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Microwave-assisted synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots: Raman characterization and their optical properties
摘要： In this report we will present completely new results on the improvement of the graphene quantum dots (GQDs) and nitrogen-doped graphene quantum dots (N-GQD) production method, using the microwave with different power levels and durations, from citric acid and urea. This is a new and unprecedented method of fabrication. The use of microwave has allowed ultra-fast fabrication of GQDs and nitrogen doped GQDs. These GQDs had their characteristics identi?ed by Raman scattering spectra for the characteristic C–C graphene vibration mode (G-peak) and defects of GQDs (D-peak). The absorption spectra of GQDs samples were fabricated under different conditions, with the expectation of different sizes, to be compared and analyzed. These absorption spectra were also compared with those of the N-GQD produced under the same conditions. The absorption mechanism of GQDs and N-GQD will be presented in detail. Measurements of the photoluminescence (PL) spectra in GQDs and N-GQD have also been recorded and analyzed. The ?uorescence mechanism will be presented, explained, and compared with other international publications of other authors. Some of the TEM and HR-TEM images of these two samples were also presented to con?rm the shape, size and in-plane spacing lattice of the GQD structure.
关键词： graphene quantum dots (GQDs),PL spectra,nitrogen-doped graphene quantum dots (N-GQD),microwave,Raman spectra,absorption spectra
更新于2025-11-19 16:56:42
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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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Silver nanoparticles on graphene quantum dots as nanozyme for efficient H <sub/>2</sub> O <sub/>2</sub> reduction in a glucose biosensor
摘要： In this work, we developed graphene quantum dot-supported silver nanoparticles (AgNPs@GQDs) as Nanozyme for efficient electrocatalytic reduction of H2O2. We applied this composite material in a glucose oxidase-based glucose sensor, by drop casting a mixture of AgNPs@GQDs and chitosan (CS) on glassy carbon electrodes (GCE). Various conditions such as thickness of the AgNPs@GQDs/CS film, pH and temperatures were optimized. The proposed sensor presented excellent selectivity and sensitivity, a linear dependence on glucose concentration in the range 0.1–10 mM and a limit of detection of ca. 0.01 mM.
关键词： hydrogen peroxide reduction,electrochemical sensor,graphene quantum dots (GQDs),silver nanoparticles (AgNPs),glucose oxidase (GOx)
更新于2025-09-19 17:13:59
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Synthesis and characterization of graphene quantum dots
摘要： Conventional inorganic semiconductor quantum dots (QDs) have numerous applications ranging from energy harvesting to optoelectronic and bio-sensing devices primarily due to their unique size and shape tunable band-gap and also surface functionalization capability and consequently, have received significant interest in the last few decades. However, the high market cost of these QDs, on the order of thousands of USD/g and toxicity limit their practical utility in many industrial applications. In this context, graphene quantum dot (GQD), a nanocarbon material and a new entrant in the quantum-confined semiconductors could be a promising alternative to the conventional toxic QDs due to its potential tunability in optical and electronic properties and film processing capability for realizing many of the applications. Variation in optical as well as electronic properties as a function of size, shape, doping and functionalization would be discussed with relevant theoretical backgrounds along with available experimental results and limitations. The review deals with various methods available so far towards the synthesis of GQDs along with special emphasis on characterization techniques starting from spectroscopic, optical and microscopic techniques along with their the working principles, and advantages and limitations. Finally, we will comment on the environmental impact and toxicity limitations of these GQDs and their hybrid nanomaterials to facilitate their future prospects.
关键词： Photoluminescence (PL),Graphene quantum dots (GQDs),Electrochemical luminescence (ECL)
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