Graphene quantum dot explained

Graphene quantum dots (GQDs) are graphene nanoparticles with a size less than 100 nm.[1] Due to their exceptional properties such as low toxicity, stable photoluminescence, chemical stability and pronounced quantum confinement effect, GQDs are considered as a novel material for biological, opto-electronics, energy and environmental applications.[2]

Properties

Graphene quantum dots (GQDs) consist of one or a few layers of graphene and are smaller than 100 nm in size.[3] [1] They are chemically and physically stable, have a large surface to mass ratio and can be dispersed in water easily due to functional groups at the edges.[4] [5] The fluorescence emission of GQDs can extend across a broad spectral range, including the UV, visible, and IR. The origin of GQD fluorescence emission is a subject of debate, as it has been related to quantum confinement effects, defect states and functional groups[6] [7] that might depend on the pH, when GQDs are dispersed in water.[8] Their electronic structure depends sensitively on the crystallographic orientation of their edges, for example zigzag-edge GQDs with 7-8 nm diameter show a metallic behavior.[9] In general, their energy gap decreases, when the number of graphene layers or the number of carbon atoms per graphene layer is increased.[10]

Health and safety

See main article: Health and safety hazards of nanomaterials and Nanotoxicology. The toxicity of graphene-family nanoparticles is a matter of ongoing research.[2] [11] The toxicity (both in vivo and cytotoxicity) of GQDs are related to a variety of factors including particle size, methods of synthesis, chemical doping and so on.[12] Many authors claim, that GQDs are biocompatible and cause only low toxicity[4] [13] as they are just composed of organic materials, which should lead to an advantage over semiconductor quantum dots.[5] Several in vitro studies, based on cell cultures, show only marginal effects of GQDs on the viability of human cells.[14] [15] [16] An in-depth look at the gene expression changes caused by GQDs with a size of 3 nm revealed that only one, namely the selenoprotein W, 1 out of 20 800 gene expressions was affected significantly in primary human hematopoietic stem cells.[17] On the contrary, other in vitro studies observe a distinct decrease of cell viability and the induction of autophagy after exposure of the cells to GQDs[18] and one in vivo study in zebrafish larvae observed the alteration of 2116 gene expressions.[19] These inconsistent findings may be attributed to the diversity of the used GQDs, as the related toxicity is dependent on particle size, surface functional groups, oxygen content, surface charges and impurities.[20] Currently, the literature is insufficient to draw conclusions about the potential hazards of GQDs.[11]

Preparation

Presently, a range of techniques have been developed to prepare GQDs. These methods are normally classified into two groups top down and bottom up. Top down approaches applied different techniques to cut bulk graphitic materials into GQDs including graphite, graphene, carbon nanotubes, coal, carbon black and carbon fibres. These techniques mainly include electron beam lithography, chemical synthesis, electrochemical preparation, graphene oxide (GO) reduction, C60 catalytic transformation, the microwave assisted hydrothermal method (MAH),[21] [22] the Soft-Template method,[23] the hydrothermal method,[24] [25] [26] and the ultrasonic exfoliation method.[27] Top down methods usually need intense purification as strong mixed acids are used in these methods. On the other hand, bottom up methods assemble GQDs from small organic molecules such as citric acid[28] and glucose. These GQDs have better biocompatibility.[12]

Application

Graphene quantum dots are studied as an advanced multifunctional material due to their unique optical, electronic,[9] spin,[29] and photoelectric properties induced by the quantum confinement effect and edge effect. They have possible applications in treatment of Alzheimer's disease, bioimaging,[30] photothermal therapy,[31] temperature sensing,[32] drug delivery,[33] [34] LEDs lighter converters, photodetectors, OPV solar cells, and photoluminescent material, biosensors fabrication.[35]

See also

Notes and References

  1. Ghosh . Shampa . Sachdeva . Bhuvi . Sachdeva . Punya . Chaudhary . Vishal . Rani . Gokana Mohana . Sinha . Jitendra Kumar . 2022-10-01 . Graphene quantum dots as a potential diagnostic and therapeutic tool for the management of Alzheimer's disease . Carbon Letters . en . 32 . 6 . 1381–1394 . 10.1007/s42823-022-00397-9 . 252188554 . 2233-4998.
  2. Henna . T. K. . Pramod . K. . May 2020 . Graphene quantum dots redefine nanobiomedicine . Materials Science & Engineering. C, Materials for Biological Applications . 110 . 110651 . 10.1016/j.msec.2020.110651 . 1873-0191 . 32204078. 213861659 .
  3. Campbell . Elizabeth . Hasan . Md Tanvir . Gonzalez-Rodriguez . Roberto . Truly . Tate . Lee . Bong Han . Green . Kayla N. . Akkaraju . Giridhar . Naumov . Anton V. . October 2021 . Graphene quantum dot formulation for cancer imaging and redox-based drug delivery . Nanomedicine: Nanotechnology, Biology and Medicine . 37 . 102408 . 10.1016/j.nano.2021.102408 . 1549-9642 . 34015513. 235075216 .
  4. 10.1016/j.mtchem.2018.09.007 . Graphene quantum dots from chemistry to applications . Materials Today Chemistry. 10 . 221–258 . 2018 . Tian . P. . Tang . L. . Teng . K.S. . Lau . S.P.. free . 10397/80356 . free .
  5. 10.1002/ppsc.201400219 . Recent Advances in Graphene Quantum Dots for Fluorescence Bioimaging from Cells through Tissues to Animals . Particle & Particle Systems Characterization . 32 . 5 . 515–523 . 2014 . Wang . Dan . Chen . Jiang-Fen . Dai . Liming. 53120598 .
  6. 10.1002/adma.200902825 . 20217780. Hydrothermal Route for Cutting Graphene Sheets into Blue‐Luminescent Graphene Quantum Dots. Advanced Materials . 22 . 6 . 734–738 . 2010 . Pan. Dengyu . Zhang . Jingchun . Li . Zhen. Wu . Minghong . 2010AdM....22..734P. 39981399.
  7. Wang . Shujun . Cole . Ivan S. . Zhao . Dongyuan . Li . Qin . The dual roles of functional groups in the photoluminescence of graphene quantum dots . Nanoscale . 2016 . 8 . 14 . 7449–7458 . 10.1039/C5NR07042B . 26731007 . 2016Nanos...8.7449W . 10072/142465 . free .
  8. 10.1039/C3NR06353D . 24589665 . A general quantitative pH sensor developed with dicyandiamide N-doped high quantum yield graphene quantum dots . Nanoscale . 6 . 7 . 3868–3874 . 2014 . Wu. Zhu Lian . Gao . Ming Xuan . Wang . Ting Ting . Wan . Xiao Yan . Zheng . Lin Ling. Huang . Cheng Zhi . 2014Nanos...6.3868W.
  9. 10.1038/nmat2378 . 19219032 . The influence of edge structure on the electronic properties of graphene quantum dots and nanoribbons . Nature Materials . 8 . 3 . 235–42 . 2009 . Ritter . Kyle A . Lyding . Joseph W . 2009NatMa...8..235R .
  10. 10.1016/j.spmi.2019.106171 . Single-particle energy – and optical absorption – spectra of multilayer graphene quantum dots . Superlattices and Microstructures . 132 . 106171. 2019 . Wimmenauer. Christian . Scheller . Julienne . Fasbender . Stefan. Heinzel . Thomas . 198435346 .
  11. Ou . Lingling . Song . Bin . Liang . Huimin . Liu . Jia . Feng . Xiaoli . Deng . Bin . Sun . Ting . Shao . Longquan . Toxicity of graphene-family nanoparticles: a general review of the origins and mechanisms . Particle and Fibre Toxicology . 31 October 2016 . 13 . 1 . 57 . 10.1186/s12989-016-0168-y . 27799056 . 5088662 . free .
  12. Wang . Shujun . Cole . Ivan S. . Li . Qin . The toxicity of graphene quantum dots . RSC Advances . 2016 . 6 . 92 . 89867–89878 . 10.1039/C6RA16516H . 2016RSCAd...689867W .
  13. 10.1039/C2CC00110A . 22410424. Graphene quantum dots: emergent nanolights for bioimaging, sensors, catalysis and photovoltaic devices. Chemical Communications . 48 . 31. 3686–3699. 2012 . Shen. Jianhua . Zhu . Yihua . Yang . Xiaoling. Li . Chunzhong .
  14. Shang . Weihu . Zhang . Xiaoyan . Zhang . Mo . Fan . Zetan . Sun . Ying . Han . Mei . Fan . Louzhen . The uptake mechanism and biocompatibility of graphene quantum dots with human neural stem cells . Nanoscale . 2014 . 6 . 11 . 5799–5806 . 10.1039/c3nr06433f . 24740121 . 2014Nanos...6.5799S .
  15. Fasbender . Stefan . Allani . Sonja . Wimmenauer . Christian . Cadeddu . Ron-Patrick . Raba . Katharina . Fischer . Johannes C. . Bulat . Bekir . Luysberg . Martina . Seidel . Claus A. M. . Heinzel . Thomas . Haas . Rainer . Uptake dynamics of graphene quantum dots into primary human blood cells following in vitro exposure . RSC Advances . 2017 . 7 . 20 . 12208–12216 . 10.1039/C6RA27829A . 2017RSCAd...712208F . free .
  16. Zhu . Shoujun . Zhang . Junhu . Qiao . Chunyan . Tang . Shijia . Li . Yunfeng . Yuan . Wenjing . Li . Bo . Tian . Lu . Liu . Fang . Hu . Rui . Gao . Hainan . Wei . Haotong . Zhang . Hao . Sun . Hongchen . Yang . Bai . Strongly green-photoluminescent graphene quantum dots for bioimaging applications . Chemical Communications . 2011 . 47 . 24 . 6858–60 . 10.1039/c1cc11122a . 21584323 .
  17. Fasbender . Stefan . Zimmermann . Lisa . Cadeddu . Ron-Patrick . Luysberg . Martina . Moll . Bastian . Janiak . Christoph . Heinzel . Thomas . Haas . Rainer . The Low Toxicity of Graphene Quantum Dots is Reflected by Marginal Gene Expression Changes of Primary Human Hematopoietic Stem Cells . Scientific Reports . 19 August 2019 . 9 . 1 . 12028 . 10.1038/s41598-019-48567-6 . 31427693 . 6700176 . 2019NatSR...912028F .
  18. Xie . Yichun . Wan . Bin . Yang . Yu . Cui . Xuejing . Xin . Yan . Guo . Liang-Hong . Cytotoxicity and autophagy induction by graphene quantum dots with different functional groups . Journal of Environmental Sciences . March 2019 . 77 . 198–209 . 10.1016/j.jes.2018.07.014 . 30573083 . 58555272 .
  19. Deng . Shun . Jia . Pan-Pan . Zhang . Jing-Hui . Junaid . Muhammad . Niu . Aping . Ma . Yan-Bo . Fu . Ailing . Pei . De-Sheng . Transcriptomic response and perturbation of toxicity pathways in zebrafish larvae after exposure to graphene quantum dots (GQDs) . Journal of Hazardous Materials . September 2018 . 357 . 146–158 . 10.1016/j.jhazmat.2018.05.063 . 29883909 . 47013910 .
  20. Guo . Xiaoqing . Mei . Nan . Assessment of the toxic potential of graphene family nanomaterials . Journal of Food and Drug Analysis . March 2014 . 22 . 1 . 105–115 . 10.1016/j.jfda.2014.01.009 . 24673908 . 6350507 .
  21. 10.1021/nn300760g . 22559247 . Deep Ultraviolet Photoluminescence of Water-Soluble Self-Passivated Graphene Quantum Dots . ACS Nano . 6 . 6 . 5102–10 . 2012 . Tang . Libin . Ji . Rongbin . Cao . Xiangke . Lin . Jingyu . Jiang . Hongxing . Li . Xueming . Teng . Kar Seng . Luk . Chi Man . Zeng . Songjun . Hao . Jianhua . Lau . Shu Ping . 10397/28413 . free .
  22. 10.1021/nn501796r . 24848545 . Deep Ultraviolet to Near-Infrared Emission and Photoresponse in Layered N-Doped Graphene Quantum Dots . ACS Nano . 8 . 6 . 6312–20 . 2014 . Tang . Libin . Ji . Rongbin . Li . Xueming . Bai . Gongxun . Liu . Chao Ping . Hao . Jianhua . Lin . Jingyu . Jiang . Hongxing . Teng . Kar Seng . Yang . Zhibin . Lau . Shu Ping .
  23. 10.1002/ppsc.201200131 . Size-Dependent Structural and Optical Characteristics of Glucose-Derived Graphene Quantum Dots . Particle & Particle Systems Characterization . 30 . 6 . 523–31 . 2013 . Tang . Libin . Ji . Rongbin . Li . Xueming . Teng . Kar Seng . Lau . Shu Ping . 10397/32222 . 96410135 . free .
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  28. Wang . Shujun . Chen . Zhi-Gang . Cole . Ivan . Li . Qin . Structural evolution of graphene quantum dots during thermal decomposition of citric acid and the corresponding photoluminescence . Carbon . February 2015 . 82 . 304–313 . 10.1016/j.carbon.2014.10.075 . 10072/69171 . free .
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  30. Lu . Huiting . Li . Wenjun . Dong . Haifeng . Wei . Menglian . September 2019 . Graphene Quantum Dots for Optical Bioimaging . Small . 15 . 36 . e1902136 . 10.1002/smll.201902136 . 1613-6829 . 31304647. 196617689 .
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