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AIP Conference Proceedings [AIP Publishing ADVANCES IN BASIC SCIENCE (ICABS 2019) - Bahal, India (7–9 February 2019)] ADVANCES IN BASIC SCIENCE (ICABS 2019) - Synthesis and optical properties of Zn(II) doped graphene quantum dots: Blue to purple emission
摘要： The Graphene Quantum dots (GQDs), fragments of graphene have attracted considerable attention in recent years due to the size, edge effects, quantum confinement and heteroatom doping. The doping of graphene based materials can effectively tune their intrinsic properties, including electronic and optical properties, surface and local chemical reactivity. Herein, we present a comprehensive study of ZnO doped GQDs prepared by a facile hydrothermal method by using ZnO and Graphne Oxide (GO) as a source materials. All the synthesized materials were characterized by UV-Visible Spectroscopy (UV-Vis), Raman Spectroscopy, Fourier Transform Infrared (FT-IR) and Photoluminescence (PL). The morphological characterizations were confirmed by transmission electron microcopy images (TEM). The hydrothermally synthesized material had a size of 5-20 nm by uniform doping of zinc nanoparticles on graphene sheet. The results of PL of Zn(II)-GQDs showed a blue to purple emission with the variation in excitation wavelength from 280nm to 380nm. These doped GQDs were found to be an efficient approach with multicolor emission for biological applications and optoelectronic devices to make the environmental friendly, cost effective and easily scalable.
关键词： optical properties,photoluminescence,Graphene Quantum dots,hydrothermal method,Zn(II) doping
更新于2025-09-12 10:27:22
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Rapid Synthesis of Highly Fluorescent Nitrogen-Doped Graphene Quantum Dots for Effective Detection of Ferric Ions and as Fluorescent Ink
摘要： Graphene quantum dots (GQDs) have attracted much attention of many researchers because of their low cytotoxicity, good optical stability, and excellent photoluminescence property, which make them novel nanostructured materials in many application fields ranging from energy to biomedicine and the environment. In this work, highly fluorescent nitrogen-doped graphene quantum dots (N-GQDs) were synthesized through microwave heating using sodium citrate and triethanolamine as raw materials. The as-prepared N-GQDs showed considerable bright blue fluorescence with a quantum yield of 8% and excellent uniform dispersion with an average diameter of approximately 5.6 nm; they also exhibited excellent stability and pH-sensitive properties. Furthermore, we demonstrated the application of N-GQDs as probes for metal ion detection. The results indicated that N-GQDs responded rapidly toward Fe3+ because of the static quenching mechanism. A detection method was proposed, with detection linear in two ranges from 20 to 70 nM (F = ?0.9666 CFe3+ (μM) + 1191.94 (R = 0.9541)); the lowest detection limit of 9.7 nM for Fe3+ was obtained. The results obtained in this work lay the foundation for the development of high-performance and robust metal ion detection sensors. Moreover, it can also possibly be used as a new type of fluorescent ink.
关键词： Nitrogen-doped,Fluorescent probe,Fluorescent ink,Fe3+ detection,Graphene quantum dots
更新于2025-09-12 10:27:22
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Graphite-N doped graphene quantum dots as semiconductor additive in perovskite solar cells
摘要： Efficient charge transport is especially important for achieving high performance of perovskite solar cells (PSCs). Here, molecularly designed graphite-nitrogen doped graphene quantum dots (GN-GQDs) act as functional semiconductor additive in perovskite film. GN-GQDs with abundant N active sites participate in the crystallization of perovskite film and effectively passivate the grain boundary (GB) trap states by Lewis base-acid interaction. Moreover, the semiconductive GN-GQDs at GBs exhibit matched energy structure with the perovskite, which facilitate the charge transport at GBs. GN-GQDs also show n-type dopant property to upshift the Fermi energy level of perovskite films. It largely improves the charge transport in PSCs and reduces the interface recombination at the same time. Profiting from these advantages, inverted planar PSCs with NiO/perovskite/PCBM/BCP structure achieves high efficiency of 19.8% with no hysteresis phenomenon. GN-GQDs modified PSCs also show high stability even without encapsulation, benefiting from the protected GBs and more hydrophobic surface of the modified film. This work highlights a judicious design method of GQDs additive to satisfy efficient and stable PSCs.
关键词： N doping,energy structure,graphene quantum dots,perovskite solar cells,charge transport
更新于2025-09-12 10:27:22
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Detection of <i>Escherichia coli</i> O157:H7 with Antibody Conjugated Amino-Functionalized Graphene Quantum Dots as Immunofluorescence Probes
摘要： Escherichia coli O157: H7 (E. coli O157: H7) is a foodborne pathogenic bacterium which can cause fever, diarrhoea and vomiting in humans. Thus, a rapid, simple, and specific bioprobe for pathogen detection in contaminated foods has been attracted more and more attention. In this work, the strong fluorescent amino-functionalized graphene quantum dots (af-GQDs) were prepared by hydrothermal method. The microtopographic height, surface morphology and spectroscopic properties of af-GQDs are characterized by the high resolution transmission electron microscope (HRTEM), atomic force microscope (AFM), UV-vis, fluorescence, Raman spectroscopic techniques. All the results showed that the af-GQDs can be effectively applied in the preparation of biocompatible immunofluorescence probe and in the detection of E. coli O157: H7. The minimum detection limit is 100 cfu/mL. It is a simple, rapid, sensitive, low-cost and easy to be popularized method, which provides a feasible way to monitor E. coli O157: H7 in food safety.
关键词： E. coli O157: H7,Bioprobe,Amino-functionalized graphene quantum dots,Foodborne bacteria,Immunofluorescence
更新于2025-09-12 10:27:22
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Insights into the formation of N doped 3D-Graphene Quantum Dots. Spectroscopic and Computational Approach
摘要： In this work, we utilize a top-down approach to synthesize nitrogen doped graphene quantum dots from a 3D-graphene precursor via an eco-friendly hydrothermal method. The nanoparticles obtained showed a 2-3 nm diameter and well dispersion behavior in aqueous media. The reaction mechanism of insertion of nitrogen from polyvinylpolypyrrolidone onto the 3D-graphene structure, via an esterification reaction, was studied by the density functional theory, in addition, the kinetic and thermodynamic magnitudes of the reaction was analyzed with the help of Eyring's transition state theory and statistical thermodynamics. After analysis by ss-NMR and XPS spectroscopies, the functional groups involved in this process were characterized, and N was found mainly as amide / amine groups. Fluorescence emission, which exhibited a red shift (552 nm) and an emission maximum at 512 nm when excited at 480 nm, demonstrated a low stoke shift (Δλ =32 nm), explained by the proposed structural model.
关键词： XPS,solid-state NMR,Nitrogen doped graphene quantum dots,DFT calculations
更新于2025-09-12 10:27:22
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Electron Transfer Kinetics at Graphene Quantum Dot Assembly Electrodes
摘要： Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (HBC and CQD) onto conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrodes states at different potentials and tunneling rate constant (Marcus-Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc+) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than –0.5 V vs Ag/Ag+. Enabled by these large densities, the electron transfer rates at the Fc/Fc+ thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This study is expected to accelerate the discovery of improved synthetic carbon electrodes by providing fast screening methodology of their electrochemical behavior.
关键词： cyclic voltammetry,kinetics,interface,electrode,electron transfer,graphene quantum dots
更新于2025-09-12 10:27:22
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Variation of Optical Properties of Nitrogen-doped Graphene Quantum Dots with Short/Mid/Long-wave Ultraviolet for the Development of the UV Photodetector
摘要： Nitrogen-doped graphene quantum dots (NGQDs) synthesized from a single glucosamine precursor are utilized to develop a novel UV-photodetector. Optical properties of NGQDs can be altered with short (254 nm), mid (302 nm) and longwave (365 nm) UV (ultra-violet) exposure leading to the reduction of absorption from deep to mid UV (200 to 320 nm) and enhancement above 320 nm. Significant quenching of blue and near-IR fluorescence accompanied by the dramatic increase of green/yellow emission of UV-treated NGQDs can be used as a potential UV-sensing mechanism. These emission changes are attributed to the reduction of functional groups detected by Fourier transformed infrared spectroscopy, and free radical-driven polymerization of the NGQDs increasing their average size from 4.70 to 11.20 nm at 60 min treatment. Due to strong UV absorption and sensitivity to UV irradiation, NGQDs developed in this work are utilized to fabricate UV photodetectors. Tested under long/mid/short-wave UV, these devices show high photo-responsivity (up to 0.59 A/W) and excellent photo-detectivity (up to 1.03X1011 Jones) with highly characteristic wavelength-dependent reproducible response. This study suggests that the optical/structural properties of NGQDs can be controllably altered via different wavelength UV-treatment leading us to fabricate NGQD-based novel UV photodetectors providing high responsivity and detectivity.
关键词： UV photodetector,Optical Properties Modification,Short/mid/long-wave UV treatment,UV sensor,Nitrogen-doped graphene quantum dots
更新于2025-09-12 10:27:22
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Interface‐Sliding‐Induced Graphene Quantum Dots Transferring to Fullerene‐Like Quantum Dots and Their Extraordinary Tribological Behavior
摘要： Carbon materials such as diamond, fullerene, graphene, and carbon nanotubes possess superior chemical and physical properties, which are widely used in various applications. Especially, since fullerene-like carbon is successfully converted to graphene during sliding, the sliding-induced microstructure transfer between carbon-based materials should be given more attention. Here, the tribological behaviors of graphene-based materials is investigated under the load of 196 N and the rotational speed of 1450 rpm using a four-ball wear machine under deionized water. Results show that the friction coefficient continuously decreases with increasing sliding time and the wear scar diameter is just about 0.224 mm. Remarkably, graphene is severely ripped and loses its lubrication performance during sliding. Sliding induces graphene quantum dots converting to fullerene quantum dots, which would cooperate with the sliding-reduced fullerene-like structures containing WO2 nanocrystals and sulfurized isobutene as extreme pressure lubricant additives instead of graphene to achieve low friction and wear. This work confirms that the low friction and wear under high load and fast rotation have a close relation to the microstructure transfer of interfacial carbon-based materials, rather graphene, and provide practical approach for investigating the tribological behaviors of carbon-based materials.
关键词： graphene quantum dots (GQDs),fullerene,sulfurized isobutene (SIB),tribological,graphene
更新于2025-09-11 14:15:04
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Manipulation of 3D nanocarbon hybrids toward synthesis of N-doped graphene quantum dots with high photoluminescence quantum yield
摘要： Synthesis of heteroatom-doped graphene quantum dots (GQDs) via a top-down approach is still challenging. Herein, we conveniently synthesized nitrogen-doped GQDs (N-GQDs) via an electrochemical method. In that, the N-containing 3D nanocarbon hybrids were prepared as the carbon and nitrogen sources, which were cut into small fragments in ammonia solution as the electrolyte. Interestingly, N-atoms from the 3D nanocarbon hybrids were successfully retained or converted into the other type of N in the obtained GQDs, resulting to a highly doped N content up to 12.3% even after excluding the amino- and pyrrolic N at edges of the N-GQDs. As a matter of fact, such synthesized N-GQDs show highly crystallized structure, and demonstrate a high photoluminescence quantum yield of ~19.3%, among the highest values of top-down approach synthesized GQDs. Moreover, it can be also used for adjusting the absorption range of GQDs. Overall, we developed a new strategy to synthesize N-doped GQDs by controlling the carbon source, which opens a new avenue toward achieving other types of heteroatom-doped GQDs.
关键词： electrochemical method,3D nanocarbon hybrids,doping,quantum yield,graphene quantum dots
更新于2025-09-11 14:15:04
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Application of PEGylated graphene quantum dots in cell imaging
摘要： Polyethylene glycol (PEG) functionalized graphene quantum dots (GQDs-PEG) with average particle size of 2.1 nm were successfully prepared by hydrothermal method with PEG as surface passivation agent. The quantum yield (QY) of GQDs-PEG was 3.7%and its physiological stability was significantly better than that of GQDs. The cell viability assay results showed that GQDs-PEG display no obvious toxicity to cells. The results of cell fluorescence imaging showed that GQDs-PEG could enter the whole cell with high fluorescence recognition.
关键词： cell imaging,graphene quantum dots,Polyethylene glycol
更新于2025-09-11 14:15:04