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Highly Efficient UV–Visible Photocatalyst from Monolithic 3D Titania/Graphene Quantum Dot Heterostructure Linked by Aminosilane
摘要： As rapidly growing environmental pollution demands the development of efficient photocatalytic materials, tremendous attention has been drawn to TiO2, a widely used photocatalytic material with cost-effectiveness, stability, and outstanding reactivity. To maximize its photocatalytic efficiency by enhancing the photogenerated charge separation, lowering the intrinsically large bandgap (3.2 eV) of TiO2 is a key problem to be overcome. Herein, a new design is reported for an efficient photocatalyst realized by heterostructuring a 3D nanostructured TiO2 monolith (3D TiO2) and graphene quantum dots (GQDs) through using 3-aminopropyltriethoxysilane (APTES) as a linker. The incorporation of APTES between the TiO2/GQD interface enables the formation of a charge injection-type heterostructure, as confirmed by transient absorption spectroscopy, providing improvement of both visible absorption and charge separation. As a result, the heterostructure exhibits a 242% enhanced photocatalytic performance compared to that of nonheterostructured 3D TiO2 under visible irradiation, demonstrating its promising potential for practical photocatalytic applications in environmental remediation.
关键词： TiO2/GQD heterostructure,graphene quantum dots,visible light photocatalysis,charge injection,3D nanostructured TiO2
更新于2025-09-19 17:13:59
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Simultaneous determination of ascorbic acid, dopamine, and uric acid using graphene quantum dots/ionic liquid modified screen-printed carbon electrode
摘要： In this work, graphene quantum dots (GQDs) and ionic liquid (IL) modified screen-printed carbon electrode (GQDs/IL-SPCE) were introduced for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). GQDs were synthesized by directly pyrolyzing citric acid and then dropped onto the surface of IL-SPCE, which was prepared by screen-printing the mixture of IL and carbon ink on a portable substrate. UV-Vis spectrophotometry, fluorescence spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize the synthesized GQDs and the modified electrodes. The GQDs/IL-SPCE exhibited excellent electrocatalytic activity for the oxidation of AA, DA, and UA in the mixture solution. Moreover, the anodic peak responses of these three analytes were also resolved into three well-defined peaks. Under the optimized conditions, the linear response ranges for AA, DA, and UA were 25 - 400 μM, 0.2 - 10 μM, and 0.5 - 20 μM, respectively, with low detection limits (σ/N = 3) of 6.64 μM, 0.06 μM, and 0.03 μM, respectively. The proposed sensor exhibited high sensitivity, low cost and successfully applied for the simultaneous detection of AA, DA, and UA in pharmaceutical products and biological samples.
关键词： Graphene quantum dots,Uric acid,Dopamine,Screen-printed carbon electrode,Ionic liquid,Ascorbic acid
更新于2025-09-19 17:13:59
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Diverse Nanoassemblies of Graphene Quantum Dots and Their Mineralogical Counterparts
摘要： Complex structures from nanoparticles are found in rocks, soils, and sea sediments but the mechanisms of their formation are poorly understood, which causes controversial conclusions about their genesis. Here we show that graphene quantum dots (GQDs) can assemble into complex structures driven by coordination interactions with metal ions commonly present in environment and serve a special role in Earth’s history, such as Fe3+ and Al3+. GQDs self-assemble into mesoscale chains, sheets, supraparticles, nanoshells, and nanostars. Specific assembly patterns are determined by the effective symmetry of the GQDs when forming the coordination assemblies with the metal ions. As such, maximization of the electronic delocalization of p-orbitals of GQDs with Fe3+ leads to GQD-Fe-GQD units with D2 symmetry, dipolar bonding potential, and linear assemblies. Taking advantage of high electron microscopy contrast of carbonaceous nanostructures in respect to ceramic background, the mineralogical counterparts of GQD assemblies are found in mineraloid shungite. These findings provide insight into nanoparticle dynamics during the rock formation that can lead to mineralized structures of unexpectedly high complexity.
关键词： self-assembly,nanoscale mineralogy,nanoparticles,graphene quantum dots,electronic conjugation
更新于2025-09-19 17:13:59
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Preparation and characterization of seleniuma??decorated graphene quantum dots with high afterglow for application in photodynamic therapy
摘要： Graphene quantum dots (GQDs) was synthesized using a simple, rapid and affordable method and decorated with selenium at different molar ratios for the first time to obtain an efficient sample for use in photodynamic therapy. Surface modification of GQDs was carried out using polyethylene glycol (PEG) for conjugation with protoporphyrin IX (PpIX). Synthesized GQDs (Se: 0.3%) at 180°C had an emission spectrum that fairly coincided with the absorption profile of PpIX. A relative decrease of about 62.48% in the emission intensity of anthracene was recorded under illumination with UVC light in the presence of GQDs (Se: 0.3%) and the reduction for clung GQDs (Se: 0.3%) and PpIX during 90 min was about 70.68%. Singlet oxygen (1O2) generation was examined using a chemical method that showed significant enhancement in decomposition rate constant in clung GQDs–PEG–PpIX compared with GQDs and PpIX alone. Afterglow over 600 s showed that GQDs (Se: 0.3%) could be effective for near skin and even deep tumours.
关键词： photodynamic therapy,selenium,afterglow,protoporphyrin IX,graphene quantum dots
更新于2025-09-19 17:13:59
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Electro-absorption spectra of magnetic states of diamond shaped graphene quantum dots
摘要： In this work, employing restricted Hartree-Fock (RHF) as well as unrestricted Hartree-Fock (UHF) mean-field theory and incorporating long-range coulomb interactions within the Pariser-Parr-Pople (PPP) model based Hamiltonian, the effect of size and electric field on the optical properties of various magnetic states of diamond shaped graphene quantum dots (DQDs) has been elucidated. Our calculations have demonstrated that the energetic ordering of excited states and consequently the sequence of electric-field induced phase transition exhibited by the different magnetic phases changes with varying size of DQDs. The optical band-gap for the AF state decreases very gradually as compared to that of the FM and NM configurations, with increase in size of DQD. It is observed that the optical spectrum of the anti-ferromagnetic (AF) state exhibits a spin-sensitive splitting, while no such splitting is observed for the ferromagnetic (FM) configuration, under the application of electric field. In addition, our computations have established that the magnitude of optical band-gap splitting and the shifting trends (red-shift or blue-shift) of the optical spectrum of spin-up orbitals with respect to that of spin-down orbitals of the AF phase, with the application of electric field, can be tuned by changing the size of DQD.
关键词： Electro-absorption spectra,Phase transition,Pariser-Parr-Pople model,Graphene quantum dots,Magnetic properties
更新于2025-09-19 17:13:59
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Synthesis of graphene quantum dots stabilized CuNPs and their applications in CuAAC reaction and 4-nitrophenol reduction
摘要： Here we report the synthesis of graphene quantum dots (GQDs) stabilized copper nanoparticles in neat water. Construction of six CuNPs 1-6 nanocomposites are accomplished by mixing GQDs and NaBH4, and followed by the addition of different amounts of copper sulfate at 0 ℃ in water, respectively. Among them, CuNP-3, with the size of 2.6 nm, exhibits excellent catalytic performance in the CuAAC reaction over than other CuNPs. Moreover, the CuNP-3 has also been successfully applied for the reduction of 4-nitrophenol with excellent catalytic activity.
关键词： 4-Nitrophenol reduction,Copper nanoparticles,CuAAC reaction,Graphene quantum dots
更新于2025-09-19 17:13:59
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A novel electrochemiluminescence sensor based on resonance energy transfer system between nitrogen doped graphene quantum dots and boron nitride quantum dots for sensitive detection of folic acid
摘要： Electrochemiluminescence resonance energy transfer (ECL-RET) between quantum dots (QDs) was firstly proposed. In this work, boron nitride quantum dots (BNQDs) as the donor and nitrogen doped graphene quantum dots (NGQDs) as the acceptor were confirmed by the absorption spectrum, the emission spectrum and fluorescence spectrum. Based on the reaction between FA and the SO4?? in the ECL system of NGQDs/BNQDs/K2S2O8, the ECL sensing platform for FA was successfully constructed. Surprisingly, a stable and strong ECL signal was obtained based on the RET, which was used for signal-off detection of FA in the presence of coreactant K2S2O8. Notably, about 10-fold enhancement was observed compared with the absence of BNQDs. The proposed sensor showed wide linear ranges of 1.0 × 10?11 M to 1.0 × 10?4 M and a low detection limit of 5.13 × 10?12 M. Simultaneously, the sensor was successfully applied to detection of FA in human serum samples with excellent recoveries. Therefore, the NGQDs/BNQDs system provided a new perspective for development of novel ECL-RET sensors.
关键词： Folic acid,Nitrogen doped graphene quantum dots,Resonance energy transfer,Boron nitride quantum dots,Electrochemiluminescence
更新于2025-09-16 10:30:52
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Advanced Electrode Materials Comprising of Structurea??Engineered Quantum Dots for Higha??Performance Asymmetric Microa??Supercapacitors
摘要： Micro-supercapacitors (MSCs) as a new class of energy storage devices have attracted great attention due to their unique merits. However, the narrow operating voltage, slow frequency response, and relatively low energy density of MSCs are still insufficient. Therefore, an effective strategy to improve their electrochemical performance by innovating upon the design from various aspects remains a huge challenge. Here, surface and structural engineering by downsizing to quantum dot scale, doping heteroatoms, creating more structural defects, and introducing rich functional groups to two dimensional (2D) materials is employed to tailor their physicochemical properties. The resulting nitrogen-doped graphene quantum dots (N-GQDs) and molybdenum disulfide quantum dots (MoS2-QDs) show outstanding electrochemical performance as negative and positive electrode materials, respectively. Importantly, the obtained N-GQDs//MoS2-QDs asymmetric MSCs device exhibits a large operating voltage up to 1.5 V (far exceeding that of most reported MSCs), an ultrafast frequency response (with a short time constant of 0.087 ms), a high energy density of 0.55 mWh cm?3, and long-term cycling stability. This work not only provides a novel concept for the design of MSCs with enhanced performance but also may have broad application in other energy storage and conversion devices based on QDs materials.
关键词： supercapacitors,electrode materials,engineering,molybdenum disulfide quantum dots,nitrogen-doped graphene quantum dots
更新于2025-09-16 10:30:52
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[IEEE 2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP) - Zatoka, Ukraine (2018.9.9-2018.9.14)] 2018 IEEE 8th International Conference Nanomaterials: Application & Properties (NAP) - Efficient Two-Photon Luminescence for Bioimaging Using Polymer Conjugations of Graphene Quantum Dots Based Materials
摘要： In this study, examination results revealed that conjugated polymers containing nitrogen and sulfur atoms lead to a higher quantum confinement of emissive energy trapped on the surface of material (graphene quantum dot (GQD)-polymers), resulting in a high luminescence quantum yield and impressive two-photon properties. Additionally, the GQD-polymers generated nonreactive oxygen species-dependent oxidative stress on cells. Furthermore, we demonstrated the effective use of two-photon excitation-mediated high two-photon luminescence intensity in an acidic environment enabled GQD-polymers to act as a promising contrast probe. When cancer cells are labeled with specific antibody GQD-polymers conjugates, molecular-specific imaging can be performed deep into a tissue phantom with extremely high signal-to-noise ratios. In situations in which imaging depths are limited by the maximum available power that can be delivered to the three-dimensional (3D) bioimaging plane without causing damage to tissue, GQD-polymers might provide sufficient brightness to extend the maximum depth of imaging. Moreover, we demonstrated that the use of GQD-polymers can expand the capabilities of two-photon imaging to allow noninvasive 3D bioimaging of a variety of new molecular signatures.
关键词： photostability,reactive oxygen species,three-dimensional bioimaging,photodynamic therapy,two-photon excitation,contrast probe,graphene,quantum dot-polymer,two-photon luminescence,two-photon,contrast agent,nitrogen-doped graphene quantum dots
更新于2025-09-16 10:30:52
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Bionanosensor based on N-doped graphene quantum dots coupled with CoOOH nanosheets and their application for in vivo analysis of ascorbic acid
摘要： Herein, we employ 3D nitrogen-doped porous graphene frameworks (3D NPG) as raw material to prepare emissive nitrogen doped graphene quantum dots (r-NGQDs) via chemical oxidation method. The as-prepared fluorescent r-NGQDs was integrated with CoOOH nanosheets to construct a sensing platform for in vivo ascorbic acid (AA) analysis. Initially, the fluorescence emission intensity of r-NGQDs was quenched by CoOOH nanosheets based on the inner filter effect (IFE). Then the quenched intensity of r-NGQDs and CoOOH nanosheets system was enlightened by the addition of AA, since AA could consume CoOOH nanosheets through redox reaction, leading to the release of r-NGQDs and fluorescence restoration. Moreover, the restored fluorescence intensity of r-NGQDs is highly dependent on the concentration of AA which endows them as a quantitative analysis of AA with a limit of detection (LOD) reach up to1.85 μM (n = 3) in aqueous solution. Finally, the as constructed bionanosensor was further employed for in vivo analysis of AA in living rat brain microdialysate with basal value up to 9.4 ± 1.4 μM (n = 3).
关键词： Nitrogen-doped porous graphene,Graphene quantum dots,Ascorbic acid,In vivo,CoOOH nanosheets
更新于2025-09-16 10:30:52