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[IEEE 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - Vancouver, BC, Canada (2020.1.18-2020.1.22)] 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - Graphene Quantum Dots Induced NiCo <sub/>2</sub> S <sub/>4</sub> as an Efficient Electrocatalyst for Hydrogen Harvest
摘要： We made an efficient electrocatalyst for hydrogen harvest, with an overpotential as low as 0.131V to achieve a current density of 10 mA/cm2. The morphology of the material was extremely delicate: branches on the nanowire, and smaller twigs on the branches, such that the specific surface area was greatly enlarged. The two-step hydrothermal process improved performance of is easily accessible. The GQD/NiCo2S4 should mainly be ascribed to graphene quantum dots (GQDs), which induce morphology change of NiCo2S4 nanowires. The delicate morphology serves as a buffer for volume change, and also a reservoir for electrolytes to transport protons [1]. In the meaning time, GQDs inherit excellent properties from both graphene and quantum dots, improving conductivity. Moreover, the addition of GQDs creates numerous defects in both the basal and edge planes for the diffusion of protons and thus help overcome the sluggish redox kinetics of the electrode, leading to improved overall performances [2].
关键词： Hydrogen harvest,Nickel-Cobalt sulfide (NiCo2S4),Electrocatalyst,Graphene Quantum Dots (GQD)
更新于2025-09-23 15:21:01
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Nitrogen-doped Graphene Quantum Dots for Remarkable Solar Hydrogen Production
摘要： We synthesized nitrogen (N)-doped graphene quantum dots (N-GQDs) using a top-down hydrothermal cutting approach. The concentration of N dopants was readily controlled by adjusting the concentration of the N source of urea. When N dopants were incorporated into GQDs, visible absorption was induced by C-N bonds, which created another pathway for generating photoluminescence (PL). Time-resolved PL data revealed that the carrier lifetime of GQDs was increased upon doping with the optimized N concentration. The photoelectrochemical properties of N-GQDs towards water splitting were studied, and the results showed that 2N-GQDs prepared with 2 g of urea produced the highest photocurrent. The photocatalytic activity of 2N-GQDs powder photocatalyst for hydrogen production was also examined under AM 1.5G illumination, showing substantial enhancement over that of pristine GQDs. Electrochemical impedance spectroscopy data further revealed a significant improvement in charge dynamics and reaction kinetics, and an increased carrier concentration as a result of N doping.
关键词： Solar Hydrogen Production,Charge Dynamics,Water Splitting,Graphene Quantum Dots,Nitrogen-doped
更新于2025-09-23 15:21:01
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Effects of Size and Localized States in Charge Carrier Dynamics and Performance of Solution Processed Graphene Quantum Dots/Silicon Heterojunction near-UV Photodetectors
摘要： Influence of size and localized defect states on photogenerated carrier recombination dynamics, which affects the performance of graphene quantum dots (GQDs) based Si-compatible near-UV heterojunction photodetectors, is reported. GQDs of varying size from ~3.0 to ~8.0 nm have been prepared by a top down method of oxidative cutting of graphene oxide followed by hydrothermal reduction and gradient centrifugation at different speeds. Structural, compositional, photophysical characteristics and photocarrier dynamics of different sized samples have been studied. Spectroscopic features and carrier dynamics of GQDs are effectively controlled by their size and localized surface states, which also determine the average recombination lifetime of photo-generated carriers. Two-terminal vertical heterojunction photodetector devices fabricated using solution processed quantum dots exhibit superior performance over a broad spectrum with a peak response in the near UV (380 nm) region. The device fabricated using ~6.0 nm diameter GQDs displayed highest peak responsivity of 3.5 A/W showing an interesting correlation with carrier dynamics. To our best knowledge, this is the only report in graphene quantum dots or carbon nanostructure genre, showing the direct correlation between size of the quantum dots and localized surface states on photocarrier dynamics and consequential performance of photodetector devices.
关键词： Graphene quantum dots,carrier dynamics,heterojunction,Si-compatible,near-UV photodetectors
更新于2025-09-23 15:21:01
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Direct carbonization of organic solvent toward graphene quantum dots
摘要： The bottom-up synthesis of graphene quantum dots (GQDs) using solvothermal method has attracted considerable attention because of their fewer defects and controllable size/ morphology. However, the influence of organic solvent on the preparation of GQDs is still unknown. Herein, a systematic study about carbonization of organic solvents toward GQDs is reported. Results show that organic solvent with the double bond or benzene ring or double hydrophilic groups could be directly decomposed into GQDs without the addition of catalysts or molecule precursors. The as-synthesized GQDs demonstrate ultra-small size distribution, high stability, and excitation wavelength-tunable and upconverted fluorescence. Both hematological and histopathological analyses studies show that the as-synthesized GQDs demonstrate a much good safety profile and excellent biocompatibility. The versatility of this synthetic strategy allows easy control of the surface group, composition, and optical properties of GQDs at the molecular level.
关键词： organic solvents,biocompatibility,fluorescence,graphene quantum dots,solvothermal synthesis
更新于2025-09-23 15:21:01
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Developing an Analytical Method Based on Graphene Quantum Dots for Quantification of Deferiprone in Plasma
摘要： In the world of nanotechnology, graphene quantum dots (GQDs) have been considerably employed in numerous optical sensing and bioanalytical applications. Herein, a simple and cost-efficient methodology was developed to the quantification of deferiprone in plasma samples by utilizing the selective interaction of the GQDs and drug in the presence of Fe3+ ions. GQDs were synthesized by a bottom-up technique as an advantageous fluorescent probe. Increasing levels of deferiprone ranging from 5 to 50 mg.L?1, leads to significant fluorescence quenching of GQDs. In addition, the calibration curve was revealed a linear response in this range with a sensitivity of 5 mg.L?1. The method validation was carried out according to the FDA guidelines to confirm the accuracy, precision, stability and selectivity of the developed method. The results show that this green and low-cost fluorescent probe could be used for the analysis of deferiprone.
关键词： Graphene quantum dots (GQDs),Fluorescent,Plasma,Deferiprone,Iron
更新于2025-09-23 15:21:01
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Construction of nitrogen and phosphorus co-doped graphene quantum dots/Bi5O7I composites for accelerated charge separation and enhanced photocatalytic degradation performance
摘要： Nitrogen and phosphorus co-doped graphene quantum dot-modified Bi5O7I (NPG/Bi5O7I) nanorods were fabricated via a simple solvothermal method. The morphology, structure, and optical properties of the as-prepared samples were investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and diffused reflectance spectroscopy. The photocatalytic performance was estimated by degrading the broad-spectrum antibiotics tetracycline and enrofloxacin under visible light irradiation. The photodegradation activity of Bi5O7I improved after its surface was modified with NPGs, which was attributed to an increase in the photogenerated charge transport rate and a decrease in the electron-hole pair recombination efficiency. From the electron spin resonance spectra, XPS valence band data, and free radical trapping experiment results, the main active substances involved in the photocatalytic degradation process were determined to be photogenerated holes and superoxide radicals. A possible photocatalytic degradation mechanism for NPG/Bi5O7I nanorods was proposed.
关键词： Charge separation,Photocatalysis,Bi5O7I,N,P co-doped graphene quantum dots,Ionic liquid
更新于2025-09-23 15:21:01
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Graphene Quantum Dot Oxidation Governs Noncovalent Biopolymer Adsorption
摘要： Graphene quantum dots (GQDs) are an allotrope of carbon with a planar surface amenable to functionalization and nanoscale dimensions that confer photoluminescence. Collectively, these properties render GQDs an advantageous platform for nanobiotechnology applications, including optical biosensing and delivery. Towards this end, noncovalent functionalization offers a route to reversibly modify and preserve the pristine GQD substrate, however, a clear paradigm has yet to be realized. Herein, we demonstrate the feasibility of noncovalent polymer adsorption to GQD surfaces, with a specific focus on single-stranded DNA (ssDNA). We study how GQD oxidation level affects the propensity for polymer adsorption by synthesizing and characterizing four types of GQD substrates ranging ~60-fold in oxidation level, then investigating noncovalent polymer association to these substrates. Adsorption of ssDNA quenches intrinsic GQD fluorescence by 31.5% for low-oxidation GQDs and enables aqueous dispersion of otherwise insoluble no-oxidation GQDs. ssDNA-GQD complexation is confirmed by atomic force microscopy, by inducing ssDNA desorption, and with molecular dynamics simulations. ssDNA is determined to adsorb strongly to no-oxidation GQDs, weakly to low-oxidation GQDs, and not at all for heavily oxidized GQDs. Finally, we reveal the generality of the adsorption platform and assess how the GQD system is tunable by modifying polymer sequence and type.
关键词： molecular dynamics simulations,Graphene quantum dots,oxidation level,ssDNA,adsorption,noncovalent functionalization,fluorescence quenching
更新于2025-09-23 15:21:01
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Fabrication and characterization of graphene quantum dots thin film for reducing cross-sectional heat transfer through smart window
摘要： Graphene and its derivatives have been reported as materials with excellent electrical and thermal conductivity, allowing for various promising applications. In particular, the large-scale surface coating of graphene-based materials can be employed to minimize cross-sectional heat transfer through the glass window. This study introduces a facile and cost-effective method to fabricate graphene quantum dots (GQDs) thin film on Fluorine-doped Tin Oxide (FTO) glass via casting of the GQDs dispersion and stabilizing with poly-vinyl-pyrrolidone (PVP). The thin film possesses excellent optical properties of GQDs and allows more than 80 % of visible transmittance. The presence of the GQDs thin film shows effective reduction in the cross-sectional thermal diffusivity of FTO glass, from 0.55 mm2/s to zero when measured with laser flash over a 4-second period. This low cost and eco-friendly GQDs thin film will be a promising material for heat management in smart window applications.
关键词： Smart window,Cross-Sectional heat transfer,Graphene quantum dots,Poly-Vinyl-Pyrrolidone,Visible transmittance
更新于2025-09-23 15:21:01
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Preparation of graphene quantum dots with high quantum yield by a facile one-step method and applications for cell imaging
摘要： The preparation and biological applications of graphene quantum dots (GQDs) have attracted much attention. Here, a one-step hydrothermal method for synthesizing nitrogen-doped GQDs (N-GQDs) using graphene oxide (GO), ethylenediamine and hydrogen peroxide, simultaneously achieved oxidative cleavage and chemical reduction of GO. The average size of the synthesized N-GQDs was about 1.84±0.28 nm and their quantum yield of the N-GQDs reached about 0.46, which was higher than that of other GQDs synthesized by top-down methods. The cytotoxicity of these N-GQDs on Hela cells was evaluated using a cell counting Kit-8 assay. The effects of N-GQDs on different cell lines and fluorescence imaging were also observed by confocal laser scanning microscopy. The results suggested that these N-GQDs penetrated into cells by endocytosis and were promising fluorescent probes for biological imaging.
关键词： Carbon materials,Hydrothermal reaction,Luminescence,Graphene quantum dots,Bio-imaging
更新于2025-09-23 15:21:01
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Determination of aminophylline based on fluorescence quenching of amino-functionalized graphene quantum dots induced by photoilluminated riboflavin-aminophylline system
摘要： A new method based on fluorescence spectroscopy for the sensitive determination of aminophylline (AP), an antiasthmatic drug, was developed in this work. Amino-functionalized graphene quantum dots (afGQDs) were synthesized based on a two-step method and they were characterized by transmission electron microscope, UV–vis absorption spectrum and infrared spectrum. The fluorescence of afGQDs was quenched by riboflavin (Rf) via both dynamic quenching and inner filter effect. Photoilluminated Rf-AP system in the presence of oxygen produced hydroxyl radicals (?OH). The latter accepted electrons from afGQDs owing to a photo-induced electron transfer process and led to the further fluorescence decline. The changing extent of the fluorescence intensity was found to be proportional to the concentration of AP in the range of 0.10–10 μg mL?1 and the limit of detection arrived at 40 ng mL?1. The proposed method was successfully employed for the determination of AP in a pharmaceutical sample and the recovery rate varied in the range of 99%–106%.
关键词： Riboflavin,Photoilluminated interaction,Amino-functionalized graphene quantum dots,Hydroxyl radicals,Aminophylline,Fluorescence quenching
更新于2025-09-23 15:21:01