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The Study on Tuning Photoluminescence of Colloidal Graphene Quantum Dots Synthesized through Laser Ablation
摘要： We report photoluminescence study of Colloidal Graphene Quantum Dots (GQDs) that synthesized from ablation of rGO solution. The rGO solution was ablated using 800 nm Ti-Sapphire femtosecond laser by varying the synthesize parameters such as laser power and ablation time. We observed that changing laser power 1 Watt to become 1.7 Watt and time ablation 20 minutes to become 60 minutes will alterate the Photoluminescence (PL) curve peak of GQDs. In case of ablation power variation, PL data shows that the PL curve peak excited by 280 nm laser changed from 369.09 nm to 371.02 nm, and when it excited by 290 nm the PL curve peak slightly changed from 388.17 nm to 393.8 nm. The alteration of Photoluminescence peak is also observed in the variation of time ablation experiment, The PL curve peaks from GQDs time ablation variation samples excited by 280 nm were slightly changed from 376.81 nm to 373.59 nm, and when it excited by 290 nm laser, the PL curve peak is 391.55 nm then changed to 392.11. The change of PL peak on laser power or time ablation variation shows that both parameters will alter either the size, shape, or the edge-type of GQDs.
关键词： Laser Ablation,Ti-Sapphire Femtosecond Laser,Graphene Quantum Dots,Photoluminescence,Reduced Graphene Oxide
更新于2025-09-16 10:30:52
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Electrical and optical properties of the specimens with graphene quantum dots prepared by different number of wet transfer
摘要： Graphene quantum dots (GQDs) are grown on the copper foil substrate by the chemical vapor deposition (CVD) synthesis. 1–3 wet transfer numbers are then used in the preparations of the GQDs/glass substrate in order to improve the density and uniformity of GQDs via the stacking of multiple layers. The CH4 input time, ?ow rate, and the number of wet transfer are determined to obtain the optimum conditions in electrical (resistivity) and optical (transmittance) properties. The multilayered graphene is characteristically close to the graphite-like material. The G-band peak intensity in Raman analyses is varied proportional to the density of GQDs. Increasing the wet transfer number can lead to increases in the mean diameter of GQDs and the amount of oxygen vacancies, thus resulting in the rise of carrier concentration and the lowering of carrier mobility. The resistivity varying with the wet transfer number is inversely proportional to the density of GQDs. A bandgap reduction can bring in the lowerings of photoluminescence peak intensities. The specimen with 2 wet transfers has the lowest resistivity and the second highest transmittance of these specimens. GQDs can bring in a signi?cant reduction of resistivity compared to the same substrate without GQD.
关键词： Graphene quantum dots,Wet transfer method,Chemical vapor deposition,Graphite-like material
更新于2025-09-16 10:30:52
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Graphene Quantum Dots Induce Autophagy and Reveal Protection Against Hydrogen Peroxide-Induced Oxidative Stress Injury
摘要： As the zero-dimension nanomaterials, graphene quantum dots (GQDs) have excellent characteristics of graphene as well as photoluminescence (PL) features that ordinary graphene does not possess for its virtue of quantum confinement effect and boundary effect, and attract lots of researchers interested in the field of biomedical applications. In this work, we found GQDs can be internalized into SGC-7901 cells, and the labeled cells exhibited bright yellow fluorescence in the form of aggregated dots. Meanwhile, GQDs effectively mitigated the injury hydrogen peroxide (H2O2)-induced in SGC-7901 cells including cytotoxicity and apoptosis. While H2O2 exposure increased ROS and decreased mitochondrial membrane potential, it could be arrested by GQDs. Furthermore, GQDs showed protective effects against the reduction of the ratio of mitochondrial apoptosis-related proteins Bcl-2/ Bax in SGC-7901 cells. Our works revealed that GQDs had the antioxidant ability against oxidative stress, which meant they had the potential to be an antioxidants. Besides, GQDs increased the level of autophagy-related protein LC3-II and induced autophagic structure observed via TEM, and subsequent the results of LC3 turnover and p62 degradation demonstrated GQDs treatment led to the activation of autophagic flux. Ultimately, GQDs were found to affect autophagy through the mTOR signaling pathway.
关键词： graphene quantum dots,apoptosis,antioxidant,oxidative stress,autophagy
更新于2025-09-16 10:30:52
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Simple preparation of graphene quantum dots with controllable surface states from graphite
摘要： Graphite is economic and earth-abundant carbon precursor for preparing graphene quantum dots (GQDs). Here, we report a facile and green approach to produce GQDs from graphite flakes via a pulsed laser ablation (PLA) method assisted by high-power sonication. A homogeneous dispersion of graphite flakes, caused by high-power sonication during PLA, leads to the formation of GQDs following a laser fragmentation in liquid (LFL) rather than laser ablation in liquid (LAL) mechanism. The final product of GQDs exhibits the distinct structural, chemical, and optical properties of pristine graphene itself. However, graphene oxide quantum dots (GOQDs) with abundant surface oxygen-rich functional groups are readily formed from graphite flakes when high-power sonication is not employed during the PLA process. GQDs and GOQDs show a significantly different luminescence nature. Hence, selective production of either functional GQDs or GOQDs can be achieved by simply turning the high-power sonication during the PLA process on and off. We believe that our modified PLA process proposed in this work will further open up facile and simple routes for designing functional carbon materials.
关键词： high-power sonication,graphene quantum dots,luminescence,pulsed laser ablation,graphite flakes
更新于2025-09-16 10:30:52
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An eco-friendly imprinted polymer based on graphene quantum dots for fluorescent detection of <i>p</i> -nitroaniline
摘要： An eco-friendly fluorescent molecularly imprinted polymer anchored on the surface of graphene quantum dots (GQDs@MIP) was developed with an efficient sol–gel polymerization for highly sensitive and selective determination of p-nitroaniline (p-NA). The GQDs@MIP was characterized in detail by Fourier-transform infrared, fluorescence spectrometer, scanning electron microscope, transmission electron microscope and ultraviolet spectrophotometer. The results showed that the imprinted layer was successfully grafted on the surface of the GQDs. The fluorescence of the GQDs@MIP is efficiently quenched when p-NA recombines with the imprinting sites based on the photo-induced electron transfer fluorescence quenching mechanism. A good linear relationship was obtained between the fluorescence quenching efficiency of the GQDs@MIP and the concentration of p-NA in the range of 0–15.0 mM with a correlation coefficient of 0.99. The practicability of the proposed method in real samples was successfully evaluated through monitoring p-NA in water and fish samples with satisfactory recovery. The developed method provides a feasible and eco-friendly strategy to fabricate MIPs anchored on GQDs with good fluorescence properties for sensitive detection of organic pollutants in complex samples.
关键词： graphene quantum dots,fluorescent molecularly imprinted polymer,p-nitroaniline,fluorescence quenching,eco-friendly
更新于2025-09-16 10:30:52
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Magnetic field induced vortices in graphene quantum dots
摘要： The energy spectrum and local current patterns in graphene quantum dots are investigated for different geometries in the presence of an external perpendicular magnetic field. Our results demonstrate that, for specific geometries and edge configurations, the quantum dot exhibits vortex and anti-vortex patterns in the local current density, in close analogy to the vortex patterns observed in the probability density current of semiconductor quantum dots, as well as in the order parameter of mesoscopic superconductors.
关键词： graphene quantum dots,magnetic field,energy spectrum,local current patterns,vortices
更新于2025-09-16 10:30:52
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Preparation and cell imaging of nitrogen-doped graphene quantum dot conjugated indomethacin
摘要： The nitrogen-doped graphene quantum dot conjugated indomethacin (N-GQD-IDM) was synthesized by an amide reaction. The results of FTIR indicated that the synthesis of N-GQD-IDM was successful. It was then co-cultured with MCF-7 cells, and obvious fluorescence was observed under a laser confocal scanning microscope. With the increase of incubation time, the material accumulated significantly in the cells and the fluorescence intensity of the cells was slightly improved. This compound could be suggested as a promising fluorescent probe in cancer cell labeling.
关键词： indomethacin,fluorescent probe,cancer cell labeling,nitrogen-doped graphene quantum dots
更新于2025-09-16 10:30:52
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A highly sensitive and selective detection of picric acid using fluorescent sulfura??doped graphene quantum dots
摘要： The development of an analytical probe to monitor highly mutagenic picric acid (PA) carries enormous significance for the environment and for health. A novel, simple and rapid fluorescence analytical assay using sulfur-doped graphene quantum dots (SGQDs) was designed for the highly sensitive and selective detection of PA. SGQDs were synthesized via simple pyrolysis of 3-mercaptopropionic acid and citric acid and characterized using advanced analytical techniques. Fluorescence intensity (FI) of SGQDs was markedly quenched by addition of PA, attributed to the inner filter effect and dominating static quenching mechanism between the two, in addition to a significant colour change. The calibration curve of the proposed assay exhibited a favourable linearity between quenched FI and PA concentration over the 0.1–100 μΜ range with a lowest detection limit of 0.093 μΜ and a correlation coefficient of 0.9967. The analytical assay was investigated for detection of trace amounts of PA in pond and rain water samples and showed great potential for practical applications with both acceptable recovery (98.0–100.8%) and relative standard deviation (1.24–4.67%). Analytical performance of the assay in terms of its detection limit, linearity range, and recovery exhibited reasonable superiority over previously reported methods, thereby holding enormous promise as a simple, sensitive, and selective method for detection of PA.
关键词： static quenching,inner filter effect,picric acid,fluorescent probe,sulfur-doped graphene quantum dots
更新于2025-09-16 10:30:52
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Sulfur and nitrogen coa??doped graphene quantum dota??assisted chemiluminescence for sensitive detection of tryptophan and mercury (II)
摘要： A simple one-step thermal treatment to prepare strong fluorescent sulfur and nitrogen co-doped graphene quantum dots (SN-GQD) using citric acid and L-cysteine as precursors was developed. The ultra-weak chemiluminescence (CL) from the reaction of hydrogen peroxide (H2O2) and periodate (IO4?) was significantly enhanced by SN-GQD in acidic medium. The enhanced CL was induced by excited-state SN-GQD (SN-GQD*), which was produced from the transfer energy of (O2)2* and 1O2 to SN-GQD and recombination of oxidant-injected holes and electrons in SN-GQD. In the presence of tryptophan (Trp), the CL intensity of the SN-GQD–H2O2–KIO4 system was greatly diminished. This finding was used to design a novel method for determination of Trp in the linear range 0.6–20.0 μM, with a limit of detection (LOD) of 58.0 nM. Furthermore, Hg2+ was detectable in the range 0.1–9.0 μM with a LOD of 64.0 nM, based on its marked enhancement of the SN-GQD–H2O2–KIO4 CL system. The proposed method was successfully applied to detect Trp in milk and human plasma samples and Hg2+ in drinking water samples, with recoveries in the range 95.7–107.0%.
关键词： tryptophan,S,N co-doped graphene quantum dots,chemiluminescence,mercury (II)
更新于2025-09-16 10:30:52
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Application of maleimide modified graphene quantum dots and porphyrin fluorescence resonance energy transfer in the design of a??a??turn-ona??a?? fluorescence sensors for biothiols
摘要： Two novel fluorescent probes were designed to detect the biothiol in foods using the highly efficient Michael addition reaction between maleimide-derived probes and the biothiol. First, maleimide functionalized GQDs (M-GQDs) were synthesized and used for biothiol identification according to the Michael addition principle. The biothiol can be detected in the range of 5× 10-9 to 4× 10-7 mol/L and the detection limit was 1.69×10-9 mol/L. Then, a fluorescence resonance energy transfer (FRET) system between M-GQDs and tetrakis (4-aminophenyl) porphyrin (TAPP) for biothiol detection was developed. However, the process of FRET was switched off in the presence of biothiols due to the switch of M-GQDs fluorescence emission to the“ON” mode following the Michael addition mechanism. The system could quickly and accurately detect the biothiol with a detection range of 6.7×10-10 to 2×10-7 mol/L and a detection limit of 2.34×10-10 mol/L. Compared to the single detection system, the FRET system had a wider detection range and lower detection limit, and the related biomolecules did not interfere with the quantitative identification of the biothiol. The proposed method was successfully applied for the determination of the biothiol in foods and human blood samples.
关键词： Porphyrin,Fluorescence “turn-on”,Biothiols,FRET,Graphene quantum dots
更新于2025-09-16 10:30:52