Graphene quantum dots (GQDs) exhibit appealing photoluminescence (PL), and their spectral characteristics can be effectively modulated through dopant incorporation and tailored surface functionalization. However, existing heteroatom-doped GQD systems remain confined to visible emission, and the role of rare-earth coordination in restructuring the GQD emissive landscape is not yet systematically established. Here, we systematically examine neodymium-doped graphene quantum dots (Nd-GQDs) as the primary broadband emissive system, using pristine GQDs, nitrogen-doped (N-GQDs), and nitrogen/sulfur co-doped (NS-GQDs) as comparative controls, to elucidate how Nd incorporation uniquely modulates excitation dynamics, emissive-state activation, and spectral breadth. Excitation-dependent PL, contour maps, and peak-tracking analyses show that pristine, N-, and NS-GQDs each maintain a single emission band with clear excitation-independent regions followed by excitation-dependent dispersion, consistent with selective population of surface/edge traps. In contrast, Nd-GQDs distinctly exhibit two emission bands at all excitations, originating from simultaneous activation of graphitic π-states and Nd-induced mid-gap states. This dual-channel behavior produces alternating excitation-dependent and independent regimes that collectively generate intrinsic UV–visible broadband emission. CIE chromaticity mapping confirms that Nd-GQDs uniquely achieve central white-light coordinates and extend toward the deep-red boundary of the visible gamut, while the PL emission spans a broad 350-750 nm window reaching the NIR-I onset, whereas the other GQDs show narrower, continuous trajectories. These findings establish Nd-GQDs as intrinsic single-component white-light emitters with Vis–NIR-I onset reach, capabilities not accessible in heteroatom-doped GQDs — providing a viable carbon-based platform for solid-state lighting, optical tagging, and dual visible–NIR photonic applications.

Nitrogen-doped graphene quantum dots (N-GQDs) are tunable nanoscale fluorophores whose photoluminescence (PL) is governed by core states, edge defects, and surface chemistry. Beyond these intrinsic factors, the surrounding medium can fundamentally alter their optical response, yet the influence of solvent-induced self-assembly on polarized emission has remained largely overlooked. Here, we provide the first direct spectroscopic evidence that solvents not only modulate emission intensity but also drive quasi-alignment of emitting dipoles in N-GQDs, producing liquid-crystal-like ordering within colloidal dispersions. Polarization-resolved PL reveals that the three principal emissive pathways of N-GQDs respond differently to solvent environments: non-polar solvents with high positive zeta potential promote tighter dipole alignment and stronger polarization anisotropy, whereas polar solvents broaden orientation distributions and stabilize excited states. These findings establish solvent-induced self-assembly as a critical mechanism for tailoring polarized emission in N-GQDs, opening new directions for solvent-responsive nanomaterials in adaptive light sources, reconfigurable optoelectronics, and next-generation energy-harvesting platforms.

As a popular process in molecular-based diagnostics, polymerase chain reaction (PCR) can be employed for amplifying small amounts of DNA/RNA from different sources such as tissue, cells, peripheral blood and so on. Thanks to the unique physicochemical characteristics of nanomaterials and their progress, researchers have been encouraged to employ them as suitable candidates to address the PCR optimization challenges for enhancing efficiency, yield, specificity, and sensitivity. In nanoparticle-assisted PCR (nanoPCR), different nanoparticles (NPs) such as carbon nanotubes (CNTs), graphene, quantum dots (QDs), and gold (Au) might be used. Among different nanoPCR assays, photothermal PCR has emerged as a technique leveraging the excellent light absorption and heat conversion capabilities of nanomaterials. In addition to presenting recent advances in nanoPCR, this review also delves into the specific use of nanomaterials for photothermal PCR, including their applications in microfluidics as one of the best platforms for miniaturization of diagnostic techniques. Different types of NPs used in PCR are comprehensively examined, and detailed charts and tables are provided that outline features such as optimal concentration and size. The appropriate choice of nanomaterials for enhancing light conversion to heat in PCR applications is discussed. Finally, the related challenges and future trends are explored. (Figure presented.)

3-Nitro-L-tyrosine (3NT) is a key biomarker of oxidative stress associated with neurodegenerative and cardiovascular diseases. Here, we report a selective optical sensing strategy based on photoluminescence (PL) quenching of nitrogen and sulfur co-doped graphene quantum dots (NS-GQDs) synthesized from garlic, a natural and sustainable precursor. PL quenching by 3NT is driven by static interactions, as revealed by single-particle near-field IR spectroscopy. Time-dependent density functional theory indicates that complexation with 3NT induces a significant reduction in the oscillator strength of key excited states in the NS-GQDs, suppressing radiative transitions and suggesting the formation of a non-emissive “dark states”. This interaction creates an unambiguous optical fingerprint for 3NT, enabling highly selective molecular recognition. Our findings establish a mechanistic blueprint for the rational design of biocompatible carbon-based nanomaterials for next-generation sensing platforms.

Understanding the relationship between the local chemical structure and photoluminescence (PL) in graphene quantum dots (GQDs) and nitrogen-functionalized GQDs (N-GQDs) is critical for their advancement in optoelectronics, sensing, and bioimaging. Ensemble measurements mask the structural and functional heterogeneity intrinsic to these quasi-zero-dimensional systems. Here, we employed single-particle photo-induced force microscopy (PiFM) to chemically map individual GQDs and N-GQDs, revealing diverse surface functional groups and bonding architectures that are obscured in bulk analyses. PiFM-IR spectra correlate well with vibrational modes predicted by density functional theory (DFT) on model structures incorporating oxygen and nitrogen functionalities. While ensemble characterization techniques such as Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy support the findings of single-particle analysis, the latter offers significantly superior spatial and chemical resolution. Optical features of the GQDs and the N-GQDs show size- and chemical structure-dependent behaviour such as excitation-dependent emission thresholds and biexponential decay dynamics. These observations support a dual recombination mechanism involving band-edge-to-band-edge transitions and surface-/dopant-mediated transition pathways. By integrating these methods, we established a robust framework for connecting a structure with optical behaviour, highlighting the importance of single-particle studies for rational design of carbon-based quantum materials.

This study explored the effects of Neodymium-doped graphene quantum dots (NdGQDs) on improving the performance efficiency of TiO2 based dye-sensitized solar cells (DSSCs). By employing in-situ physical assisted mixing, DSSCs with optimized NdGQDs in TiO2 photoanodes showed a power conversion efficiency of 8.76 %, a significant improvement compared to the 6.01 % efficiency of pristine TiO2-based DSSCs under 100 mW cm⁻2 illumination (AM 1.5). Notably, the short-circuit current density increased by 74 %. HRTEM analysis revealed that the NdGQDs have a size range of approximately 7–9 nm. UV–visible spectroscopy and Mott-Schottky analysis revealed a positive shift in the Fermi level, promoting better electron transfer and increased photocurrent density at the expenses of the open circuit voltage. Electrochemical impedance spectroscopy characterization of DSSCs incorporating NdGQD-modified photoanodes revealed a reduction in electron transfer resistance at the photoanode|dye|electrolyte interface, accompanied by an increase in recombination resistance within the device suppressing the electron recombination rate.

The publication presents a streamlined and economical technique for fabricating advanced electrode materials to enhance the energy storage capabilities of supercapacitors (SCs). The focus is on synthesizing neodymium-doped graphene quantum dots (Nd-GQDs) via a microwave-assisted hydrothermal (MAH) process. This method uses microwave irradiation's rapid heating and efficient energy transfer under low pressure and minimal reaction time. The resulting Nd-GQDs exhibit enhanced electrochemical properties, including increased capacitance and improved charge storage, making this approach practical and effective for advancing supercapacitor technology. An exceptional specific capacitance of 618 F g−1 at a 5 mV s−1 scan rate is demonstrated using Nd-GQDs as the SC electrode material. Due to their high specific capacitance, Nd-GQDs, when combined with polyaniline (PANI), improve the energy and power density of SCs. Nd-GQDs/PANI composites with varying amounts of Nd-GQDs in symmetric SCs are fabricated to demonstrate their promising properties for SC applications. SCs fabricated with 20 mL of Nd-GQDs in the PANI matrix showed a superior specific capacitance of 354 F g−1 at a current density of 1 A g−1, while the energy density and power density were 49.15 Wh kg−1 and 2000 W kg−1, respectively.

Black phosphorus (BP) has been studied extensively as a recently developed mono-elemental nanomaterial due to its intriguing physical properties, which include a layer-based tunable band gap, elevated carriers' movement, outstanding mechanical resistance, and unique in-plane anisotropic optical, thermal, and vibrational properties. As a novel two-dimensional (2D) BP may be skinned into nanosheets. Due to its 2D shape, inherent high strength, and remarkable electrical capabilities, black phosphorene, like 2D graphene, delivered an ability to be employed as nano additives to enrich diverse applications. Nevertheless, the unsteadiness induced by chemical deterioration of its surface has made future uses difficult. To address this issue, a targeted BP/polymers (BP/P′) strategy was recently designed and applied, resulting in the development of BP/P′ with improved stability as well as remarkable thermal, mechanical, electrical, and optical characteristics. Many efforts have recently been made to stabilize BP in the air to increase its compatibility with polymers. In this chapter, we discussed the synthesis methods, chemical functionalization, and key characters of BP/P′, after that a comprehensive area of their diverse purposes, which include optoelectronics, biomedicine, flame retardancy, energy storage, catalysis, mechanical, and thermal properties. The primary methodologies for chemical modifications of 2D BP with diverse organic and inorganic stuff as extremely stable and multifunctional polymer nanocomposites, as well as its recent advancements in the area of energy and catalysis, are also discussed. Conclusively, the potential problems and future directions of BP were emphasized and explored in accordance with the present developments.

Polymer nanocomposites (PNCs) have grown into a fashionable area of recent research with high concert, conquering the flaws of mass polymers (Ps) and meeting the demands of civilization and the market in tribological and rheological applications. Ps together with ultrahigh molecular mass Ps are hugely widespread Ps in present-day research in rheology, including tribology. This study accurately analyses current PNC advancements in tribology and rheology. The effects of various nanofiller (NF) divisions, such as carbon-based, silicon-based, and hybrid fillers combined with metal oxide, on the rheological and tribological applications of PNCs are investigated. Because the rheological and tribological actions of PNCs are never innate, nevertheless, they rely on sliding assets and direct co-relation surrounded by distinct divisions of NF as a choice of similar NF of differing morphologies and structures is never reasonable. Wear and irritation rates are fair to indicate provisional enhancement through different NFs. Prominence is simulated to the effect of NF absorption and superficial functionalization of NFs for wear resistance, irritation, transfer film arrangement, and wear structure like its composites. Constraints and forthcoming research capacity on rheology, together with tribology of PNCs, are concluded.

The thermoelectric (TE) phenomenon, which involves the direct interconversion of heat and electricity, holds huge promise for green energy generation and refrigeration. The TE option, however, faces a major materials bottleneck-the TE conversion efficiency of known materials is very low, which seriously restricts their application in real-life devices. A substantial amount of effort has been directed during the past three decades to design and develop new materials with enhanced TE conversion efficiency. In this regard, 2D semiconductors have attracted special attention in recent times due to the novel transport mechanisms observed in such materials. Many 2D semiconductors allow independent tuning of electrical and thermal conduction while maintaining reasonably high thermal voltage gradient, which is a prerequisite for enhanced TE efficiency. In this chapter, we discuss the challenges and opportunities of some important 2D semiconductors as potential high-efficiency TE materials.

The current invention pertains to the expeditious simple synthesis of electrode materials that improve the storage capacity of supercapacitors (SCs). Sulfur and nitrogen co-doped graphene quantum dots (SN-GQDs) are synthesized using a microwave-assisted hydrothermal (MAH) process at low pressure and with a short reaction time. The utilization of SN-GQDs in conjunction with Polyaniline (PANI) has the potential to enhance the supercapacitor's energy and power density, owing to their notable specific capacitance. Implementing SN-GQDs material as an SCs electrode, exhibiting an outstanding specific capacitance of 1040 F/g at an applied current density of 0.5 A g−1. Furthermore, a composite of SN-GQDs/PANI is synthesized and the electrochemical performance is compared with the as-synthesized PANI. The symmetrical SCs are fabricated using SN-GQDs/PANI composite, and PANI. At a current density of 0.5 A g−1 SN-GQDs/PANI composite-based SC displays a superior energy density of 44.25 Wh/kg at a power density of 1.227 kW/kg. This is high in comparison to PANI-based SC which shows an energy density of 18.71 Wh/kg at 0.8 kW/kg power density at the same current density. The SC created using SN-GQDs/PANI composite exhibits superior properties and is a promising material for SC applications.

Incorporating heteroatoms into graphene lattice results in enhanced electrical conductivity and electrochemically active sites and has significant importance in developing high-performance supercapacitors. In this study, sulfur and nitrogen co-doped graphene aerogel is synthesized via hydrothermal technique followed by a simple but effective freeze-thawing and ambient pressure drying process (referred to as SN-GA). The process requires low-cost raw materials and cost-effective equipment without the utilization of any special instrument that operates at ultra-low temperatures, under high pressure, or vacuum environment. Ammonium sulfate [(NH4)2SO4] and ethylenediamine are used as a source of sulfur and nitrogen and as a reducing agent. (NH4)2SO4 with different molarities (0, 12, 24, and 36 mM) are used to synthesize four different aerogel samples marked as GA, SN-GA1, SN-GA2, and SN-GA3. The electrode is prepared using an SN-GA2 sample, exhibiting an outstanding specific capacitance of 244 F g−1 at an applied current density of 1 A g−1 with almost 98.5% Coulomb efficiency. Furthermore, based on the SN-GA2 sample, the symmetrical supercapacitor is fabricated, displaying an energy density of 18.14 Wh kg−1 at a power density of 498.4 W kg−1. Hence, SN-GA2 renders a promising material for supercapacitor applications.

A luminescent silicon nanoparticle embedded gel-glass, prepared by room temperature hydrolysis and reduction of aminosilane, exhibits intriguing dual photoluminescence (PL) from opposite faces of the glass. The face, which is excited with UV, exhibits excitation energy dependent blue-green emission. As the excitation energy is varied from 350 nm to 450 nm the PL peaks shift from 435 nm to 506 nm. The opposite surface, on the other hand emits nearly excitation independent green light – the PL peak shifts by ∼17 nm as the excitation energy is varied from 350 nm to 450 nm. The luminescent properties provide interesting insights into the light emission mechanism from nanostructured silicon. Spectral filtering by reabsorption and photon reabsorption-reemission in a size distributed nanoparticle system having different optical gaps play a combined role in the observed dual emission. We show that the dual emission can be tuned by simply varying the thickness of the glass. Such dual emission renders the luminescent glass amenable for several applications as a novel solid state display material.

Biopolymer microgels present many opportunities in biomedicine and tissue engineering. To understand their in vivo behavior in therapeutic interventions, long-term monitoring is critical, which is usually achieved by incorporating fluorescent materials within the hydrogel matrix. Current research is limited due to issues concerning the biocompatibility and instability of the conventional fluorescent species, which also tend to adversely affect the bio-functionality of the hydrogels. Here, we introduce a microfluidic-based approach to generate nitrogen-functionalized graphene quantum dot (NGQD) incorporated gelatin methacryloyl (GelMA) hydrogel microspheres, capable of long-term monitoring while preserving or enhancing the other favorable features of 3D cell encapsulation. A multilayer droplet-based microfluidic device was designed and fabricated to make monodisperse NGQD-loaded GelMA hydrogel microspheres encapsulating skeletal muscle cells (C2C12). Control over the sizes of microspheres could be achieved by tuning the flow rates in the microfluidic device. Skeletal muscle cells encapsulated in these microgels exhibited high cell viability from day 1 (82.9 ± 6.50%) to day 10 (92.1 ± 3.90%). The NGQD-loaded GelMA microgels encapsulating the cells demonstrated higher metabolic activity compared to the GelMA microgels. Presence of sarcomeric α-actin was verified by immunofluorescence staining on day 10. A fluorescence signal was observed from the NGQD-loaded microgels during the entire period of the study. The investigation reveals the advantages of integrating NGQDs in microgels for non-invasive imaging and monitoring of cell-laden microspheres and presents new opportunities for future therapeutic applications.

Up-conversion photoluminescence (UCPL) and dual-band photoluminescence (DBPL) are two widely-reported, exotic properties of graphene quantum dots (GQDs). However, both these phenomena can be associated with measurement artefacts. In case of excitation with monochromatic radiation derived from a white light source, the second order of the excitation or the emission signal can cause misleading impressions of UCPL and DBPL. Laser excitations can also generate spurious UCPL and/or DBPL signals due to leaking radiations. Using a spatially separated femtosecond pulsed laser, we find that in nitrogen-functionalized GQDs there is no evidence for DBPL although a real UCPL is hidden behind spurious signals.

Nano-inks, which are usually formed by dispersing a nanostructured material in some solvent, have shown great promise as security inks that can be used to develop anticounterfeiting technologies. A variety of nanomaterials such as carbon-based zero-dimensional materials (carbon dots and graphene quantum dots), semiconductor quantum dots, lanthanide nanocrystals, nano-polymers, nanostructured perovskites, metal organic frameworks have been investigated for potential applications as security inks. Nanostructured material-based inks are preferred as security inks owing to their unique and robust photophysical properties, ease of functionalization, fast stimulus-responsive system, and cost-effectiveness. Different types of luminescence observed in a wide variety of nanoscale materials are usually employed to make security marks that are invisible under visible light but become distinct under some external stimuli. Based on this simple principle, high-security data encryption and decryption with nano-inks have been demonstrated. In this chapter, we discuss the various types of nanostructure-based security-inks developed, their strengths and limitations, projected applications, and the governing mechanisms of each application.

Excitation-dependent, multicolor emission from different varieties of 0D carbon systems has attracted immense research attention. It is generally accepted that some variants of 0D carbon exhibit excitation dependent emission, while other variants do not. A third variant exhibits both excitation dependent as well as excitation independent emission. In this work we investigate the structure, composition, steady-state emission-excitation and photoluminescence decay dynamics of three distinctly different variants of 0D carbon-amorphous carbon dots (aCDs), graphene quantum dots (GQDs) and nitrogen-doped GQDs (NGQDs). We find that despite significant differences in the structure and composition there is a striking similarity in the excitation energy dependence of the emission characteristics of these three different dots. All of them exhibit excitation energy independent emission below some threshold wavelength (λth), and above this threshold the emission becomes excitation dependent. We also demonstrate that a similar trend is apparent for nearly all variants of 0D carbon reported in the literature. The threshold wavelength correlates well with the excitation wavelength for the most intense emission and the photoluminescence excitation peaks, suggesting a common origin of light emission in these carbon dots. The findings provide important clues for developing a unified general picture for understanding the light emission mechanism in 0D carbon nanostructures. This journal is

Nitrogen-functionalized graphene quantum dots embedded in a polyaniline matrix (NGQD-PANI) are extremely promising candidates for the development of next-generation sensors and for thermoelectric materials design with the distinct advantage of tunability of electronic properties by controlled doping and/or by controlling the inherent disorder in the microstructure. While their application is increasing in photovoltaics, energy storage, and sensing technologies, a clear understanding of conduction in these hybrid systems is lacking. Here, we report a comprehensive study of NGQD-PANI composites with varying NGQD doping levels over a wide range of temperature. We show distinct regimes of conduction as a function of temperature, which include: a transition from Efros-Shklovskii and Larkin-Khmelnitskii variable range hopping at low temperatures to thermally driven electron transport at higher temperatures. Importantly, we find a remarkable 50-fold enhancement in conductivity for 10% NGQD-doped samples and tunability of the crossover temperature between different regimes as a function of the applied voltage bias and doping. Our work provides a general framework to understand the interplay of extrinsic parameters like temperature and voltage bias with intrinsic material properties like doping, which drives the electronic properties in these hybrid systems of technological importance.

A composite of self-passivated amorphous carbon dots (CDs) and chitosan has been developed and utilized to form fluorescent inks and luminescent films. The ink is invisible under visible light but glows brightly under external excitation. Cross-linking between the numerous surface groups present in the highly disordered CDs and chitosan, endow the inks and films with enhanced optical and mechanical properties. The amorphous CD based ink is capable of writing on nearly all types of surfaces and exhibits excellent anti-clogging and anti-smearing properties. The luminescent films on the other hand are characterized by good mechanical strength (σUTS ≈ 61.3 MPa) along with high luminescence efficiency. The luminescence yield, ultimate tensile stress, hydrophobicity and glass transition temperature of the films were found to scale similarly with the concentration of CDs in chitosan. All the parameters initially improved with increasing CD concentration but then deteriorated beyond some optimal CD loading due to agglomeration effect. We demonstrate that the amorphous carbon dot-based inks and films outperform all other carbon-based fluorescent inks and films prepared from the more expensive crystalline structures.

Apparently mundane, amorphous nanostructures of carbon have optical properties which are as exotic as their crystalline counterparts. In this work we demonstrate a simple and inexpensive mechano-chemical method to prepare bulk quantities of self-passivated, amorphous carbon dots. Like the graphene quantum dots, the water soluble, amorphous carbon dots too, exhibit excitation-dependent photoluminescence with very high quantum yield (~40%). The origin and nature of luminescence in these high entropy nanostructures are well understood in terms of the abundant surface traps. The photoluminescence property of these carbon dots is exploited to detect trace amounts of the nitro-aromatic explosive - 2,4,6-trinitrophenol (TNP). The benign nanostructures can selectively detect TNP over a wide range of concentrations (0.5 to 200 μM) simply by visual inspection, with a detection limit of 0.2 μM, and consequently outperform nearly all reported TNP sensor materials.

A very simple facile method of preparation of carbon dots, by acid assisted ultrasonic chemical method has been demonstrated. Dextrose can be efficiently and simply synthesised into water-soluble photoluminescent carbon dot (CDs). The HRTEM confirms its size less than 15nm and its amorphous nature. We have tried to emphasized that even amorphous carbon dot has its own importance in the advance materials world by combinedly showing different possible applications of amorphous carbon dots. CDs were used in making fluorescent ink, flexible film and in sensing picric acid (TNP). The presence of surface states was shown by FTIR spectroscopy. The UV-Vis absorption spectra demonstrate the n-π∗ transition and the π-π∗ transition. The emission peak of PL spectra is near blue luminescent region. Significant changes were observed in the UV-Vis and PL spectra of CDs in the presence of TNP (Tri-Nitro phenol). The synthesized CDs has been showed as a source for direct applications in sensing explosives, as an invisible ink and as a flexible photo luminescent thin film.