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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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A graphene quantum dots-Pb2+ based fluorescent switch for selective and sensitive determination of D-penicillamine
摘要： Taking consideration of metal-induced fluorescence quenching and excellent coordination effect of D-penicillamine (D-PA), a graphene quantum dots (GQDs)-based fluorescent switch for D-PA detection was designed and established firstly with the help of lead ions. GQDs obtained from citric acids made them rich in carboxyl and hydroxyl groups, giving GQDs the ability to combine with lead ions. As anticipated, the fluorescence intensity was quenched by Pb2+ through electron transfer process. Further, the addition of D-PA effectively recovered the fluorescence due to the departure of Pb2+ from GQDs aroused by the strong coordination between D-PA and Pb2+. Thus, a fluorescent switch was activated for D-PA detection. The fluorescence recovery efficiencies were found to be proportional to the concentration of D-PA in the range of 0.6–50 μmol L-1 and the detection limit was 0.47 μmol L-1. The real sample detection was performed in human urea sample and satisfactory recoveries of 96.84%-102.13% were obtained. The GQDs-Pb2+ based fluorescent switch sensing method was firstly established with low detection limit and wide linear range, making it a supplement and improvement for D-PA detection.
关键词： lead ions,graphene quantum dots,D-penicillamine,fluorescent switch
更新于2025-09-12 10:27:22
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Facile method for the preparation of high-performance photodetectors with a GQDs/perovskite bilayer heterostructure
摘要： A high-performance nitrogen doped graphene quantum dots (GQDs)/all-inorganic (CsPbBr3) perovskite nanocrystals (NCs) heterostructure photodetector was fabricated on a quartz substrate, using the low cost spin coating technique followed by hot plate annealing. The GQDs/CsPbBr3 NCs heterostructure photodetector exhibits a high overall performance with a photoresponsivity of 0.24 AW?1, on/off ratio of 7.2 × 104, and specific detectivity of up to 2.5 × 1012 Jones. The on/off ratio of the hybrid device was improved by almost ten orders of magnitude, and the photoresponsivity was enhanced almost three times compared to the single layer perovskite NCs photodetector. The performance enhancement of the hybrid device was due to its highly efficient carrier separation at the GQDs/CsPbBr3 NCs interface. This results from the coupling of the GQDs layer, which efficiently extracts and transports the photogenerated carriers, with the CsPbBr3 NCs layer, which has a large absorption coefficient and high quantum efficiency. The interfacial charge transfer from the CsPbBr3 NCs to the GQDs layer was demonstrated by the quenching in the photoluminescence (PL) spectra, and the fast-average decay time in the time-resolved photoluminescence (Trpl) spectra of the hybrid photodetector. Moreover, the performance-enhancement mechanism of the hybrid GQDs/CsPbBr3 photodetector was elucidated by analyzing the band alignment of the GQDs and CsPbBr3 under laser illumination.
关键词： Carrier separation,Charge transfer,CsPbBr3 nanocrystals,Photodetectors,Graphene quantum dots
更新于2025-09-12 10:27:22
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Electrochemical synthesis of phosphorus and sulfur co-doped graphene quantum dots as efficient electrochemiluminescent immunomarkers for monitoring okadaic acid
摘要： In this study, water-dispersed, uniform-sized phosphorus and sulfur co-doped graphene quantum dots (P, S-GQDs) were prepared by the one-step electrolysis of a graphite rod in an alkaline solution containing sodium phytate and sodium sulfide. Compared with GQDs and mono-doped GQDs (P-GQDs and S-GQDs), the P, S-GQDs dramatically improved the electrochemiluminescence (ECL) performance. Therefore, they were used as bright ECL signaling markers through conjugation with a monoclonal antibody against okadaic acid (anti-OA-MAb). Moreover, as an effective matrix for OA immobilization, the carboxylated multiwall carbon nanotubes-poly(diallyldimethylammonium) chloride-Au nanocluster (CMCNT-PDDA-AuNCs) composite promoted electron transfer and enlarged the surface area. Owing to the multiple amplifications, a competitive indirect ECL immunosensor for highly sensitive quantitation of OA has been developed. Under the optimized conditions, the 50% inhibitory concentration (IC50) of the immunosensor was 0.25 ng mL-1, and its linear range was 0.01–20 ng mL-1 with a low detection limit of 0.005 ng mL-1. Finally, the proposed ECL sensor was successfully utilized to detect OA contents in mussel samples. Therefore, this study provides new insights into the designation of ECL luminophores and expands application of co-doped GQDs in fabrication of ECL immunosensors for shellfish toxin determination.
关键词： immunosensor,electrolysis,okadaic acid,electrochemiluminescence,phosphorus and sulfur co-doped graphene quantum dots
更新于2025-09-12 10:27:22
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A synthesis of graphene quantum dots/hollow TiO2 nanosphere composites for enhancing visible light photocatalytic activity
摘要： Given the versatility and value of the semiconductor composites for photocatalysis, we reported a new, friendly environment, high specific surface area material of the graphene quantum dots/hollow titanium dioxide nanosphere (GQDs/H-TiO2) composites which are synthesized through a simple hydrothermal method. GQDs (~ 5 nm) exhibit highly photoluminescent and widely visible light absorption properties. H-TiO2 has high surface area and abundant exposed active sites for photocatalysis. The research demonstrates that GQDs coupled on H-TiO2 can effectively enlarge the light absorption of the H-TiO2 to visible region (~ 650 nm) and enhance the electron–hole pair separation efficiency of GQDs/H-TiO2 composites owing to GQDs acting as an electron repository and electron transport bridge. In our delight, the photocurrent enhancement of newly prepared GQDs-3.0/H-TiO2 composite electrode was almost 3.5 times higher in comparison with that in pure H-TiO2 electrode at an applied voltage of 0.5 V using Na2SO4 (0.5 M) solution as the electrolyte. In addition, the photocatalytic activity of the prepared GQDs-3.0/H-TiO2 (96.9%) on the degradation of Rhodamine B (RhB) was also significantly enhanced compared with that of pure H-TiO2 (33.3%) after 180 min. The protocol is suitable not only for the GQDs-modified semiconductors photocatalysts but also provides further insights to apply GQDs to other energy conversion devices.
关键词： composites,graphene quantum dots,hollow TiO2 nanosphere,visible light photocatalytic activity
更新于2025-09-12 10:27:22
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Boosting Performance of Perovskite Solar Cells with Graphene quantum dots decorated SnO2 Electron Transport Layers
摘要： In this work, Graphene quantum dots (GQDs) was decorated on the SnO2 electron transport layers (ETLs) to boost the performance of perovskite solar cells (PSCs). The power conversion efficiency (PCE) of 21.1% was acquired with the combination of SnO2 and GQDs. Compared with the SnO2-only ETL devices (18.6%), the PCE of SnO2/GQDs based devices is greatly enhanced in PCE by the value of 13.4% as well as in the stability. Investigation reveals that with the combination of SnO2 and GQDs, the open circuit voltage (VOC) and the short circuit current density (JSC) could increase. Various advanced optical and electrical characterizations were carried out to explore the action mechanism of GQDs. The experimental results convinced that the introduction of GQDs leads to the better carrier transportation and extraction by increasing the electronic coupling and matching the energy levels between the perovskite and SnO2 ETL. Also, the perovskite film quality deposited on the GQDs decorated SnO2 ETL is better compared with the SnO2 only. Furthermore, the device stability based on the GQDs modified SnO2 is evidently improved contrast to the SnO2-only device. Its performance kept above 80% of initial value after 720 h storage.
关键词： electron transport layer,graphene quantum dots,SnO2,perovskite solar cells
更新于2025-09-12 10:27:22
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Graphene quantum dots modified flower like Bi2WO6 for enhanced photocatalytic nitrogen fixation
摘要： Graphene quantum dots modified Bi2WO6 (GQD/Bi2WO6) composites is applied to photocatalytic N2 fixation. The as-prepared GQD/Bi2WO6 samples showed considerable increase in photocatalytic nitrogen fixation compared to the pure Bi2WO6 and GQD. The results revealed that GQD uniformly placed on the surface of Bi2WO6 and tight junction between the two samples helped to boost the photocatalytic activity. The PL, photocurrent and EIS analyses further demonstrated that the composite had the low recombination rate of photo-generated charges. Photocatalytic nitrogen fixation test indicated that GQD/Bi2WO6 with 10 wt% GQDs exhibited the highest ammonia synthesis rate in the presence of visible light, which is 8.88-fold and 33.8-fold higher than pure Bi2WO6 and GQD. Simultaneously, the GQD/Bi2WO6 sample has high stability.
关键词： Bi2WO6,Photocatalytic N2 fixation,Graphene quantum dots
更新于2025-09-12 10:27:22
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Multifunctional single-layered graphene quantum dots used for diagnosis of mitochondrial malfunction-related diseases
摘要： Mitochondria are critical organelles in eukaryotes that efficiently generate ATP for various biological activities and any defect in the process of ATP synthesis may lead to mitochondrial dysfunction and directly link to a variety of medical disorders. Monitoring the ATP variations in cells is key for innovative early diagnosis of mitochondrial diseases. Herein, multifunctional single-layered graphene quantum dots (s-GQDs) with bright green emission were constructed, which exhibit strong binding a?nity for ATP and good mitochondria targeting ability. Using the proposed s-GQDs we successfully achieved to discriminate the primary smooth muscle cells isolated from the transgenic mouse (heterozygote Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) 2 C674S knock-in mouse) with mitochondrial disorders or their littermate controls, indicating s-GQDs as promising probes for the study of cell metabolism and mitochondrial malfunction-related diseases, and targeting endoplasmic reticulum stress is an effective way to modulate metabolic pathways relevant to SERCA 2 inactivity mitochondrial dysfunction.
关键词： graphene quantum dots,ATP,mitochondrial disorders,endoplasmic reticulum stress,sarco/endoplasmic reticulum Ca2+ ATPase
更新于2025-09-12 10:27:22
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Dual Role of Graphene Quantum Dots in Active Layer of Inverted Bulk Heterojunction Organic Photovoltaic Devices
摘要： Graphene quantum dots (GQDs) have shown broad application prospects in the field of photovoltaic devices due to their unique quantum confinement and edge effects. Here, we prepared GQDs by a photon-Fenton reaction as reported in our previous work, which has great advantage in the preparation scale. The photoelectric properties of the inverted hybrid solar cells based on poly(3-hexylthiophene) (P3HT): (6,6)-phenyl-C61 butyric acid methylester (PCBM):GQDs and P3HT:GQDs with different contents of GQDs as the active layers are demonstrated, as well as their morphology and structure by atomic force microscopy images. Then, the different roles of GQDs played in the ternary (P3HT:PCBM:GQDs) and binary (P3HT:GQDs) hybrid solar cells are studied systematically. The results indicate that the GQDs provide an efficient excition separation interface and charge transport channel for the improvement of hybrid solar cells. The preliminary exploration and elaboration of the role of GQDs in hybrid solar cells will be beneficial to understand the interfacial procedure and improve device performance in the future.
关键词： photovoltaic devices,hybrid solar cells,PCBM,photon-Fenton reaction,P3HT,Graphene quantum dots
更新于2025-09-12 10:27:22
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Biodegradable blends of graphene quantum dots and thermoplastic starch with solid-state photoluminescent and conductive properties
摘要： Polymer composites based on blends of graphene quantum dots (GQDs) with thermoplastic starch (TPS) were prepared by melt-extrusion combined with hot pressing. The GQDs/TPS films were characterized as potential novel, high-performance, and ecofriendly composites replacing traditional non-biodegradable plastic packaging materials. GQDs stock solutions of different concentrations were incorporated into TPS matrices in order to analyze the solid-state fluorescent properties and conductive properties of GQDs/TPS films. The fluorescent, conductive, morphological, mechanical, and optical properties of the GQDs/TPS films were characterized by ultraviolet–visible spectroscopy, surface resistance measurement, scanning electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, tensile testing, and X-ray diffraction (XRD). FT-IR studies indicated hydrogen bonding between the oxygen-containing groups on GQDs surfaces and the –OH groups in the TPS. The mechanical testing results showed the optimum GQDs loading of 10.9 wt% in the blend. XRD and TEM studies indicated uniform graphene dispersions in the TPS matrix for ≤10.9 wt% GQDs loading; further increases in loading caused agglomeration. The maximum photoluminescence intensity and conductivity of the materials were obtained at 10.9 wt% GQDs loading. These materials have potential applicability in flexible optoelectronic packaging materials.
关键词： Solid-state photoluminescence,Film,Thermoplastic starch,Graphene quantum dots,Conductive property
更新于2025-09-12 10:27:22