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1
Ku, Tien-Hsiung, Wen-Ting Shen, Chien-Te Hsieh, Grace Shiahuy Chen, and Wei-Chung Shia. "Specific Forms of Graphene Quantum Dots Induce Apoptosis and Cell Cycle Arrest in Breast Cancer Cells." International Journal of Molecular Sciences 24, no. 4 (February 17, 2023): 4046. http://dx.doi.org/10.3390/ijms24044046.
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Graphene quantum dots (GQDs), nanomaterials derived from graphene and carbon dots, are highly stable, soluble, and have exceptional optical properties. Further, they have low toxicity and are excellent vehicles for carrying drugs or fluorescein dyes. Specific forms of GQDs can induce apoptosis and could be used to treat cancers. In this study, three forms of GQDs (GQD (nitrogen:carbon = 1:3), ortho-GQD, and meta-GQD) were screened and tested for their potential to inhibit breast cancer cell (MCF-7, BT-474, MDA-MB-231, and T-47D) growth. All three GQDs decreased cell viability after 72 h of treatment and specifically affected breast cancer cell proliferation. An assay for the expression of apoptotic proteins revealed that p21 and p27 were up-regulated (1.41-fold and 4.75-fold) after treatment. In particular, ortho-GQD-treated cells showed G2/M phase arrest. The GQDs specifically induced apoptosis in estrogen receptor-positive breast cancer cell lines. These results indicate that these GQDs induce apoptosis and G2/M cell cycle arrest in specific breast cancer subtypes and could potentially be used for treating breast cancers.
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Zhang, Zheng, Yun Lei, Liyang Zhao, Zicong Jiang, and Zhong Ouyang. "Graphene Quantum Dots Decorated Al-doped ZnS for Improved Photoelectric Performance." Materials 11, no. 8 (August 16, 2018): 1452. http://dx.doi.org/10.3390/ma11081452.
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Graphene quantum dots (GQDs) decorated Al-doped ZnS composites were prepared using the solvothermal process, and the hydrothermal method was used to prepare GQDs. Various spectroscopic techniques were used to characterize the products, and the results show that Al-ZnS attached GQD composites present lattice fringes that can be assigned to ZnS and GQDs, respectively. The absorption peaks of Al-ZnS/GQDs are red-shifted because of the doping of aluminum and the incorporation of GQDs. The luminescence intensity of Al-ZnS/GQDs shows a downward trend with the addition of GQDs. As the GQD content changes from 0.6 wt % to 1.8 wt %, the photocurrent density achieves a maximum at the addition of 1.2 wt %. The photocurrent of Al-ZnS/GQDs composites are about 700% and 200% of pure ZnS and Al-ZnS, respectively. The results indicate that Al doping can reduce the energy bandgap of ZnS and produce more photogenerated electrons. The photogenerated electrons from Al-ZnS can be extracted and transferred to GQDs, which act as conducting materials to decrease the recombination rate and improve the photogenerated electron-transfer.
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Yim, Sang-Gu, Yong Kim, Ye-Eun Kang, Byung Moon, Eun Jung, and Seung Yang. "Size Fractionation of Fluorescent Graphene Quantum Dots Using a Cross-Flow Membrane Filtration System." Nanomaterials 8, no. 11 (November 21, 2018): 959. http://dx.doi.org/10.3390/nano8110959.
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Graphene quantum dots (GQDs) have received great attention as optical agents because of their low toxicity, stable photoluminescence (PL) in moderate pH solutions, and size-dependent optical properties. Although many synthetic routes have been proposed for producing GQD solutions, the broad size distribution in GQD solutions limits its use as an efficient optical agent. Here, we present a straightforward method for size fractionation of GQDs dispersed in water using a cross-flow filtration system and a track-etched membrane with cylindrical uniform nanopores. The GQD aqueous suspension, which primarily contained blue-emitting GQDs (B-GQDs) and green-emitting GQDs (G-GQDs), was introduced to the membrane in tangential flow and was fractionated with a constant permeate flow of about 800 L m−2 h−1 bar−1. After filtration, we observed a clear blue PL spectrum from the permeate side, which can be attributed to selective permeation of relatively small B-GQDs. The process provided a separation factor (B-GQDs/G-GQDs) of 0.74. In the cross-flow filtration system, size-dependent permeation through cylindrical nanochannels was confirmed by simulation. Our results demonstrate a feasible method facilitating size fractionation of two-dimensional nanostructures using a cross-flow membrane filtration system. Since membrane filtration is simple, cost-effective, and scalable, our approach can be applied to prepare a large amount of size-controlled GQDs required for high performance opto-electronics and bio-imaging applications.
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Golubewa, Lena, Tatsiana Kulahava, Aliona Klimovich, Danielis Rutkauskas, Ieva Matulaitiene, Renata Karpicz, Nikita Belko, et al. "Visualizing hypochlorous acid production by human neutrophils with fluorescent graphene quantum dots." Nanotechnology 33, no. 9 (December 9, 2021): 095101. http://dx.doi.org/10.1088/1361-6528/ac3ce4.
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Abstract In living organisms, redox reactions play a crucial role in the progression of disorders accompanied by the overproduction of reactive oxygen and reactive chlorine species, such as hydrogen peroxide and hypochlorous acid, respectively. We demonstrate that green fluorescence graphene quantum dots (GQDs) can be employed for revealing the presence of the hypochlorous acid in aqueous solutions and cellular systems. Hypochlorous acid modifies the oxygen-containing groups of the GQD, predominantly opens epoxide ring C–O–C, forms excessive C=O bonds and damages the carbonic core of GQDs. These changes, which depend on the concentration of the hypochlorous acid and exposure time, manifest themselves in the absorbance and fluorescence spectra of the GQD, and in the fluorescence lifetime. We also show that the GQD fluorescence is not affected by hydrogen peroxide. This finding makes GQDs a promising sensing agent for selective detecting reactive chlorine species produced by neutrophils. Neutrophils actively accumulate GQDs allowing to visualize cells and to examine the redox processes via GQDs fluorescence. At high concentrations GQDs induce neutrophil activation and myeloperoxidase release, leading to the disruption of GQD structure by the produced hypochlorous acid. This makes the GQDs a biodegradable material suitable for various biomedical applications.
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George, Deepak, Anirudh Suri, Khushboo Dutta, and Sunita Nayak. "Targeted Drug Delivery Using Graphene Quantum Dots: Approaches, Limitations and Future Perspectives." ECS Transactions 107, no. 1 (April 24, 2022): 16081–98. http://dx.doi.org/10.1149/10701.16081ecst.
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This mini-review centers on the framework of GQDs to function as a drug delivery system (DDS), that is both target-specific and efficient. Researchers exploit GQDs for the unique pharmacokinetic properties they possess, that make them an ideal multi-functional drug delivery vehicle. We cannot enhance the therapeutic efficacy of drugs merely by focusing on drug delivery mechanisms. The conjugation of the drug with GQD allows more flexibility in controlling the kinetics and circulation time of drug in the body, the characteristic which is highly regarded in modern therapeutics. GQDs possess properties such as enhanced water solubility, lower cytotoxicity, tunable photoluminescence properties, larger specific surface area, large surface to volume ratio, and ease of surface functionalization, which make them highly effective drug molecular loading cores. Also, the review addresses the various methods of synthesis of GQDs, that include top-down and bottom-up approaches; top-down modes being more feasible and advantageous. The review touches on the various modes of GQD drug-loaded delivery- release systems (DDRS). The review also addresses the limitations associated with drug delivery using GQDs. Insufficient information about the translocation of GQDs limits their application in biomedical field and make it difficult for GQD-based carriers to pass clinical trials. Through this review, we look to summarize the important concepts of drug delivery using GQDs, and their biomedical applications and scope in nanomedicine in foreseeable future
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Saud, Asif, Haleema Saleem, Nazmin Munira, Arqam Azad Shahab, Hammadur Rahman Siddiqui, and Syed Javaid Zaidi. "Sustainable Preparation of Graphene Quantum Dots for Metal Ion Sensing Application." Nanomaterials 13, no. 1 (December 28, 2022): 148. http://dx.doi.org/10.3390/nano13010148.
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Over the past several years, graphene quantum dots (GQDs) have been extensively studied in water treatment and sensing applications because of their exceptional structure-related properties, intrinsic inert carbon property, eco-friendly nature, etc. This work reported on the preparation of GQDs from the ethanolic extracts of eucalyptus tree leaves by a hydrothermal treatment technique. Different heat treatment times and temperatures were used during the hydrothermal treatment technique. The optical, morphological, and compositional analyses of the green-synthesized GQDs were carried out. It can be noted that the product yield of GQDs showed the maximum yield at a reaction temperature of 300 °C. Further, it was noted that at a treatment period of 480 min, the greatest product yield of about 44.34% was attained. The quantum yields of prepared GQDs obtained after 480 min of treatment at 300 °C (named as GQD/300) were noted to be 0.069. Moreover, the D/G ratio of GQD/300 was noted to be 0.532 and this suggested that the GQD/300 developed has a nano-crystalline graphite structure. The TEM images demonstrated the development of GQD/300 with sizes between 2.0 to 5.0 nm. Furthermore, it was noted that the GQD/300 can detect Fe3+ in a very selective manner, and hence the developed GQD/300 was successfully used for the metal ion sensing application.
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Liu, Thomas, Claire Tonnelé, Christine Elias, Loïc Rondin, Baptiste Carles, Daniel Medina Lopez, Yannick Chassagneux, et al. "(Invited) Influence of Vibrations on the Emission Properties of Single Graphene Quantum Dots." ECS Meeting Abstracts MA2022-01, no. 9 (July 7, 2022): 741. http://dx.doi.org/10.1149/ma2022-019741mtgabs.
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Recent years have shown an increasing number of studies dedicated to new light emitters for diverse applications such as optoelectronics, bio-imaging, and quantum technologies. In this context, graphene quantum dots (GQD) have important assets since bottom-up chemistry allows complete control of the structure, opening the way to wide customization of their electronic, optical, and spin properties [1-3]. The full benefit from these opportunities requires addressing GQD’s intrinsic photophysical properties.To do so, single molecule photoluminescence experiment is a powerfull tool [4]. Here, we highlight the influence of vibrations on GQDs’ optical properties, by comparing optical studies to extensive DFT/TDDFT calculations combined with molecular dynamics simulations. Specifically, we discussed their role in the transitions' oscillator strengths [5]. In order to get deeper in the photophysics of GQD, we investigate the spectroscopy of single GQDs at cryogenic temperatures. In particular, we show a narrowing of the emission lines at low temperature, that allows us to characterize and identify vibrational replicas that are characteristic to GQDs [6]. [1] M. G. Debije, J. Am. Chem. Soc. 2004, 126, 4641 [2] X. Yan, X. Cui, and L.-s. Li, J. Am. Chem. Soc. 2010 132, 5944 [3] A. Konishi et al, J. Am. Chem. Soc. 2010, 132, 11021 [4] S. Zhao et al, Nature Communications, 2018, 9, 3470 [5] T. Liu et al, under review [6] T. Liu et al, in preparation
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Zhang, Jie, Yong-qiang Ma, Na Li, Jing-li Zhu, Ting Zhang, Wei Zhang, and Bin Liu. "Preparation of Graphene Quantum Dots and Their Application in Cell Imaging." Journal of Nanomaterials 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/9245865.
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Objective. This study aims to increase the fluorescence quantum yield by improving the conditions of preparing graphene quantum dots (GQDs) through the solvothermal route and observe the GQDs performance in imaging oral squamous cells.Methodology. The following experimental conditions of GQDs preparation through the solvothermal route were improved: graphene oxide (GO)/N-N dimethyl formamide (DMF) ratio, filling percentage, and reaction time. A fluorescence spectrophotometer was used to measure photoluminescence, and the peak values were compared. Methylthiazolyldiphenyl-tetrazolium (MTT) bromide was used to detect the cytotoxicity of GQDs, which was compared with that of cadmium telluride quantum dots (CdTe QDs). GQDs were cultured with tongue cancer cells. After the coculture, a laser scanning confocal microscope (LSCM) was used to observe cell imaging.Results. The optimal conditions of GQD preparation through the solvothermal route included the following: 10 mg/mL GO/DMF ratio, 80% filling percentage, 12 h reaction time, and 17.4% fluorescence quantum yield. As the cell concentration increased, the GQD and CdTe QD groups exhibited a decreasing cell survival rate, with the decrease in the CdTe QD group being more significant. The LSCM observations showed bright green fluorescence images.Conclusion. The improved experimental conditions increased the fluorescence quantum yield of GQDs. In this study, the prepared GQDs exhibited low cytotoxicity level and satisfactory cell imaging performance.
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Qiu, Zhongzhu, Lin Li, Qunzhi Zhu, Ruitang Guo, Yuan Yao, Congcong Wu, Shengnan Li, and Peng Li. "Physical Stability, Rheology, Thermal Conductivity and Optical and Corrosion Properties of a Graphene Quantum Dot Fluid." Journal of Nanoscience and Nanotechnology 21, no. 10 (October 1, 2021): 5312–18. http://dx.doi.org/10.1166/jnn.2021.19306.
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Because of their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility and small size, Graphene quantum dots (GQDs) have received a lot of attention. However, insufficient investigations have been carried out on GQD fluids. In this paper, the properties of a prepared GQD fluid are studied experimentally, involving the physical stability, rheology, thermal conductivity, optical properties and corrosion characteristics. It is found that a highly physically stable GQD fluid could be easily achieved because the selected GQDs are well dispersed. It is also found that the addition of GQDs had a slight effect on the base fluid viscosity, but it could significantly increase the thermal conductivity of the fluid. In addition, the investigation of the optical properties shows that the GQD fluid exhibited high absorption to sunlight. The transmittance of ultraviolet and near-infrared light is close to zero. In contrast, the transmittance of GQDs to visible light is high at low weight concentrations, but significantly decreases with the increase of the proportion of GQDs. The corrosion characteristics of the copper and carbon steel samples in the selected GQD fluid or deionized water were experimentally investigated. It is found that the selected GQD fluid can greatly accelerate the corrosion of copper. However, nearly the same corrosion rate is observed for carbon steel in the GQD fluid as that in deionized water. The high stability, low viscosity, enhanced thermal conductivity and unique optical and corrosion properties allowed the GQD fluid to have excellent potential for applications in the energy sector.
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Walton-Raaby, Max, Riley Woods, and Subha Kalyaanamoorthy. "Investigating the Theranostic Potential of Graphene Quantum Dots in Alzheimer’s Disease." International Journal of Molecular Sciences 24, no. 11 (May 30, 2023): 9476. http://dx.doi.org/10.3390/ijms24119476.
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Alzheimer’s disease (AD) is one of the leading causes of death worldwide, with no definitive diagnosis or known cure. The aggregation of Tau protein into neurofibrillary tangles (NFTs), which contain straight filaments (SFs) and paired helical filaments (PHFs), is a major hallmark of AD. Graphene quantum dots (GQDs) are a type of nanomaterial that combat many of the small-molecule therapeutic challenges in AD and have shown promise in similar pathologies. In this study, two sizes of GQDs, GQD7 and GQD28, were docked to various forms of Tau monomers, SFs, and PHFs. From the favorable docked poses, we simulated each system for at least 300 ns and calculated the free energies of binding. We observed a clear preference for GQD28 in the PHF6 (306VQIVYK311) pathological hexapeptide region of monomeric Tau, while GQD7 targeted both the PHF6 and PHF6* (275VQIINK280) pathological hexapeptide regions. In SFs, GQD28 had a high affinity for a binding site that is available in AD but not in other common tauopathies, while GQD7 behaved promiscuously. In PHFs, GQD28 interacted strongly near the protofibril interface at the putative disaggregation site for epigallocatechin-3-gallate, and GQD7 largely interacted with PHF6. Our analyses revealed several key GQD binding sites that may be used for detecting, preventing, and disassembling the Tau aggregates in AD.
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Santiago, Ana M., Carla I. M. Santos, Leandro M. O. Lourenço, Inês F. A. Mariz, João P. C. Tomé, and Ermelinda Maçôas. "Graphene Quantum Dots and Phthalocyanines Turn-OFF-ON Photoluminescence Nanosensor for ds-DNA." Nanomaterials 12, no. 11 (May 31, 2022): 1892. http://dx.doi.org/10.3390/nano12111892.
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Supramolecular hybrids of graphene quantum dots (GQDs) and phthalocyanine (Pc) dyes were studied as turn-OFF-ON photoluminescence nanosensors for detection of ds-DNA. Pcs with four (Pc4) and eight (Pc8) positive charges were selected to interact with negatively charged GQDs. The photoluminescence of the GQDs was quenched upon interaction with the Pcs, due to the formation of non-emissive complexes. In the presence of ds-DNA, the Pcs interacted preferentially with the negatively charged ds-DNA, lifting the quenching effect over the photoluminescence of the GQDs and restoring their emission intensity. The best performance as a sensor of ds-DNA was registered for the GQD-Pc8, with a limit of detection (LOD) in the picomolar range. The LOD for GQD-Pc8 was more than one order of magnitude lower and its sensitivity was about a factor of three higher than that of the analogue GQD-Pc4 nanosensor. The sensitivity and selectivity of this simple GQD-Pc8 nanosensor is comparable to those of the more sophisticated carbon-based nanosensors for DNA reported previously.
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Ch, Seshendra Reddy, Ravindra N. Bulakhe, Jeevan Kumar Reddy Modigunta, G. Murali, Reddy Sivasankar A., Jiyeong Kim, Eunji Park, et al. "Tin Oxide/Nitrogen-Doped Graphene Quantum Dots Composite Nanotubes: An Efficient Electrode for Supercapacitors." Journal of Nanomaterials 2022 (July 13, 2022): 1–14. http://dx.doi.org/10.1155/2022/3167809.
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Tin oxide (SnO2) and nitrogen-doped graphene quantum dots (N-GQDs) composite nanotubes (SnO2/N-GQD NTs) were fabricated by the electrospinning technique and followed by the thermal annealing method for the application in supercapacitor as an electrode. SnO2/N-GQD NTs with different ratio of N-GQDs were prepared by adding different ratios of N-GQDs along with tin chloride during the electrospinning process. The prepared composite's structure and morphological properties were characterized by using different techniques like XRD, FE-SEM, TEM, and XPS. The supercapacitor performance of the SnO2/N-GQD NTs composite was analyzed by the electrochemical studies such as cyclic voltammetry and galvanostatic charge-discharge (GCD) measurement in 2 M KOH solution as electrolyte. The electrochemical analyses of SnO2/N-GQD NTs was tested at different scan rates and current densities. SnO2/N-GQD NTs prepared using 3 wt.% of N-GQDs showed an excellent capacity retention even after 5000 GCD cycles and exhibited a maximum specific capacitance of 420 mF g-1 at a current density of 8 mA cm-2 in comparison to pure SnO2 NTs (230 mF cm-2).
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Vatanparast, Morteza, and Zahra Shariatinia. "Revealing the role of different nitrogen functionalities in the drug delivery performance of graphene quantum dots: a combined density functional theory and molecular dynamics approach." Journal of Materials Chemistry B 7, no. 40 (2019): 6156–71. http://dx.doi.org/10.1039/c9tb00971j.
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The role of different N-functionalities was investigated on the drug delivery performance of N-GQDs. Results suggested that the center N-GQD had a better performance than the pristine and edge N-GQDs.
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Le, Thi Hoa, Hyun Jong Lee, Ji Hyeon Kim, and Sang Joon Park. "Highly Selective Fluorescence Sensor Based on Graphene Quantum Dots for Sulfamethoxazole Determination." Materials 13, no. 11 (June 1, 2020): 2521. http://dx.doi.org/10.3390/ma13112521.
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In our research, a reliable fluorescence sensor for the detection of sulfamethoxazole (SMZ) was developed. This method relies on graphene quantum dots (GQDs) entrapped in a silica molecularly imprinted polymer (GQDs@SMIP), which was synthesized by the polymerization using GQDs, SMZ, tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as fluorescence material, template, cross-linker, and functional monomers, respectively. The GQDs@SMIP was characterized by fluorometry, Fourier-transform infrared spectroscopy, transmission and scanning electron microscopies, X-ray photoelectron spectroscopy, and powder X-ray diffraction. The GQDs@SMIP exhibited a good capacity to absorb SMZ from solution, which resulted in the quenching of the GQD fluorescence intensity. The intensity of GQDs@SMIP decreased linearly with the SMZ concentration in the range of 1 to 100 µM with a correlation coefficient of 0.99537. In addition, the fluorescence responses of GQDs@SMIP to interfering substances were investigated. The results indicated that there was no effect of interfering substances on SMZ detection. Thus, the highly selective GQDs@SMIP fluorescence sensor is an effective and promising device for SMZ detection and analysis.
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Sajjad, M., V. Makarov, M. S. Sultan, W. M. Jadwisienczak, B. R. Weiner, and G. Morell. "Synthesis, Optical, and Magnetic Properties of Graphene Quantum Dots and Iron Oxide Nanocomposites." Advances in Materials Science and Engineering 2018 (2018): 1–8. http://dx.doi.org/10.1155/2018/3254081.
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The combination of nanomaterial graphene quantum dots (GQDs) with magnetic nanoparticles offers a unique set of optical and magnetic properties for future energy and medical applications. We report on the synthesis and engineering of GQDs and iron oxide (Fe3O4) nanocomposites (NCs) by using a pulsed laser discharge technique. High-resolution transmission electron microscopy (HRTEM) images showed a high yield of pure GQDs with 2–10 nm diameter. The hexagonal structures and lattice fringes associated with the C–C bond in GQDs were clearly identifiable. The structural and optical changes in GQDs and GQDs-Fe3O4 NC samples induced by UV light were investigated by the absorption and emission spectroscopy over the deep UV–visible spectral range. The photoluminescence spectra have shown subband π→π∗ transitions in GQDs-Fe3O4 NC. Magnetic properties of the GQDs-Fe3O4 NC samples have shown room temperature ferromagnetism induced by pure Fe3O4 nanoparticles and from the substantial spin polarized edges of GQD nanoparticles. It is concluded that the observed optical and magnetic properties could be further tailored in the studied nanocomposites for prospective medical applications.
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Al Jahdaly, Badreah Ali, Mohamed Farouk Elsadek, Badreldin Mohamed Ahmed, Mohamed Fawzy Farahat, Mohamed M. Taher, and Ahmed M. Khalil. "Outstanding Graphene Quantum Dots from Carbon Source for Biomedical and Corrosion Inhibition Applications: A Review." Sustainability 13, no. 4 (February 17, 2021): 2127. http://dx.doi.org/10.3390/su13042127.
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Graphene quantum dots (GQD) is an efficient nanomaterial composed of one or more layers of graphene with unique properties that combine both graphene and carbon dots (CDs). It can be synthesized using carbon-rich materials as precursors, such as graphite, macromolecules polysaccharides, and fullerene. This contribution emphasizes the utilization of GQD-based materials in the fields of sensing, bioimaging, energy storage, and corrosion inhibitors. Inspired by these numerous applications, various synthetic approaches have been developed to design and fabricate GQD, particularly bottom-up and top-down processes. In this context, the prime goal of this review is to emphasize possible eco-friendly and sustainable methodologies that have been successfully employed in the fabrication of GQDs. Furthermore, the fundamental and experimental aspects associated with GQDs such as possible mechanisms, the impact of size, surface alteration, and doping with other elements, together with their technological and industrial applications have been envisaged. Till now, understanding simple photo luminance (PL) operations in GQDs is very critical as well as there are various methods derived from the optical properties of manufactured GQDs can differ. Lack of determining exact size and morphology is highly required without loss of their optical features. Finally, GQDs are promising candidates in the after-mentioned application fields.
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Kadyan, Pooja, Rohit Malik, Saurabh Bhatia, Ahmed Al Harrasi, Syam Mohan, Mansi Yadav, Sunita Dalal, Seema Ramniwas, Sudhir Kumar Kataria, and Thillai Arasu. "Comprehensive Review on Synthesis, Applications, and Challenges of Graphene Quantum Dots (GQDs)." Journal of Nanomaterials 2023 (January 26, 2023): 1–26. http://dx.doi.org/10.1155/2023/2832964.
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Carbon-based nanomaterials are contemporary and are outpacing the technology platform. Graphene quantum dots (GQDs) had a significant impact on the subject of bioengineering, pharmaceuticals, biomedicine, biosensors, fuel, energy, etc. Depending on how quickly this field is developing, it is important to recognize the new difficulties that GQDs have to overcome. This is incredibly significant because many novel applications and innovations that have made GQD synthesis easier recently have not been systematically evaluated in prior studies. Their ability to combine the benefits of quantum dots, sp2 carbon materials (large specific surface area), and have rich functional groups at the edge makes them special. The naturally occurring inert carbon helps to stabilize chemical and physical characteristics and makes significant advancements in the creation of benchmark photocatalysts. Moreover, current challenges and potential of these rapidly developing GQDs are emphasized. The future of GQD research is limitless, according to the assessment in this review, notably if future research focuses on simplicity of purification and ecofriendly synthesis. This feature article offers a realistic summary on recent developments in the synthesis, characteristics, and uses of GQDs. Frequent review articles focusing on the progress of GQDs for specific applications are published but a thorough review article on GQDs for their numerous uses has not yet been published. The recent trends of scientific research based on new optical biosensing applications, including the comprehensive applications of different zero-dimensional nanomaterials, specially GQDs are discussed in this study.
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Gupta, Sanju, Tyler Smith, Alexander Banaszak, and John Boeckl. "Graphene Quantum Dots Electrochemistry and Development of Ultrasensitive Enzymatic Glucose Sensor." MRS Advances 3, no. 15-16 (2018): 831–47. http://dx.doi.org/10.1557/adv.2018.324.
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AbstractGraphene quantum dots (GQDs) - zero-dimensional materials - are sheets of a few nanometers in lateral dimension and exhibit quantum confinement and edge site effects where sp2-bonded carbon nanocore surrounded with edged plane functional moieties is promising as advanced electroactive sensing platforms. In this work, GQDs are synthesized by solvothermal and hydrothermal techniques, with optimal size of 5 nm. Their potential in fundamental (direct electron transfer) and applied (enzymatic glucose biosensor) electrochemistry are demonstrated. Glucose oxidase (GOx) immobilized on glassy carbon (GC) electrodes modified with GQDs are investigated by means of cyclic voltammetry, differential pulse voltammetry, and amperometry. Well-defined quasi-reversible redox peaks observed under various electrochemical parameters helped to determine diffusion coefficient (D) and first-order electron transfer rate (kET). The cyclic voltammetry curves showed homogeneous ion transport for GQD with D ranging between 8.45 × 10−9 m2 s−1 and 3 × 10−8 m2 s−1 following GO < rGO < GQD < GQD (with FcMeOH as redox probe) < GOx/rGO < GOx/GO < HRP/GQDs < GOx/GQDs. The developed GOx-GQDs biosensor responds efficiently and linearly to the presence of glucose over concentrations ranging 10 μM and 3 mM with limit of detection 1.35 μM and sensitivity 0.00769 μA μM−1·cm−2 as compared with rGO (0.025 μA μM−1 cm−2, 4.16 μM) and GO (0.064 μA μM−1 cm−2, 4.82 μM) nanosheets. The high performance and stability of GQDs is attributed to sufficiently large surface-to-volume ratio, excellent biocompatibility, abundant hydrophilic edge site density, and partially hydrophobic planar sites that favors GOx adsorption on the electrode surface and versatile architectures to ensure rapid charge transfer and electron/ion conduction (<10 ms). We also carried out similar studies with other enzymatic protein biomolecules on electrode surfaces prepared from GQD precursors for electrochemical comparison, thus opening up potential sensing applications in medicine as well as bio-nanotechnology.
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Le, Thi Hoa, Dal Ho Lee, Ji Hyeon Kim, and Sang Joon Park. "Polypyrrole/Graphene Quantum Dot Composites as a Sensor Media for Epinephrine." Journal of Nanoscience and Nanotechnology 20, no. 7 (July 1, 2020): 4005–10. http://dx.doi.org/10.1166/jnn.2020.17588.
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In this paper, we discuss a new biosensor for simple and rapid detection of epinephrine (EP) based on polypyrrole/graphene quantum dot (PPy/GQD) composites. Presence of amine groups on the PPy backbone leads to surface passivation of GQDs. As a result, the composites exhibit strong fluorescence emission, which can be up to three times that of pristine GQDs. In neutral to alkaline solution, the EP on the surface of PPy/GQD composites is converted to a quinone, which triggers the fluorescence quenching of PPy/GQD composites via a photoinduced electron transfer process. Hence, the concentration of EP can be effectively monitored by measuring the variation in the fluorescence signal of PPy/GQD composites. The quenched fluorescence intensity of PPy/GQDs was proportional to the concentration of EP (0.7–400 μM). We used our method to determine the concentration of EP in human serum samples and obtained satisfactory results.
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Park, Kwang Hyun, and Sung Ho Song. "Graphene Quantum Dots with Blue and Yellow Luminescence Fabricated by Modulating Intercalation State." Materials 15, no. 19 (September 22, 2022): 6567. http://dx.doi.org/10.3390/ma15196567.
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The development of graphene quantum dots (GQDs) with low toxicity, excellent dispersibility, and high photostability has led to extensive progress in bio-imaging and optical sensing applications. However, one-pot synthesis and mass production of GQDs, and tuning their photoluminescence, remains a challenge. Here we demonstrate a simple and scalable method for fabricating GQDs with high size uniformity and chemical stability, via a sequential process of inserting alkali metal into graphite (Stage I: KC8 and Stage II: KC24) and exfoliation to GQDs in a selected solvent. Structural and optical measurements were conducted, and the emitted colors of the as-prepared GQDs were blue (KC8) and yellow (KC24), respectively. The stage of graphite intercalation in the compounds played an important role in the size and thickness of the GQD. The as-prepared GQDs had clear characteristic peaks consistent with the quantum confinement effect and intrinsic/extrinsic states. Our approach will provide great potential for a wide variety of bioimaging and bioanalysis applications.
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Jovanovic, Svetlana, Olaf C. Haenssler, Milica Budimir, Duška Kleut, Jovana Prekodravac, and Biljana Todorovic Markovic. "Reduction of graphene oxide and graphene quantum dots using nascent hydrogen: The investigation of morphological and structural changes." Resolution and Discovery 5, no. 1 (December 11, 2020): 1–4. http://dx.doi.org/10.1556/2051.2020.00073.
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AbstractIn order to modify both chemical and electrical properties of graphene-based nanomaterials, we conducted the chemical modification of graphene oxide (GO) and graphene quantum dots (GQDs). The reaction of the reduction with nascent hydrogen was conducted on both materials. The structure and morphology of produced chemically reduced GO and GQDs were analyzed. While the chemical composition of both GQD and GO changed significantly, GO showed also significant changes in morphology as opposite to GQDs where were morphological changes were not observed.
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Bhaloo, Adam, Steven Nguyen, Bong Han Lee, Alina Valimukhametova, Roberto Gonzalez-Rodriguez, Olivia Sottile, Abby Dorsky, and Anton V. Naumov. "Doped Graphene Quantum Dots as Biocompatible Radical Scavenging Agents." Antioxidants 12, no. 8 (July 31, 2023): 1536. http://dx.doi.org/10.3390/antiox12081536.
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Oxidative stress is proven to be a leading factor in a multitude of adverse conditions, from Alzheimer’s disease to cancer. Thus, developing effective radical scavenging agents to eliminate reactive oxygen species (ROS) driving many oxidative processes has become critical. In addition to conventional antioxidants, nanoscale structures and metal–organic complexes have recently shown promising potential for radical scavenging. To design an optimal nanoscale ROS scavenging agent, we have synthesized ten types of biocompatible graphene quantum dots (GQDs) augmented with various metal dopants. The radical scavenging abilities of these novel metal-doped GQD structures were, for the first time, assessed via the DPPH, KMnO4, and RHB (Rhodamine B protectant) assays. While all metal-doped GQDs consistently demonstrate antioxidant properties higher than the undoped cores, aluminum-doped GQDs exhibit 60–95% radical scavenging ability of ascorbic acid positive control. Tm-doped GQDs match the radical scavenging properties of ascorbic acid in the KMnO4 assay. All doped GQD structures possess fluorescence imaging capabilities that enable their tracking in vitro, ensuring their successful cellular internalization. Given such multifunctionality, biocompatible doped GQD antioxidants can become prospective candidates for multimodal therapeutics, including the reduction of ROS with concomitant imaging and therapeutic delivery to cancer tumors.
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Far’ain, Noor, Muhamad Mat Salleh, Muhammad Ashraf, Mohd Yusri Abd Rahman, and Akrajas Ali Umar. "Synthesis of Blue-Luminescence Graphene Quantum Dots Using Hydrothermal Method." Solid State Phenomena 268 (October 2017): 259–63. http://dx.doi.org/10.4028/www.scientific.net/ssp.268.259.
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This paper described the synthesis of graphene quantum dot (GQDs) by hydrothermal method using graphene (average thickness of 7 nm) as a precursor material. At first, graphene was diluted in n-butyl acetate to obtain uniform mixture through sonication. Then, graphene was transferred into Teflon-lined autoclave and to be heated at different period of times to obtain resultant GQDs.The synthesised GQDs was characterized by using FT-IR Spectrometer (FTIR), UV-VIS Spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). Typically, the absorption peak of GQDs were observed around 260 nm and 330 nm in UV-VIS spectra due to π →π * transition of aromatic sp2 domain. This GQD has a broad peak and emit strong PL, light centred at 440 nm upon excitation at 260 nm. Thus, blue-luminescent GQDs are demonstrated, with a material performance that is competitive with GQDs produced by other methods.
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Lee, Bong Han, Ryan Lee McKinney, Md Tanvir Hasan, and Anton V. Naumov. "Graphene Quantum Dots as Intracellular Imaging-Based Temperature Sensors." Materials 14, no. 3 (January 29, 2021): 616. http://dx.doi.org/10.3390/ma14030616.
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Non-invasive temperature sensing is necessary to analyze biological processes occurring in the human body, including cellular enzyme activity, protein expression, and ion regulation. To probe temperature-sensitive processes at the nanoscale, novel luminescence nanothermometers are developed based on graphene quantum dots (GQDs) synthesized via top-down (RGQDs) and bottom-up (N-GQDs) approaches from reduced graphene oxide and glucosamine precursors, respectively. Because of their small 3–6 nm size, non-invasive optical sensitivity to temperature change, and high biocompatibility, GQDs enable biologically safe sub-cellular resolution sensing. Both GQD types exhibit temperature-sensitive yet photostable fluorescence in the visible and near-infrared for RGQDs, utilized as a sensing mechanism in this work. Distinctive linear and reversible fluorescence quenching by up to 19.3% is observed for the visible and near-infrared GQD emission in aqueous suspension from 25 °C to 49 °C. A more pronounced trend is observed with GQD nanothermometers internalized into the cytoplasm of HeLa cells as they are tested in vitro from 25 °C to 45 °C with over 40% quenching response. Our findings suggest that the temperature-dependent fluorescence quenching of bottom-up and top-down-synthesized GQDs studied in this work can serve as non-invasive reversible/photostable deterministic mechanisms for temperature sensing in microscopic sub-cellular biological environments.
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Chinnusamy Jayanthi, Sowbaranigha, Ravneet Kaur, and Folarin Erogbogbo. "Graphene Quantum Dot - Titania Nanoparticle Composite for Photocatalytic Water Splitting." MRS Advances 1, no. 28 (2016): 2071–77. http://dx.doi.org/10.1557/adv.2016.470.
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ABSTRACTGraphene quantum dots (GQDs) of different sizes were synthesized by the top-down approach, using charcoal as the precursor material. Size and absorption characteristics of synthesized GQDs were analyzed using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Photoluminescence Spectroscopy (PL), and UV-vis Spectroscopy. The results showed that GQDs with an average height of 8.5 nm, synthesized at a relatively lower temperature of 85°C, exhibited higher UV and visible light absorption. GQD concentration was varied to form 0.5, 1, 2.5, and 5 wt.% GQD-titania (TiO2) nano composites. Surface morphology of the composite was examined using Scanning Electron Microscopy (SEM). Photocatalytic activity of the samples was assessed from methylene blue dye degradation in UV irradiation at 340nm. A distinguishable trend for pure TiO2 and composites at various concentrations were observed.
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Kurniawan, Darwin, Yan-Yi Chen, Neha Sharma, Michael Ryan Rahardja, and Wei-Hung Chiang. "Graphene Quantum Dot-Enabled Nanocomposites as Luminescence- and Surface-Enhanced Raman Scattering Biosensors." Chemosensors 10, no. 12 (November 23, 2022): 498. http://dx.doi.org/10.3390/chemosensors10120498.
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Graphene quantum dots (GQDs) are a zero-dimensional (0D) carbon-based nanomaterial with a unique quantum confinement effect that have captured the eyes of many researchers. In addition to their luminescence properties, a high biocompatibility and large surface area have enabled GQDs to be used for many applications, and even be integrated with either organic or inorganic materials to produce GQD nanocomposites to enhance the application performances and broaden the application scope. In this review, we aim to highlight the exquisite properties and synthesis methods of GQDs, recent advances in the fabrication of GQD nanocomposites with both organic and inorganic materials, and their corresponding luminescence-based and surface enhanced Raman scattering (SERS)-based biosensing applications. Finally, this review article concludes with a summary of current challenges and prospects.
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Gupta, Sanju, Jared Walden, Alexander Banaszak, and Sara B. Carrizosa. "Facile Synthesis of Water-Soluble Graphene Quantum Dots/Graphene for Efficient Photodetector." MRS Advances 3, no. 15-16 (2018): 817–24. http://dx.doi.org/10.1557/adv.2018.14.
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ABSTRACTGraphene quantum dots (GQDs) are zero-dimensional material with characteristics derived from functionalized graphene precursors are graphene sheets a few nanometers in the lateral dimension having a several-layer thickness. Combining the structure of graphene with the quantum confinement and edge effects, GQDs possess unique chemical behavior and physical properties. Intense research activity in GQDs is attributed to their novel phenomena of charge transport and light absorption and photoluminescence excitation. The optical transitions are known to be available up to 6 eV in GQDs, applicable for ultraviolet photonics and optoelectronics devices, biomedical imaging capabilities and technologies. We present facile hydrothermal and solvothermal methods for synthesizing homogenous dispersed and uniform sized GQDs with a strong greenish and violet blue emission peaks at ∼10-14% yield. This approach enabled a large-scale production of aqueous GQD dispersions without the need for chemical stabilizers. The structure and emission mechanism of the GQDs have been studied by combining extensive characterization techniques and rigorous control experiments. We further demonstrate the distinctive advantages of such GQDs as high-performance photodetectors (PDs). Here we also report high-efficient photocurrent (PC) behaviors consisting of multilayer GQDs sandwiched between monolayer graphene sheets. It is conceivable that the observed unique PD characteristics proved to be dominated by tunneling of charge carriers which occurs through the multiple energy states within the bandgap of GQDs, based on bias-dependent variation of the band profiles. This results in novel dark current and PC behaviors. The external quantum efficiency (η) is predicted to be 47% at applied potential 2 V. These findings highlight rich photophysics and comparable performance of graphene/graphene oxide hybrids opening up potential applications as optoelectronic devices.
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Lee, Bong Han, Ryan L. McKinney, Md Tanvir Hasan, and Anton V. Naumov. "Top Down and Bottom Up Synthesized Graphene Quantum Dots As Nanothermometers For I n Vitro Imaging." ECS Meeting Abstracts MA2022-01, no. 8 (July 7, 2022): 698. http://dx.doi.org/10.1149/ma2022-018698mtgabs.
Full textAbstract:
Non-invasive temperature sensing is necessary to analyze biological processes occurring in the human body, including cellular enzyme activity, protein expression, and ion regulation. To probe temperature-sensitive processes at the nanoscale, novel luminescence nanothermometers are developed based on graphene quantum dots (GQDs) synthesized via top-down (RGQDs) and bottom-up (N-GQDs) approaches from reduced graphene oxide and glucosamine precursors, respectively. Because of their small 3–6 nm size, non-invasive optical sensitivity to temperature change, and high biocompatibility, GQDs enable biologically safe sub-cellular resolution sensing. Both GQD types exhibit temperature-sensitive yet photostable fluorescence in the visible and near-infrared for RGQDs, utilized as a sensing mechanism in this work. Distinctive linear and reversible fluorescence quenching by up to 19.3% is observed for the visible and near-infrared GQD emission in aqueous suspension from 25 °C to 49 °C. A more pronounced trend is observed with GQD nanothermometers internalized into the cytoplasm of HeLa cells as they are tested in vitro from 25 °C to 45 °C with over 40% quenching response. Our findings suggest that the temperature-dependent fluorescence quenching of bottom-up and top-down-synthesized GQDs studied in this work can serve as non-invasive reversible/photostable deterministic mechanisms for temperature sensing in microscopic sub-cellular biological environments. Figure 1
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Tran, Hai Linh, Win Darmanto, and Ruey-An Doong. "Ultrasensitive Detection of Tetracycline Using Boron and Nitrogen Co-Doped Graphene Quantum Dots from Natural Carbon Source as the Paper-Based Nanosensing Probe in Difference Matrices." Nanomaterials 10, no. 9 (September 20, 2020): 1883. http://dx.doi.org/10.3390/nano10091883.
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Herein, the boron and nitrogen co-doped 0-dimensional graphene quantum dots (B,N-GQDs) with high quantum yield (QY) were synthesized via microwave-assisted hydrothermal method at 170 °C for 20 min using fresh passion fruit juice and boric acid as the starting materials. The 3–6 layers of B,N-GQDs with mean particle size of 9 ± 1 nm were then used for ultra-sensitive and selective detection of tetracycline in aqueous and biological media. The hybridization of boron and nitrogen atoms into the GQD structures increases the intensity of electronegative, resulting in the enhancement of QY to 50 ± 1%. The B,N-GQDs show their excellent analytical performance on tetracycline determination after 2 min of reaction under an optimal condition at pH 5. The linear range of 0.04–70 µM and with limits of detection (LOD) of 1 nM in phosphate buffer saline (PBS), 1.9 nM in urine and 2.2 nM in human serum are obtained. Moreover, the high selectivity of tetracycline by B,N-GQDs over the other 23 interferences is observed. The π-π interaction and electron donor-acceptor principle play pivotal roles in enhancing the ultra-sensitivity and selectivity of B,N-GQDs toward TC detection. Moreover, the B, N-GQD based paper nanosensor exhibits an excellent analytical performance on visual detection of 0.1–30 µM TC in human serum. Results of this study clearly indicate the feasibility of synthesis of B,N-GQDs derived from passion fruit juice for ultrasensitive tetracycline detection, which can open an avenue to use natural products for the preparation of environmentally benign and biocompatible carbon nanomaterials for highly sensitive detection of drugs, antibiotics, organic compounds and biomarkers.
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Naik, M. Jaya Prakash, Sourajit Mohanta, Peetam Mandal, and Mitali Saha. "N-Doped Graphene Quantum Dots Using Different Bases." International Journal of Nanoscience 18, no. 01 (January 24, 2019): 1850017. http://dx.doi.org/10.1142/s0219581x18500175.
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Photoluminescent graphene quantum dots (GQDs) have received tremendous attention due to their sui generis chemical, electronic and optical properties but fabricating the pristine quality of GQD is extremely challenging. Herein, we have reported the pyrolysis of citric acid which in the presence of different bases viz. triethylamine, ammonium hydroxide and urea, produced N-doped GQDs at different pH. The effect of different pH has been studied in detail to optimize the formation conditions of the GQD. Ultraviolet–visible (UV–Vis) spectroscopy and normalized fluorescence spectra were applied to analyze the optical properties of the GQD. The mean particle size was analyzed by a particle size analyzer (dynamic light dispersion).
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Chen, Weifeng, Guo Lv, Weimin Hu, Dejiang Li, Shaona Chen, and Zhongxu Dai. "Synthesis and applications of graphene quantum dots: a review." Nanotechnology Reviews 7, no. 2 (April 25, 2018): 157–85. http://dx.doi.org/10.1515/ntrev-2017-0199.
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AbstractAs a new class of fluorescent carbon materials, graphene quantum dots (GQDs) have attracted tremendous attention due to their outstanding properties and potential applications in biological, optoelectronic, and energy-related fields. Herein, top-down and bottom-up strategies for the fabrication of GQDs, mainly containing oxidative cleavage, the hydrothermal or solvothermal method, the ultrasonic-assisted or microwave-assisted process, electrochemical oxidation, controllable synthesis, and carbonization from small molecules or polymers, are discussed. Different methods are presented in order to study their characteristics and their influence on the final properties of the GQDs. The respective advantages and disadvantages of the methods are introduced. With regard to some important or novel methods, the mechanisms are proposed for reference. Moreover, recent exciting progresses on the applications of GQD, such as sensors, bio-imaging, drug carriers, and solar cells are highlighted. Finally, a brief outlook is given, pointing out the issues still to be settled for further development. We believe that new preparation methods and properties of GQDs will be found, and GQDs will play more important roles in novel devices and various applications.
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Zhao, Pin Hui, Yi Luo, and Ling Yun Kong. "One-Step Preparation of Green Fluorescent Graphene Quantum Dots from Petroleum Asphalt." Journal of Nano Research 45 (January 2017): 76–83. http://dx.doi.org/10.4028/www.scientific.net/jnanor.45.76.
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Inherently benefiting from the natural nanosize graphene-structure in raw asphalt material. Asphalt-derived graphene quantum dots ( GQDs ) are prepared through, a facile route, one-step chemical oxidation of cheap petroleum asphalt. The as-prepared GQD sample may be well dissolved in water with a good homogeneous size at an average diameter of 2.44 nm, luminescing bright green light by excitation of 365 nm with a high quantum yield up to 16.13%. Furthermore, they are much smaller and thinner than most of the reported GQDs, presenting excellent fluorescent properties, such as excitation-tuned photoluminescence and good resistance to photobleaching. They are much smaller and thinner than most of the reported GQDs
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Liang, Lijun, Xin Shen, Mengdi Zhou, Yijian Chen, Xudong Lu, Li Zhang, Wei Wang, and Jia-Wei Shen. "Theoretical Evaluation of Potential Cytotoxicity of Graphene Quantum Dot to Adsorbed DNA." Materials 15, no. 21 (October 23, 2022): 7435. http://dx.doi.org/10.3390/ma15217435.
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As a zero-dimensional (0D) nanomaterial, graphene quantum dot (GQD) has a unique physical structure and electrochemical properties, which has been widely used in biomedical fields, such as bioimaging, biosensor, drug delivery, etc. Its biological safety and potential cytotoxicity to human and animal cells have become a growing concern in recent years. In particular, the potential DNA structure damage caused by GQD is of great importance but still obscure. In this study, molecular dynamics (MD) simulation was used to investigate the adsorption behavior and the structural changes of single-stranded (ssDNA) and double-stranded DNA (dsDNA) on the surfaces of GQDs with different sizes and oxidation. Our results showed that ssDNA can strongly adsorb and lay flat on the surface of GQDs and graphene oxide quantum dots (GOQDs), whereas dsDNA was preferentially oriented vertically on both surfaces. With the increase of GQDs size, more structural change of adsorbed ssDNA and dsDNA could be found, while the size effect of GOQD on the structure of ssDNA and dsDNA is not significant. These findings may help to improve the understanding of GQD biocompatibility and potential applications of GQD in the biomedical field.
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Gu, Siyong, Chien-Te Hsieh, Chih-Peng Kao, Chun-Chieh Fu, Yasser Ashraf Gandomi, Ruey-Shin Juang, and Kenneth David Kihm. "Electrocatalytic Oxidation of Glucose on Boron and Nitrogen Codoped Graphene Quantum Dot Electrodes in Alkali Media." Catalysts 11, no. 1 (January 13, 2021): 101. http://dx.doi.org/10.3390/catal11010101.
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A novel solvothermal technique has been developed in the presence of C/N/B precursor for synthesizing B-N-coped graphene quantum dots (GQDs) as non-metal electrocatalysts towards the catalytic glucose oxidation reaction (GOR). Both N-doped GQD and B-N-codoped GQD particles (~4.0 nm) possess a similar oxidation and amidation level. The B-N-codoped GQD contains a B/C ratio of 3.16 at.%, where the B dopants were formed through different bonding types (i.e., N‒B, C‒B, BC2O, and BCO2) inserted into or decorated on the GQDs. The cyclic voltammetry measurement revealed that the catalytic activity of B-N-codoped GQD catalyst is significantly higher compared to the N-doped GQDs (~20% increase). It was also shown that the GOR activity was substantially enhanced due to the synergistic effect of B and N dopants within the GQD catalysts. Based on the analysis of Tafel plots, the B-N-codoped-GQD catalyst electrode displays an ultra-high exchange current density along with a reduced Tafel slope. The application of B-N-codoped GQD electrodes significantly enhances the catalytic activity and results in facile reaction kinetics towards the glucose oxidation reaction. Accordingly, the novel design of GQD catalyst demonstrated in this work sets the stage for designing inexpensive GQD-based catalysts as an alternative for precious metal catalysts commonly used in bio-sensors, fuel cells, and other electrochemical devices.
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Dorontic, Sladjana, Aurelio Bonasera, Michelangelo Scopelliti, Olivera Markovic, Danica Bajuk Bogdanović, Gabriele Ciasca, Sabrina Romanò, et al. "Gamma-Ray-Induced Structural Transformation of GQDs towards the Improvement of Their Optical Properties, Monitoring of Selected Toxic Compounds, and Photo-Induced Effects on Bacterial Strains." Nanomaterials 12, no. 15 (August 7, 2022): 2714. http://dx.doi.org/10.3390/nano12152714.
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Structural modification of different carbon-based nanomaterials is often necessary to improve their morphology and optical properties, particularly the incorporation of N-atoms in graphene quantum dots (GQDs). Here, a clean, simple, one-step, and eco-friendly method for N-doping of GQDs using gamma irradiation is reported. GQDs were irradiated in the presence of the different ethylenediamine (EDA) amounts (1 g, 5 g, and 10 g) and the highest % of N was detected in the presence of 10 g. N-doped GQDs emitted strong, blue photoluminescence (PL). Photoluminescence quantum yield was increased from 1.45, as obtained for non-irradiated dots, to 7.24% for those irradiated in the presence of 1 g of EDA. Modified GQDs were investigated as a PL probe for the detection of insecticide Carbofuran (2,2-Dimethyl-2,3-dihydro-1-benzofuran-7-yl methylcarbamate) and herbicide Amitrole (3-amino-1,2,4-triazole). The limit of detection was 5.4 μmol L−1 for Carbofuran. For the first time, Amitrole was detected by GQDs in a turn-off/turn-on mechanism using Pd(II) ions as a quenching agent. First, Pd(II) ions were quenched (turn-off) PL of GQDs, while after Amitrole addition, PL was recovered linearly with Amitrole concentration (turn-on). LOD was 2.03 μmol L−1. These results suggest that modified GQDs can be used as an efficient new material for Carbofuran and Amitrole detection. Furthermore, the phototoxicity of dots was investigated on both Gram-positive and Gram-negative bacterial strains. When bacterial cells were exposed to different GQD concentrations and illuminated with light of 470 nm wavelength, the toxic effects were not observed.
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Milenković, Mila, Aleksandra Mišović, Dragana Jovanović, Ana Popović Bijelić, Gabriele Ciasca, Sabrina Romanò, Aurelio Bonasera, et al. "Facile Synthesis of L-Cysteine Functionalized Graphene Quantum Dots as a Bioimaging and Photosensitive Agent." Nanomaterials 11, no. 8 (July 22, 2021): 1879. http://dx.doi.org/10.3390/nano11081879.
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Nowadays, a larger number of aggressive and corrosive chemical reagents as well as toxic solvents are used to achieve structural modification and cleaning of the final products. These lead to the production of residual, waste chemicals, which are often reactive, cancerogenic, and toxic to the environment. This study shows a new approach to the modification of graphene quantum dots (GQDs) using gamma irradiation where the usage of reagents was avoided. We achieved the incorporation of S and N atoms in the GQD structure by selecting an aqueous solution of L-cysteine as an irradiation medium. GQDs were exposed to gamma-irradiation at doses of 25, 50 and 200 kGy. After irradiation, the optical, structural, and morphological properties, as well as the possibility of their use as an agent in bioimaging and photodynamic therapy, were studied. We measured an enhanced quantum yield of photoluminescence with the highest dose of 25 kGy (21.60%). Both S- and N-functional groups were detected in all gamma-irradiated GQDs: amino, amide, thiol, and thione. Spin trap electron paramagnetic resonance showed that GQDs irradiated with 25 kGy can generate singlet oxygen upon illumination. Bioimaging on HeLa cells showed the best visibility for cells treated with GQDs irradiated with 25 kGy, while cytotoxicity was not detected after treatment of HeLa cells with gamma-irradiated GQDs.
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Wang, Lu, Jing Yang, Yukai Zhang, and Dianzhong Wen. "Dual-Tunable Memristor Based on Carbon Nanotubes and Graphene Quantum Dots." Nanomaterials 11, no. 8 (August 11, 2021): 2043. http://dx.doi.org/10.3390/nano11082043.
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Nanocarbon materials have the advantages of biocompatibility, thermal stability and chemical stability and have shown excellent electrical properties in electronic devices. In this study, Al/MWCNT:GQD/ITO memristors with rewritable nonvolatile properties were prepared based on composites consisting of multiwalled carbon nanotubes (MWCNTs) and graphene quantum dots (GQDs). The switching current ratio of such a device can be tuned in two ways. Due to the ultraviolet light sensitivity of GQDs, when the dielectric material is illuminated by ultraviolet light, the charge capture ability of the GQDs decreases with an increasing duration of illumination, and the switching current ratio of the device also decreases with an increasing illumination duration (103–10). By exploiting the charge capture characteristics of GQDs, the trap capture level can be increased by increasing the content of GQDs in the dielectric layer. The switching current ratio of the device increases with increasing GQD content (10–103). The device can be programmed and erased more than 100 times; the programmable switching state can withstand 105 read pulses, and the retention time is more than 104 s. This memristor has a simple structure, low power consumption, and enormous application potential for data storage, artificial intelligence, image processing, artificial neural networks, and other applications.
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Nangare, Sopan, Shweta Baviskar, Ashwini Patil, and Pravin Patil. "Design of “Turn-Off” Fluorescent Nanoprobe for Highly Sensitive Detection of Uric Acid using Green Synthesized Nitrogen-Doped Graphene Quantum Dots." Acta Chimica Slovenica 69, no. 2 (June 15, 2022): 437–47. http://dx.doi.org/10.17344/acsi.2022.7333.
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Green synthesized graphene quantum dots (GQD) have been doped with nitrogen in an attempt to boost their optical characteristics and application sectors. In the present investigation, the blue luminescent nitrogen-doped GQDs (N-GQDs) were synthesized by single-step hydrothermal synthesis using tamarind shell powder as a precursor. The particle size and zeta potential of N-GQDs were found to be 11.40 nm and be –35.53 mV, respectively. A quantum yield as high as 23.78 % was accomplished at an excitation wavelength of 330 nm at neutral pH. It gets quenched sensitively in the existence of uric acid (UA) combining static quenching, electron transfer, and an inner filter effect mechanism. A linear range was obtained for UA from 10 μM to 100 μM, with a limit of detection (LOD) of 401.72 ± 0.04 pM. Additionally, the N-GQDs were selective toward UA in presence of metal ions and biomolecules that indicated its impending use to monitor UA in clinical samples. In conclusion, this work demonstrates that the N-GQDs as a sensing probe for UA recognition with notable advantages including socioeconomic, simple, and less time-consuming methods as compared to other methods. In the future, it can be potentially explored as a biosensor for UA detection in clinical samples.
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Kang, Hyun Kyoung, Dong Jin Kim, Min Soo Kim, Da-Hyun Kim, Jin Young Lee, Eun-Ah Sung, Madina Sarsenova, Seong Chae Park, Byung Hee Hong, and Kyung-Sun Kang. "Improved hepatoblast differentiation of human pluripotent stem cells by coffee bean derived graphene quantum dots." 2D Materials 9, no. 3 (May 30, 2022): 035012. http://dx.doi.org/10.1088/2053-1583/ac6ba8.
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Abstract Graphene quantum dots (GQDs) have been found to promote the efficient differentiation of stem cells into a variety of cell types. However, their bioactivity and signaling mechanisms in the hepatic lineage have not been fully investigated. Here, we report that the hepatoblast (HB) differentiation rate can be promoted by using Ca2+-rich coffee bean (CB)-derived GQDs, where the incorporated calcium ions activate the signaling of insulin-like growth factor 1 receptor (IGF1R)-protein kinase B (AKT). We also found that the human pluripotent stem cell (hPSC)-derived HBs from the CB-GQD treatment tend to upregulate the maturation into hepatocyte-like cells and downregulate the differentiation towards cholangiocytes, thereby successfully obtaining a large number of functional hepatocyte-like cells. Moreover, the activation of IGF1R from the CB-GQD treatment enhances the HB differentiation efficiency regardless of growth factors, implying that chelated calcium may play a key role in activating IGF1R. Our findings suggest that CB-GQDs with independent bioactivity can be widely used in place of IGF1 and represent a cost-effective growth factor as well as a potential differentiation factor.
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Murdaka, Fiqhri Heda, Ahmad Kusumaatmaja, Isnaeni, and Iman Santoso. "The Role of Reduced Graphene Oxide Concentration as Ablated Material on Optical Properties of Graphene Quantum Dots." Materials Science Forum 948 (March 2019): 267–73. http://dx.doi.org/10.4028/www.scientific.net/msf.948.267.
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We report the synthesize of Graphene Quantum Dots (GQDs) using ablation method with reduced Graphene Oxide (rGO) solution as a starting material. We have varied the concentration of rGO as following: 0.5, 2, 5 mg/ml and then have ablated them using 800 nm Ti-Sapphire femtosecond laser to obtain GQDs. From the UV-Vis data, we observed that the more concentration of rGO is being ablated, the more secondary absorption peak at 255.1 nm appeared. This secondary absorption peak is a characteristic of n-π* bonding due to the presence of oxygen defect which occurs as a result of the interaction between the laser and the water in rGO solution. We conclude that the population of oxigen defect in GQDs is increasing, following the increase of rGO concentration and could alter the optical properties of GQD. On the other hand, using Tauc’s plot, we confirm that the increase of rGO concentration as the ablated material does not alter GQDs optical band gap. However, it will slightly reduce both, direct and indirect Oxygen defect related optical band gap.
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Bui, Thi Ai Ngoc, Trung Viet Huynh, Hai Linh Tran, and Ruey-an Doong. "Erbium-Doped GQD-Embedded Coffee-Ground-Derived Porous Biochar for Highly Efficient Asymmetric Supercapacitor." Nanomaterials 12, no. 11 (June 6, 2022): 1939. http://dx.doi.org/10.3390/nano12111939.
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A nanocomposite with erbium-doped graphene quantum dots embedded in highly porous coffee-ground-derived biochar (Er-GQD/HPB) was synthesized as a promising electrode material for a highly efficient supercapacitor. The HPB showed high porosity, with a large surface area of 1295 m2 g−1 and an average pore size of 2.8 nm. The 2–8-nanometer Er-GQD nanoparticles were uniformly decorated on the HPB, subsequently increasing its specific surface area and thermal stability. Furthermore, the intimate contact between the Er-GQDs and HPB significantly reduced the charge-transfer resistance and diffusion path, leading to the rapid migration of ions/electrons in the mesoporous channels of the HPB. By adding Er-GQDs, the specific capacitance was dramatically increased from 337 F g−1 for the pure HPB to 699 F g−1 for the Er-GQD/HPB at 1 A g−1. The Ragone plot of the Er-GQD/HPB exhibited an ultrahigh energy density of 94.5 Wh kg−1 and a power density of 1.3 kW kg−1 at 1 A g−1. Furthermore, the Er-GQD/HPB electrode displayed excellent cycling stability, and 81% of the initial capacitance remained after 5000 cycles. Our results provide further insights into a promising supercapacitance material that offers the benefits of both fast ion transport from highly porous carbons and electrocatalytic improvement due to the embedment of Er-doped GQDs to enhance energy density relative to conventional materials.
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Xu, Yao, Yihua Lu, Jiagen Li, Rulin Liu, and Xi Zhu. "Effect of graphene quantum dot size on plant growth." Nanoscale 12, no. 28 (2020): 15045–49. http://dx.doi.org/10.1039/d0nr01913e.
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Luk, C. M., B. L. Chen, K. S. Teng, L. B. Tang, and S. P. Lau. "Optically and electrically tunable graphene quantum dot–polyaniline composite films." J. Mater. Chem. C 2, no. 23 (2014): 4526–32. http://dx.doi.org/10.1039/c4tc00498a.
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Tang, Chengli, and Limei Zhang. "GQD/Bi2O3 Composite for high-efficient photocatalysts." E3S Web of Conferences 213 (2020): 02037. http://dx.doi.org/10.1051/e3sconf/202021302037.
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Bismuth oxide (Bi2O3) is one of the potential visible-light photocatalytic materials, however, due to low electron mobility and short minority carrier diffusion length, the photocatalytic activity of Bi2O3 is restricted. The GQD/Bi2O3 composites were synthesized stably depositing single-crystalline graphene quantum dots (GQDs) with absorption edge at ~10nm, prepared by using a top-down method. The GQDBi2O3 heterojunctions were successfully established, the photo-generated electrons transfer from the Bi2O3 to the GQDs at the interface of the GQD-Bi2O3 heterojunctions, result in efficient electron-hole pairs separation and higher photocatalytic efficiency. The optimum visible performance is achieved at GQD content of 1.0 wt %, the RhB dye was nearly completely decoloured after 90 min of visible-light irradiation, and then decrease at higher doping levels due to the thicker GQD layer will cover the active sites of Bi2O3, thus leading to the greatly reduced catalytic activity.
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Hosseini, Z. S., A. Iraji zad, M. A. Ghiass, S. Fardindoost, and S. Hatamie. "A new approach to flexible humidity sensors using graphene quantum dots." Journal of Materials Chemistry C 5, no. 35 (2017): 8966–73. http://dx.doi.org/10.1039/c7tc01740e.
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Saleem, Haleema, Pei Sean Goh, Asif Saud, Mohammad Aquib Wakeel Khan, Nazmin Munira, Ahmad Fauzi Ismail, and Syed Javaid Zaidi. "Graphene Quantum Dot-Added Thin-Film Composite Membrane with Advanced Nanofibrous Support for Forward Osmosis." Nanomaterials 12, no. 23 (November 24, 2022): 4154. http://dx.doi.org/10.3390/nano12234154.
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Forward osmosis (FO) technology for desalination has been extensively studied due to its immense benefits over conventionally used reverse osmosis. However, there are some challenges in this process such as a high reverse solute flux (RSF), low water flux, and poor chlorine resistance that must be properly addressed. These challenges in the FO process can be resolved through proper membrane design. This study describes the fabrication of thin-film composite (TFC) membranes with polyethersulfone solution blown-spun (SBS) nanofiber support and an incorporated selective layer of graphene quantum dots (GQDs). This is the first study to sustainably develop GQDs from banyan tree leaves for water treatment and to examine the chlorine resistance of a TFC FO membrane with SBS nanofiber support. Successful GQD formation was confirmed with different characterizations. The performance of the GQD-TFC-FO membrane was studied in terms of flux, long-term stability, and chlorine resistance. It was observed that the membrane with 0.05 wt.% of B-GQDs exhibited increased surface smoothness, hydrophilicity, water flux, salt rejection, and chlorine resistance, along with a low RSF and reduced solute flux compared with that of neat TFC membranes. The improvement can be attributed to the presence of GQDs in the polyamide layer and the utilization of SBS nanofibrous support in the TFC membrane. A simulation study was also carried out to validate the experimental data. The developed membrane has great potential in desalination and water treatment applications.
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Lee, Bong, Gretel A. Stokes, Alina Valimukhametova, Steven Nguyen, Roberto Gonzalez-Rodriguez, Adam Bhaloo, Jeffery Coffer, and Anton V. Naumov. "Automated Approach to In Vitro Image-Guided Photothermal Therapy with Top-Down and Bottom-Up-Synthesized Graphene Quantum Dots." Nanomaterials 13, no. 5 (February 22, 2023): 805. http://dx.doi.org/10.3390/nano13050805.
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Graphene-based materials have been the subject of interest for photothermal therapy due to their high light-to-heat conversion efficiency. Based on recent studies, graphene quantum dots (GQDs) are expected to possess advantageous photothermal properties and facilitate fluorescence image-tracking in the visible and near-infrared (NIR), while surpassing other graphene-based materials in their biocompatibility. Several GQD structures including reduced graphene quantum dots (RGQDs) derived from reduced graphene oxide via top-down oxidation and hyaluronic acid graphene quantum dots (HGQDs) hydrothermally bottom-up synthesized from molecular hyaluronic acid were employed to test these capabilities in the present work. These GQDs possess substantial NIR absorption and fluorescence throughout the visible and NIR beneficial for in vivo imaging while being biocompatible at up to 1.7 mg/mL concentrations. In aqueous suspensions, RGQDs and HGQDs irradiated with a low power (0.9 W/cm2) 808 nm NIR laser facilitate a temperature increase up to 47.0 °C, which is sufficient for cancer tumor ablation. In vitro photothermal experiments sampling multiple conditions directly in the 96-well plate were performed using an automated simultaneous irradiation/measurement system developed on the basis of a 3D printer. In this study, HGQDs and RGQDs facilitated the heating of HeLa cancer cells up to 54.5 °C, leading to the drastic inhibition of cell viability from over 80% down to 22.9%. GQD’s fluorescence in the visible and NIR traces their successful internalization into HeLa cells maximized at 20 h suggesting both extracellular and intracellular photothermal treatment capabilities. The combination of the photothermal and imaging modalities tested in vitro makes the GQDs developed in this work prospective agents for cancer theragnostics.
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Yu, Hui, Wenjian Zhu, Hu Zhou, Jianfeng Liu, Zhen Yang, Xiaocai Hu, and Aihua Yuan. "Porous carbon derived from metal–organic framework@graphene quantum dots as electrode materials for supercapacitors and lithium-ion batteries." RSC Advances 9, no. 17 (2019): 9577–83. http://dx.doi.org/10.1039/c9ra01488h.
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Zeng, Cheng. "Relation between structural defects and trap states in graphene quantum dots perovskite solar cell." Applied and Computational Engineering 7, no. 1 (July 21, 2023): 24–28. http://dx.doi.org/10.54254/2755-2721/7/20230319.
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Graphene quantum dots (GQDs) have recently been developed as promising interfacial engineering materials for modifying perovskite solar cells (PSC) surfaces due to their low toxicity and good charge mobility compared to other metallic-based quantum dots in semiconductors. However, the side effect of decorating PSC with GQD is that it creates more structural defects that might cause shallow trap states and non-radiative recombination, leading to decreased PSC performance. This paper reviews the impact of structural defects and trap state of GQDs and the combined corresponding influence on the performance of PSC based on thermally stimulated current (TSC) and density-voltage (J-V) plots. This paper then offers new guidelines to minimize the trade-off of GQD by suggesting a well-controlled fabrication process.
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Kuo, Wen-Shuo, Yen-Sung Lin, Ping-Ching Wu, Chia-Yuan Chang, Jiu-Yao Wang, Pei-Chi Chen, Miao-Hsi Hsieh, Hui-Fang Kao, Sheng-Han Lin, and Chan-Chi Chang. "Two-Photon–Near Infrared-II Antimicrobial Graphene-Nanoagent for Ultraviolet–Near Infrared Imaging and Photoinactivation." International Journal of Molecular Sciences 23, no. 6 (March 17, 2022): 3230. http://dx.doi.org/10.3390/ijms23063230.
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Nitrogen doping and amino group functionalization through chemical modification lead to strong electron donation. Applying these processes to a large π-conjugated system of graphene quantum dot (GQD)-based materials as electron donors increases the charge transfer efficiency of nitrogen-doped amino acid-functionalized GQDs (amino-N-GQDs), resulting in enhanced two-photon absorption, post-two-photon excitation (TPE) stability, TPE cross-sections, and two-photon luminescence through the radiative pathway when the lifetime decreases and the quantum yield increases. Additionally, it leads to the generation of reactive oxygen species through two-photon photodynamic therapy (PDT). The sorted amino-N-GQDs prepared in this study exhibited excitation-wavelength-independent two-photon luminescence in the near-infrared region through TPE in the near-infrared-II region. The increase in size resulted in size-dependent photochemical and electrochemical efficacy, increased photoluminescence quantum yield, and efficient two-photon PDT. Therefore, the sorted amino-N-GQDs can be applicable as two-photon contrast probes to track and localize analytes in in-depth two-photon imaging executed in a biological environment along with two-photon PDT to eliminate infectious or multidrug-resistant microbes.