Temperature-dependent Raman investigation and photoluminescence of graphene quantum dots with and without nitrogen-dopin
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Temperature-dependent Raman investigation and photoluminescence of graphene quantum dots with and without nitrogen-doping Pham Nam Thang1, Le Xuan Hung2,3, Dao Nguyen Thuan1, Nguyen Hai Yen1, Nguyen Thi Thuc Hien4, Vu Thi Hong Hanh5, Nguyen Cao Khang6, Julien Laverdant7, and Pham Thu Nga1,3,4,* 1
Institute of Materials Science, Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet Road, Cau Giay Dist, Hanoi, Vietnam 2 Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam 3 Faculty of Natural Sciences, Duy Tan University, Da Nang 550000, Vietnam 4 Institute of Theoretical and Applied Research, Duy Tan University, Hanoi 100000, Vietnam 5 Thai Nguyen University of Education, Thai Nguyen, Vietnam 6 Center for Nanoscience and Technology, Hanoi National University of Education, 136 Xuan Thuy, Hanoi, Vietnam 7 Institut Lumière Matière, UMR5306, Université Lyon 1, 69622 Villeurbanne, France
Received: 13 August 2020
ABSTRACT
Accepted: 13 November 2020
The study of the temperature dependence of Raman spectrum of graphene quantum dots is important for further understanding of the fine structure and properties of the material such as atomic bonds, thermal expansion, and thermal conductivity. In this work, we present new results on the temperature dependence of the frequency of G peak in the Raman spectra of bare GQDs and nitrogen-doped graphene quantum dots (N-GQDs), respectively. The nature of these GQDs is investigated using high-resolution transmission electron microscopy together with Raman, absorption, and photoluminescence spectra. We monitored a shift in G peak frequency toward lower frequencies with the temperature ranging from 81 to 663 K. In addition, a slight decrease in G peak intensity and an increase in D peak intensity have been observed, which is especially clear for Raman spectra of N-GQD sample. From the linear relationship of G peak frequency with temperature, we determine for the first time the value of the temperature coefficient v of the G mode. Values of - 0.0222 ± 0.001 cm-1 K-1 for GQDs, and - 0.0243 ± 0.0013 cm-1 K-1 for N-GQDs were deduced. These results show a clear heat expansion in the graphene lattice, although small in size, when sample temperature is increased from 81 to 663 K. Our result is important to further understand physical effects
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Handling Editor: Pedro Camargo.
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https://doi.org/10.1007/s10853-020-05578-3
J Mater Sci
induced by anharmonic phonons in QGDs and should be taken to account when designing efficient nanoelectronic devices employing GQDs.
Introduction Graphene quantum dots (GQDs) have drawn much attention for research in recent years due to their quantum confinement effect, after being initially synthesized and published by Ponomarenko and Geim in 2008 [1], with blue fluorescence properties first published by Pan [2] and Yan [3] in 2010. Various properties were investigated, such as good chemic
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