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Carbon and graphene quantum dots: a review on syntheses, characterization, biological and sensing applications for neurotransmitter determination
摘要： Neuro-transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro-transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro-chemical sensors possess features of robustness, selectivity, and sensitivity as well as real-time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon-based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, inertness, high specific surface areas, plenty of edge sites for functionalization, and strong chemical versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano-materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon-based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development.
关键词： Carbon quantum dots,Graphene quantum dots,Neurotransmitters,Biological applications,Sensing applications,Electrochemical sensors
更新于2025-09-23 15:19:57
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Secondary toxic effect of graphene oxide and graphene quantum dots alters the expression of miR-21 and miR-29a in human cell lines
摘要： For in vitro studies, non-toxic doses of nanomaterials are routinely selected by quantification of live cells after exposing to different concentrations of nanoparticles but considering only morphological changes or viability of cells is not sufficient to conclude that these nanomaterials are non-cytotoxic. Here we investigated if secondary toxicity is active in the cells exposed to non-toxic doses of graphene oxide (GO) and graphene quantum dots (GQD). Non-cytotoxic dose of 15 μg mL-1 of GO (100 nm) and GQDs (50 nm) was selected according to MTT and Hoechst 33342/PI double staining assays. In order to investigate the secondary toxicity, the expression of miR-21, miR-29a and three genes at both mRNA and protein level were evaluated in MCF-7, HUVEC, KMBC/71 cells 4 and 24 h post exposure. Mitochondrial membrane potential (MMP) was assessed by Rhodamine 123 staining. According to our results, there was no significant decrease in viability of cells after exposure to the no-cytotoxic dose of GO and GQD, but we observed significant alterations in the expression level of miR-21, miR-29a, Bax, Bcl2 and PTEN genes after treatment in all three cells. In addition to molecular changes, we observed alteration in mitochondrial activity at cellular level. However, we also observed that GO influenced the basal level of genes and influenced MMP more compare to GQDs-50. Considering that all these genes are involved in breast tumor development and metastasis, the observed changes in miRNA expression and protein synthesis may alter cell fate and susceptibility and cause deviation in the desired outcome of GO-100 and GQDs-50 application in medical researches.
关键词： Graphene oxide,MCF-7 cells,HUVEC cells,MicroRNA-21,Graphene quantum dots,MicroRNA-29a
更新于2025-09-23 15:19:57
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Highly Efficient Orange Emissive Graphene Quantum Dots Prepared by Acid-Free Method for White LEDs
摘要： Graphene quantum dots (GQDs) have wide prospective applications for optoelectronic fields owing to their unique characteristics, such as tunable bandgaps, high chemical and optical stability, as well as good biocompatibility. In this work, we offered a convenient proposal to obtain uniform blue-green emissive GQDs and modified efficient orange-emitting graphene quantum dots (D-GQDs) derived from fullerene (C60) under acid-free condition. The as-prepared D-GQDs demonstrate remarkable conversion efficiency which quantum yield is up to 52.4% with the emission peak of 617 nm. Also, GQDs and D-GQDs were blended with poly(vinyl alcohol) (PVA) to prepare transparent photo-luminescent films, which show excellent flexibility and preferable white emission property meeting the requirements of commercial white LEDs.
关键词： Graphene quantum dots,Quantum yield,Acid-free condition,WLEDs
更新于2025-09-23 15:19:57
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Nitrogen-Sulfur-Doped Graphene Quantum Dots with Metal Ion-Resistance for Bioimaging
摘要： The development of ultra-stable and highly fluorescent heteroatoms-doped graphene quantum dots (GQDs) for bioimaging remains a challenge due to the fluorescence quenching caused by binding between the heteroatoms-based functional groups of the GQDs and common metal ions in biological systems. Here, we developed a facile hydrothermal method to prepare nitrogen-sulfur doped GQDs (NS-GQDs). The fluorescence signals of the NS-GQDs are highly stable in the existence of different metal ions. Two natural products, aspartic acid and cysteine, were utilized as the carbon precursors and heteroatomic (nitrogen and sulfur) sources. The produced NS-GQDs showed a quantum yield up to 19.3 ± 1.7 % with a maximum emission of 480 nm under the excitation of 400 nm. The elemental analysis, including X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR), were performed to characterize the composition and surface groups of NS-GQDs. Additionally, the NS-GQDs not only showed notable photostability, but also thermostability and chemical stability. Moreover, the NS-GQDs demonstrated very low cellular cytotoxicity in vitro. Finally, the NS-GQDs were applied for fluorescence imaging of cells, which also exhibited excellent fluorescent stability even with treatment of copper ions. The results indicated that the developed novel NS-GQDs have a promising potential to be used as ultra-stable fluorescent agent in the field of bioimaging and biosensing.
关键词： bioimaging,nitrogen doping,sulfur doping,fluorescence,Graphene quantum dots
更新于2025-09-23 15:19:57
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A Facile Microwave-Assisted Hydrothermal Synthesis of Graphene Quantum Dots for Organic Solar Cell Efficiency Improvement
摘要： Carbon-based nanomaterials have successively remained at the forefront of different research fields and applications for years. Understanding of low-dimension carbon material family (CNT, fullerenes, graphene, and graphene quantum dots) has arrived at a certain extension. In this report, graphene quantum dots were synthesized from graphene oxide with a microwave-assisted hydrothermal method. Compared with conventional time-consuming hydrothermal routes, this novel method requires a much shorter time, around ten minutes. Successful formation of quantum dots derived from graphene sheets was verified with microscopic and spectroscopic characterization. Nanoparticles present a diameter of about 2-8 nm, blue emission under ultraviolet excitation, and good dispersion in polar solvents and can be collected in powder form. The synthesized graphene quantum dots were utilized as a hole transport layer in organic solar cells to enhance the cell quantum efficiency. Such quantum dots possess energy levels (Ec and Ev) relevant to HOMO and LUMO levels of conductive polymers. Mixing P3HT:PCBM polymer and graphene quantum dots of sufficient extent notably helps reduce potential difference at interfaces of the two materials. Overall efficiency consequently advances to 1.43%, an increase of more than 44% compared with pristine cells (0.99%).
关键词： microwave-assisted hydrothermal synthesis,organic solar cells,graphene quantum dots,efficiency improvement
更新于2025-09-23 15:19:57
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Polarizing Graphene Quantum Dots towards Long-acting Intracellular Reactive Oxygen Species Evaluation and Tumour Detection
摘要： The evaluation of intracellular reactive oxygen species (ROS) would greatly deepen the understanding of cell metabolism/proliferation and tumour detection. However, current long-acting level tracking techniques for intracellular ROS remain unsuited to practical application. To solve this problem, we synthesized cyclotriphosphazene doped graphene quantum dots (C-GQDs) whose quantum yield is highly sensitive to ROS (increased by 400% from 0.12 to 0.63). Electron cloud polarisation of oxidized cyclotriphosphazene rings in C-GQDs is confirmed to account for this novel optical property by density functional theory calculation and experimental results. In combination with excellent biological stability, C-GQDs achieve a long-acting evaluation of intracellular ROS level (more than 72 h) with an accuracy of 98.3%. In addition, recognition rates exceeding 90% are demonstrated to be feasible for eight kinds of tumour cell lines cultured with C-GQDs, which can also be expanded to in vivo detection. C-GQDs also show a high recognition rate (82.33%) and sensitivity (79.65%) for tumour cells in blood samples.
关键词： CTC,tumour detection,intracellular reactive oxygen species,photoluminescence,graphene quantum dots
更新于2025-09-23 15:19:57
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One-stop radiotherapeutic targeting of primary and distant osteosarcoma to inhibit cancer progression and metastasis using 2DG-grafted graphene quantum dots
摘要： The application of radiotherapy (RT) to treat osteosarcoma (OS) has been limited, but this is starting to change as the ability to target radiation energy to niches improves. Further, lung cancer from highly metastatic OS is a major cause of death, so it is critical to explore new strategies to tackle metastasis. In this study, we designed a nanoscale radiosensitizer by grafting 2-deoxy-d-glucose (2DG) on to graphene quantum dots (GQD) to achieve OS targeting and boost RT efficacy. Combining the use of 2DG-grafted GQDs (2DG-g-GQD) with RT produced a significant increase in oxidative stress response and DNA damage in the 143B OS cell line compared with RT alone. Moreover, 2DG-g-GQDs selectively associated with 143B cells, and demonstrated inhibition of migration in a scratch assay. We also demonstrated remarkable improvement in ability to inhibit tumour progression and lung metastasis in an OS xenograft mouse model. Our results show that the use of 2DG-g-GQDs as an OS-targeting radiosensitizer improves the therapeutic outcome and exhibits potential for use in low-dose precision RT for OS.
关键词： osteosarcoma,radiotherapy,metastasis,2-deoxy-d-glucose,graphene quantum dots
更新于2025-09-23 15:19:57
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White luminescent single-crystalline chlorinated graphene quantum dots
摘要： White luminescent materials have been generating much excitement because of their wide-ranging potential applications. However, challenging synthesis, cytotoxicity and performance of current reported white luminescent materials still hinder their potential applications. Owing to their non-toxicity, excellent optical properties, and amenability to surface modification, white-light-emitting graphene quantum dots (WGQDs) are considered to be a next-generation white luminescent material to replace these above-mentioned conventional materials. The inherent challenge in WGQDs is their massive defects are known to give poor white optical properties. In the proof-of-concept, we designed and synthesized a novel WGQDs via a solvothermal molecular fusion route. The modulation of chlorine doping amount and reaction temperature gives the WGQDs a single-crystalline structure, bright white fluorescence and novel white phosphorescence performance for the first time. An optimum fluorescence quantum yield of WGQDs is 34%, which exceeds the majority of reported WGQDs and other white luminescent materials. The WGQDs display broad-spectrum absorption within almost the entire visible light region, broad full width at half maximum and extend their phosphorescence emission to the entire white long-wavelength region. This unique dual-mode optical characteristic of the WGQDs enlarges their applications in white light emission devices, cell nuclei imaging, and information encryption.
关键词： solvothermal molecular fusion,white luminescent materials,fluorescence,graphene quantum dots,phosphorescence,chlorine doping
更新于2025-09-23 15:19:57
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Yellow emissive nitrogen-doped graphene quantum dots as a label-free fluorescent probe for Fe3+ sensing and bioimaging
摘要： Rapid and sensitive fluorescence nanomaterials sensor with satisfactory selectivity has gained numerous importance for detecting multiple metal ions. Graphene quantum dot (GQD) has attracted a great deal of attentions. Herein, yellow emissive GQDs with a high quantum yield of 0.34 were achieved by nitrogen-doping. The as-prepared N-GQDs exhibited excitation-independent behavior and high optical stability. Furthermore, based on the complexation between Fe3+ and N-GQDs, the fluorescence intensity of the N-GQDs could be greatly quenched by the addition of a small amount of Fe3+ ions. The linearity range is 0-80 μM with a detection limit of 63 nM. For this reason, the proposed method was demonstrated to be selective and suitable for Fe3+ analysis in natural water samples. And, N-GQDs with the biosafety has the potentials for intracellular Fe3+ detection.
关键词： Fe3+ sensing,Photoluminescence,Electron transfer,Graphene quantum dots
更新于2025-09-23 15:19:57
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Optically active polymer nanocomposite composed of polyaniline, polyacrylonitrile and green-synthesized graphene quantum dot for supercapacitor application
摘要： Development of stable and optically active composite film that can show efficient supercapacitor activity is a challenging research interest in material science. A polymer nanocomposite film composed of a green synthesised graphene quantum dot (GQD, G) doped polyacrylonitrile (PAN) and polyaniline (PANI) systems, designated as PAN-PANI@G, have been prepared. The critical loading concentration of prepared composite and its effect on the physicochemical, optical and electrical analysis were systematically studied in detail. PAN-PANI@G composite showed an appreciable electrical conductivity (2.362 × 10?6 S m?1) and optical absorbance at λmax ~270 nm. Physicochemical characterizations by XRD, FTIR and TEM analysis reveal chemical interaction between the individual components via intermolecular hydrogen bonding. Analysed particle size of GQD in the polymer membrane was found to be about two times lesser than that of the pure GQD highlighting synergic interaction between the individual GQD and PAN/PANI matrix. A specific capacitance value of the polymer composites that have been modified on screen-printed carbon electrode were tested by cyclic voltammetric and galvanostatic charge-discharge techniques in 0.1 M H2SO4 solution. Calculated supercapacitor values at an applied current density, 670 mA g?1 are in a range of 105?587 F g?1 cm?2 which are approximately 2?1300 times higher than the values reported for polypyrrole and polyaniline based polymer composite film in the literature. As a preliminary extension of this study, the optimal PAN/PANI@G nanocomposite of GQD loading, 1.5 wt% was extended to prototype supercapacitor cell application in combination with a dilute solution of NaCl along with suitable conducting plates. When 3 V DC power was supplied for 4 min, the prototype cell produced an operating voltage of 1.4 V for 1 h of operating time.
关键词： Supercapacitor,Polyacrylonitrile-polyaniline composite,Prototype cell,Synergic interaction,Graphene quantum dots,IeV analysis
更新于2025-09-23 15:19:57