• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.272-278
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• 2017

Two-dimensional (2D) materials, especially graphene and $MoS_2$ sheets, have gained much attention and shown great promise for the application in supercapacitors. To widely use the 2D materials for supercapacitors, highly efficient, low cost, and environmentally friendly synthetic methods for the preparation of 2D materials should be developed. Here, we will review recently developed solution-based processes for preparing 2D materials for supercapacitors. Chemical exfoliation-reduction, chemical intercalation, and liquid phase exfoliation methods will be introduced. Moreover, the electrochemical characteristics of graphene and $MoS_2$-based electrodes for supercapacitors are summarized. In addition to solution-based processes, other challenges and opportunities are discussed in terms of controlling nanosheet compositions, sizes, and thicknesses.

• Journal of Sensor Science and Technology
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• v.31 no.4
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• pp.228-237
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• 2022

Two-dimensional (2D) nanomaterials have demonstrated the potential to replace silicon and compound semiconductors that are conventionally used in photodetectors. These materials are ultrathin and have superior electrical and optoelectronic properties as well as mechanical flexibility. Consequently, they are particularly advantageous for fabricating high-performance photodetectors that can be used for wearable device applications and Internet of Things technology. Although prototype photodetectors based on single microflakes of 2D materials have demonstrated excellent photoresponsivity across the entire optical spectrum, their practical applications are limited due to the difficulties in scaling up the synthesis process while maintaining the optoelectronic performance. In this review, we discuss facile methods to mass-produce 2D material-based photodetectors based on the exfoliation of van der Waals crystals into nanosheet dispersions. We first introduce the liquid-phase exfoliation process, which has been widely investigated for the scalable fabrication of photodetectors. Solution processing techniques to assemble 2D nanosheets into thin films and the optoelectronic performance of the fabricated devices are also presented. We conclude by discussing the limitations associated with liquid-phase exfoliation and the recent advances made due to the development of the electrochemical exfoliation process with molecular intercalants.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.252.1-252.1
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• 2013

Hexagonal boron nitride (h-BN) is a two dimensional material which has high band-gap, flatness and inert properties. This properties are used various applications such as dielectric for electronic device, protective coating and ultra violet emitter so on. 1) In this report, we were growing h-BN sheet directly on sapphire 2"wafer. Ammonia borane (H3BNH3) and nickel were deposited on sapphire wafer by evaporate method. We used nickel film as a sub catalyst to make h-BN sheet growth. 2) During annealing process, ammonia borane moved to sapphire surface through the nickel grain boundary. 3) Synthesized h-BN sheet was confirmed by raman spectroscopy (FWHM: ~30cm-1) and layered structure was defined by cross TEM (~10 layer). Also we controlled number of layer by using of different nickel and ammonia borane thickness. This nickel film supported h-BN growth method may propose fully and directly growing on sapphire. And using deposited ammonia borane and nickel films is scalable and controllable the thickness for h-BN layer number controlling.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.75-79
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• 2016

A helical nanosturctrue can be obtained by self-assembly method. Utilizing DPD simulation coarse-grained model, we patterned 2D layer nanosheets with repeated diagonal defects and grafts, and programed to self-roll into hollow helix structure. The defected pattern side caused anisotropy, and formed helix or helix-like structure. This opens the possibility to control the helix pitch or cavity radius. In this work, we designed several patterns about diagonal defect with a variety of defect side densities and defect widths and then simulation was carried out. Thus, our results have that parameters are affecting self-assembly of nanosheets and their conformation.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2041-2043
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• 2013

A layered perovskite of Dion-Jacobson phase, $RbLaTa_2O_7$, was successfully exfoliated into colloidal suspension via successive ion-exchange and intercalation reaction. The pristine perovskite $RbLaTa_2O_7$ was synthesized by conventional solid-state reaction, and then, it was ion-exchanged with hydrochloric acid to obtain a protonic form of perovskite. The resulting proton-exchanged perovskite was reacted with ethylamine to increase interlayer spaces for further intercalation reaction. Finally, the ethylamine-intercalated form was exfoliated into nanosheets via an intercalation of bulky organic cations (tetrabutylammonium). According to X-ray diffraction (XRD) analysis, the TBA-intercalated form showed remarkably increased interlayer spacing (${\Delta}d$ = 1.67 nm) in comparison with that of the pristine material. Transmission electron microscopic image of exfoliated perovskite clearly revealed that the present exfoliated perovskite were composed of very thin layers. This exfoliated perovskite nanosheets could be applicable as building blocks for fabricating functional nanocomposites.

• Advances in nano research
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• v.16 no.1
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• pp.81-90
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• 2024

In the oil and gas industry, composite materials should exhibit high flexibility and strength for offshore structures. Therefore, weak points in the composites should be improved, such as brittleness, moisture penetration, and diffusion of detrimental ions into nanometric pores. This study aimed to increase the strength, flexibility, and plugging of nanopores using single-layer graphene oxide (SGO) nanosheets. Therefore, SGO is added to unsaturated polyester resin at concentrations of 0.015 and 0.15 % with Normal Methyl Pyrrolidone (NMP) as a solvent for the formation of Nanographene Oxide Reinforced Polymer (NGORP). The mechanical properties of the prepared samples were tested using tensile testing (ASTM-D 638). It has been shown that incorporating SGO, approximately 0.015%, into the base resin resulted in enhanced properties such as rupture resistance forces increased by 745.61 N, applied stress tolerances increased by 4.1 MPa, longitude increased to 1.58 mm, elongation increased by about 2.38%, and rupture energy increased by about 204.51 J. Despite the decrease in tensile force strength properties in the manufactured nanocomposite with 0.15% SGO, it has exclusive flexibility properties such as a high required energy level for rupture of 5,576 times and a formability of 40% more than the base sample. It would be best to use NGORP manufactured from 0.015% nanosheets with exclusive properties rather than base samples for constructing parts and equipment, such as rebars, composite sheets, and transmission pipes, on offshore platforms.

• Advances in nano research
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• v.10 no.5
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• pp.415-422
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• 2021

Silicene, a 2D allotrope of silicon, is predicted to be a potential material for future transistor that might be compatible with present silicon fabrication technology. Similar to graphene, silicene exhibits the honeycomb lattice structure. Consequently, silicene is a semimetallic material, preventing its application as a field-effect transistor. Therefore, this work proposes the uniform doping bandgap engineering technique to obtain the n-type silicene nanosheet. By applying nearest neighbour tight-binding approach and parabolic band assumption, the analytical modelling equations for band structure, density of states, electrons and holes concentrations, intrinsic electrons velocity, and ideal ballistic current transport characteristics are computed. All simulations are done by using MATLAB. The results show that a bandgap of 0.66 eV has been induced in uniformly doped silicene with phosphorus (PSi₃NW) in the zigzag direction. Moreover, the relationships between intrinsic velocity to different temperatures and carrier concentration are further studied in this paper. The results show that the ballistic carrier velocity of PSi₃NW is independent on temperature within the degenerate regime. In addition, an ideal room temperature subthreshold swing of 60 mV/dec is extracted from ballistic current-voltage transfer characteristics. In conclusion, the PSi₃NW is a potential nanomaterial for future electronics applications, particularly in the digital switching applications.

• Polymer(Korea)
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• v.37 no.5
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• pp.638-641
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• 2013

GNS/PVDF composites were prepared using graphite nanosheets (GNS) and poly(vinylidene fluoride) (PVDF) for flexible thermoelectric application. We measured the electrical conductivity, thermal conductivity and Seebeck coefficient of GNS/PVDF composites with different contents of GNS and then evaluated the thermoelectric properties of GNS/PVDF composites. The electrical conductivity of GNS/PVDF composites increased from 389 to 1512 S/m with increasing the content of GNS from 10 to 70 wt%. While the electrical conductivity dramatically increased, Seebeck coefficient and thermal conductivity did not show any big difference as the content of GNS increases. In this study, we demonstrated that GNS/PVDF composites improved the thermoelectric properties by decreasing the thermal conductivity due to the phonon scattering at the interfaces between polymer and GNS nanoplatelets.