102 M−1 for TCP and 6.189 × 102 M−1 for DHBBI(MA)2. The limit of detection (LOD) was 0.12 nM for TCP and 0.135 nM for DHBBI(MA)2. TCP proved to be approximately 1.72 and 1.12 times more efficient in TNP detection than DHBBI(MA)2 in terms of Ksv value and LOD. At higher temperatures beyond the LCST of the polymer, TCP exhibits additional fluorescence quenching, making it effective for NAC detection. This switch in fluorescence quenching near the cloud point temperature (TCP) of PNIPAM in aqueous media indicates TCP's potential for real-world applications, including rapid detection and identification of nitroaromatics and environmental monitoring in soil and water.
Impact of red lead on 0.65 and 1.3 μm emissions of Pr3+ ions in a non-conventional antimony oxide glass system for application in optical communication
Rao Y.D., Venkatramaiah N., Sekhar A.V., Purnachand N., Kumar V.R., Veeraiah N.
Article, Journal of Materials Science: Materials in Electronics, 2023, DOI Link
View abstract ⏷
This research delves into the influence of red lead content on the red and NIR emission characteristics of Pr3+ ions within a nonconventional antimony silicate glass system. The glasses were synthesized across a composition spectrum of (40 − x) Pb3O4‒49Sb2O3‒(10 + x)SiO2:1Pr2O3, where x ranged from 0 to 35 mol%. Characterization was carried out using XRD, DSC, XPS, and IR spectroscopy. These analyses unveiled the presence of antimony ions in both Sb3+ and Sb5+ states and lead ions in Pb4+ and Pb2+ states within these glass compositions. Optical absorption and emission spectra (at λexc = 445 nm) were recorded within the wavelength range of 400‒1800 nm. Luminescence decay profiles of two pivotal transitions, namely, 3P0 → 3F2 (red emission) and 1G4 → 3H5 (1.3 µm NIR emission), were also recorded. Various radiative parameters from these spectra were extracted using the J–O theory. The findings indicated that, as the Pb3O4 content declined from 40 to 10 mol%, the covalent nature of the samples diminished, resulting in a remarkable amplification in the intensity of both the red and NIR emission bands of Pr3+ ions. The glass containing 10 mol% of Pb3O4 exhibited the most elevated radiative parameters and quantum efficiency. This augmentation was attributed to the reduction of Pb4+ and Sb5+ ions within the glass network or the augmentation of Pb2+ ions, serving as modifiers that mitigated phonon losses. Consequently, glasses with 10 mol% Pb3O4 demonstrate great potential for telecommunications applications, owing to their significant enhancement in PL emission for the 3P0 → 3F2 and 1G4 → 3H5 transitions.
Effect of thermal treatment on zeolite for real-time gas sensing of oxygenated volatile organic compounds
Joshi N., Gawas P., Bora A., Sivachandiran L., Sivalingam Y., Nutalapati V.
Article, Surfaces and Interfaces, 2023, DOI Link
View abstract ⏷
The breathable air is severally polluted due to the emission of various pollutants like volatile organic compounds (VOCs) and dust particles of submicron sizes. These pollutants have several adverse health hazards, which can cause fatal accidents and mortalities. In the current study, we have modified the FAU type of Zeolite (ZE) with the Si/Al to 1 and treated at different temperatures (300–600 °C) in a 10% H2 + 90% N2 mixture to achieve different distributions of oxygen vacancies. The presence of oxygen vacancy and electrons in the lattice is confirmed by EDAX, XPS and ESR techniques. The charge irregularities generated due to trapped electrons are exploited for detection of different VOCs like acetone, ethyl methyl ketone, isopropyl alcohol, ethanol, n-hexane, and benzene using the scanning kelvin probe (SKP) technique. The oxygen vacancies raise the distribution of Lewis and Brønsted basic sites, which impacts the interaction of VOCs with the sample surface and the amount of VOCs uptake. The untreated ZE and treated at 600 °C (ZE600) exhibited n-type behavior with 13.8% oxygen deficient sites with ∼1.9 μmol/g of total basic sites and 3 μmol/g of total acidic sites. The thermal treatment for ZE600 leads to ∼280 folds enhancement in surface photovoltage towards acetone with ∼ 67% of recovery concerning untreated ZE.
Significance of Zn Complex Concentration on Microstructure Evolution and Corrosion Behavior of Al/WS2
Gawas P.P., Pandurangan P., Rabiei M., Palevicius A., Vilkauskas A., Janusas G., Hosseinnezhad M., Ebrahimi-Kahrizsangi R., Nasiri S., Nunzi J.M., Nutalapati V.
Article, Molecules, 2023, DOI Link
View abstract ⏷
Corrosion is a harmful processes which by definition is a chemical or electrochemical reaction between a substance (usually a metal) and the environment which leads to a change in the properties of the substance and has destructive effects. In this study, new composites consisting of Al/WS2/ZnTerp-2TH with 5 and 10 wt.% ZnTerp-2TH were prepared and the results were fully compared. Al/WS2 played the role of matrix and ZnTerp-2TH played the role of reinforcement. In other words, as a novelty to prevent the corrosion of Al/WS2, ZnTerp-2TH is designed and synthesized and showed good results when the corrosion ratio was reduced by the existence of ZnTerp-2TH. Furthermore, the NMR and mass analysis of ZnTerp-2TH were carried out, and the thermal properties, X-ray diffraction, Fourier-transform infrared (FTIR) spectroscopy, morphology, energy-dispersive X-ray spectroscopy (EDX) analysis and corrosion behavior of the composites were also discussed in detail. The crystal size values of composites were calculated by the modified Scherrer method 34, 26 and 27 nm for Al/WS2, Al/WS2/5 wt.% ZnTerp-2TH and Al/WS2/10 wt.% ZnTerp-2TH, respectively. The microstructural examination of the specimens showed that the reinforcing phase (ZnTerp-2TH) has a favorable distribution on the surface of Al/WS2 when it covers the cracks and holes. In addition, the corrosion investigation results showed that the addition of ZnTerp-2TH to Al/WS2 can improve the corrosion resistance when the Ecorr and Icorr values of Al/WS2/10 wt.% ZnTerp-2TH were recorded in tandem −724 mV/decade and 5 uA cm−2.
Fluoranthene-based derivatives for multimodal anti-counterfeiting and detection of nitroaromatics
Selvaraj K., Palanisamy P., Manikandan M., Managutti P.B., Sangeetha P., Mohamed S., Pamanji R., Selvin J., Nasiri S., Kment S., Nutalapati V.
Article, Materials Advances, 2023, DOI Link
View abstract ⏷
In this study, we developed two novel sky blue fluorescent fluorophores comprising ethyl alcohol (FOH) and ethanethiol (FSH) units appended to fluoranthene at the periphery. Single Crystal X-Ray Diffraction (SC-XRD) studies reveal that the molecular flexibility of alkyl chains leads to distinct diagonal (FOH) and ladder (FSH) shaped supramolecular arrangements in the crystal lattices. Detailed photophysical and DFT studies showed that FOH and FSH demonstrate high sensitivity and selectivity towards the detection of trinitrophenol (TNP). FSH exhibits high quenching efficiency (∼84%), a rate constant of KSV = 1.1 × 104 M−1 with a limit of detection of ∼97 ppm in THF, and ∼76 ppm in river water. Mechanistic investigation through NMR and SC-XRD of the FSH adduct with 1,3-dinitrobenzene (DNB) reveal strong π-π interactions (3.518 Å). Furthermore, photoinduced electron transfer occurs from the fluorophores to the nitro analytes and leads to strong intermolecular interactions using the static quenching mechanism. Both fluorophores were employed in advanced surveillance to identify finger marks on a wide range of substrates (glass, cellophane tape, aluminium foil and floor tiles) with different resolutions to provide an unadorned and lucrative method for viewing the latent fingerprints (LFPs) with exceptionally consistent evidence of up to level 3 and without the requirement for post-treatments, leading to promising applications for onsite forensic analysis. Furthermore, FOH and FSH were evaluated in 72 hpf zebrafish larvae/embryos to demonstrate the non-toxicological behaviour and fluorescence imaging/tracking.
Fluoranthene-terminated terpyridine ensemble for fluorescence light up and ratiometric chemical sensor for multi toxic metals
Selvaraj K., Palanisamy P., Ramakrishna B., Pamanji R., Selvin J., Srikanth K., Nasiri S., Kment S., Nutalapati V.
Article, Analytica Chimica Acta, 2023, DOI Link
View abstract ⏷
A novel π-electron rich fluoranthene embellished with a phenyl spacer and coupled with terpyridine (TS1) was developed through Diels-Alder reaction. Single crystal X-ray structure evidences the variations in dihedral angles between the fluoranthene and the phenyl unit responsible for development of non-coplanar interactions and stabilized by a wave-like molecular packing in the crystal lattice with weak π-π interaction of 4.125 Å. The peripheral terpyridine of TS1 endows an efficient binding with multiple metal ions by colorimetric and fluorometric methods. TS1 exhibits a ratiometric fluorescence response from sky blue to yellow colour upon the addition of Zn2+ ions with a limit of detection (LOD) of 0.05 ppm. The other metal ions such as Cu2+, Co2+ and Fe2+ demonstrate fluorescence quenching behaviour with LODs of 0.1, 0.3 and 0.7 ppm, respectively. The intramolecular charge transfer (ICT) shows the variation in TS1 emission behaviour upon metal ions interaction and quantitatively discriminates the metal ion concentrations. TS1 conferred a visual colorimetric change from colourless to magenta, enabling naked-eye detection of Fe2+ and showing clear discrimination between Fe2+ and Fe3+ ions for the real-time water samples. Furthermore, we have investigated the effect of TS1 in Zebrafish larvae/embryos and cytotoxicity in human urinary tract transitional cell carcinoma cells (UM-UC-3).
Modified Scherrer equation to calculate crystal size by XRD with high accuracy, examples Fe2O3, TiO2 and V2O5
Nasiri S., Rabiei M., Palevicius A., Janusas G., Vilkauskas A., Nutalapati V., Monshi A.
Article, Nano Trends, 2023, DOI Link
View abstract ⏷
A key parameter in the analysis of compounds and the study of their physical, chemical, and mechanical properties is the knowledge of the crystal size. There are two common techniques for determining this size: transmission electron microscopy (TEM) and Brunauer-Emmett-Teller theory (BET). These methods are time-consuming and expensive; thus, the calculation of this size by X-ray diffraction (XRD) is proposed. There are several methods for calculating the crystal size by X-ray diffraction, but not all peaks were considered and the errors were very large. In this study, the Modified Scherrer method is practically explained, and three important rules for obtaining crystal size values with high accuracy are introduced and applied. For better understanding, this study explains the Modified Scherrer method for iron oxide (Fe2O3), titanium oxide (TiO2) and vanadium oxide (V2O5) powders as examples. Crystal size values were calculated using the modified Scherrer method for Fe2O3, TiO2, and V2O5 as 30.94, 16.57, and 24.30 nm, respectively. Furthermore, the extracted crystal size values of ∼ 31, 18 and 30 nm for Fe2O3, TiO2, and V2O5 were tandemly recorded by TEM. Moreover, the crystal size values for Fe2O3, TiO2, and V2O5 were calculated to 32.96, 15.87 and 16.66 nm by BET tandemly. The results show that the Modified Scherrer method has high accuracy and agreement with the analyses of TEM and BET. Thus, this method is proposed for calculating each crystalline compound as it has high accuracy and XRD analysis is available and cheaper.
The Influence of Silver Ions on the Dielectric Dispersion Dipolar Relaxation Dynamics and Dielectric Breakdown Strength of Zinc Selenium Phosphate Glass System
Reddy G.N.K., Kostrzewa M., Sekhar A.V., Ingram A., Reddy A.S.S., Venkatramaiah N., Raju G.N., Kumar V.R., Veeraiah N.
Article, Physica Status Solidi (A) Applications and Materials Science, 2023, DOI Link
View abstract ⏷
Herein, a study on the dielectric properties of ZnO–P2O5–SeO2 glass ceramics containing varied contents of Ag2O is presented. Structural analysis of the samples by X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, Fourier transform infrared spectra, and optical absorption techniques indicated that the glasses are embedded with Ag3PO4, Ag2SeO3, and Zn3(PO4)2 anisotropic crystal phases along with Ag+ ions and Ag0 particles. Dielectric properties, ac conductivity (σac), and dielectric breakdown strength (DBS) are investigated as functions of Ag2O concentration. The results show the maximal concentration of Ag+ ions and Ag0 metallic particles in the sample containing 0.6 mol% of Ag2O. Dielectric parameters and (σac) increase with increasing Ag2O up to 0.6 mol%, while the DBS and electrical impedance decrease. The observed dipolar effects are quantitatively analyzed and possible dipoles are identified. Ionic contribution is predominant up to 0.6 mol% of Ag2O, beyond which the polaronic tunneling phenomenon prevails. These findings indicate that 0.6 mol% of Ag2O is the optimal concentration for using these glass ceramics as solid electrolytes in ionic batteries. Moreover, glass ceramics containing Ag2O beyond 0.6 mol% have exhibited larger polaronic conductivity, hence such glasses can be considered suitable candidates for electrodes in ionic batteries.
Investigation of the influence of persulfurated benzene derivatives on optical and carrier mobility properties
Nasiri S., Palanisamy P., Rabiei M., Hosseinnezhad M., Palevicius A., Vilkauskas A., Janusas G., Nutalapati V.
Article, Materials Letters, 2023, DOI Link
View abstract ⏷
In this research, two persulfurated benzene molecules consisting of amine and carboxylic acid derivatives were designed, synthesized and the effect of substitution in para position on absorption, fluorescence, and aggregation induced emission (AIE) were investigated. Moreover, taking into account the simpler method, the space charge limited current (SCLC) was considered and the temperature dependence on carrier mobility (μ) of the derivatives was investigated. The maximum value of hole mobility (μh) at 298 K was calculated to be 7.50 × 10-4 [Formula Presented]. Since the crystallite size of the compound consisting of the NH2 group was higher (100.07 nm), the (μ) at 298 K and 77 K were also higher than the other counterpart. As a result, the NH2 substitution played a more effective role in increasing the (μ).
Dynamical behavior of Ag ions on structural and dielectric features of As2O3 glass ceramics containing chalcogenide oxides
Suryanarayana V., Sekhar A.V., Bafti A., Pavic L., Reddy A.S.S., Reddy G.N.K., Venkatramaiah N., Kumar V.R., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2023, DOI Link
View abstract ⏷
In this work, As2O3 glasses mixed with two chalcogenide oxides (SeO2 and TeO2) and doped with varied contents of Ag2O were prepared and heat-treated. Characterized by various techniques suggested that these glasses were embedded with Ag3AsO4 crystal phases and Ag0 metallic particles (MPs). Later, different dielectric parameters viz., dielectric constant (ε′), electric modulus (M), electrical impedance (Z). conductivity a.c. conductivity a.c. conductivity and σac were measured over broad frequency (ω) and temperature (T) regions. Observed decrement in ε′, σac with Ag2O up to 0.5 mol% was understood due to the increased fraction of As5+ ions that occupy network-forming positions with AsO4 units. The observed increase of these parameters with Ag2O beyond 0.5 mol% was attributed to the growing fraction of Ag0 MPs that acted as modifiers. The variation of σac with Ag2O content was analyzed using different conduction mechanisms. Overall, it is predicted that greater than 0.5 mol% of silver oxide is preferable for achieving better ionic conductivity in these glasses
Substituent Effect on Stimuli-Responsive Donor-Acceptor Framework-Based 2-Thiohydantoins for Monitoring Nonanal Vapors
Gawas P.P., Bora A., Reji R.P., Ramakrishna B., Managutti P.B., Gob C.R., Mohamed S., Kawazoe Y., Velappa Jayaraman S., Sivalingam Y., Nutalapati V.
Article, Journal of Physical Chemistry C, 2023, DOI Link
View abstract ⏷
Tuning the π-conjugation and varying the functional units can improve the response behavior with superior sensitivity and selectivity. Herein, we report on five novel donor-acceptor (D-A) molecular ensembles developed through C5 substitution on 2-thiohydantoin (2TH) with π-conjugation having different electron-donating groups. The structure-property relationships were investigated by single-crystal X-ray diffraction (SC-XRD) analysis, photophysical, electrochemical, and computational studies. The structural influence of 2TH derivatives on surface interactions with volatile organic compounds (VOCs) were analyzed by binding affinities, kinetics, and other intrinsic parameters (work function, surface photovoltages (SPVs), and response and recovery times). N,N-diMeAPh-2TH exhibits mechanochromic and vapochromic behavior, shows red-shifted emission at ∼554 nm upon exposure to nonanal vapors with a visual color change from orange-red to brown, and shows vivid color variations with different VOCs. N,N-diMeAPh-2TH shows reversible vapochromic behavior as well. Ph-2TH, 4-OMePh-2TH, and 2,4-diOMePh-2TH exhibit n-type behavior with the greater SPV response achieved for Ph-2TH (90%), but good recovery (58%) in SPV in 439 s is observed in the case of 2,4-diOMePh-2TH. In contrast, 3,4-diOMePh-2TH and N,N-diMeAPh-2TH exhibit p-type behavior toward nonanal vapors with a high SPV response obtained for N,N-diMeAPh-2TH (94%) within 293 s as well as recovery (87%) in surface PVT in 692 s. The results demonstrate that electron-donating substituents −N(CH3)2 can improve sensing performance by increasing electron density, whereas steric hindrance on the phenyl unit can modulate sensing performance.
Amplification of blue emission of Tm3+ ions in Li2O-HfO2-SiO2 glass system by means of Au0 metallic particles
Devi P.P.K., Sekhar A.V., Kumar V.R., Baskaran G.S., Venkatramaiah N., Kumar V.R., Veeraiah N.
Article, Luminescence, 2023, DOI Link
View abstract ⏷
Li2O-HfO2-SiO2-Tm2O3:Au2O3 glass samples (containing fixed content of Tm2O3 and different concentration of Au2O3) were prepared and characterized. Bearing of Au0 metallic particles (MPs) on improving blue emission of thulium ions (Tm3+) ions was explored. Optical absorption (OA) spectra exhibited multiple bands excited from 3H6 of Tm3+. Additionally, a broad peak in the wavelength range 500–600 nm due to surface plasmon resonance (SPR) of Au0 MPs was noticed in the spectra. Photoluminescence (PL) spectra (of thulium free glasses) indicated a peak in the visible range due to sp → d electronic transition of Au0 MPs. Luminescence spectra of Tm3+ and Au2O3 co-doped glasses exhibited intense blue emission with substantial increase of intensity with increase of Au2O3 content. Bearing of Au0 MPs on the reinforcement of blue emission of Tm3+ was discussed in detail with kinetic rate equations.
Metal-Free, Photoredox-Catalyzed Synthesis of Quinazolin-4(3H)-ones and Benzo[4,5]imidazo[1,2-c]quinazolines Using Trialkylamines as Alkyl Synthon
Arumugam A., Palani P., Anandan M., Nutalapati V., Senadi G.C.
Article, European Journal of Organic Chemistry, 2023, DOI Link
View abstract ⏷
Highly functionalized quinazolin-4(3H)-ones were synthesized from reactions of N-aryl-2-aminobenzamides with trialkylamines under photocatalytic conditions by using eosin Y (EY) as a catalyst. The reaction proceeds under mild conditions in aqueous acetonitrile and has a broad substrate scope. Mechanistic studies disclosed the electron-donor nature of the intermediate 2,3-dihydroquinazolin-4(1H)-one (3’) in the photocatalytic cycle to afford the 2,3-disubstituted-quinazolin-4(3H)-ones (3). This methodology has been extended to synthesize benzo [4,5] imidazole[1,2-c] quinazolines and 3 aa on a large scale. Furthermore, the synthesis of potent central nervous system depressant (CNS) drug molecules such as methaqualone (3 la) and mecloqualone (3 pa) was also achieved successfully.
Influence of Au0 particles on luminescence efficiency of Ho3+ ions in PbO-B2O3-SeO2 glass ceramics: The role of free volume defects – exploration using PALS studies
Reddy A.S.S., Kostrzewa M., Purnachand N., Baskaran G.S., Venkatramaiah N., Kumar V.R., Veeraiah N.
Book chapter, Luminescent Materials: Fundamentals and Applications, 2023, DOI Link
The influence of Au2O3 on insulating character of ZnO–P2O5–SeO2 glass system: investigation by means of dielectric studies
Reddy G.N.K., Sekhar A.V., Pavic L., Bafti A., Pisk J., Reddy A.S.S., Venkatramaiah N., Raju G.N., Kumar V.R., Veeraiah N.
Article, Applied Physics A: Materials Science and Processing, 2023, DOI Link
View abstract ⏷
Zinc selenium phosphate glasses added with the traces of Au2O3 were prepared and heat-treated. XRD, TEM, DSC, FT-IR and optical absorption (OA) spectroscopy methods were used for the structural assessment of these samples. Later, different dielectric parameters viz., dielectric constant (ε′), electric moduli (M), impedance (Z) and a.c. conductivity (σac) were measured over wide regions of frequency (ω) and temperature (T) as functions of Au2O3 concentration. Dielectric breakdown strength (DBS) of these samples was also measured at ambient conditions. The characterization studies indicated that multiple crystal grains were entrenched in the residual amorphous phase of the samples. The X-ray diffraction studies revealed that the bulk glasses consisted of Au2(SeO3)3 crystal phase and Au0 metallic particles (MPs). As Au2O3 content was raised, the intensity of the XRD peak related to Au3+ crystal phase indicated a growing trend, whereas that of Au0 MPs showed a decreasing trend. The results of XPS studies revealed similar inferences. The FT-IR results pointed out an improved degree of augmentation of the glass network as the content of Au2O3 was increased. Optical absorption (OA) - spectra of the glasses indicated a broad absorption band in the spectral range of 500–600 nm due to the surface plasmon resonance (SPR) of Au0 MPs. The intensity of the band was observed to decrease as Au2O3 content was increased and indicated decreasing proportion of Au0 metallic particles in the samples. The dielectric parameters exhibited a decreasing trend, whereas the dielectric breakdown strength (DBS) and electrical impedance indicated a substantial hike due to the increasing concentration of Au2O3. Overall, the presence of Au2O3 caused a significant improvement in the insulating strength of the ZnO added SeO2-P2O5 glasses and hence such glasses may be considered as insulating layers in the display panel devices.
Design of fluorescent polymeric thermometers based on anthrapyrazolone functionalized oligo(ethylene glycol) methacrylates
Saravanan S., Babu A., Merckx R., Zhong Z., Anandan M., Nutalapati V., De Geest B.G., Hoogenboom R., Jerca V.V., Maji S.
Article, Materials Chemistry Frontiers, 2023, DOI Link
View abstract ⏷
Temperature is one of the most important parameters for a wide range of applications, including biological and chemical systems, because it affects cellular activity by controlling metabolic processes within the cells as well as molecular diffusion and reaction kinetics. The anthrapyrazolone moiety has been used in a variety of applications due to its attractive photophysical characteristics. Nevertheless, its employment as a fluorescent probe for temperature sensing has been barely reported. In this contribution, we investigated the phase transition of poly(2-(2-methoxyethoxy)ethyl methacrylate) [P(MEO2MA)] and poly[oligo(ethylene glycol) methyl ether methacrylates] [P(OEGMA300 and OEGMA500)], end-functionalized with a fluorescent anthrapyrazolone moiety [7-chloro-2-(2-hydroxyethyl) dibenzo[cd,g]indazol-6(2H)-one] (Cl-dye-OH) in aqueous solutions for the development of fluorescent polymeric thermometers. A fluorescence investigation revealed that P(MEO2MA) displays nearly 100% fluorescence quenching above its TCP, making it suitable as a sensor for a critical temperature, while the fluorescence intensity of the P(OEGMA) copolymers decreases gradually with increasing temperature, showing their promising potential for application as fluorescent thermometers. In vitro cytotoxicity tests on DC2.4 cells showed that none of the polymers were cytotoxic at the low concentrations that are used for sensing applications (i.e., 10 and 100 ng mL−1). Unexpectedly, the P(OEGMA)-based fluorescence thermometers have a very broad sensing regime that spans the whole liquid water temperature range, which is significantly broader than the sharp LCST phase transition that usually spans only 10 °C. These polymers may be used to assess intracellular temperature since their fluorescence intensity decreases linearly with temperature. In contrast, P(MEO2MA) can be used as a fluorescent probe to sense whether the temperature is below or above 25 °C. These polymeric temperature sensors are promising for future development of probes for intracellular temperature measurements.
CO2 uptake and storage by small organic functional phenothiazine molecule – An experimental study
Gawas P., Joshi N., Sivachandiran L., Nutalapati V.
Article, Materials Science and Engineering: B, 2022, DOI Link
View abstract ⏷
Globally, CO2 levels are rising and thus, dedicated efforts are driven towards CO2 capture and storage. In this work, we have demonstrated for the first time CO2 adsorption and storage by phenothiazine (Pheno) molecule. The amine functionalities of Pheno are exploited for the chemisorption of CO2. A maximum of 0.4 mmol/g of CO2 is adsorbed which equates to 17.6 mg CO2 captured/g of Pheno molecule. This value may seem less but the small size, simplistic functionalities, and cheap cost make this study relevant for CO2 mitigation. The CO2 stored on the Pheno molecule is chemisorbed to form strong carbamide (amide linkage) and thus, difficult to desorb even at a temperature of 150 °C. This shows that CO2 is stored strongly (via chemical bond formation) and safely thus, could reduce the accidents resulting from accidental leakage/desorption of CO2 which could be fatal. Pheno based sorbent shows linear response over various concentrations ranging from atmospheric concentration of CO2, 400 ppm to 15% concentrations of CO2 at ambient conditions. The adsorption efficacy of Pheno exponentially decreases with an increase in temperature above room temperature. However, the adsorption efficiency increases with an increase in relative humidity as non-condensable water molecules further provide an additional site for CO2 dissolution and bicarbonate formation which increases CO2 uptake.
Importance of the donor unit on fluoranthene for selective detection of nitro aromatic explosives
Selvaraj K., Managutti P.B., Mohamed S., Talam S., Nutalapati V.
Article, Journal of Photochemistry and Photobiology A: Chemistry, 2022, DOI Link
View abstract ⏷
In this work, two aggregation-induced emission enhancement (AIEE) materials encompassing phenyl (M1) and thiophene (T1) units flanked to fluoranthene were synthesized. We report a new packing polymorphic phase of M1 and the molecular interactions in the crystal lattice were stabilized by C[sbnd]H···π (2.882 Å) interactions. Single crystal X-ray diffraction (SXRD) studies revealed that high torsional angles of phenyl/thiophene unit on the fluoranthene endow weak π-π intermolecular interactions in the crystal lattice. The photophysical properties of M1 and T1 were explored in solution, solid-state and their AIEE phenomenon was studied in THF/water systems. Both the compounds show strong sky-blue emission at 453 nm (M1) and 460 nm (T1). The fluorescence lifetime and quantum yields are varied significantly in the aggregated form. The emission enhancement ascribed due to restricted intramolecular rotation (RIR) of thiophene/phenyl with central π-conjugated fluoranthene in the aggregation state. Distinct changes in the surface morphology, variation in the photophysical properties and energy levels by varying the THF/water ratios furnish its potential towards trace detection of different nitroaromatics. Both materials show high sensitivity and selectivity towards detection of Trinitrophenol (TNP), however, T1 showed a high quenching rate constant at fw = 90 % (KSV = 5.81 × 104 M−1) with LOD of 0.6 ppm at fw = 70 %. The observed fluorescence quenching is attributed due to photoinduced electron transfer from fluoranthene to nitroaromatics through static quenching process. The remarkable efficiency of these fluorescent probes were further explored towards the analysis of river/tap water samples, suggesting their high potential for use in field analysis.
Curcumin conjugated dextran coated Fe3O4 Nanoparticles: Cytotoxic effect on lung cancer cell line A549
Sugumaran A., Sadhasivam J., Gawas P., Nutalapati V., Pandian R., Kumar Perumal S.
Article, Materials Science and Engineering: B, 2022, DOI Link
View abstract ⏷
Surface coating of Magnetic Nanoparticles (MNPs) plays a key role in the prohibition of agglomeration, improved colloidal stability, and biocompatibility. This research aims to develop and evaluate curcumin-conjugated dextran-coated MNPs for the cytotoxic potential of lung cancer cell A549. Fe3O4 NPs were prepared by a simple co-precipitation method followed by surface coating with dextran. FT-IR, micro Raman, and powder XRD results confirm that functionalization does not alter the crystallinity of Fe3O4 and the particle size varied from ∼ 147–216 nm. The surface morphology of the conjugate shows that the drug-polymer embedded homogeneously over the surface. The in vitro release of the drug shows ∼ 77.80 ± 5.4 % and ∼ 5.15 ± 3.3 % from Cur-Dex-Fe3O4 NPs and curcumin suspension over 24 h. The IC50 value of 22.5 μg/mL with significant changes in the chromatin of cells was observed in the MTT assay and Hoechst 33,528 staining. The developed Cur-Dex-Fe3O4 NPs can effective against the A549 lung cancer cell line.
Visible Light Driven Metal-Free Photoredox Catalyzed α-benzylation and α-oxygenation of N-substituted Tetrahydroisoquinolines: Applications to Synthesis of Natural Products
Elavarasan S., Preety J., Abinaya R., Saravanan T., Balasubramanian K.K., Venkatramaiah N., Baskar B.
Article, Chemistry - An Asian Journal, 2022, DOI Link
View abstract ⏷
Herein, visible light mediated organophoto redox catalysed simple and convenient method for the α-benzylation and α-oxygenation of tertiary amines is demonstrated. Synthesis of novel thiophenol based donor acceptor organophotoredox catalysts 4 a–4 d were investigated along with commercial catalyst 4-CzIPN (4 e). A diverse biologically active α-benzylated tetrahydroisoquinolines and natural products such as (±)-Norlaudanosine, (±)-laudanosine and (±)-xylopinine have been synthesized under the optimized conditions in yields ranging from from 62–91%. Exploitation of synthesized α-benzylated compound using present phtoredox catalyzed conditions gave rise to dehydyrogenative benzylic oxidation product under oxygen atmosphere which is known to display biologically and structurally important properties. Also, various N-protected tertiary amines were found to be suitable for the α-oxygenation reactions using catalyst 4 e and resulted in good yields (61–85%).
Luminescence efficiency of Sm3+ ions in hafnia added lithium silicate glass system-the impact of Au0 particles
Devi P.P.K., Kumar V.R., Sekhar A.V., Reddy A.S.S., Venkatramaiah N., Kumar V.R., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2022, DOI Link
View abstract ⏷
In this study, Li2O-HfO2-SiO2-Sm2O3-Au2O3 glasses (doped with fixed concentration of Sm2O3 and varied contents of Au2O3) were synthesized and characterized. The role of Au0 particles on improvisation of red emission of Sm3+ ions was investigated. Optical absorption (OA) spectra of these glasses indicated a number of bands excited from 6H5/2 of Sm3+ ions. A broad band in the greenish-yellow spectral region due to surface plasmon resonance (SPR) of Au0 nanoparticles was also detected in these spectra. Photoluminescence (PL) spectra of (Sm free glasses) embedded with Au0 metallic particles (MPs) showed a wide band in the visible region ascribed to the transition of electrons from sp → d energy bands. Luminescence spectra of Sm3+ doped glasses revealed bright orange and red emission bands with substantial increased intensities with increased concentration of Au2O3. Effect of Au0 MPs on the red emission efficiency of Sm3+ ions was emphasized with kinetic rate equations.
Spectroscopic and luminescent properties of Ce3+ -doped TeO2-WO3-GeO2 glasses
Pullaiah G., Venkata Rao K., Jamalaiah B.C., Madhu N., Nutalapati V.
Article, Materials Science and Engineering: B, 2022, DOI Link
View abstract ⏷
Different concentrations of Ce3+-doped TeO2-WO3-GeO2-Ce2O3 (TWGCe) glasses were prepared by melt-quenching method and characterized. Different spectroscopic and luminescence properties were evaluated using room temperature absorption and emission spectra. The absence of sharp X-ray diffraction peaks and the presence of broad band from 18° to 35° shows the amorphous phase of studied glasses. The Fourier transform infrared absorption spectra show the presence of various vibrational bonds. The optical properties of TWGCe glasses were studied by exciting the glass samples at 323 nm ultraviolet wavelength. The quenching in luminescence is noticed at × = 0.5 mol% along with a red-shift at higher Ce3+ concentrations. The decay time was found decrease with increase of concentration of Ce3+ ions. These glasses emit intense blue luminescence with CIE coordinates (0.161, 0.018) when excited at 323 nm radiation. These glasses are favourable as blue light sources in the design of phosphor-based white LEDs.
Structural and optical analysis of YAl3(BO3)4: Pr3+ phosphors for lighting applications
Jamalaiah B.C., Madhu N., Surya Narayana Reddy A., Gawas P., Nutalapati V.
Article, Optik, 2022, DOI Link
View abstract ⏷
A series of Pr3+ activated YAl3(BO3)4 phosphors were fabricated by solid-state reaction technique and they were characterized via phase, morphology and photoluminescence studies. Powder X-ray diffraction peaks were suitably matched to JCPDS No. 72–1978. The presence of various vibrational bonds was identified using Fourier transform infrared spectroscopy. High resolution scanning electron microscopic investigations show that the phosphor particles were distributed uniformly and presented a rod-like shape. The photoluminescence results show that the studied phosphors were easily excited by visible wavelength to produce intense-yellow to pale-yellow tunable emission. The decrease in luminescence intensity and lifetime was assigned to dipole-dipole interaction energy-transfer among excited Pr3+ ions. Observed results show that the 0.05 mol% of Pr3+ activated phosphor produce intense-yellow luminescence at 480 nm excitation.
Effect of hydroxy groups on nonlinear optical behaviour of encapsulated freebase porphyrin thin films in a borate glass matrix
Beniwal R., Gawas P., Prabha Charan C., Nutalapati V., Murali Krishna Mariserla B.
Article, Materials Science and Engineering: B, 2022, DOI Link
View abstract ⏷
The development of nonlinear optical (NLO) materials are crucial for technological advancement in the field of optoelectronics and photonics. In this direction, porphyrin molecules are appeared to be a possible building material to play a key role in the light-matter interactions owing to their high degree of delocalized π-electrons. In this report, our primary focus is to understand the effect of hydroxy phenyl derivatives of meso-substituted porphyrins in an encapsulated borate glass matrix through linear and nonlinear optical measurements. The encapsulated porphyrin molecules show strong red shifted Soret (B) and Q-band absorption pattern in the range 455–460 nm and 680–700 nm, respectively, and structure is modified. The Q-band is able to tune by varying the number of hydroxy groups on the phenyl ring of the porphyrin molecule. A similar red shift is observed in the emission spectra of the encapsulated porphyrin along with the appearance of a new emission peak due to impede N-B vibrations in the glass matrix. The NLO behaviour of the encapsulated porphyrin thin films in borate glass matrix show reverse saturable absorption (RSA) at lower intensity region and crossover to saturable absorption (SA) at higher intensity. With the tunable intensity variations across the focal region, these porphyrin thin films exhibit switching behaviour from RSA to SA unclog its potential to act as an optical limiter (in the intensity range less than 10 GW/cm2) and an optical switch (in the high intensity range above ∼ 10 GW/cm2).
Visible Light-Promoted Fluorescein/Ni-Catalyzed Synthesis of Bis-(β-Dicarbonyls) using Olefins as a Methylene Bridge Synthon
Palani P., Arumugam A., Anandan M., Nutalapati V., Govindan K., Lin W.-Y., Senadi G.C.
Article, Asian Journal of Organic Chemistry, 2022, DOI Link
View abstract ⏷
Herein, we report the synthesis of methylene-bridged bis-1,3-dicarbonyls from olefins and 1,3-dicarbonyls using a photoredox/nickel-catalyzed synergistic approach. Styrene is reported as methylene one-carbon (C1) synthons in the synthesis of bis-(β-dicarbonyls) for the first time. The deuterated study showed the incorporation of styrene-d3 in the product by NMR and Mass analysis. Fluorescence quenching and cyclic voltammetry (CV) suggest that the reaction proceeds via an energy transfer process (EnT). The key aspects of the protocol are the use of benign photocatalyst fluorescein, peroxide-free, air as oxidant, broader substrate scope, and 56% to 99% product yields. The synthetic application of the product has been extended to construct tetrasubstituted pyridines in a sequential one-pot manner, bis-isoxazole, and bis-pyrazole.
Green luminescent Sr3Gd(PO4)3: Tb3+ phosphors for lighting applications
Jamalaiah B.C., Khan P.S., Madhu N., Gawas P., Nutalapati V., Narayana Reddy A.S., Reddy G.V.L.
Article, Ceramics International, 2022, DOI Link
View abstract ⏷
The inorganic phosphors doped with different rare earth ions are of more significant to develop new class of lighting devices to fulfill the present technological desires owing to their compact size, high colour rendering index with high luminescence efficiency, eco-friendly behaviour. The present research work reports the synthesis, structural, morphological and optical analysis of Sr3Gd(PO4)3: Tb3+ phosphors for lighting applications. These phosphors were synthesized via modified citrate gel-combustion technique with varied concentrations of Tb3+ and they were crystallized into BCC phase. The morphological investigations reveal an agglomeration of particles distributed non-uniformly in the crystal lattice. Upon excited at near UV radiation, the phosphors emit intense green luminescence through 5D4 → 7FJ transitions. The colour perception studies were carried out by evaluating the chromaticity coordinates (x, y). The experimental investigations explore that the studied phosphors are more suitable for lighting applications.
Influence of nanosized defects on photoluminescence efficiency of Er3+ ions co-doped with Au2O3 in a lead boroselenate glass ceramic system: a novel approach using positron annihilation lifetime spectroscopy
Siva Sesha Reddy A., Kostrzewa M., Ravi Kumar V., Ingram A., Venkatramaiah N., Sahaya Baskaran G., Ravi Kumar V., Veeraiah N.
Article, Luminescence, 2022, DOI Link
View abstract ⏷
This study consists of the results of an investigation into the influence of the free-volume space (fv) defects on luminescence efficiency (LE) of erbium ions in Au2O3-doped PbO–B2O3–SeO2 (PBS) glass ceramics. Glass ceramics containing fixed concentrations of Er3+ ions and varied concentrations of Au2O3 were synthesized. X-ray diffraction studies indicated that the samples contained Au2(SeO3)3 crystalline phase and nano gold metallic particles. The concentration of defects entrenched in the glass ceramics estimated in terms of Au2O3 content using positron annihilation lifetime spectroscopy measurement indicated the highest content in the glass ceramic containing 0.075 mol% of Au2O3. Optical absorption and the photoluminescence (PL) spectra of the glass ceramics were studied in the visible region. The observed increase of PL efficiency was attributed to the enhanced concentration of free-volume imperfections in the samples. A perfect correlation could be achieved between the free-volume fraction and the PL efficiency of erbium ions in these glass ceramics.
Sublethal effects of zinc oxide nanoparticles induced toxicity and oxidative stress in Pila virens: A validation of homology modelling and docking
Thummala H., Venkata Raju N., Manasa B., Paritala V., Srikanth K., Nutalapati V.
Article, Materials Science and Engineering: B, 2022, DOI Link
View abstract ⏷
Materials of nano-range are ranked as the sixth most emerging pollutant which are reaching the aqueous ecosystem and causing harm to the inhabiting organisms. Nanomaterials of zinc oxide are applied in wide range of applications. However, the toxicity of zinc oxide nanoparticles (ZnONPs) on fresh water mollusc Pila virens is scarce. The median lethal concentration of ZnONPs on P. virens for 96 h was found to be 180.49 µg/L. In the present study P. virens were treated with sublethal concentration of 135 μg/L of ZnONPs for 24 and 96 h respectively. The reactive oxygen species, protein carbonyl and lipid peroxidation levels were increased in P. virens treated with 135 μg/L of ZnONPs in comparision to their control values at two different time intervals (24 and 96 h). Moreover, the glutathione sulfotransferase and glutathione peroxidase activity in P.virens exposed to 135 μg/L of ZnO NPs for 24 and 96 h were found to decrease when compared to their control values. An in silico approach was also taken to understand the loss of GST activity wherein the target protein was modelled and found to strongly bind with ZnONPs at its active site when subject to molecular docking. The current study affirms that P. virens are relevant invertebrate biomonitor to evaluate the nanoparticles toxicity.
Evaluation of oxidative stress biomarkers in Pila virens exposed to spinel Co3O4 nanoparticles
Raju N.V., Prasanth P., Harsha T., Naravula J., Srikanth K., Nutalapati V.
Article, Materials Science and Engineering: B, 2022, DOI Link
View abstract ⏷
Cobalt oxide nanoparticles (Co3O4NPs) are used in various devices including magnetic and energy storage, sensors, pigments, and catalysts, thereby imparting enhanced production and use. The current work aims to investigate on the toxicity of Co3O4NPs on fresh water edible snail Pila virens (P. virens). A total of ten P. virens were chosen for acute toxicity studies (96 h) and the lethal concentration (LC50) for Co3O4NPs was found to be 509.45 µg/L. Based on the LC50 value P. virens was exposed to ½ (254 µg/L) and ¼ (127 µg/L) of LC50 concentration for 24 h. The current findings revealed that an increase in lipid peroxidation, catalase, glutathione sulfotransferase, and reduction in reduced glutathione and glutathione peroxidase activity in P. virens upon exposure to 127 and 254 µg/L concentration of Co3O4NPs for 24 h. The Co3O4NPs induced toxicity in fresh water snail P. virens via oxidative stress. P. virens fits as the best organism for the toxicological assessment of Co3O4NPs contaminating the environment.
Influence of Gold Nano Particles on Dielectric Features A.C. Conductivity and Dielectric Breakdown Strength of PbO-B2O3-SeO2:Ho2O3 Glass Ceramics
Siva Sesha Reddy A., Kostrzewa M., Purnachand N., Ingram A., Sahaya Baskaran G., Venkatramaiah N., Ravi Kumar V., Veeraiah N.
Article, ECS Journal of Solid State Science and Technology, 2022, DOI Link
View abstract ⏷
The objective of this study is to report the results of dielectric properties and dielectric breakdown strength (DBS) of PbO-B2O3-SeO2:Ho2O3 (PBSH) glass ceramics as functions of Au2O3 content and to correlate the results with spectroscopic properties. PBSH glass ceramics with traces of Au2O3 were fabricated and characterized with different techniques that include positron annihilation spectroscopy (PAS). Several dielectric parameters and DBS were studied as functions of Au2O3 concentration. Observed increase of ϵ′ with Au2O3 content was attributed to a hike in the space charge polarization (scp) due to the increased concentration of structural imperfections. Dipolar relaxation phenomenon exhibited by electric moduli was analyzed using Cole-Cole plots. σ ac (a c, conductivity) showed an increasing tendency with Au2O3 content. Such increase was attributed to the polaronic exchange between two structural groups of SeO2. Inferences drawn from dielectric and DBS studies were found to be in agreement with different spectroscopic properties of these glass ceramics.
Impact of silver ions on dielectric properties and conductivity of lithium silicate glass system mixed with red lead
Keerti Kut T.V.N., Marijan S., Pisk J., Sekhar A.V., Reddy A.S.S., Venkatramaiah N., Raju G.N., Pavic L., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2022, DOI Link
View abstract ⏷
Glasses of the composition (40-x)Li2O-10Pb3O4-50SiO2 doped with different contents of Ag2O were fabricated and were subsequently subjected to heat-treatment. The quantitative analysis of the results of different characterization techniques indicated increasing magnitude of internal connectivity of the glass network with increasing Ag2O content. Several dielectric parameters viz., ε′, M, Z and σacin the frequency (ω) region 0.01 Hz – 1 MHz and in the region of temperature (T) 30 –250 °C of these glasses were measured as functions of Ag2O content. ε′ showed a decreasing tendency with Ag2O content which may be attributed to the decrease in the space charge polarization (scp) due to the increasing order of augmentation of glass network. Such a decrease of scp was attributed to the growing presence of PbO4 units and also Ag0 particles in these samples. The plots of electric modulus vs ω and T indicated relaxation character. Such relaxation phenomena were discussed in detail with the help of Cole-Cole diagrams. Probable dipoles responsible for such effects were recognized and analyzed. σac (conductivity) exhibited a decreasing trend with Ag2O content. The mechanism of conduction was analyzed using polaronic tunneling effect in the intermediate ω and high T ranges, whereas in the low T range it is predicted to follow QMT model. These conclusions were observed to follow the results of various spectroscopic studies. In conclusion, presence of red lead seemed to be an obstruction for the conductivity in the fast ion conducting glasses.
Optical analysis of Pr3+-doped Li6AlGd(BO3)4 phosphors for white LEDs
Raghupathi P., Jamalaiah B.C., Nutalapati V., Jayasimhadri M., Kaur H., Pavani K., Madhu N., Khan P.S.
Article, Journal of Materials Science: Materials in Electronics, 2022, DOI Link
View abstract ⏷
A series of LAGBPr phosphors of composition Li6AlGd(1–x)(BO3)4: x Pr3+ (0 ≤ x ≤ 2.0 mol%) were prepared by solid-state reaction method and characterized through thermal, structural, morphological and photoluminescence studies. Thermal investigation shows that the LAGBPr phosphors crystallize at 640 °C. The powder X-ray diffraction studies show that the size of crystallites is of the order of 77 nm. The excitation spectra reveal a charge transfer band due to O2– → Pr3+ (230–250 nm), host-related (Gd3+) bands from 205 to 315 nm and some f-f transitions of Pr3+ ions from 420 to 500 nm. The fluorescence properties were investigated by exciting within the host and within dopant (Pr3+) ions. A tunable fluorescence from orange-red to white to bluish-white was observed when excited at 274 nm and a bluish-white fluorescence at 449 nm excitation. Upon 449 nm excitation, a blue-shift is observed with increase of concentration of Pr3+ ions. The optimal concentration of Pr3+ ions for efficient fluorescence is confirmed to be 1.0 mol%, and a quenching in fluorescence was noticed and it was ascribed to the non-radiative transfer of energy through [3P0, 3H4] → [1D2, 3H6], [3P0, 3H4] → [3H6, 1D2] and [1D2, 3H4] → [3H4, 1D2] channels. The LAGBPr1.0 phosphor has more proficiency to be used in LED applications.
Dielectric dispersion impedance spectroscopy and polaron tunneling phenomenon in Au2O3 mixed PbO-B2O3-SeO2:Er2O3 glass ceramics
Reddy A.S.S., Kostrzewa M., Devi P.P.K., Purnachand N., Ingram A., Venkatramaiah N., Kumar V.R., Veeraiah N.
Article, Journal of Alloys and Compounds, 2022, DOI Link
View abstract ⏷
The glass ceramics of the composition PbO-B2O3-SeO2:Er2O3 (PBSE) doped with small concentrations of Au2O3 were synthesized. The results of detailed studies on various characterization techniques and also different spectroscopic investigations suggested that these glass ceramics are entrenched with Au2(SeO3)3 crystal phases and Au0 metallic particles (MPs). These studies further revealed increasing concentration of [SeO3]2- groups and Au0 metallic particles with the increase of Au2O3 content upto 0.075 mol%. Such [SeO3]2- groups are predicted to induce structural imperfections in the glass ceramic. Optical absorption (OA) and photoluminescence (PL) spectral studies also indicated increasing concentration of imperfections with increase of Au2O3 content. The dielectric viz, dielectric permittivity (ε′), electrical modulus (M), electrical impedance (Z) and a.c. conductivity (σac) spectra in the frequency (ω) region 4 Hz to 8 MHz and in the temperature (T) region 303–633 K of these glass ceramic samples were measured as functions of Au2O3 concentration. The dielectric permittivity (ε′) exhibited an increasing trend with Au2O3 concentration and it is ascribed to the increase in the magnitude of the space charge polarization (scp) due to the increase in the concentration of structural defects induced by [SeO3]2- units and Au0 metallic particles. The plots of electric modulus (M) with frequency and temperature exhibited dipolar relaxation phenomena. Such effects were analyzed further using Cole-Cole diagrams and the possible dipoles responsible for these effects were identified. A.C. conductivity (σac) exhibited increasing trend with the concentration of Au2O3 (up to 0.075 mol%) and such increase is attributed to the polaronic exchange between different structural groups of selenium oxide. The conduction mechanism is analyzed using polaronic tunneling effect in the middle frequency and high temperature regions, whereas in the lower temperature region QMT model seems to be applicable. Conclusions drawn from dielectric properties were found to be well in accordance with the results of spectroscopic properties.
Tuning the π-Conjugation of 2-Thiohydantoins toward a Rigorously Defined Detection of Volatile Organic Compounds by Surface Photovoltage
Gawas P.P., Bora A., Reji R.P., Sarath Kumar C.B., Ramakrishna B., Nalluri V., Jayaraman S.V., Sivalingam Y., Nutalapati V.
Article, ACS Applied Electronic Materials, 2022, DOI Link
View abstract ⏷
The design of portable devices by immobilization of sensory probes using donor-acceptor (D-A) architectures enables the visual detection and onsite analysis of volatile organic compounds (VOCs). In this work, we have reported on the synthesis of different D-A architectures of 2-thiohydantoin (2TH) derivatives by extending the conjugation with phenyl (Ph-2TH), naphthalene (Naptha-2TH), and anthracene (Anthra-2TH) moieties at the C5 position. Single-crystal X-ray analysis reveals that extending the conjugation leads to variation in the molecular arrangement in the crystal lattice. Ph-2TH and Naptha-2TH show ribbon-like self-assembled layered arrangements, whereas Anthra-2TH crystallized in herringbone packing in the crystal lattice. The C-S···H interactions were varied with interatomic distances of 2.67, 2.63, and 2.27 Å, respectively, for phenyl, naphthalene, and anthracene. The photophysical and excited-state gas-phase interactions using scanning kelvin probe studies reveal that 2TH ensembles alter their surface photovoltages toward recognition of different VOCs (like ethanol, acetone, toluene, triethylamine, nonanal, and chloroform) depending on their donor and acceptor nature. All three 2TH derivatives showed n-type behavior with high selectivity toward nonanal, and Anthra-2TH exhibited high response (91.02%) within 278 s as well as recovery (92.83%) in surface photovoltages in 647 s. Combined experimental and computational studies demonstrate that the aromatic moieties appended 2TH ensembles would be an efficient D-A ensemble for the detection of VOCs containing carbonyl and alcohol functionalities aiding strong intermolecular interactions.
Investigation of the effect of Au2O3 dopant on elastic properties of PbO-B2O3-SeO2: Er2O3 glass ceramics by ultrasonic techniques
Siva Sesha Reddy A., Kityk A.V., Jedryka J., Rakus P., Wojciechowski A., Venkatramaiah N., Ravi Kumar V., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2022, DOI Link
View abstract ⏷
Various elastic coefficients of Au2O3 doped PbO-B2O3-SeO2:Er2O3 (PBSE) glass ceramics were evaluated as functions of Au2O3 content using ultrasonic velocity measurements. The elastic coefficients and micro-hardness showed a decreasing tendency with the concentration of Au2O3. Such decrease is attributed to the increasing concentration of gold metallic particles and [SeO3]2− groups that acted as modifiers and induced imperfections in these samples. Obtained results were observed to be consistent with the conclusions drawn from spectroscopic studies that include X-ray photoelectron spectroscopy (XPS), infrared (IR), photoluminescence (PL) and positron annihilation (PAL) spectroscopy studies. Overall, these studies have revealed that even though, the presence of gold metallic particles is preferable for achieving superior luminescence and electrical properties, presence of such particles caused to decrease the elastic coefficients and micro-hardness of these glass ceramics. However, when the concentration of Au2O3 is increased beyond 0.075 mol%, we have observed a slight increase of elastic coefficients and micro-hardness.
Combinatorial selectivity with an array of phthalocyanines functionalized TiO2/ZnO heterojunction thin film sensors
Sivalingam Y., Magna G., Kalidoss R., Murugan S., Chidambaram D., Nutalapati V., Jayaraman S.V., Paolesse R., Di Natale C.
Article, Nanotechnology, 2022, DOI Link
View abstract ⏷
The development of electronic noses requires the control of the selectivity pattern of each sensor of the array. Organic chemistry offers a manifold of possibilities to this regard but in many cases the chemical sensitivity is not matched with the response of electronic sensor. The combination of organic and inorganic materials is an approach to transfer the chemical sensitivities of the sensor to the measurable electronic signals. In this paper, this approach is demonstrated with a hybrid material made of phthalocyanines and a bilayer structure of ZnO and TiO2. Results show that the whole spectrum of sensitivity of phthalocyanines results in changes of the resistance of the sensor, and even the adsorption of compounds, such as hexane, which cannot change the resistance of pure phthalocyanine layers, elicits changes of the sensor resistance. Furthermore, since phthalocyanines are optically active, the sensitivity in dark and visible light are different. Thus, operating the sensor in dark and light two different signals per sensors can be extracted. As a consequence, an array of 3 sensors made of different phthalocyanines results in a virtual array of six sensors. The sensor array shows a remarkable selectivity respect to a set of test compounds. Principal component analysis scores plot illustrates that hydrogen bond basicity and dispersion interaction are the dominant mechanisms of interaction.
The role of gold metallic particles on improving green and NIR emissions of Ho3+ ions in non-conventional SeO2 based glass ceramics
Reddy A.S.S., Purnachand N., Kostrzewa M., Brik M.G., Venkatramaiah N., Kumar V.R., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2022, DOI Link
View abstract ⏷
This study is devoted to investigate the role of Au0 particles on the improvement of luminescence efficiency of Ho3+ ions in a non-conventional lead boroselenate glass ceramic. Characterization by different spectroscopic techniques indicated that the samples consist of [SeO3]2− and [SeO4]2− structural groups. Among them, the fraction of [SeO3]2− groups exhibited an increasing trend with increase of Au2O3 content. These studies have further revealed that a part of Au3+ ions reduced in to gold nano particles during ceramicization process. Optical absorption (OA) spectra of these samples exhibited a wide absorption band with gradual growth with the Au2O3 concentration. This band is attributed to the surface plasmon resonance (SPR) of gold nanoparticles. Additionally, the OA spectra exhibited several characteristic bands of Ho3+ ions in the spectral region of 450–2000 nm. Photoluminescence (PL) spectra of (Ho free samples) containing gold particles exhibited a broad band in the green to red spectral region, identified due to the transition of electrons from sp → d energy bands of gold nanoparticles. PL spectra of co-doped samples exhibited the emission bands in the green, orange and red regions with enhanced intensities as Au2O3 content is increased. OA and PL spectra were characterized using Judd-Ofelt theory and various radiative parameters were estimated. The impact of Au0 particles on the PL efficiency of holmium ions is comprehensively discussed using kinetic rate equations. The crucial role of gold particles as sensitizers in enhancing the luminescence efficiency especially the green emission is quantitatively explained.
Copper ferrite nanoparticles induced cytotoxicity and oxidative stress in Channel catfish ovary cells
Article, Chemosphere, 2022, DOI Link
View abstract ⏷
Nanomaterials are the sixth most emerging contaminants that are entering into aquatic habitat posing a risk to the inhabiting organisms. Nanoparticles of copper ferrite have been extensively used in biomedical applications. However, very limited studies are available on the cytotoxicity evaluation of copper ferrite nanoparticles (CuFe2O4NPs) on different cell lines. The current work investigates on the cytotoxicity, oxidative stress and morphological variations triggered by CuFe2O4NPs in Channel catfish ovary (CCO) cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT), neutral red uptake (NRU), lipid peroxidation (LPO), catalase (CAT), reduced glutathione (GSH), glutathione sulfotransferase (GST) and glutathione peroxidase (GPX) assays after 24 h of treatment. Dose dependent decline in cell survival was noticed in MTT and NRU assays. A significant increase in LPO, GST and GPX was observed in CCO cells exposed to CuFe2O4NPs after 24 h of treatment. However, the CAT and GSH levels in CCO cells exposed to CuFe2O4NPs decreased significantly after 24 h. The CCO cells exposed to 10 μg/mL concentration of CuFe2O4NPs for 24 h showed remarkable changes in their morphology. Further, the study also describes the detailed mechanism of toxicity of CuFe2O4NPs in other model cell lines to probe the risk of inhabiting organisms.
Multifunctional hydantoins: Recent advances in optoelectronics and medicinal drugs from Academia to the chemical industry
Gawas P.P., Ramakrishna B., Veeraiah N., Nutalapati V.
Review, Journal of Materials Chemistry C, 2021, DOI Link
View abstract ⏷
Imidazilidine-2,4-dione, also well known as hydantoin (TH), is a prominent five-membered heterocyclic compound with four versatile points of functionalities in its framework. Since the discovery of TH, various synthetic strategies have been developed through functionalization and the corresponding derivatives have been found to have versatile applications in various fields of science. Furthermore, its sulphur analogue thiohydantoin (2TH) is a fascinating and potential compound of the hydantoin family with five possible diverse reactive points, which has been explored extensively owing to its simple synthesis, resulting in desirable reactivity patterns and attractive properties via appropriate peripheral functionalization. This review provides a detailed survey on the structural modifications at various positions of 2TH and the promising applications of the resultant derivatives reported in the literature are thoroughly discussed. Functionalization of 2TH shows high potential for biological, medical and pharmaceutical activity. The commercialization of hydantoin-based drugs, their technology in the market and the capital of income generated are explored. TH derivatives display a plethora of properties and a wide range of applications such as sensors, chemical sensory materials towards the detection of toxic anions, metal ions, and biosensing/imaging as labelling markers in living cells and tissues. Furthermore, this review assesses the basic understanding of the photophysical properties of hydantoins given that this field is ripe for new ideas, which can enable their use in optoelectronics and prototypes to translate laboratory products into commercial products.
Naphthalene appended diketopyrrolopyrrole derivatives functionalized on ZnO nanostructures: An investigation on gas adsorption induced surface potential changes at room temperature
Marappan G., Pushparaj K., Sivalingam Y., Nutalapati V., Surya V.J.
Article, Materials Letters, 2021, DOI Link
View abstract ⏷
ZnO nanostructures prepared at different pH (9 and 11) were functionalized with naphthalene appended diketopyrrolopyrrole derivatives with thiophene (TDPP) and phenyl (PDPP) functionals. The functionalization was ascertained through various characterization techniques like XRD, FESEM, UV-Visible absorption and PL studies. Gas adsorption-induced surface potential of functionalized samples were studied through scanning Kelvin probe system at room temperature in the presence of various volatile organic compounds (VOCs) like acetone, benzene, ethanol, nonanal, n-hexane, 1-hexanol and triethylamine (TEA). Interestingly, the functionalized ZnO nanostructures obtained at pH 9 showed ~1.5 times better response towards 1-hexanol when compared to the functionalized pH 11 ZnO counterparts. Density functional theory calculations revealed that the DPP derivatives showed higher binding affinity towards ethanol, 1-hexanol and nonanal. Overall, this combined experimental and computational studies suggested that the DPP derivatives functionalized ZnO nanostructures would be useful for detection of VOCs such as alcohols and aldehydes.
Core modified freebase porphyrins in glass matrix for nonlinear optical properties
Beniwal R., Gawas P., Prabha Charan C., Nutalapati V., Mariserla B.M.K.
Article, Materials Letters, 2021, DOI Link
View abstract ⏷
Two different types of freebase porphyrins with variation in the central core, namely H2TPP (meso-5,10,15,20- tetrakis phenyl porphyrin) and HSTPP (meso-tetrakis 5,10,15,20-tetra-phenyl-23-H-21-thiaporphyrin) were introduced into the borate glass matrix and developed the thin films by melt quenching technique. Due to core modification and extended non-planarity in the glass matrix, the absorption spectrum of HSTPP shows a strong redshift in the soret and Q bands. Emission spectra of HSTPP show an intense emission at 739 nm (S1 → S0) and ~ 505 nm due to coordination of boron atom at the central core and freezing of N-BO3 vibrations furnishes slow relaxation from higher energy states. Comparison studies are made by treating with BF3O(C2H5)2 to mimic structure in the borate glass matrix due to boron coordination at the central core. The excited state lifetimes are shortened due to BF3 interaction in the solution as well as in the borate glass matrix endowing its potential to develop the optical limiting devices. Nonlinear optical studies reveal reverse saturable absorption (RSA) behaviour in the picosecond (ps) region and show enhanced two photon absorption (TPA) by core modification. Optical power limiting measurements on HSTPP in glass matrix delivers a better limiting threshold value of 15.2 mJ/cm2.
Polymorphism induced gas adsorption on naphthalic imide appended phenothiazine for the detection of volatile organic compounds
Selvaraj K., Marappan G., Gawas P., Raviteja S., Dinesh Kumar G., Jayaraman Surya V., Sivalingam Y., Nutalapati V.
Article, Materials Letters, 2021, DOI Link
View abstract ⏷
In this work, we have developed a new polymorphic phase of 2-(4-(10H-phenothiazin-10-yl)phenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione(NIPTZ-DM) and compared it with the reported polymeric phase (NIPTZ-C). Single crystal XRD analysis revealed that NIPTZ-C existed in herringbone molecular arrangement and NIPTZ-DM showed a zigzag pattern. The photophysical properties of the two phases in the solid state were explored. The unique crystalline phases were investigated for photo- response behaviour with saturated vapours of volatile organic compounds (VOCs). The gas interaction study was carried with Scanning Kelvin Probe (SKP) system with different VOCs such as acetone, triethylamine (TEA), ethanol, and n-hexane. NIPTZ-DM demonstrated excellent gas response towards acetone vapours and showed a high photo response behaviour. NIPTZ-C exhibits both p-type and n-type behaviour, whereas NIPTZ-DM exhibits only n-type behaviour under UV-light illumination.
Highly fluorescent 2D-BCNO sheets based chemical sensor for selective detection of the explosive Dunnite and 4-nitrophenol in aqueous medium
Sekar S., Gawas P., Bhat S.V., Nutalapati V.
Article, Environmental Science: Nano, 2021, DOI Link
View abstract ⏷
Highly fluorescent 2D-BCNO (boron carbon oxynitride) sheets were synthesizedviaa new facile and simple approach for selective and sensitive detection of nitro-aromatic compounds, namely 4-nitrophenol and Dunnite, in aqueous medium. 2D-BCNO sheets exhibited strong blue fluorescence emission in aqueous medium. The detailed photophysical properties and pH-dependent studies were performed. 2D-BCNO sheets showed a high fluorescence quenching towards explosive nitro-analytes and showed an unprecedented selectivity for Dunnite and 4-nitrophenol with a limit of detection (LOD) of 2.1 and 0.22 ppb respectively. The remarkable sensitivity during the fluorescence quenching phenomena arose due to the unique inner filter effect (IFE) and photo-induced electron transfer process through electrostatic interactions. The promising results from real-time sample analysis of river and tap water as well as interference studies in the presence of other nitro-analytes elucidated the potential practical application of sensor technology based on the 2D-BCNO sheets. Furthermore, the rapid and visual identification of Dunnite and 4-nitrophenol at picogram levels with a contact mode approach on solid substrates demonstrated that the developed sensor technology is suitable for onsite field analysis.
Pila virens as sentinel of silica nanoparticles toxicity induced oxidative stress
Srikanth K., Venkata Raju N., Pamanji R., Nutalapati V.
Article, Materials Letters, 2021, DOI Link
View abstract ⏷
The aquatic ecosystem is under threat due to the continuous inlet of various emerging contaminants affecting the inhabiting organisms. The Silica nanoparticles (SiNPs) are among the most abundantly produced nanoparticles globally posing a threat to the aquatic organisms because of their entry into aquatic ecosystem through various point and nonpoint sources. In this work, we report the toxicological impacts of SiNPs on fresh water snail Pila virens (P.virens) as a biomonitor. The acute toxicity of SiNPs on P. virens was performed in a 96 h static renewal tests. The median lethal concentration of SiNPs for 96 h on P. virens is 366.92 µg/L. The P. virens were exposed to 165 µg/L for 24 and 48 h respectively shown a significant increase in lipid peroxidation, protein carbonyl, superoxide dismutase and reduction in total glutathione content in comparison to their controls. The fresh water edible snail P. virens serve as model organisms for other engineered nanomaterials toxicity.
Dielectric Relaxation Dynamics and Polaronic Tunneling Conduction Mechanism of Electrical Conductivity of Fe2O3-Doped PbO–ZrO2–SiO2 Glass Ceramics
Chandrakala C., Siva Sesha Reddy A., Kostrzewa M., Purnachand N., Venkatramaiah N., Naga Raju G., Ravi Kumar V., Veeraiah N.
Article, Physica Status Solidi (A) Applications and Materials Science, 2021, DOI Link
View abstract ⏷
This study consists of comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3. The observed increase in dielectric permittivity with the content of Fe2O3 is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σac) shows a rising trend with an increase in Fe2O3 beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe2+ and Fe3+ ions. The conduction mechanism is well explained using a polaron tunneling model in the middle-frequency and high-temperature regions.
Studies on near infrared emission of Yb3+ ions in a SeO2 based glass system
Naresh P., Ravi Kumar V., Sesha Reddy A.S., Kostrzewa M., Venkatramaiah N., Krishna Mohan N., Ravi Kumar V., Veeraiah N.
Article, Physica B: Condensed Matter, 2021, DOI Link
View abstract ⏷
SeO2 based glasses of the composition 39 PbO–(60-x) B2O3– xSeO2:1.0 Yb2O3 (with 10 ≤ x ≤ 50) was synthesized. Analysis of the results of structural studies of the samples revealed that the glass network consists of [SeO4]2− and [SeO3]2− units; the studies further indicated an increasing fraction of [SeO3]2− units and decreasing concentration of [SeO4]2− groups with increase of SeO2 content. Optical Absorption (OA) and photoluminescence (PL) spectra have exhibited bands due to 2F7/2 → 2F5/2 and 2F5/2 → 2F7/2 transitions, respectively. Evaluated absorption and emission cross-sections and lifetime of the excited state of Yb3+ ions exhibited an increase with increase of SeO2 content. Results of PL studies indicated nearly fourfold increase of PL output with increase of SeO2 content up to 50%. Such increase is attributed to the increased concentration of isolated [SeO3]2- pyramidal groups. Overall, the rise of SeO2 content in Yb3+ doped PbO–B2O3–SeO2 glass system facilitated the increase of PL emission of Yb3+ ions largely.
Emission features of Er3+ ions in an exotic SeO2 based glass system
Naresh P., Kostrzewa M., Brik M.G., Venkatramaiah N., Kumar V.R., Mohan N.K., Kumar V.R., Piasecki M., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2021, DOI Link
View abstract ⏷
In this work we have studied impact of SeO2 concentration on luminescence properties of 39PbO-(60-x)B2O3-xSeO2:1.0 Er2O3 ( 10 ≤ x ≤ 50) glass system. The structural analysis of the samples carried out by XRD, SEM indicated that the prepared samples are in amorphous phase. IR, Raman and XPS studies revealed increasing presence of isolated selenite [SeO3]2−groups and decreasing concentration of [SeO4]2−(selenate) groups with increasing content of SeO2 in the glass network. Optical absorption (OA) spectra revealed absorption bands due to 4I15/2 → 4F7/2, 9/2, 2H11/2, 4S3/2, 4I9/2, 11/2, 13/2 transitions of Er3+ ions. Using J-O theory, the spectra were characterized and the evaluated Ωλ parameters are found to be in the order: Ω2 > Ω4 > Ω6. The PL spectra recorded at λexc= 378 nm exhibited the emission bands due to 2H11/2→4I15/2 (B), S3/2→4I15/2(G), 4F9/2→4I15/2(O) and 4I13/2→4I15/2 (NIR) transitionsof Er3+ ions. With the gradual increase SeO2 content, the PL emission bands (especially green and NIR bands) have exhibited significant growth. The spectra were quantitatively analysed using kinetic rate equations and the causes for enhancement of PL emission were recognised and discussed. From the gain co-efficient G(λ) of the 4I13/2→4I15/2 transition, its lasing behaviour is detected for a population inversion of nearly 50%.
Nitrogen-Doped Microporous Carbons Synthesized from Indole-Based Copolymer Spheres for Supercapacitors and Metal-Free Electrocatalysis
Deka N., Barman J., Gawas P., Parse H.B., Kakade B., Nutalapati V., Dutta G.K.
Article, Energy and Fuels, 2021, DOI Link
View abstract ⏷
Indole-based copolymer spheres serve as a precursor for the facile and easily scalable synthesis of a series of nitrogen-rich microporous carbons. The influence of chemical activation and carbonization parameters on the morphology, chemical composition, and electrochemical behavior of the porous carbons has been monitored. The copolymers exhibit an inherent porous framework, which ensures abundant microporosity and BET surface area as high as 1255 m2 g-1 in the porous carbon materials. Homogeneously distributed high nitrogen doping in the copolymer was maintained up to 3.8% even at a high carbonization temperature of 900 °C. The carbon material ITS-2-700 displays high specific capacitance in aqueous acidic (420 F g-1) and alkaline (357 F g-1) electrolytes. Moreover, the complete capacitance retention in both electrolytes emphasizes its feasibility as suitable supercapacitor materials. At a higher carbonization temperature of 900 °C, the porous carbon material (ITS-2-900) shows excellent ORR catalytic activity with a 0.99 V (vs RHE) onset potential and a high limiting current density (5.1 mA cm-2). ITS-2-900 exhibits superior durability and resistance toward methanol oxidation when compared with the commercial Pt/C electrocatalyst.
Dielectric investigations on metal (Ni and Cu) tetrahydroxy phenyl porphyrins in PMMA polymer matrix
Prasanth P., Talam S., Ramakrishna B., Nagarjuna G., Busi R., Rao M.C., Nutalapati V.
Conference paper, Materials Today: Proceedings, 2021, DOI Link
View abstract ⏷
The present work reports on the dielectric behaviour of two different metallo porphyrins (NiTPPOH4 and CuTPPOH4) doped in poly (methyl methacrylate) (PMMA) polymer matrix. Different dielectric parameters such as dielectric constant, tangent loss and a.c. conductivity were measured at frequency ranges from 1-100 kHz in the temperature range 35–100 °C. The dielectric constant e' for NiTPPOH4 and CuTPPOH4 was found to be in the range of 2.42–5.45 and dielectric loss (tan d) in the range of 0.0122–0.0756. The dielectric constant and loss are found to be higher for CuTPPOH4. Variation in the dielectric loss with temperature at different frequencies show a shoulder peak indicating dipolar relaxation character. The a.c. conductivity of the materials increased with temperature and frequency. The activation energy was decreased with rise in temperature and shifting of relaxation regions towards low temperature is observed. Detailed analysis reveal that CuTPPOH4 doped polymer exhibit significant dielectric properties.
Pyrazoloanthrone-functionalized fluorescent copolymer for the detection and rapid analysis of nitroaromatics
Saravanan S., Ahmad R., Kasthuri S., Pal K., Raviteja S., Nagaraaj P., Hoogenboom R., Nutalapati V., Maji S.
Article, Materials Chemistry Frontiers, 2021, DOI Link
View abstract ⏷
The development of sensors for rapid detection of chemical explosives with high sensitivity and selectivity is the focus of many research groups. In this work, we have developed a simple and straightforward synthesis of a block (co)polymer functionalized with pyrazoloanthrone (SP). The block (co)polymer was synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization of 2-hydroxyethyl acrylate using a PEG-functionalized RAFT-agent. Subsequently, the SP was coupled to the poly(2-hydroxyethyl acrylate) block through DCC coupling. The structural and physicochemical properties of the (co)polymer were studied to explore its potential towards the detection of nitroaromatics as a model for explosives. A systematic comparison is made on the chemosensing behavior of the (co)polymer and three small molecule pyrazoloanthrone analogues with different functional groups (SP, SP-OH and SP-COOH). Fluorescence studies demonstrated a significant decrease in the fluorescence intensity of the four fluorophores in the presence of different nitroaromatics and showed unprecedented selectivity for 2,4,6 trinitrophenol (TNP). The Stern-Volmer rate constants (Ksv) of the SP-functionalized copolymer (Ksv = 9.74 × 104 M-1) showed an ∼3.7 times higher quenching rate constant than its monomer analog (SP) for TNP with a limit of detection (LOD) of 19 ppm. A static quenching mechanism with photoinduced electron transfer process, intermolecular hydrogen bonding and electrostatic interactions induce turn off fluorescence behavior. The interference studies with other nitroaromatics in an aqueous medium and real-time analysis in the solid-state methods demonstrate the potential of the block (co)polymer towards practical applications.
Broadband optical power limiting with the decoration of TiO2 nanoparticles on graphene oxide
Krishna Mariserla B.M., Alee K.S., Kasthuri S., Gawas P., Rao D.N., Nutalapati V.
Article, Optical Materials, 2020, DOI Link
View abstract ⏷
Graphene, in its pristine form and analogs, is revolutionizing the architecture and designing of materials for high-performance optoelectronic devices. The functionalization of graphene is very attractive and emerging field of interest for nonlinear optical devices. In this work, we have synthesized Graphene oxide (GO) decorated with TiO2 semiconducting nanoparticles for nonlinear photonic devices. The nonlinear optical (NLO) measurements of GO-TiO2 composite were studied with a popular Z-scan technique for optical power limiting applications. Functionalized graphene oxide with TiO2 nanoparticles exhibits a strong enhancement in optical-response with nanosecond laser pulses. The composite show fingerprints of reverse saturable absorption (RSA) dominated by two-photon absorption (TPA) along with enhanced nonlinear absorption due to transfer of electrons/energy between TiO2 nanoparticles and graphene oxide. The systematic spectroscopic studies with TEM, XRD, FT-IR, micro-Raman, steady-state and time-resolved photoluminescence reveals that successful conjugation of GO and TiO2 nanoparticles and probes the structural and optical properties. The nonlinear optical measurements demonstrate that GO-TiO2 composite exhibits promising optical power limiting features than individual counterparts implicating the potential contingent towards broadband optical limiting applications.
Influence of gold ions on visible and NIR luminescence features of Er3+ ions in lead boroselenate glass ceramics
Siva Sesha Reddy A., Lakshminarayana G., Purnachand N., Ravi Kumar V., Venkatramaiah N., Ravi Kumar V., Veeraiah N.
Article, Journal of Luminescence, 2020, DOI Link
View abstract ⏷
This work is focused on the amplification of green (G), orange (O) and NIR (1.5 μm) emissions of Er3+ ions by co-doping with varying contents (traces ≤ 0.1 mol%) of Au2O3 in an exotic PbO-B2O3-SeO2 glasses ceramic. The glasses were synthesized by conventional melt quenching method and were crystallized by heat-treating them at crystallization temperature for a period of 24 h. Initial characterization of the samples by means of SEM, XRD, XPS, IR and Raman studies suggested that the post-heated samples are entrenched with poly-crystal grains (with sizes varying from 100 to 500 nm). These studies have also revealed that the concentration of such nano-crystallites is increased with increased content of Au2O3 up to 0.075 mol%. The XRD studies, in particular, have indicated that the glass ceramics are composed of Au2(SeO3)2(SeO4) (crystal phase containing Se ions of mixed valence states) and Au0 nano particles. The XPS studies have also indicated the presence of Se and gold ions in different valence states in these samples. IR and Raman spectra have suggested increased degree of internal chaos in the glass ceramic with increasing concentration of Au2O3. Optical absorption (OA) spectra of Au2O3 doped glass ceramic samples (without Er3+ ions) exhibited a broad band in the visible region identified as surface plasmon resonance (SPR) band of gold metallic particles. The photoluminescence (PL) spectra of these samples exhibited an emission peak due to inter-band transition from sp to d energy bands of Au0 metallic particles. This emission is identified to play a crucial role in enhancing PL emission of Er3+ ions in the visible and NIR regions. Finally, we have recorded optical absorption, photoluminescence spectra and decay profiles of the Er3+ doped (with Au2O3 as co-dopant) glass ceramics. The spectra were characterized using J–O theory and different radiative parameters (viz., transition probabilities, branching ratios, radiative lifetime) of green, orange and NIR emission transitions of Er3+ ions were evaluated. The results indicated a significant reinforcement of green (4S3/2 → 4I15/2), orange (4F9/2 → 4I15/2) and NIR (4I13/2 → 4I15/2) emissions of Er3+ ions due to co-doping with Au2O3. Quantitative analysis of the results of PL emission indicated that 0.075 mol% of Au2O3 is the optimal concentration for achieving the highest quantum yield of these three emissions in this glass ceramic. Additional population of 4S3/2, 4F9/2 and 4I13/2 energy levels of Er3+ ions from the excited state of Au0 metallic particles is found to be the reason for such enhancement of quantum efficiency.
Investigation on visible light assisted gas sensing ability of multi-walled carbon nanotubes coated with pyrene based organic molecules
Elakia M., Gobinath M., Sivalingam Y., Palani E., Ghosh S., Nutalapati V., Surya V.J.
Article, Physica E: Low-Dimensional Systems and Nanostructures, 2020, DOI Link
View abstract ⏷
In this work, we have investigated the visible light assisted gas sensing properties of multiwalled carbon nanotubes (MWCNTs) functionalized with two organic molecules namely pyrene tetratopic ligands (PTL), and 1-pyrene acetic acid (PAA). Structural, optical and electrical properties have been examined on pure and functionalized samples using FESEM, Raman spectroscopy, UV–Visible spectroscopy, Photoluminescence (PL) spectroscopy, and current -voltage (I–V) characteristics. Sensor devices have been fabricated and tested in a gas sensor setup by passing saturated vapours of different VOCs like ethanol, n-hexane and triethylamine under dark and visible light conditions. Scanning Kelvin probe (SKP) studies have demonstrated that pyrene-MWCNTs hybrids significantly alter the contact potential difference upon interaction with volatile organic compounds (VOCs) and the response depends on the functional groups. The PTL+MWCNTs (sensitivity = 9.99 × 10−4 ppm−1) hybrid has outperformed when compared to PAA functionalized counterparts (sensitivity = 2.27 × 10−5 ppm−1) with triethylamine exposure. The presence of additional –COOH groups in PTL furnishes strong intermolecular hydrogen bonding through donor-acceptor interactions with the VOCs. Overall, our results suggests that the MWCNTs coated with pyrene molecules bearing suitable functional groups can be efficient sensors for detection of VOCs.
Third-order nonlinear optical features of zirconia-added lead silicate glass ceramics embedded with Pb2Fe2O5 perovskite crystal phases and role of Fe ions
Chandrakala C., Reddy A.S.S., Jedryka J., Kumar V.R., Raju G.N., Venkatramaiah N., Kumar V.R., Lakshminarayana G., Veeraiah N.
Article, Applied Physics A: Materials Science and Processing, 2020, DOI Link
View abstract ⏷
This study is aimed to identify the role of Fe2O3 in enhancing the efficiency of THG beam of Nd:YAG laser in lead zirconium silicate glass ceramics. The PbO–ZrO2–SiO2:Fe2O3 glass ceramics were synthesized by heat-treating the glasses for a prolonged time. XRD and SEM studies were performed to identify different crystalline phases in the samples. The SEM pictures have shown the presence of multiple crystallites of size in the range 0.1–0.6 µm, while characterization by XRD technique indicated the glass ceramic samples consist of perovskite Pb2FeIII 2O5, FeII 2SiO4, crystal phases. These studies have also demonstrated that there is an enhancement in the concentration of Fe3+ (Oh) crystalline phases with increasing quantity of Fe2O3 in the samples. Spectroscopic investigations (viz., IR and optical absorption) have further reinforced the above result and additionally indicated an increased degree of internal chaos in the material. The intensity of third harmonic generation (THG) beam of Nd:YAG laser (λ = 1064 nm) measured in the reflected regime after the pre-photopolarization of the samples indicated the largest intensity for the samples containing the highest concentration of Fe2O3. Thorough analysis of these results indicated that the tilted glass samples heat-treated with 0.5 mol% of Fe2O3 have significant chaotic internal structure and paved the way for obtaining intense THG signal with minimal phonon losses. Hence, such glass ceramics are predicted to be useful materials in the design of different optoelectronic devices.
Transforming waste polystyrene foam into N-doped porous carbon for capacitive energy storage and deionization applications
Deka N., Barman J., Kasthuri S., Nutalapati V., Dutta G.K.
Article, Applied Surface Science, 2020, DOI Link
View abstract ⏷
We have utilized cheap and readily available expanded polystyrene (EPS) foam waste as a raw material for the synthesis of a hypercrosslinked polymer. Using this polymeric scaffold, we have synthesized a series of nitrogen-doped porous carbons (PSC-3-X) via KOH activation at different temperatures. The optimized carbon material (PSC-3-700) exhibits a specific surface area of 810 m2 g−1 and optimum porosity suitable for capacitive applications such as supercapacitors and capacitive deionization. Moreover, the high nitrogen (5.23%) and oxygen (8.93%) contents present in the material enhances the electrochemical performance. PSC-3-700 exhibits the highest specific capacitance of 327 F g−1 at 1.0 A g−1 in 1 M H2SO4 aqueous electrolyte and 100% capacitance retention even after 10,000 charge–discharge cycles. It also displays a high electrosorption capacity of 34.8 mg g−1 for 500 mg L−1 NaCl solution at an applied voltage of 1.6 V in capacitive deionization application. The charge storage mechanism and electrosorption kinetics of the material have been investigated in detail.
Marine applications
Book chapter, Food, Medical, and Environmental Applications of Polysaccharides, 2020, DOI Link
View abstract ⏷
This chapter mainly emphasizes on the recent advancement in polysaccharide-based materials development in the large variety of marine applications such as wastewater treatment, corrosion inhibitors, drag reducer, antifouling agents, and in marine polymer coatings. Owing to the intrinsic properties of polysaccharide, functionalization of chitin, chitosan with metal nanoparticles for identification of the toxic ions present in the marine water by chemical and electrochemical methods are explored. The different separation methods for the removal of toxic ions and classification of the different types of polysaccharides were discussed in detail. Strategies toward the development of anticorrosive materials by natural and synthetic polysaccharides with different formulation were screened as marine polymer coatings in detail, pointing out their salt spray resistance, ionic conductivity, and prospective applications.
Fluorometric detection of fluoride and thiocyanate ions using novel anthrapyrazolone derivatives
Saravanan S., Rani T.M.S., Nazare A.D., Nutalapati V., Maji S.
Conference paper, Materials Today: Proceedings, 2020, DOI Link
View abstract ⏷
Anion recognition and sensing via artificial receptors have attracted a great deal of attention due to their significant role in chemical, biological, medical, and environmental applications. In the present investigation, we have demonstrated facile and straightforward synthesis of three low molecular weight fluorophore molecules designated as 2,7 - dihydrobenzo [1,2,3 - cd:4,5,6-c'd']bis(indazole) [DHBBI], 2-(benzo[1,2,3-cd:4,5,6-c'd']bis(indazole)-2(7H)-yl)ethanol [DHBBI-OH] and 2-(benzo[1,2,3-cd:4,5,6-c' d']bis(indazole)-2(7H)-yl)ethyl methacrylate [DHBBI-MA] for the fluorometric detection of fluoride and thiocyanate ions in solution phase. DHBBI was synthesized by a condensation reaction of 1,5-dichloroanthraquinone with hydrazine monohydrate. DHBBI-OH was synthesized by the reaction of DHBBI with 2-bromoethanol using K2CO3 as base whereas, DHBBI-MA was synthesized by the reaction of DHBBI-OH with methacrylic anhydride using dimethylamino pyridine (DMAP). Novel three molecules were characterized by 1H NMR, FT-IR, HR-MS and UV-Vis spectroscopy. The strong fluorescence nature of the compounds was further analyzed towards the detection of different ions. All the compounds DHBBI, DHBBI-OH, and DHBBI-MA showed turn on fluorescence behavior for fluoride (F-) ion and turn off fluorescence behavior for thiocyanate (SCN-) ion respectively.
UV excited SrAl2O4:Tb3+ nanophosphors for photonic applications
Jamalaiah B.C., Venkatramaiah N., Rao T.S., Rasool S.N., Rao B.N., Ram D.V.R., Narayana Reddy A.S.
Article, Materials Science in Semiconductor Processing, 2020, DOI Link
View abstract ⏷
A series of Sr(1-x)Al2O4:xTb3+ (SAOTx; 0 ≤ x ≤ 10.0 mol%) nanophosphors were prepared by solid state reaction technique for various photonic applications. The sintering temperature was estimated to be 1050 °C to crystallize SAOT phosphors into monoclinic structure. The powder X-ray diffraction profiles were well consistent with JCPDS No. 34–0379. Upon 375 nm excitation, the SAOT phosphors displayed two groups of emission bands corresponding to 5D3 → 7FJ and 5D4 → 7FJ transitions. A quenching in luminescence was noticed beyond 5.0 mol% of Tb3+ concentration due to the transfer of energy at higher concentrations. The emission spectra of SAOTx phosphors showed an intense green luminescence through 5D4 → 7F5 (546 nm) transition. The colour purity of SAOTx phosphors was analyzed by evaluating the chromaticity coordinates. The SAOT5 phosphor could be the best choice for various photonic applications.
Bioactive behaviour of NiO substituted CaF2–CaO–B2O3–BaO–P2O5 glasses by means of spectroscopic studies
Vijaya Kumari C., Gandhi Y., Sobhanachalam P., Siva Sesha Reddy A., Venkatramaiah N., Venkateswara Rao P., Ravi Kumar V.
Article, Optical Materials, 2019, DOI Link
View abstract ⏷
In this study, we have reported results of the investigation related to the influence of nickel ions on in vitro bio-activity of CaF2–CaO–B2O3–BaO–P2O5 glasses. The studies carried out are, degradation studies of the glass samples in SBF for a long time (for about a month), XRD, SEM and spectroscopic properties performed before and after immersion in simulated fluid suggested a thin coating of HAp crystalline grains on the surface of the glasses. IR and Raman spectral studies have further confirmed the formation of HAp layer. Magnitude of fraction of the samples that are degraded in the fluid is evaluated by weight loss and pH of remaining fluid. Degradation results along with characterization studies as a function of concentration of NiO indicated an increasing quantity of HAp deposited on the samples with the rise of NiO quantity up to 0.6 mol%. Spectroscopic investigations have further indicated the nickel ions occupied Oh and Td positions in the glass network. The studies have also suggested Oh occupancy of these ions is dominant in the glass doped with 0.6 mol% of nickel oxide while the fraction of tetrahedral nickel ions is minimal in this glass. The scrutiny of the degradation study results in combination with spectroscopy studies indicated that higher concentration of octahedral nickel ions are preferable for achieving higher quantity of crystalline HAp layer on the surface of the samples while the tetrahedral nickel ions are hindrance in promoting the growth of HAp layer.
Nickel nanoparticles induces cytotoxicity, cell morphology and oxidative stress in bluegill sunfish (BF-2) cells
Poornavaishnavi C., Gowthami R., Srikanth K., Bramhachari P.V., Venkatramaiah N.
Article, Applied Surface Science, 2019, DOI Link
View abstract ⏷
The rationale of the current study was to assess the suitability of BF-2 cell line as a model to assess nanotoxicity in the caudal fin cells of bluegill sunfish in vitro. The current study investigates the potential toxicity, morphological changes and oxidative stress of nickel nanoparticles (Ni NPs) in bluegill sunfish cells (BF-2) using mitochondrial, neutral red uptake and lactate dehydrogenase assays. Results indicated a concentration dependent cytotoxic effect after 24 h in mitochondrial, lysosomal and lactate dehydrogenase activities. BF-2 cells morphology was altered when exposed to 30 μg ml −1 concentrations of Ni NPs for 24 h. Dose dependent increase of oxidative stress was evidenced in BF-2 cells when exposed to Ni NPs, showed significant escalation in peroxidation of lipids (LPO), protein carbonyl (PC), glutathione sulfo-transferase (GST) and glutathione peroxidase (GPX) as compared to their experimental controls. However, the catalase (CAT) and total glutathione content (TGSH) was found to decrease dose dependently in BF-2 cells exposed to Ni NPs. The current study demonstrated that BF-2 cells may serve as a sensitive indicator for aquatic contaminant evaluations in toxicological research.
Influence of alkyl chains on fluoranthene ensembles towards fluorescence-based detection of 2,4,6-trinitrophenol
Kasthuri S., Shiv K., Raviteja S., Buthanapalli R., Samarendra M., Veeraiah N., Venkatramaiah N.
Article, Applied Surface Science, 2019, DOI Link
View abstract ⏷
A series of novel π-electron rich fluoranthene derivatives (P1–P3) adorned with symmetrical and unsymmetrical alkoxy chains were developed using Diels-Alder reaction. The use of peripheral triethyleneglycol (TEG) chains on fluoranthene enhances its electron donating ability and furnishes decrease in their energy levels and optical band gap. The intense sky-blue fluorescence exhibiting fluoranthene ensembles have been investigated as potential fluorescent chemosensors for the detection of explosive nitroaromatics (NACs). Fluorescence studies demonstrate that emission intensity of P1–P3 was efficiently decreased upon interaction with picric acid (PA) in a dominant static quenching phenomena which is attributed to photoinduced electron transfer process. The limit of detection (LOD) was found to be in the range of 2–20 ppb. The vapour phase sensing study involving thin films of P1–P3 showed efficient quenching response and sensing process is found to be highly reversible. Surface morphology of thin films significantly varied with the type of alkyl chain present on fluoranthene. The thin films are highly selective towards PA in aqueous medium containing commonly interfering nitro-explosives. Contact mode approach using silica gel substrates allows femto-gram detection of trinitrotoluene (TNT) and PA makes these materials as potential chemosensors for real time applications.
Structural and dielectric features of silver doped sodium antimonate glass ceramics
Ashok J., Kostrzewa M., Ingram A., Venkatramaiah N., Srinivasa Reddy M., Ravi Kumar V., Piasecki M., Veeraiah N.
Article, Journal of Alloys and Compounds, 2019, DOI Link
View abstract ⏷
The objective of this work is to explore the Ag ion concentration dependence on structural and dielectric characteristics of Na2O–Sb2O3: Ag2O glass ceramics. The prepared glass ceramics were characterized by XRD, XPS, SEM, TEM, EDS and DSC techniques. These studies have revealed that the samples are composed of multiple crystal grains entrenched in the remnant amorphous phase. The IR and Raman spectroscopic studies indicated increasing degree of polymerization of the glass network with increase of Ag2O concentration up to 0.1 mol%. This is attributed to increasing concentration of tetrahedral Sb5+ ions that take part in the glass network forming. Optical absorption spectra have exhibited surface plasmon resonance (SPR) band in the wavelength region 400–450 nm. Quantitative studies on dielectric properties were performed over wide ranges of frequency and temperature and the variations of these properties with the concentration of Ag2O are discussed in the light of various polarization processes. Dipolar orientational effects exhibited by electric moduli spectra suggested multiple relaxation times for electric dipoles. The observed decrease of A.C. conductivity (that contains both ionic and polaronic components) with increase of Ag2O content up to 0.1 mol% is attributed to the increasing degree of polymerization of the glass network that hinders the migration of charge carriers. The polaronic conduction is understood due to exchange of polarons between Sb3+ ‒ Sb5+ and Ag0 – Ag+ ions, while ionic conductivity is predicted due to transport of monovalent silver and Na+ ions. A changeover of polaronic to ionic conductivity seemed to take place at about 0.1 mol% Ag2O.
Selective Detection of Trinitrophenol by Amphiphilic Dimethylaminopyridine-Appended Zn(II)phthalocyanines at the Near-Infrared Region
Kasthuri S., Gawas P., Maji S., Veeraiah N., Venkatramaiah N.
Article, ACS Omega, 2019, DOI Link
View abstract ⏷
Novel amphiphilic Zn(II)phthalocyanines (ZnPcs) peripherally substituted with four and eight dimethylaminopyridinium units (ZnPc1 and ZnPc2) were synthesized by cyclotetramerization of the corresponding phthalonitriles. The effect of aggregation and photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation) properties was investigated. The chemosensing ability of ZnPcs toward explosive nitroaromatic compounds was explored in aqueous medium. This study demonstrates that ZnPc1 and ZnPc2 show fluorescence quenching behavior upon interaction with different nitro analytes and show unprecedented selectivity toward 2,4,6-trinitrophenol with a limit of detection (LOD) of 0.7-1.1 ppm with a high quenching rate constant (K sv ) of 1.6-2.02 × 10 5 . The near-infrared (NIR) fluorescence in thin films was quenched efficiently because of the photoinduced electron-transfer process through strong intermolecular Ï-Ï and electrostatic interactions. The sensing process is highly reversible and free from the interference of other commonly encountered nitro analytes. Further, experiments were performed to demonstrate the use of ZnPcs as efficient heterogeneous photocatalysts in the reduction of nitro explosives. The smart dual performance of multicharged ZnPcs in aqueous media quantifies them as attractive candidates in developing sensor materials at the NIR region and to possibly convert the toxic explosives into useful scaffolds. These results provide an interesting perspective toward elaboration of stable fluorescent systems for the selective sensing behavior of nitro explosives and their facile heterogeneous catalytic behavior in the reduction reactions.
Triazine based polyimide framework derived N-doped porous carbons: A study of their capacitive behaviour in aqueous acidic electrolyte
Deka N., Patidar R., Kasthuri S., Venkatramaiah N., Dutta G.K.
Article, Materials Chemistry Frontiers, 2019, DOI Link
View abstract ⏷
Nitrogen-doped porous carbon materials have been synthesized from nitrogen and oxygen rich triazine based polyimide (TPI-P/TPI-N) frameworks using ZnCl 2 as an activating agent at different temperatures (600 and 700 °C) for electrochemical energy storage applications. The morphology and structural features of the materials were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopic techniques. The resultant carbon materials possess large specific surface area and rich nitrogen contents. In particular, the material obtained at 700 °C (TPI-P-700) exhibits a surface area of up to 1650 m 2 g -1 and a nitrogen content of up to 6.3%, and shows an excellent specific capacitance of 423 F g -1 in an aqueous acid electrolyte (1 M H 2 SO 4 ) in a three electrode system. Moreover, the material also demonstrates nearly 100% capacitance retention up to 10000 charge-discharge cycles. A symmetrical supercapacitor device assembled using TPI-P-700 as an active material delivered an energy density of 10.5 W h kg -1 at 0.5 A g -1 .
Structural and physical characteristics of Au2O3-doped sodium antimonate glasses – Part II electrical characteristics
Ashok J., Kostrzewa M., Ingram A., Nalluri P., Venkatramaiah N., Srinivasa Reddy M., Ravi Kumar V., Veeraiah N.
Article, Journal of the American Ceramic Society, 2019, DOI Link
View abstract ⏷
In continuation of our earlier investigations on structural and physical characteristics of Au2O3-doped sodium antimonate glass-ceramics (Part-1), in this part we have investigated the influence of gold ions on electrical characteristics of the Na2O–Sb2O3: Au2O3 glass-ceramics. The study contains the results of quantitate investigations on dielectric properties, impedance spectra and A.C. conductivity in larger ranges of continuous frequencies (4 Hz-8 MHz) and temperatures (300-630 K). The variations exhibited by dielectric parameters with temperature and also with frequency were discussed in terms of various polarization mechanisms. The observed dielectric relaxation effects were analyzed using pseudo Cole-Cole plot method and the analysis indicated spreading of relaxation times for dipoles. A.c. conductivity and also d.c. conductivity were found to decrease (to three orders of magnitude) with increase in Au2O3 concentration upto 0.1 mol%. The decrement is ascribed to the increasing concentration of Sb5+ ions that were predicted to participate in the glass network forming with SbO4 units. Even though, both ionic and polaronic contributions are possible for conduction in the studied material, quantitative analysis of these results indicated that the polaronic conduction (due to intervalence transfer between Sb3+ ↔ Sb5+ and Au0 ↔ Au3+) is prevalent. The results have also suggested that there is a gradual decrement in the ionic component with increase in Au2O3 concentration. Variation in σac in the low-temperature region could satisfactorily be explained using quantum mechanical tunneling (QMT) model. Analysis of the results of d.c. conductivity indicated that the small polaron hoping (SPH) model is valid, especially in a high-temperature region while the low temperature part of d.c. conductivity is analyzed based on variable range hopping (VRH) model. Overall, the increase in Au2O3 dopant concentration in the studied glass-ceramics caused a decrement in the magnitude of the conductivity or increase in the insulating strength of the material.
Aggregation behavior in naphthalene-appended diketopyrrolopyrrole derivatives and its gas adsorption impact on surface potential
Dutta G.K., Kasthuri S., Marappan G., Jayaraman S.V., Sivalingam Y., Di Natale C., Nutalapati V.
Article, Journal of Materials Chemistry C, 2019, DOI Link
View abstract ⏷
Diketopyrrolopyrrole derivatives containing phenyl and thiophene units adorned with alkoxynaphthalene (Naph-PDPP and Naph-TDPP) were synthesized by a Suzuki cross-coupling reaction. The effect of the phenyl/thiophene units on the aggregation behavior and detailed photophysical properties were investigated by UV-visible, steady-state, and time-resolved fluorescence spectroscopy. The absorption and fluorescence spectra of Naph-PDPP and Naph-TDPP in the solid-state exhibit red-shifted spectral patterns due to strong intermolecular interactions. The concentration-dependent photophysical properties reveal the formation of J-type aggregates at higher concentrations and in the solid state. The extent of aggregate formation is higher for Naph-TDPP. DFT and TD-DFT studies showed that Naph-TDPP containing a thiophene ring in the backbone adopts a more planar geometry than Naph-PDPP and undergoes strong π-π stacking interactions that favor the formation of J-aggregates. Scanning Kelvin probe measurements on the thin films of Naph-PDPP and Naph-TDPP were performed (both in the dark and under visible light) upon exposure to different volatile organic vapors (ethanol and triethylamine). The study reveals that under visible light illumination, the Naph-PDPP thin film has significant gas adsorption towards ethanol vapors and alters its sign of response.
Positron annihilation spectroscopy and third harmonic generation studies on MnO mixed lead zirconium silicate glass ceramics
Basha S.J., Sesha Reddy A.S., Kostrzewa M., Ingram A., Venkatramaiah N., Kityk I.V., Kumar V.R., Veeraiah N.
Article, Optical Materials: X, 2019, DOI Link
View abstract ⏷
This work is intended to report pertinent studies covering several aspects viz., spectroscopic, higher order non-linear optical studies and positron annihilation spectroscopic studies on lead zirconium silicate glass ceramics admixed with different contents of MnO. Lead zirconium silicate glasses mixed with small contents (up to 1.0 mol%) of MnO were prepared and crystallized by subjecting them to the prolonged heat treatment at crystallization temperature ∼ 830 °C. The structural analysis of the samples carried out using XRD, TEM, EDS and differential scanning calorimetric techniques has suggested that the glass ceramics are entrenched with coagulated poly-crystallites viz., Mn2SiO4, Pb2MnO4 and Pb3Mn7O15 that contain manganese ions in multiple oxidation states. These studies have also suggested that Mn2+ ions occupy octahedral as well as tetrahedral positions and the tetrahedral occupancy is predominant in the glass ceramic sample mixed 0.6 mol% of MnO (M6). Infrared, Raman, optical absorption and photoluminescence spectral investigations have further supported the above conclusions and indicated an increasing rigidity of the glass network (attributed to the enhanced tetrahedral occupancy of manganese ions) with increasing concentration of MnO up to 0.6 mol%. Positron annihilation lifetime spectroscopic studies (carried out with 22Na isotope source of strength 0.1 MBq) suggested the sample M6 contains the lowest magnitude of free volume space. This is attributed to the participation of the maximal concentration of Mn2+ ions in the glass network forming. Non-linear optical (NLO) studies using NIR Er-glass laser (λ = 1540 nm) indicated the highest intensity third harmonic generation (THG) beam in the glass ceramics doped with small contents (∼0.2 mol%) of MnO. Overall analysis of these results suggested that the samples with lower concentrations of MnO possess highly disordered internal structure and facilitated the increase of intensity of THG beam; Hence, such samples may be considered as potential candidates for the applications in the fabrication of various micro sized opto-electronic devices, for example, optical switches, optical cross-connectors, microbolometers, photovoltaics, light sensors etc.
Synthesis and in vitro characterization of cerium oxide mixed calcium oxy fluoro borophosphate bioactive glasses by means of spectroscopic studies
Sobhanachalam P., Ravi Kumar V., Venkatramaiah N., Gandhi Y., Veeraiah N.
Article, Journal of Non-Crystalline Solids, 2018, DOI Link
View abstract ⏷
The main objective of this study is to achieve Ce substituted hydroxy apatite (HAp) deposition on the surface of the bio-active glasses which is more affective in antibacterial activity. Calcium oxy fluoro borophosphate glasses (with BaO as modifier) doped with different concentrations of Ce2O3 were prepared by melt quenching techniques. In vitro bioactivity studies were performed by soaking the samples in simulated body fluid (SBF) for about 30 days. The XRD and SEM studies have revealed the deposition of cerium substituted crystalline HAp coating on the surface of the post immersed glasses. The formation of HAp layer is further confirmed by IR and Raman spectral studies. The possible site preference of cerium ions in the HAp layer has been discussed using the results of above mentioned studies. The information regarding dependence of the magnitude of HAp layer developed on the concentration of Ce2O3 dopant is obtained by degradation studies viz., weight loss of the samples and the variation of pH of the residual solutions. The analysis of the results of degradability together with X-ray diffraction (XRD), Infrared (IR), Raman and optical absorption spectra indicated the increasing magnitude of Ce-HAp with the concentration of Ce2O3. Some of the characterization studies have also pointed out the co-presence of Ce ions in Ce4+ oxidation state along with Ce3+ state in the glass samples. The simultaneous presence of cerium ions in these two states in the crystalline HAp layer is predicted to be more useful in promoting the antibacterial activity of the glasses.
Efficient Blue and Yellow Organic Light-Emitting Diodes Enabled by Aggregation-Induced Emission
Venkatramaiah N., Kumar G.D., Chandrasekaran Y., Ganduri R., Patil S.
Article, ACS Applied Materials and Interfaces, 2018, DOI Link
View abstract ⏷
A new class of donor-bridge-acceptor (D-π-A) π-conjugated light-emitting molecules comprising carbazole as donor and maleimide (Cbz-MI, Cbz-MI(d)), phthalimide (Cbz-Pth) as acceptor units with phenyl ring as spacer have been synthesized in good yields. These compounds exhibit high quantum yield with three distinct emission colors yellowish-green (Cbz-MI), bright yellow Cbz-MI(d), and sky blue (Cbz-Pth) in the solid state. Single-crystal X-ray and quantum chemical calculations reveals that twisting of the phenyl rings with high torsional angle on maleimide and phthalimide units reduce the effective inter-chromophore electronic coupling, furnish dramatic changes in their photophysical properties in solution and solid states. Intriguingly, Cbz-MI(d) and Cbz-Pth exhibits a unique aggregation-induced blue-shifted emission (AIBSE) due to restricted intramolecular rotation (RIR) process, while Cbz-MI shows red-shifted emission in the solid state. The solvatochromic study reveal that combined RIR and excited state migration augment AIE (aggregation-induced emission) properties. The electrochemical properties reveal that Cbz-MI exhibits high oxidation propensity while Cbz-Pth shows low reduction values. Subsequently, organic light-emitting diodes (OLEDs) were fabricated with a simple three-layer device containing Cbz-Pth and Cbz-MI(d) as emitting layers. Cbz-MI(d) exhibits high performance yellow OLED with an external quantum efficiency exceeding ∼4.1% and a brightness exceeding ∼73915 cd/m2, which is among the best performance reported for bright yellow fluorescence organic light-emitting diodes.
Third order nonlinear optical effects of ZnO–ZrO2–B2O3 glass ceramics embedded with ZnZrO3 perovskite crystal phases
Reddy A.S.S., Kityk I.V., Kumar V.R., Jedryka J., Ozga K., Venkatramaiah N., Veeraiah N.
Article, Journal of Materials Science: Materials in Electronics, 2017, DOI Link
View abstract ⏷
Zinc zirconium borate glasses crystallized with varying concentrations of ZrO2 by heat treating at the onset of the predicted crystallization temperature for prolonged times have been fabricated. The prepared samples were characterized by XRD and SEM techniques. The results of these measurements have indicated that the bulk samples are entrenched with ZnZrO3 (tetragonal/cubic) crystal phases with varying sizes and concentration, depending upon the content of ZrO2 present in the bulk material. The IR spectral studies have further confirmed that the zirconium ions mainly exist in octahedral coordination that are predicted to play crucial role in inducing third harmonic generation (THG). Later, the samples were optically poled by cw 532 nm green laser along with illumination by 9.4 μm CO2 laser. The infrared laser (CO2 laser) treatment was performed before the 532 nm laser treatment in order to activate the phonon modes (both harmonic and anharmonic modes). Later, intensity of the induced THG (of wavelength 355 nm) of the pre- and post-heated samples was measured using Nd:YAG 1064 nm 20 ns pulsed laser with the fundamental beam power varying up to 200 J/m2. The measurements were performed as functions of power of photoinduced 532 nm cw laser beam and also the concentration of the crystallizing agent ZrO2. Quantitative analysis of these results indicated that the samples crystallized with 5.0 mol% of ZrO2 exhibited the maximal intensity of THG. Further, the comparison of the obtained results with those of corresponding pre-crystallized samples pointed out that the crystallization has enhanced the THG intensity by many folds. The enhancement is attributed to the presence of ZnZrO3 perovskite crystal phases embedded in the residual glass phase of the bulk crystallized samples. The obtained results may be useful for considering the material for different optoelectronic devices especially for nonlinear optical triggering devices.
Physical characteristics of PbO−ZrO2−SiO2:TiO2 glass ceramics embedded with Pb2Ti2O6 cubic pyrochlore crystal phase: Part-I electrical properties
Subba Rao A., Ashok J., Suresh B., Naga Raju G., Venkatramaiah N., Ravi Kumar V., Kityk I.V., Veeraiah N.
Article, Journal of Alloys and Compounds, 2017, DOI Link
View abstract ⏷
This study is mainly focused on electrical characteristics of PbO−ZrO2−SiO2: TiO2 glass ceramics embedded with Pb2Ti2O6 cubic pyrochlore crystal phases. The samples were synthesized by usual melt quenching technique and subsequent heat treating at crystallization temperature for prolonged times. The samples were characterized by XRD, SEM and DSC, IR, EPR and optical absorption spectroscopy techniques. Later, dielectric properties viz., dielectric constant, loss tangent, electric moduli, electrical impedance and a.c. conductivity over wide ranges of frequency and temperature, have been measured as a function of TiO2 content. The results of characterization techniques viz., XRD, SEM and DSC, indicated that the samples are embedded with multiple crystal grains (with sizes varying from 0.1 to 1 μm) cemented with residual glass phase. The volume fraction of the crystal grains is found to increase with increase of TiO2 content. The XRD studies on PbO−ZrO2−SiO2:TiO2 glass ceramics revealed that Pb2Ti2O6 cubic pyrochlore crystal phase is the principal phase present in the bulk samples. The studies have also confirmed that a small part of Pb(Zr 0.5Ti0.5)O3 and Ti2O3 crystal grains are also present in the titled glass ceramics. The results of IR spectral studies have indicated that there is an increasing degree of polymerization of glass network with increasing TiO2 content up to 0.6 mol%. This is attributed to the presence of Ti ions predominantly in Ti4+ state (in this concentration range of TiO2) that take part in the network forming positions with TiO4 and also substitutionally positioned octahedral sites. The results of optical absorption and EPR spectral studies have pointed out that a part of the Ti ions were reduced to Ti3+ state and such ions were predicted to act as modifiers. These studies have also indicated that the concentration of Ti3+ ions is higher in the samples crystallized with 0.8 and 1.0 mol%. The values of dielectric parameters are decreased with increasing of crystallizing agent. The decrease is attributed to the participation of Ti ions in the formation of Pb2Ti2O6 cubic pyrochlore crystalline phases with TiO4 structural units. Quantitative analysis of the dielectric properties of PbO−ZrO2−SiO2:TiO2 glass ceramics together with the results of spectroscopic studies indicated that the electrical insulating strength is the highest for the glass crystallized with 0.6 mol% of TiO2.
Third order optical nonlinear studies and its use to estimate thickness of sandwiched films of tetra-phenyl porphyrin derivatives
Rao A.S., Dar M.H., Venkatramaiah N., Venkatesan R., Sharan A.
Article, Journal of Nonlinear Optical Physics and Materials, 2016, DOI Link
View abstract ⏷
Third-order nonlinear optical properties of tetra-phenyl porphyrin (H2TPP) derivatives viz., H2TPP(OH)4 and Zn(II)TPP doped in boric acid glass thin films were measured using single beam Z-scan and forward degenerate four-wave mixing (DFWM) techniques. Excited state lifetimes and absorption cross-sections were estimated from these experiments. Thickness of the porphyrin doped sandwich glass films were determined using DFWM technique for the first time. The values of nonlinear refractive index (n2) obtained for these systems are are found to be sensitive to the nature of substituents in porphyrin molecule. These results are interpreted in terms of delocalized electrons contributing to the third-order optical nonlinearity.
Tetraphenylethene-Based Conjugated Fluoranthene: A Potential Fluorescent Probe for Detection of Nitroaromatic Compounds
Article, Chemistry - A European Journal, 2016, DOI Link
View abstract ⏷
This study reports the synthesis and photophysical properties of a star-shaped, novel, fluoranthene-tetraphenylethene (TFPE) conjugated luminogen, which exhibits aggregation-induced blue-shifted emission (AIBSE). The bulky fluoranthene units at the periphery prevent intramolecular rotation (IMR) of phenyl rings and induces a blueshift with enhanced emission. The AIBSE phenomenon was investigated by solvatochromic and temperature-dependent emission studies. Nanoaggregates of TFPE, formed by varying the water/THF ratio, were investigated by SEM and TEM and correlated with optical properties. The TFPE conjugate was found to be a promising fluorescent probe towards the detection of nitroaromatic compounds (NACs), especially for 2,4,6-trinitrophenol (PA) with high sensitivity and a high Stern-Volmer quenching constant. The study reveals that nanoaggregates of TFPE formed at 30 and 70 % water in THF showed unprecedented sensitivity with detection limits of 0.8 and 0.5 ppb, respectively. The nanoaggregates formed at water fractions of 30 and 70 % exhibit high Stern-Volmer constants (Ksv=79 998 and 51 120 m-1, respectively) towards PA. Fluorescence quenching is ascribed to photoinduced electron transfer between TFPE and NACs with a static quenching mechanism. Test strips coated with TFPE luminogen demonstrate fast and ultra-low-level detection of PA for real-time field analysis.
Crystal structure of a compact three-dimensional metal-organic framework based on Cs+ and (4,5-dicyano-1,2-phenylene)bis(phosphonic acid)
Mendes R.F., Venkatramaiah N., Tome J.P.C., Paz F.A.A.
Article, Acta Crystallographica Section E: Crystallographic Communications, 2016, DOI Link
View abstract ⏷
A new metal-organic framework compound, poly[[μ7-dihydrogen (4,5-dicyano-1,2-phenylene)diphosphonato](oxonium)caesium], [Cs(C8H4N2O6P2)(H3O)] n (I), based on Cs+ and the organic linker 4,5-dicyano-1,2-phenylene)bis(phosphonic acid, (H4cpp), containing two distinct coordinating functional groups, has been prepared by a simple diffusion method and its crystal structure is reported. The coordination polymeric structure is based on a CsO8N2 complex unit comprising a monodentate hydronium cation, seven O-atom donors from two phosphonium groups of the (H2cpp)2- ligand, and two N-atom donors from bridging cyano groups. The high level of connectivity from both the metal cation and the organic linker allow the formation of a compact and dense three-dimensional network without any crystallization solvent. Topologically (I) is a seven-connected uninodal network with an overall Schäfli symbol of {417.64}. Metal cations form an undulating inorganic layer, which is linked by strong and highly directional O - H⋯O hydrogen-bonding interactions. These metallic layers are, in turn, connected by the organic ligands along the [010] direction to form the overall three-dimensional framework structure.
A ladder coordination polymer based on Ca2+ and (4,5-dicyano-1,2-phenylene)bis(phosphonic acid): Crystal structure and solution-state NMR study
Venkatramaiah N., Mendes R.F., Silva A.M.S., Tome J.P.C., Paz F.A.A.
Article, Acta Crystallographica Section C: Structural Chemistry, 2016, DOI Link
View abstract ⏷
The preparation of coordination polymers (CPs) based on either transition metal centres or rare-earth cations has grown considerably in recent decades. The different coordination chemistry of these metals allied to the use of a large variety of organic linkers has led to an amazing structural diversity. Most of these compounds are based on carboxylic acids or nitrogen-containing ligands. More recently, a wide range of molecules containing phosphonic acid groups have been reported. For the particular case of Ca2+-based CPs, some interesting functional materials have been reported. A novel one-dimensional Ca2+-based coordination polymer with a new organic linker, namely poly[[diaqua[μ4-(4,5-dicyano-1,2-phenylene)bis(phosphonato)][μ3-(4,5-dicyano-1,2-phenylene)bis(phosphonato)]dicalcium(II)] tetrahydrate], {[Ca2(C8H4N2O6P2)2(H2O)2]·4H2O}n, has been prepared at ambient temperature. The crystal structure features one-dimensional ladder-like ∞1[Ca2(H2cpp)2(H2O)2] polymers [H2cpp is (4,5-dicyano-1,2-phenylene)bis(phosphonate)], which are created by two distinct coordination modes of the anionic H2cpp2- cyanophosphonate organic linkers: while one molecule is only bound to Ca2+ cations via the phosphonate groups, the other establishes an extra single connection via a cyano group. Ladders close pack with water molecules through an extensive network of strong and highly directional O - H⋯O and O - H⋯N hydrogen bonds; the observed donor-acceptor distances range from 2.499 (5) to 3.004 (6) Å and the interaction angles were found in the range 135-178°. One water molecule was found to be disordered over three distinct crystallographic positions. A detailed solution-state NMR study of the organic linker is also provided.
Photodynamic inactivation of Escherichia coli with cationic ammonium Zn(II) phthalocyanines
Rocha D.M.G.C., Venkatramaiah N., Gomes M.C., Almeida A., Faustino M.A.F., Almeida Paz F.A., Cunha A., Tome J.P.C.
Article, Photochemical and Photobiological Sciences, 2015, DOI Link
View abstract ⏷
The aim of this work was the development of a family of novel water soluble Zinc(ii) phthalocyanines (Pc) for the photodynamic inactivation of Gram-negative bacteria. Pc derivatives 1a, 2a and 3a containing trimethylammonium groups with varied number and nature of the groups at peripheral positions were synthesized by cyclotetramerization of dimethyl amino substituted phthalonitriles in the presence of zinc powder, using 1-chloronaphthalene as a solvent, followed by cationization using dimethyl sulfate. The solubility, singlet oxygen generation (1O2) and stability/photostability of each Pc were evaluated as well as the affinity to bacterial cells and their photosensitizing potential against a recombinant bioluminescent Escherichia coli strain, used as a biological model for Gram negative bacteria. The efficiency of photodynamic inactivation was assessed under white and red light at an irradiance of 150 mW cm-2. All Pc were soluble in phosphate buffer saline and in dimethyl sulfoxide and demonstrated good stability/photostability. The photochemical parameters reveal that Pc 2a and 3a are more efficient singlet oxygen producers than Pc 1a, for which singlet oxygen generation could not be demonstrated. Pc 2a and 3a caused photosensitization in E. coli. The inactivation factors attained with red light were, however, generally higher than those with white light. Under red light Pc 3a and 2a caused, respectively, 5.6 and 4.9 log reduction in the bioluminescence of the E. coli while, with white light, the corresponding inactivation factors were 2.5 and 0.5 log. The order of the PDI efficiency (3a > 2a ⋙ 1a) was determined by the combined effect of solubility, singlet oxygen generation ability and affinity to bacterial cells. Ammonium phthalocyanines with eight charges or containing halogen atoms such as chlorine, when irradiated with red light can, therefore, be regarded as promising photosensitizers for the inactivation of Gram-negative bacteria.
Phosphonate appended porphyrins as versatile chemosensors for selective detection of trinitrotoluene
Venkatramaiah N., Pereira C.F., Mendes R.F., Paz F.A.A., Tome J.P.C.
Article, Analytical Chemistry, 2015, DOI Link
View abstract ⏷
Fluorescent molecular probes based on phosphonate-functionalized porphyrin derivatives have been designed for selective detection of nitroaromatics. It is shown that molecular recognition is based on cooperative hydrogen bonding and π-π stacking interactions with electron-deficient molecules (nitroaromatic compounds, NACs), displaying superior detection toward trinitrotoluene (TNT). The P=O functional groups decrease the lowest unoccupied molecular orbital (LUMO) energy level of the porphyrins and, consequently, facilitate the electron inoculation to TNT through a photoinduced electron transfer (PET) process. The hydroxyl groups of the phosphonates and pyrrole -NH protons are further engaged in donor-acceptor interactions with TNT by strong intermolecular hydrogen bonding interactions (as evidenced by single crystal X-ray, NMR, and density functional theory (DFT)) showing turn off fluorescence behavior. The nonplanarity of the porphyrins induced by protonation at the central core of the porphyrin H<inf>4</inf>TPPA<sup>2+</sup> undergoes additional interactions, furnishing an anomalous increase in the selectivity of TNT at nanomolar levels in solution (limit of detection, LOD ∼ 5 nM). Porphyrin-doped hybrid PMMA [poly(methyl methacrylate)] polymer films demonstrate the reversibility of the fluorescence behavior and exhibit high photostability. The formation of discrete molecular aggregates on the surface of hybrid films and efficient diffusion of TNT vapors (10 ppb) displayed high selectivity in the solid state. The hybrid films are further used to demonstrate the detection of NACs in the aqueous medium, ultimately providing a platform for a practical strategy and implementation for the detection of toxic NACs.
Synthesis and photophysical characterization of dimethylamine-derived Zn(II)phthalocyanines: Exploring their potential as selective chemosensors for trinitrophenol
Venkatramaiah N., Rocha D.M.G.C., Srikanth P., Almeida Paz F.A., Tome J.P.C.
Article, Journal of Materials Chemistry C, 2015, DOI Link
View abstract ⏷
We report a novel synthetic approach, with good yields, for the synthesis of selective dimethylamine-substituted phthalonitriles (1-3) in the presence of triethyl phosphite and dimethylformamide at 160°C. The peripherally modified dimethylamine substituted Zn(ii)phthalocyanines (ZnPc1-3) with varied numbers and positions of dimethylamine groups were prepared for a systematic investigation of the effect of the substituents on their electronic and spectroscopic properties. Compounds show strong aggregation behaviour in methanol and this behaviour decreases with the increase of the alkyl chain length of the alcohol solvents (i.e., from methanol to octanol). The fluorescence quantum yields of ZnPc1-3 showed an excellent correlation with the extent of the molecular aggregation. The versatility of the ZnPc1-5 compounds possessing both electron donating and electron withdrawing substituents at their periphery is investigated towards the detection of nitroaromatic compounds (NACs) in solution and in the vapour phase. It was found that ZnPc1-5 exhibit high selectivity towards trinitrophenol (TNP). A good linearity of fluorescence detection using ZnPc3 as the fluorescent probe was observed in the concentration range of 50 × 10-6 to 450 × 10-6 M in chloroform, with a detection limit (LOD) of 11 ± 2 ppm. Stern-Volmer (SV) and DFT studies reveal that the fluorescence quenching behaviour occurs through photo-induced electron transfer from the excited state of ZnPcs to TNP with static quenching behaviour occurring in a predominant fashion. The formation of a porous morphology of ZnPc3 thin films promotes high selectivity and accessibility to TNP vapours (7.7 × 10-3 ppb).
Study of spatial rings in TPPOH4 doped in boric acid glass
Allam S.R., Dar M.H., Venkatramaiah N., Venkatesan R., Sharan A.
Conference paper, IOP Conference Series: Materials Science and Engineering, 2015, DOI Link
View abstract ⏷
Single beam optical nonlinearity is studied in TPPOH4 doped in boric acid sandwiched films between two microscope glass slides at three different molar concentrations (4×10-4M, 1×10-4M, 5×10-5M). It shows absorption peak at 700nm with bandwidth of 70nm. We have used diode laser output at 671nm to probe resonant optical nonlinearities. We have observed interesting phenomena of formation of spatial concentric rings centered on the z-axis of the sample. To our knowledge this is first such observation of spatial rings in these systems. We have carried out studies to separate the contribution to the ring formation due to absorptive/refractive optical nonlinearity and the thermal nonlinearity.
Dual functionality of phosphonic-acid-appended phthalocyanines: Inhibitors of urokinase plasminogen activator and anticancer photodynamic agents
Venkatramaiah N., Pereira P.M.R., Almeida Paz F.A., Ribeiro C.A.F., Fernandes R., Tome J.P.C.
Article, Chemical Communications, 2015, DOI Link
View abstract ⏷
Phthalocyanines (Pcs) bearing phosphonic acid groups at the periphery exhibit a potential photodynamic effect to induce phototoxicity on human bladder cancer epithelial cells (UM-UC-3). In vitro photophysical and biological studies show high intrinsic ability to inhibit the activity of urokinase plasminogen activator (uPA) and matrix metalloproteinase-9 (MMP-9).
Fast detection of nitroaromatics using phosphonate pyrene motifs as dual chemosensors
Venkatramaiah N., Firmino A.D.G., Almeida Paz F.A., Tome J.P.C.
Article, Chemical Communications, 2014, DOI Link
View abstract ⏷
A new class of dual fluorescent chemosensors for nitroaromatic compounds (NACs) based on phosphonated pyrene derivatives is reported, showing high selectivity towards trinitrotoluene (TNT). The strong intermolecular interactions (π–π stacking and hydrogen bonding) allow high fluorescence quenching with visual detection in short response times. © 2014 The Royal Society of Chemistry.
Photophysical, electrochemical and solid state properties of diketopyrrolopyrrole based molecular materials: Importance of the donor group
Article, Journal of Materials Chemistry C, 2014, DOI Link
View abstract ⏷
Diketopyrrolopyrrole (DPP) based molecular semiconductors have emerged as promising materials for high performance active layers in organic solar cells. It is imperative to comprehend the origin of such a property by investigating the fundamental structure property correlation. In this report we have investigated the role of the donor group in DPP based donor-acceptor-donor (D-A-D) structure to govern the solid state, photophysical and electrochemical properties. We have prepared three derivatives of DPP with varying strengths of the donor groups, such as phenyl (PDPP-Hex), thiophene (TDPP-Hex) and selenophene (SeDPP-Hex). The influence of the donor units on the solid state packing was studied by single crystal X-ray diffraction. The photophysical, electrochemical and density functional theory (DFT) results were combined to elucidate the structural and electronic properties of three DPP derivatives. We found that these DPP derivatives crystallized in the monoclinic space group P21/c and show herringbone packing in the crystal lattice. The derivatives exhibit weak π-π stacking interactions as two neighboring molecules slip away from each other with varied torsional angles at the donor units. The high torsional angle of 32° (PDPP-Hex) between the phenyl and lactam ring results in weak intramolecular interactions between the donor and acceptor, while TDPP-Hex and SeDPP-Hex show lower torsional angles of 9° and 12° with a strong overlap between the donor and acceptor units. The photophysical properties reveal that PDPP-Hex exhibits a high Stokes shift of 0.32 eV and SeDPP-Hex shows a high molar absorption co-efficient of 33600 L mol-1 cm-1 with a low band gap of ∼2.2 eV. The electrochemical studies of SeDPP-Hex indicate the pronounced effect of selenium in stabilizing the LUMO energy levels and this further emphasizes the importance of chalcogens in developing new n-type organic semiconductors for optoelectronic devices. This journal is © the Partner Organisations 2014.
Optical transmission control in graphene oxide and its organic composites with ultrashort laser pulses
Bala Murali Krishna M., Venkatramaiah N., Narayana Rao D.
Article, Journal of Optics (United Kingdom), 2014, DOI Link
View abstract ⏷
Nonlinear optical transmission of graphene oxide-(Cu, Zn, Sn, H 2) porphyrin composites was investigated using the Z-scan technique at 532 nm with picosecond (ps) and 800 nm with femtosecond laser pulses. Pure porphyrins show saturable absorption (SA) in reverse saturable absorption (RSA) behaviour and graphene oxide shows complete RSA behaviour, observed in an open aperture Z-scan curve. Interestingly, composites have shown a switch-over from reverse RSA to SA and back to RSA behaviour, observed with variation of intensity towards the focus, due to strong two-photon absorption as well as excited state absorption in the ps regime. This switching behaviour was interpreted as due to long lifetimes and saturation of the excited states. This may find application in optical switching. © 2014 IOP Publishing Ltd.
Fluoranthene based derivatives for detection of trace explosive nitroaromatics
Article, Journal of Physical Chemistry C, 2013, DOI Link
View abstract ⏷
A series of fluoranthene derivatives (F1-F5) varied with nature and type of substituents were synthesized via Diels-Alder reaction followed by in situ decarbonylation. The solid state structures have been established through single crystal X-ray diffraction (XRD). The presence of extended conjugation and having two alkyloxy chains on phenyl rings induces flexibility to orient opposite to each other and interacts with another fluoranthene unit with weak π-π interactions and show unique supramolecular arrangements. The envisaged photophysical and DFT studies demonstrated that HOMO-LUMO levels were effectively tuned by different substituents with an optical band gap from 3.44 to 3.88 eV provoked to examine as sensitive fluorescent chemosensors for the detection of nitroaromatic compounds (NACs). The sensitivity toward the detection of NACs was evaluated through fluorescence quenching in solution (aqueous and non-aqueous) and solid state (vapor and contact mode). Fluorescence studies demonstrated that electron transfer occurs from the electron rich fluoranthene fluorophores to the electron deficient NACs by the dominant static quenching mechanism and the quenching process is reversible. It was found that the detection sensitivity increases with extent of conjugation on fluoranthene unit. The contact mode approach using thin layer silica chromatographic plates exhibits a femtogram (1.15 fg/cm2) detection limit for trinitrotoluene (TNT) and picric acid (PA), while the solution state fluorescence quenching shows for PA detection at the 2-20 ppb level. The sensing performance of fluoranthene thin films to NACs in aqueous solution reveals that fluorophores are highly selective towards the detection of PA. The smart performances of thin film fluorophores with high photostability have great advantage than those of conjugated polymers with superior sensitive detection of PA in groundwater. © 2013 American Chemical Society.
Facile synthesis of highly stable BF3-induced meso-tetrakis (4-sulfonato phenyl) porphyrin (TPPS4)-J-aggregates: Structure, photophysical and electrochemical properties
Venkatramaiah N., Ramakrishna B., Venkatesan R., Almeida Paz F.A., Tome J.P.C.
Article, New Journal of Chemistry, 2013, DOI Link
View abstract ⏷
We report herein, a novel method for the formation of highly stable BF 3-induced J-aggregates by interaction between meso-tetrakis(4- sulfonatophenyl)porphyrin (TPPS4) and BF3O(C 2H5)2. The aggregates were characterized by NMR (1H, 11B and 19F), optical absorption, cyclic voltammetry, FT-IR and fluorescence spectroscopic techniques. TPPS4 readily forms a 1:2 adduct with BF3 which further converts into BF3-induced TPPS4 aggregates whose spectroscopic properties strongly depend on the concentration of BF3. The optical absorption spectrum shows the formation of J-type aggregates with an apparent association constant (logKapp) of 4.2 ± 0.1. The steady state emission shows formation of 1:2 (TPPS4-BF3) adducts at ∼685 nm and J-aggregates exhibit emission at 732 nm with a red shift of ∼17 nm in comparison to J-aggregates of TPPS4 with TFA. The fluorescence lifetime of TPPS4:BF3 (1:2) adducts exhibits ∼3.68 ns and aggregates show a lifetime of 4.32 ± 0.2 ns with major abundance. NMR study reveals that proton transfer occurs from pyrrole N-H to the SO3- groups and J-aggregates were stabilized by strong intermolecular hydrogen bonding interaction between N2-BF2 and SO3H. Cyclic voltammetry shows a decrease in the reduction peak current along with a change in the peak potentials for the aggregates. The PXRD pattern of the aggregates exhibits orthorhombic structure with interplanar distance of 4.87 Å. The variations in unusual stability, photophysical, electrochemical properties and nature of the aggregates were rationalized with aggregates of TPPS4 dication. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Influence of side-chain on structural order and photophysical properties in thiophene based diketopyrrolopyrroles: A systematic study
Naik M.A., Venkatramaiah N., Kanimozhi C., Patil S.
Article, Journal of Physical Chemistry C, 2012, DOI Link
View abstract ⏷
In this work, we have synthesized a series of TDPP derivatives with different alkyl groups such as n-hexyl (-C6H13) 3a, 2-ethylhexyl (-(2-C2H5)C6H12) 3b, triethylene glycol mono methyl ether (-(CH2CH2O) 3cH3, TEG) 3c, and octadodecyl (-(8-C8H 17)C12H22) 3d. N,N dialkylation of thiophene-diketopyrrolopyrrole (TDPP, 1) strongly influences its solubility, solid state packing, and structural order. These materials allow us to explicitly study the influence of alkyl chain on solid state packing and photophysical properties. TDPP moiety containing two different alkyl groups 3e (TEG and 2-ethylhexyl) and 3f (TEG and n-hexyl) were synthesized for the first time. The absorption spectra of all derivatives exhibited a red shift in solid state when compared to their solution spectra. The type of alkyl chains leads to change in the optical band gaps in solid state. The fluorescence study reveals that TDPP derivatives have strong π-π interaction in the solid state and the extent of bathochromic shift is due to combination of intramolecular interaction and formation of aggregates in solid state. This behavior strongly depends on the nature of alkyl chain. The presence of strong C-H···O inter chain interactions and CH-π interactions in solid state exhibits strong influence on the photophysical properties of TDPP chromophore. © 2012 American Chemical Society.
Femtogram detection of explosive nitroaromatics: Fluoranthene-based fluorescent chemosensors
Article, Chemistry - A European Journal, 2012, DOI Link
View abstract ⏷
Herein we report a novel fluoranthene-based fluorescent fluorophore 7,10-bis(4-bromophenyl)-8,9-bis[4-(hexyloxy)phenyl]fluoranthene (S 3) and its remarkable properties in applications of explosive detection. The sensitivity towards the detection of nitroaromatics (NACs) was evaluated through fluorescence quenching in solution, vapor, and contact mode approaches. The contact mode approach using thin-layer silica chromatograp- hic plates exhibited a femtogram (1.15 fg cm -2) detection limit for trinitrotoluene (TNT) and picric acid (PA), whereas the solution-phase quenching showed PA detection at the 2-20 ppb level. Fluorescence lifetime measurements revealed that the quenching is static in nature and the quenching process is fully reversible. Binding energies between model binding sites of the S 3 and analyte compounds reveal that analyte molecules enter into the cavity created by substituted phenyl rings of fluoranthene and are stabilized by strong intermolecular interactions with alkyl chains. It is anticipated that the sensor S 3 could be a promising material for the construction of portable optical devices for the detection of onsite explosive nitroaromatics. Explosive discoveries: A novel fluoranthene-based fluorescent fluorophore 7,10-bis(4-bromophenyl)-8,9-bis[4-(hexyloxy)phenyl]fluoranthene (S 3) and its remarkable properties in applications of explosive detection is reported (see figure). It is anticipated that sensor S 3 could be a promising material in the construction of portable optical devices for onsite detection of explosive nitroaromatics. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Synthesis and structural, spectroscopic and nonlinear optical measurements of graphene oxide and its composites with metal and metal free porphyrins
Bala Murali Krishna M., Venkatramaiah N., Venkatesan R., Narayana Rao D.
Article, Journal of Materials Chemistry, 2012, DOI Link
View abstract ⏷
In this paper we present the structure and spectroscopic, photophysical and nonlinear optical studies of covalently functionalized novel graphene oxide-[Cu, Zn, Sn, H 2 (metal free), VO] porphyrin composites. The composites were characterized by Field Enhanced Scanning Electron Microscopy (FE-SEM), micro-Raman, optical absorption, Fourier transform infrared (FT-IR), steady state and time resolved fluorescence spectroscopic techniques. The composites exhibit strong fluorescence quenching, suggesting strong electronic interactions between the porphyrin and graphene oxide molecules. Nonlinear optical absorption (NLA) studies of graphene oxide-porphyrin composites were investigated using the Z-scan technique at 532 and 800 nm with nanosecond (ns) and femtosecond (fs) laser pulses. Composites show strong two-photon absorption (TPA) as well as excited state absorption (ESA) leading to reverse saturable absorption (RSA) behaviour in the ns regime and saturable absorption (SA) behaviour was observed in fs regime. The metal free porphyrin-graphene oxide (GO) composite shows significant nonlinear absorption behaviour as well as highest fluorescence quenching behaviour compared to other GO-porphyrin composites. We further observed the enhanced figure of merit (FOM) values for composites in comparison with individual molecules. © 2012 The Royal Society of Chemistry.
Enhanced stokes shift of S 2 → S 0 emission and structural investigations of Sn(IV)Porphyrins doped hybrid borate glasses
Venkatramaiah N., Ramakrishna B., Kumar A.R., Veeraiah N., Venkatesan R.
Article, Journal of Alloys and Compounds, 2012, DOI Link
View abstract ⏷
In the present study, we report our results on Sn(IV)TPP and its derivatives doped hybrid borate glasses. The photophysical and structure of Sn(IV)Porphyrins in borate glass matrix was studied through micro-Raman, optical absorption, steady state and time resolved fluorescence emission techniques. The optical absorption spectrum shows red shift in Soret band and change in the intensity of Q-bands. Upon exposure to UV light at 260 nm, the glass samples exhibit strong blue emission and red emission at 365 nm. Steady state fluorescence emission spectrum of hybrid glasses exhibits dual emission bands originating from the S 2 → S 0 and S 1 → S 0 states. The appearance of large stokes shift (Δυ), enhanced S 2 → S 0 emission at ∼482 nm and excitation dependent of S 1 → S 0 emission indicates that the structure of Sn(IV)Porphyrins were inherently modified in the borate glass matrix. Time resolved fluorescence of S 2 → S 0 emission was found to be in the range of 0.23-0.36 ns, S 1 → S 0 emission shows 1.23-1.57 ns and 9.12-9.63 ns, respectively. The results obtained in glass matrix were correlated with solution medium and the possible structures were investigated. © 2011 Elsevier B.V. All rights reserved.
Role of modifier oxide in emission spectra and kinetics of Er-Ho codoped Na 2SO 4-MO-P 2O 5 glasses
Rao P.R., Venkatramaiah N., Gandhi Y., Kumar V.R., Kityk I.V., Veeraiah N.
Article, Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 2012, DOI Link
View abstract ⏷
The glasses of the composition 19Na 2SO 4-20MO-60P 2O 5: 1.0Ho 2O 3/1.0Er 2O 3 (M = Mg, Ca, and Ba) have been synthesized. Optical absorption and fluorescence spectra (in the spectral range 350-2100 nm were studied at ambient temperature. The spectra were characterized using Judd-Ofelt theory. From the luminescence spectra, various radiative properties like transition probability A, branching ratio β and the radiative life time τ for blue (B), green (G) and red (R) emission levels of these glasses have been evaluated. The energy transfer between the two rare earth ions (Ho 3+ and Er 3+) in co-doped Na 2SO 4-MO-P 2O 5 glass systems in the visible and NIR regions has also been investigated. Highest intensity, the highest quantum efficiency and maximum energy transfer with low phonon losses of B, G, and R lines has been observed in BaO mixed glasses. The reasons for such higher values of these parameters have been discussed in the light of varying field strengths at the rare earths ion site due to replacement of one modifier oxide with the other. The enhanced intensity of NIR emission (at 2.0 μm) has also been discussed in terms of cross relaxation of Er 3+ ions from 4I 13/2 level to 5I 7 of Ho 3+ ions. © 2011 Elsevier B.V. All rights reserved.
Graphene oxide (GO)-Semiconductor (ZnO, TiO2) nanoparticles for broadband optical limiting
Krishna M.B.M., Venkatramaiah N., Venkatesan R., Rao D.N.
Conference paper, Optics InfoBase Conference Papers, 2012,
View abstract ⏷
Graphene oxide-ZnO/TiO2nanoparticles are synthesized for optical limiting. Micro Raman studies reveal that GO sheets are limited to 6-8 layers. UV-Vis and FTIR results demonstrated that GO with ZnO/TiO2nanoparticles are successfully conjugated.
Graphene oxide (GO)-semiconductor (ZnO, TiO2) nanoparticles for broadband optical limiting
Krishna M.B.M., Venkatramaiah N., Venkatesan R., Rao D.N.
Conference paper, 2012 International Conference on Fiber Optics and Photonics, PHOTONICS 2012, 2012, DOI Link
View abstract ⏷
Graphene oxide-ZnO/TiO2 nanoparticles are synthesized for optical limiting. Micro Raman studies reveal that GO sheets are limited to 6-8 layers. UV-Vis and FTIR results demonstrated that GO with ZnO/TiO2 nanoparticles are successfully conjugated. © 2012 OSA.
A new diketopyrrolopyrrole-based co-polymer for ambipolar field-effect transistors and solar cells
Tandy K., Dutta G.K., Zhang Y., Venkatramaiah N., Aljada M., Burn P.L., Meredith P., Namdas E.B., Patil S.
Article, Organic Electronics, 2012, DOI Link
View abstract ⏷
A new thieno[3,2-b]thiophenediketopyrrolopyrrole-benzo[1,2-b:4,5-b′] dithiophene based narrow optical gap co-polymer (PTTDPP-BDT) has been synthesized and characterized for field-effect transistors and solar cells. In field-effect transistors the polymer exhibited ambipolar charge transport behaviour with maximum hole and electron mobilities of 10-3 cm 2 V-1 s-1 and 10-5 cm2 V-1 s-1, respectively. The respectable charge transporting properties of the polymer were consistent with X-ray diffraction measurements that showed close molecular packing in the solid state. The difference in hole and electron mobilities was explained by density functional theory calculations, which showed that the highest occupied molecular orbital was delocalized along the polymer backbone with the lowest unoccupied molecular orbital localized on the bis(thieno[3,2-b]thiophene)diketopyrrolopyrrole units. Bulk heterojunction photovoltaic devices with the fullerene acceptor PC70BM were fabricated and delivered a maximum conversion efficiency of 3.3% under AM1.5G illumination. © 2012 Elsevier B.V. All rights reserved.
Nonlinear optical properties of graphene- (OH, Sn) porphyrin composites in picosecond regime
Krishna M.B.M., Venkatramaiah N., Venkatesan R., Rao D.N.
Conference paper, AIP Conference Proceedings, 2011, DOI Link
View abstract ⏷
The nonlinear optical (NLO) properties of covalently linked Graphene-(Sn, OH) porphyrin composite materials were investigated using Z-scan technique at 532 nm with picosecond laser pulses. We have observed enhanced figure of merit values for composites in comparison with individual graphene, copper and zinc porphyrin. The enhanced figure of merit values for graphene-porphyrin composite material should be attributed to two-photon absorption and excited state absorption. We also observed different behavior, reverse saturable absorption to saturable absorption and back to reverse saturable absorption in composite molecules leading to better ultrafast nonlinear optical switching applications. © 2011 American Institute of Physics.
Environment effect on the optical and photophysical investigation of Al(III)Porphyrins doped hybrid borate glasses
Article, Materials Chemistry and Physics, 2011, DOI Link
View abstract ⏷
Hybrid borate glasses containing a series of Al(III)Porphyrins were prepared by rapid melt quench technique at 230 °C. The hybrid glass samples were characterized by X-ray diffraction, optical absorption, steady state and time resolved fluorescence emission. Upon exposure to UV light at 260 nm, the glass samples exhibit strong blue emission and red emission at 365 nm. The appearance of large stokes shift (Δυ) and enhanced S2 → S0 emission at ∼495 nm indicates that structure of Al(III)Porphyrins were inherently modified in glass matrix. Time resolved fluorescence of the hybrid glasses shows three exponential decay with τ1 = 0.11-0.59 ns, τ2 = 3.13-3.95 ns and τ3 = 8.13-9.56 ns. In the present study, we investigate the influence of glassy environment on the photophysical properties and the structure of Al(III)Porphyrins in borate glass was modeled through DFT calculations. © 2011 Elsevier B.V. All rights reserved.
Emission features of Ho3 ion in Nb2O5, Ta2O5 and La2O3 mixed Li 2OZrO2SiO2 glasses
Srikumar T., Brik M.G., Rao C.S., Venkatramaiah N., Gandhi Y., Veeraiah N.
Article, Physica B: Condensed Matter, 2011, DOI Link
View abstract ⏷
Li2OZrO2SiO2: Ho3 glasses mixed with three interesting d-block elemental oxides, viz., Nb2O 5, Ta2O5 and La2O3, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb 2O5 and Ta2O5 mixed Li 2OZrO2SiO2 glasses (free of Ho3 ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta5 and Nb5 ions in the glass network. The JuddOfelt theory was successfully applied to characterize Ho3 spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio βr and the radiative lifetime τr, for 5S2 emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for 5S2 level of Ho3 ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La2O3 mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho3 ions. © 2011 Elsevier B.V.
Optical and luminescence investigations of hydroxy substituted porphyrins in borate glasses
Article, Solid State Sciences, 2011, DOI Link
View abstract ⏷
Hybrid borate glasses containing various hydroxy phenyl derivatives of porphyrin were prepared by melt quenching technique. The effect of hydroxy functional groups on the photophysical properties was investigated by means of optical absorption, steady-state fluorescence and time resolved fluorescence spectroscopy. The optical absorption spectra show red shift in Soret and Q-band with increase in the number of -OH groups on the phenyl ring of the porphyrin. The steady-state emission spectrum shows strong S2→S0 emission around 498-540 nm and red shifted S1→S0 emission around 669-803 nm. Time resolved fluorescence shows three exponential decay with τ1 = 11 ± 2 ps (64.56%), τ2 = 0.16 ± 0.1 ns (24.54%), and τ3 = 2.94 ± 0.1 ns (10.9%) for 2 mg of H2OHP doped glass. The appearance of strong S2→S0 emission indicates that the structure of porphyrin inherently modified in the glass matrix. The boron ions of the borate network interact at the central core of the porphyrin and also form oxy bridge at the periphery. The effect of porphyrin concentration on photophysical properties and the possible structures of porphyrin in the borate glass matrix were investigated. © 2010 Elsevier Masson SAS. All rights reserved.
Microstructural, dielectric and spectroscopic properties of Li 2ONb2O5ZrO2SiO2 glass system crystallized with V2O5
Srikumar T., Srinvasa Rao Ch., Gandhi Y., Venkatramaiah N., Ravikumar V., Veeraiah N.
Article, Journal of Physics and Chemistry of Solids, 2011, DOI Link
View abstract ⏷
Li2ONb2O5ZrO2SiO2 glasses mixed with different concentrations of V2O5 were crystallized. The samples were characterized by XRD, SEM and DTA techniques. The SEM pictures indicated that the samples contain well defined and randomly distributed crystal grains. The X-ray diffraction studies have revealed the presence of several crystalline phases in these samples. Optical absorption, ESR and photoluminescence spectral studies on these samples have indicated that a considerable proportion of vanadium ions do exist in V4 state in addition to V5 state and the redox ratio seems to be increasing with increase in the concentration of crystallizing agent V2O5. The infrared spectral studies have pointed out the existence of conventional SiO4, ZrO4, NbO6, VO structural units in the glass ceramic network. The study of dielectric properties suggested a decrease in the insulating character of the glass ceramics with increase in the crystallizing agent. A.C. conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from V4↔V5 ions. © 2010 Elsevier Ltd All rights reserved.
Nonlinear optical properties of covalently linked graphene-metal porphyrin composite materials
Krishna M.B.M., Kumar V.P., Venkatramaiah N., Venkatesan R., Rao D.N.
Article, Applied Physics Letters, 2011, DOI Link
View abstract ⏷
The nonlinear optical (NLO) and optical limiting (OL) properties of covalently linked graphene-porphyrin composite materials were investigated using Z-scan technique in nanosecond regime. We observed enhanced NLO and OL properties of graphene-porphyrin composites in comparison to the individual graphene and porphyrins. The improved OL property of composites is attributed to energy transfer between porphyrin and graphene, which improved excited state absorption and nonlinear scattering. Nonlinear optical susceptibilities X(3) of graphene and graphene-porphyrin composites were, in the order of 10 -12 esu, measured using degenerate four wave mixing technique in nanosecond regime. High values of excited state absorption and two-photon absorption were observed for the composites. © 2011 American Institute of Physics.
Porphyrin based hybrid borate glasses: Structure and photophysical investigation
Article, Materials Chemistry and Physics, 2011, DOI Link
View abstract ⏷
Freebase tetra phenyl porphyrin (H2TPP) and its derivatives in different concentration ranges (0.5-2.0 mg per 12 g of boric acid) were incorporated into borate glass matrix by melt quenching technique at 230 °C. The formed glasses were stable and in green colour. The optical absorption and emission properties are different from that observed in solutions. The absorption spectrum shows a two line pattern Soret band at 435-454 nm and Q-band at 665-701 nm. The emission spectrum shows strong S2 → S 0 emission at 490-520 nm region and S1 → S 0 emission at 725-810 nm. The time resolved fluorescence decay of S1 → S0 emission shows three exponential decay. For example, in the case of 2 mg of H2THP doped glass the lifetimes were found to be τ1 = 0.511 ns (26.7%), τ2 = 10 ps (64.68%) and τ3 = 3.965 ns (8.62%). These unusual photophysical properties were found to arise from different structural motifs of porphyrin in the glass. These structures were further modeled through reactions of porphyrin with BF3O(C2H5) in solution and DFT calculations. © 2010 Elsevier B.V. All rights reserved.
Spectroscopic and dielectric studies of meso-tetrakis(p-sulfonatophenyl) porphyrin doped hybrid borate glasses
Article, Journal of Alloys and Compounds, 2011, DOI Link
View abstract ⏷
Hybrid borate glasses containing different concentrations of meso-tetrakis(p-sulfonatophenyl) porphyrin sodium salt (TPPS4) were prepared. The obtained glass samples were found to be transparent and homogeneous. Formation of TPPS4-J-aggregates in borate glass was investigated by means of optical absorption, steady state and time resolved fluorescence spectroscopy. The hybrid glasses exhibit a strong S 2→S0 emission at ∼473 nm and J-aggregates show emission at ∼733 nm. Time resolved fluorescence show two exponential decay with lifetime of τ1 = 65 ± 10 ps (∼80%) and τ2 = 3.87 ± 0.1 ns (∼20%) respectively. Dielectric properties such as dielectric constant (ε′), dielectric loss (tan δ) and ac conductivity (σac) over a range of frequency and temperature of these glasses were studied. The ac conductivity was found to be proportional to ωs (where s < 1). The observed change in dielectric parameters due to different concentrations of TPPS4 has been analyzed in light of different polarization mechanisms. © 2010 Elsevier B.V. All rights reserved.
Optical and photophysical investigation of Meso, Proto and Hematoporphyrin(IX)dimethylester doped hybrid borate glasses
Article, Physica B: Condensed Matter, 2011, DOI Link
View abstract ⏷
Hybrid borate glasses containing different concentrations (0.52.0 mg in 12 g of boric acid) of Mesoporphyrin(IX)dimethylester, Protoporphyrin(IX) dimethylester and Hematoporphyrin(IX)dimethylester were prepared by rapid melt quench technique at 230 °C. The hybrid glass samples were characterized by X-ray diffraction, optical absorption, steady state and time-resolved fluorescence emission. The optical absorption spectrum shows red-shift in Soret band along with change in Q-band pattern. The intensity of Q-band was found to increase with increase in the concentration of porphyrin in the glass. Steady state emission spectrum shows strong S2→S0 emission in the range 462495 nm and blue shift in S1→S0 emission. Time-resolved fluorescence emission and fluorescence excitation spectra showed that different structures of porphyrins were exist in the glass samples. The variation in the spectral behaviour in the glass was correlated with those in solution medium and possible structures of porphyrin in borate glass were explored. © 2010 Elsevier B.V. All rights reserved.
Influence of crystallization on the luminescence characteristics of Pr 3+ ions in PbO-Sb2O3-B2O3 glass system
Satyanarayana T., Brik M.G., Venkatramaiah N., Kityk I.V., Plucinski K.J., Ravikumar V., Veeraiah N.
Article, Journal of the American Ceramic Society, 2010, DOI Link
View abstract ⏷
PbO-Sb2O3-B2O3 glasses mixed with different concentrations of Pr2O3 (ranging from 0 to 0.6 mol%) were crystallized. The samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy techniques. The XRD studies have revealed the presence of Pb5Sb2O8, Pb 3(SbO4)2, PbB4O7, β-PrSbO4, Pr3SbO7, and Pr 3Sb5O12 crystalline phases. Optical absorption (in the visible and NIR regions) and fluorescence spectra of these samples have been recorded at room temperature. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of Pr 3+ ions in these samples. From the luminescence spectra, various radiative properties like transition probability A, branching ratio βr, and the radiative lifetime τr for various emission levels originating from the 3P0 level of Pr 3+ ion in the glasses glass ceramic samples have been evaluated. The radiative lifetime of the 3P0→3H 6 transition is measured and the quantum efficiency has been estimated. The crystallization causes to improve the luminescence efficiency to a large extent. The changes observed in the radiative properties due to crystallization have been discussed in the light of varying co-ordinations of antimony ions in the glass network. © 2010 The American Ceramic Society.
Spectroscopic investigations on PbO-As2O3 glasses crystallized with TiO2
Nagarjuna G., Satyanarayana T., Ravi Kumar V., Venkatramaiah N., Satyanarayana P.V.V., Veeraiah N.
Article, Philosophical Magazine, 2009, DOI Link
View abstract ⏷
PbO-As2O3 glasses mixed with different concentrations of TiO2 (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy (EDS) techniques. Studies were extended to optical absorption, IR, ESR, luminescence and magnetic susceptibility on these samples. The X-ray diffraction studies reveal the presence of Pb3O4, Ti(As2O7), Pb(As2O6), Pb3(AsO4)2 PbTi3O7 and Ti2O3 crystal phases. The optical absorption studies together with ESR and magnetic susceptibility measurements indicated that the titanium ions exist in both Ti3+ and Ti4+ states in all the samples and there is an increase in titanium ions in the trivalent state with increasing concentration of nucleating agent TiO2. The quantitative analysis of these results indicated that there is a growing degree of disorder in the glass network with increasing concentration of the crystallizing agent. The luminescence studies indicated that the samples crystallized with low concentrations of TiO2 show high luminescence efficiency in the visible region.
Spectroscopic and dielectric properties of ZnF2-As2O3-TeO2 glass system doped with V2O5
Gandhi Y., Venkatramaiah N., Ravi Kumar V., Veeraiah N.
Article, Physica B: Condensed Matter, 2009, DOI Link
View abstract ⏷
ZnF2-As2O3-TeO2 glasses mixed with different concentrations of V2O5 (ranging from 0 to 0.6 mol%) were synthesized. The amorphous nature of these glasses was checked by X-ray diffraction and scanning electron microscopy techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra and dielectric properties (constant ε′, loss tan δ, ac conductivity σac over a wide range of frequency and temperature) of these glasses have been explored. The optical absorption, electron spin resonance studies together indicated vanadium ions coexist in V4+ with V5+state in these samples. The IR spectra of these samples have exhibited bands due to νs-TeO2ax and AsO3 structural groups; these results indicated the most structural disorder in the network as the concentration of V2O5 is increased. Luminescent emission spectra recorded at room temperature of these glasses excited at 640 nm have exhibited a broad emission band in the spectral wavelength range of 750-850 nm. The luminescence efficiency is found to be the highest for the sample doped with 0.6 mol%. The dielectric parameters viz., ε′, tan δ and σa.c are found to increase and the activation energy for ac conduction is found to decrease with the increase in the concentration of V2O5 up to 0.6 mol%, reflecting an increase in the concentration of V4+ ions that take part modifying positions in the glass network. The ac conduction in these glasses could satisfactorily be explained by both classical activation energy and the tunneling phenomena. © 2009 Elsevier B.V. All rights reserved.
Fe2O3-induced crystallization and the physical properties of lead arsenate glass system
Nagarjuna G., Venkatramaiah N., Satyanarayana P.V.V., Veeraiah N.
Article, Journal of Alloys and Compounds, 2009, DOI Link
View abstract ⏷
PbO-As2O3 glasses mixed with different concentrations of Fe2O3 (ranging from 0 to 2.0 mol%) were crystallized. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques. Studies were extended to optical absorption, IR, ESR and magnetic susceptibility on these glass ceramic samples. The X-ray diffraction and scanning electron microscopic studies reveal the presence of PbFe4(As5O11)2, Fe2PbAs2O6 crystal phases. The optical absorption studies together with ESR and magnetic susceptibility measurements indicated the dominant presence of iron ions in the trivalent state when the concentration of nucleating agent Fe2O3 is less than 0.3 mol%. The analysis of the IR spectra indicated a gradual transformation of iron ions from tetrahedral sites to octahedral sites as the concentration of Fe2O3 is increased beyond 0.3 mol%. © 2008 Elsevier B.V. All rights reserved.
Features of the local structural disorder in Li2O-CaF2-P2O5 glass-ceramics with Cr2O3 as nucleating agent
Murali Krishna G., Gandhi Y., Venkatramaiah N., Venkatesan R., Veeraiah N.
Article, Physica B: Condensed Matter, 2008, DOI Link
View abstract ⏷
Li2O-CaF2-P2O5 glasses mixed with different concentrations of Cr2O3 (ranging from 0 to 1.0 mol%) were crystallized. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy (EDS), differential thermal analysis and conventional spectroscopic techniques. The X-ray diffraction and scanning electron microscopic studies reveal the presence of lithium phosphate, calcium phosphate and chromium phosphate (complexes of Cr3+, Cr5+ and Cr6+ ions) crystal phases. The study on DTA suggests that the crystallization is predominantly due to the surface crystallization when the concentration of nucleating agent Cr2O3 is around 0.8 mol%. The IR and Raman spectral studies of these samples indicate that the sample crystallized with 0.8 mol% Cr2O3 is more compact and possesses high rigidity due to the presence of chromium ions largely in tetrahedral positions. © 2007 Elsevier B.V. All rights reserved.
Induced crystallization and physical properties of Li2O-CaF2-P2O5:TiO2 glass system. Part I. Characterization, spectroscopic and elastic properties
Krishna G.M., Veeraiah N., Venkatramaiah N., Venkatesan R.
Article, Journal of Alloys and Compounds, 2008, DOI Link
View abstract ⏷
Li2O-CaF2-P2O5 glasses mixed with different concentrations of TiO2 (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The samples are characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. Spectroscopic properties (IR and Raman) and elastic properties (viz., Young's modulus E, shear modulus G and micro-hardness H) at room temperature are studied. The X-ray diffraction and the scanning electron microscopic studies revealed the presence of lithium phosphate, lithium titanium phosphate and titanium phosphate crystal phases. The differential thermal analysis traces of these samples exhibit three crystalline temperatures. The IR and Raman spectra of these samples have exhibited bands due to TiO4 and TiO6 structural units in addition to the conventional bands due to various phosphate structural groups. The analysis of these results indicated that the sample crystallized with 0.6 mol% of TiO2 possesses the highest density, high mechanical strength and more compact network. © 2006 Elsevier B.V. All rights reserved.
Induced crystallization and physical properties of Li2O-CaF2-P2O5:TiO2 glass system. Part II. Electrical, magnetic and optical properties
Krishna G.M., Veeraiah N., Venkatramaiah N., Venkatesan R.
Article, Journal of Alloys and Compounds, 2008, DOI Link
View abstract ⏷
The results of various physical properties namely, dielectric properties (dielectric constant, loss tan δ, ac conductivity σ, over a wide range of frequency and temperature and dielectric breakdown strength in air medium at room temperature), optical absorption, electron spin resonance (ESR) at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li2O-CaF2-P2O5:TiO2 glass-ceramics have been reported. The optical absorption and magnetic susceptibility studies indicated that the titanium ions exist in Ti3+ state in addition to Ti4+ state in these samples. However, the reduction seems to be the lowest in the sample containing 0.6 mol% of TiO2. The dielectric constant and loss variation with the concentration of TiO2 have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analyzed by a pseudo Cole-Cole plot method and the spreading of dielectric relaxation has been observed. The ac conductivity in the high temperature region seems to be related both with electronic and ionic movements. The low temperature (or the nearly temperature independent) part of conductivity could be explained on the basis of quantum mechanical tunneling model. The studies on dielectric breakdown strength indicated the highest insulating strength for the sample containing 0.6 mol% of TiO2. © 2006 Elsevier B.V. All rights reserved.
