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Recent Progress in Graphene and 2D Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Carbon Materials".

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 13552

Special Issue Editors


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Guest Editor
School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Suwon, Gyeonggi-do 16419, Korea
Interests: graphene; 2D materials; pseudo-2D materials; chain-based 1D/2D materials; van der Walls heterostructures

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Guest Editor
Department of Materials Science and Engineering and Energy Systems Research, Ajou University, 2016 World Cup-ro, Suwon 16499, Gyeonggi-do, Korea
Interests: 2D nanomateirlas; 2D-based sensors
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Special Issue Information

Dear Colleagues,

Research into the production of two-dimensional (2D) layered materials by resurfacing three-dimensional (3D) crystals, currently used in various aspects of our lives, has progressed rapidly since the discovery of simple approaches to synthesizing single-layer graphene over a decade ago. As a result, dozens of 2D layered materials that possess the characteristics of semiconductors, conductors, and insulators have been discovered. Previously, only small flakes of 2D layered materials could be synthesized, but, gradually, it has become possible to synthesize 2D layered materials with a larger area and single-crystalline structure. Very recently, the controlled stacking of 2D layered materials at the atomic level revealed new physical and chemical phenomena. Based on this fundamental research, new electronic, optical, energy, and sensor devices are being developed that can overcome the physical limitations of current mainstream technology.

This Special Issue is devoted to providing the latest cutting-edge fundamental and applied research across all aspects of graphene and 2D layered materials. Full papers, communications, and reviews on experimental and theoretical studies of 2D layered structures and materials are all welcome.

Prof. Dr. Jae Young Choi
Prof. Dr. Jae-Hyun Lee
Guest Editors

Manuscript Submission Information

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Keywords

  • Graphene and graphene-derived materials
  • 2D layered materials (TMDCs, hBN, MXene, Xene, etc.)
  • Pseudo-2D materials
  • Chain-based 1D/2D materials
  • Van der Waals heterostructures
  • Applications of devices based on 2D layered materials

Published Papers (4 papers)

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Research

12 pages, 7251 KiB  
Article
Green Preparation of Aqueous Graphene Dispersion and Study on Its Dispersion Stability
by Liangchuan Li, Ming Zhou, Long Jin, Youtang Mo, Enyong Xu, Huajin Chen, Lincong Liu, Mingyue Wang, Xin Chen and Hongwei Zhu
Materials 2020, 13(18), 4069; https://doi.org/10.3390/ma13184069 - 14 Sep 2020
Cited by 11 | Viewed by 2733
Abstract
The large-scale preparation of stable graphene aqueous dispersion has been a challenge in the theoretical research and industrial applications of graphene. This study determined the suitable exfoliation agent for overcoming the van der Waals force between the layers of expanded graphite sheets using [...] Read more.
The large-scale preparation of stable graphene aqueous dispersion has been a challenge in the theoretical research and industrial applications of graphene. This study determined the suitable exfoliation agent for overcoming the van der Waals force between the layers of expanded graphite sheets using the liquid-phase exfoliation method on the basis of surface energy theory to prepare a single layer of graphene. To evenly and stably disperse graphene in pure water, the dispersants were selected based on Hansen solubility parameters, namely, hydrophilicity, heterocyclic structure and easy combinative features. The graphene exfoliation grade and the dispersion stability, number of layers and defect density in the dispersion were analysed under Tyndall phenomenon using volume sedimentation method, zeta potential analysis, scanning electron microscopy, Raman spectroscopy and atomic force microscopy characterization. Subsequently, the long-chain quaternary ammonium salt cationic surfactant octadecyltrimethylammonium chloride (0.3 wt.%) was electrolyzed in pure water to form ammonium ions, which promoted hydrogen bonding in the remaining oxygen-containing groups on the surface of the stripped graphene. Forming the electrostatic steric hindrance effect to achieve the stable dispersion of graphene in water can exfoliate a minimum of eight layers of graphene nanosheets; the average number of layers was less than 14. The 0.1 wt.% (sodium dodecylbenzene sulfonate: melamine = 1:1) mixed system forms π–π interaction and hydrogen bonding with graphene in pure water, which allow the stable dispersion of graphene for 22 days without sedimentation. The findings can be beneficial for the large-scale preparation of waterborne graphene in industrial applications. Full article
(This article belongs to the Special Issue Recent Progress in Graphene and 2D Materials)
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11 pages, 3602 KiB  
Communication
Highly Efficient n-Type Doping of Graphene by Vacuum Annealed Amine-Rich Macromolecules
by Young-Min Seo, Wonseok Jang, Taejun Gu and Dongmok Whang
Materials 2020, 13(9), 2166; https://doi.org/10.3390/ma13092166 - 08 May 2020
Cited by 10 | Viewed by 2901
Abstract
Flexible transparent conducting electrodes (FTCE) are an essential component of next-generation flexible optoelectronic devices. Graphene is expected to be a promising material for the FTCE, because of its high transparency, large charge carrier mobilities, and outstanding chemical and mechanical stability. However, the electrical [...] Read more.
Flexible transparent conducting electrodes (FTCE) are an essential component of next-generation flexible optoelectronic devices. Graphene is expected to be a promising material for the FTCE, because of its high transparency, large charge carrier mobilities, and outstanding chemical and mechanical stability. However, the electrical conductivity of graphene is still not good enough to be used as the electrode of an FTCE, which hinders its practical application. In this study, graphene was heavily n-type doped while maintaining high transmittance by adsorbing amine-rich macromolecules to graphene. The n-type charge-transfer doping of graphene was maximized by increasing the density of free amine in the macromolecule through a vacuum annealing process. The graphene adsorbed with the n-type dopants was stacked twice, resulting in a graphene FTCE with a sheet resistance of 38 ohm/sq and optical transmittance of 94.1%. The figure of merit (FoM) of the graphene electrode is as high as 158, which is significantly higher than the minimum standard for commercially available transparent electrodes (FoM = 35) as well as graphene electrodes doped with previously reported chemical doping methods. Furthermore, the n-doped graphene electrodes not only show outstanding flexibility but also maintain the doping effect even in high temperature (500 K) and high vacuum (~10−6 torr) conditions. These results show that the graphene doping proposed in this study is a promising approach for graphene-based next-generation FTCEs. Full article
(This article belongs to the Special Issue Recent Progress in Graphene and 2D Materials)
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9 pages, 3053 KiB  
Communication
Pattern Pick and Place Method for Twisted Bi- and Multi-Layer Graphene
by Jae-Young Lim, Hyeon-Sik Jang, Hyun-Jae Yoo, Seung-il Kim and Dongmok Whang
Materials 2019, 12(22), 3740; https://doi.org/10.3390/ma12223740 - 13 Nov 2019
Cited by 3 | Viewed by 3462
Abstract
Twisted bi-layer graphene (tBLG) has attracted much attention because of its unique band structure and properties. The properties of tBLG vary with small differences in the interlayer twist angle, but it is difficult to accurately adjust the interlayer twist angle of tBLG with [...] Read more.
Twisted bi-layer graphene (tBLG) has attracted much attention because of its unique band structure and properties. The properties of tBLG vary with small differences in the interlayer twist angle, but it is difficult to accurately adjust the interlayer twist angle of tBLG with the conventional fabrication method. In this study, we introduce a facile tBLG fabrication method that directly picks up a single-crystalline graphene layer from a growth substrate and places it on another graphene layer with a pre-designed twist angle. Using this approach, we stacked single-crystalline graphene layers with controlled twist angles and thus fabricated tBLG and twisted multi-layer graphene (tMLG). The structural, optical and electrical properties depending on the twist angle and number of layers, were investigated using transmission electron microscopy (TEM), micro–Raman spectroscopy, and gate-dependent sheet resistance measurements. The obtained results show that the pick and place approach enables the direct dry transfer of the top graphene layer on the as-grown graphene to fabricate uniform tBLG and tMLG with minimal interlayer contamination and pre-defined twist angles. Full article
(This article belongs to the Special Issue Recent Progress in Graphene and 2D Materials)
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9 pages, 2219 KiB  
Article
Thickness-Dependence Electrical Characterization of the One-Dimensional van der Waals TaSe3 Crystal
by Bum Jun Kim, Byung Joo Jeong, Seungbae Oh, Sudong Chae, Kyung Hwan Choi, Tuqeer Nasir, Sang Hoon Lee, Hyung Kyu Lim, Ik Jun Choi, Min-Ki Hong, Hak Ki Yu, Jae-Hyun Lee and Jae-Young Choi
Materials 2019, 12(15), 2462; https://doi.org/10.3390/ma12152462 - 02 Aug 2019
Cited by 13 | Viewed by 3719
Abstract
Needle-like single crystalline wires of TaSe3 were massively synthesized using the chemical vapor transport method. Since the wedged-shaped single TaSe3 molecular chains were stacked along the b-axis by weak van der Waals interactions, a few layers of TaSe3 flakes could [...] Read more.
Needle-like single crystalline wires of TaSe3 were massively synthesized using the chemical vapor transport method. Since the wedged-shaped single TaSe3 molecular chains were stacked along the b-axis by weak van der Waals interactions, a few layers of TaSe3 flakes could be easily isolated using a typical mechanical exfoliation method. The exfoliated TaSe3 flakes had an anisotropic planar structure, and the number of layers could be controlled by a repeated peeling process until a monolayer of TaSe3 nanoribbon was obtained. Through atomic force and scanning Kelvin probe microscope analyses, it was found that the variation in the work function with the thickness of the TaSe3 flakes was due to the interlayer screening effect. We believe that our results will not only help to add a novel quasi-1D block for nanoelectronics devices based on 2D van der Waals heterostructures, but also provide crucial information for designing proper contacts in device architecture. Full article
(This article belongs to the Special Issue Recent Progress in Graphene and 2D Materials)
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