scholarly journals Quasi-Unidirectional Transport Bilayer Two-Dimensional Nanopores for Highly-Efficient Molecular Sieving

2021 ◽  
Vol 9 ◽  
Author(s):  
Chengzhen Sun ◽  
Cheng Liu ◽  
Kailin Luo ◽  
Bofeng Bai
Keyword(s):  
Hexagonal Boron Nitride ◽  
Single Layer ◽  
Molecular Transport ◽  
Single Layer Graphene ◽  
Porous Membranes ◽  
Two Dimensional ◽  
Gas Molecules ◽  
Dynamics Simulations ◽  
Two Sides ◽  
Molecular Sieving

Two-dimensional nanopores are very promising for high-permeance molecular sieving, but the molecular backflow from permeate-side to feed-side is not beneficial for improving molecular permeance. We study the quasi-unidirectional molecular transport through a graphene-hexagonal boron nitride bilayer nanopore, aiming to realize a high-permeance molecular sieving. Molecular dynamics simulations of CO2/CH4 separations show that the bilayer pore presents 3.7 times higher selectivity comparing to the single-layer graphene nanopore with the same size. The quasi-unidirectional molecular transport is attributed to the distinctive adsorption abilities of gas molecules on the two sides of bilayer nanopores and the inhibited molecular backflow from permeate-side to feed-side. This work provides a promising way to realize the ultra-permeable porous membranes with molecular permeance even higher than the single-layer atomic-thickness membranes.

scholarly journals Unconventional satellite resistance peaks in moiré superlattice of h-BN/ AB-stacked tetralayer-graphene heterostructures

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Fumiya Mukai ◽  
Kota Horii ◽  
Ryoya Ebisuoka ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Fermi Surface ◽  
Energy Gap ◽  
Hexagonal Boron Nitride ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Multilayer Graphene ◽  
Two Dimensional ◽  
Layer Graphene ◽  
Superlattice Structure

AbstractMost studies on moiré superlattices formed from a stack of h-BN (two-dimensional hexagonal boron nitride) and graphene have focused on single layer graphene; graphene with multiple layers is less understood. Here, we show that a moiré superlattice of multilayer graphene shows features arising from the anisotropic Fermi surface affected by the superlattice structure. The moiré superlattice of a h-BN/AB-stacked tetralayer graphene heterostructures exhibited resistivity peaks showing a complicated dependence on the perpendicular electric field. The peaks were not due to secondary Dirac cones forming, but rather opening of the energy gap due to folding of the anisotropic Fermi surface. In addition, superlattice peaks resulted from mixing of light- and heavy-mass bilayer-like bands via the superlattice potential. The gaps did not open on the boundary of the superlattice Brillouin zone, but rather opened inside it, which reflected the anisotropy of the Fermi surface of multilayer graphene.

scholarly journals Millisecond lattice gasification for high-density CO2- and O2-sieving nanopores in single-layer graphene

2021 ◽  
Vol 7 (9) ◽  
pp. eabf0116
Author(s):  
Shiqi Huang ◽  
Shaoxian Li ◽  
Luis Francisco Villalobos ◽  
Mostapha Dakhchoune ◽  
Marina Micari ◽  
...  
Keyword(s):  
Single Layer ◽  
High Density ◽  
Single Layer Graphene ◽  
Pore Density ◽  
Vacancy Defects ◽  
Carbon Gasification ◽  
Layer Graphene ◽  
Gas Molecules ◽  
Good Agreement

Etching single-layer graphene to incorporate a high pore density with sub-angstrom precision in molecular differentiation is critical to realize the promising high-flux separation of similar-sized gas molecules, e.g., CO2 from N2. However, rapid etching kinetics needed to achieve the high pore density is challenging to control for such precision. Here, we report a millisecond carbon gasification chemistry incorporating high density (>1012 cm−2) of functional oxygen clusters that then evolve in CO2-sieving vacancy defects under controlled and predictable gasification conditions. A statistical distribution of nanopore lattice isomers is observed, in good agreement with the theoretical solution to the isomer cataloging problem. The gasification technique is scalable, and a centimeter-scale membrane is demonstrated. Last, molecular cutoff could be adjusted by 0.1 Å by in situ expansion of the vacancy defects in an O2 atmosphere. Large CO2 and O2 permeances (>10,000 and 1000 GPU, respectively) are demonstrated accompanying attractive CO2/N2 and O2/N2 selectivities.

Thermal conductivity of two-dimensional BC3: a comparative study with two-dimensional C3N

2019 ◽  
Vol 21 (24) ◽  
pp. 12977-12985 ◽  
Author(s):  
Jieren Song ◽  
Zhonghai Xu ◽  
Xiaodong He ◽  
Yujiao Bai ◽  
Linlin Miao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Comparative Study ◽  
Molecular Dynamics Simulations ◽  
Environmental Temperature ◽  
Single Layer ◽  
Two Dimensional ◽  
Vacancy Defects ◽  
Dynamics Simulations ◽  
External Strain

The thermal conductivities of single-layer BC3 (SLBC) sheets and their responses to environmental temperature, vacancy defects and external strain have been studied and compared with those of single-layer C3N (SLCN) sheets by molecular dynamics simulations.

scholarly journals A Molecular Dynamics Study on Wrinkles in Graphene with Simply Supported Boundary under In-Plane Shear

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Jianzhang Huang ◽  
Qiang Han
Keyword(s):  
Molecular Dynamics ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Propagation Process ◽  
Plane Shear ◽  
Simply Supported ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Formation And Evolution ◽  
Dynamics Simulations

The formation and evolution mechanisms of wrinkling in a rectangular single layer graphene sheet (SLGS) with simply supported boundary subjected to in-plane shear displacements are investigated using molecular dynamics simulations. Through investigating the out-of-plane displacements of the key point atom, we clarify the wrinkling growth and propagation process. Our results show that the boundary condition plays important roles in the wrinkling deformation. And the dependence of wrinkling parameters on the applied shear displacements is captured. Based on the elasticity theory, the formation mechanism of graphene wrinkling is revealed from the viewpoint of elastic energy. The effects of aspect ratio of graphene, temperature, and loading velocity on graphene wrinkling parameters and patterns are also investigated.

scholarly journals Bottom-up synthesis of graphene films hosting atom-thick molecular-sieving apertures

2021 ◽  
Vol 118 (37) ◽  
pp. e2022201118 ◽  
Author(s):  
Luis Francisco Villalobos ◽  
Cédric Van Goethem ◽  
Kuang-Jung Hsu ◽  
Shaoxian Li ◽  
Mina Moradi ◽  
...  
Keyword(s):  
High Performance ◽  
State Of The Art ◽  
Scale Up ◽  
Single Layer ◽  
Chemical Vapor ◽  
Single Layer Graphene ◽  
Bottom Up ◽  
Vacancy Defects ◽  
Graphene Lattice ◽  
Molecular Sieving

Incorporation of a high density of molecular-sieving nanopores in the graphene lattice by the bottom-up synthesis is highly attractive for high-performance membranes. Herein, we achieve this by a controlled synthesis of nanocrystalline graphene where incomplete growth of a few nanometer-sized, misoriented grains generates molecular-sized pores in the lattice. The density of pores is comparable to that obtained by the state-of-the-art postsynthetic etching (1012 cm−2) and is up to two orders of magnitude higher than that of molecular-sieving intrinsic vacancy defects in single-layer graphene (SLG) prepared by chemical vapor deposition. The porous nanocrystalline graphene (PNG) films are synthesized by precipitation of C dissolved in the Ni matrix where the C concentration is regulated by controlled pyrolysis of precursors (polymers and/or sugar). The PNG film is made of few-layered graphene except near the grain edge where the grains taper down to a single layer and eventually terminate into vacancy defects at a node where three or more grains meet. This unique nanostructure is highly attractive for the membranes because the layered domains improve the mechanical robustness of the film while the atom-thick molecular-sized apertures allow the realization of large gas transport. The combination of gas permeance and gas pair selectivity is comparable to that from the nanoporous SLG membranes prepared by state-of-the-art postsynthetic lattice etching. Overall, the method reported here improves the scale-up potential of graphene membranes by cutting down the processing steps.

scholarly journals Theoretical Prediction of the Structural and Electronic Properties of a Single Layer Graphene-like Two-dimensional Janus GaInSTe

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
Nguyen Van Chuong ◽  
Nguyen Ngoc Hieu ◽  
Nguyen Van Hieu
Keyword(s):  
Electric Field ◽  
Band Gap ◽  
Electronic Properties ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Two Dimensional ◽  
Direct Band Gap ◽  
Structural And Electronic Properties ◽  
Direct Band ◽  
New Type

This paper constructs a new type of two-dimensional graphene-like Janus GaInSTe monolayer and systematically investigates its structural and electronic properties as well as the effect of external electric field using first-principles calculations. In the ground state, Janus GaInSTe monolayer is dynamically stable with no imaginary frequencies in its phonon spectrum and possesses a direct band gap semiconductor. The band gap of Janus GaInSTe monolayer can be tuned by applying an electric field, which leads the different transitions from semiconductor to metal, and from indirect to direct band gap. These findings show a great potential application of Janus GaInSTe material for designing next-generation devices.

Molecular Dynamics Simulation of the Thermal Conductivity of Silicon-Germanene Nanoribbon (SiGeNR): A Comparison with Silicene Nanoribbon (SiNR) and Germanene Nanoribbon (GeNR)

2015 ◽  
Vol 1105 ◽  
pp. 285-289 ◽  
Author(s):  
Jessa Mae P. Tagalog ◽  
Cachey Girly Alipala ◽  
Giovanni J. Paylaga ◽  
Naomi T. Paylaga ◽  
Rolando V. Bantaculo
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Germanium ◽  
Large Scale ◽  
Room Temperature ◽  
Single Layer ◽  
Dynamics Simulation ◽  
Two Dimensional ◽  
Silicon And Germanium ◽  
Dynamics Simulations

This study examines the nature of thermal transport properties of single layer two-dimensional honeycomb structures of silicon-germanene nanoribbon (SiGeNR), silicene nanoribbon (SiNR) and germanene nanoribbon (GeNR) which have not yet been characterized experimentally. SiGeNR, SiNR and GeNR are the allotropes of silicon-germanium, silicon and germanium, respectively, withsp2hybridization. The thermal conductivity of the materials has been investigated using Tersoff potential through LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) by performing the molecular-dynamics simulations. The temperature is varied (50 K, 77 K, 150 K, 300 K, 500 K, 700 K, 1000 K, and 1200 K) with fixed nanoribbon dimension of 50 nm × 10 nm. The length is also varied (10 nm, 20 nm, 30 nm, 40 nm, and 50 nm) while the temperature is fixed at room temperature and the width is also fixed at 10 nm. The obtained results showed that the thermal conductivity of SiGeNR at room temperature is approximately 10 times higher than GeNR and approximately 6 times higher compared to SiNR. The thermal conductivity increases as the temperature is increased from 50 K – 300 K, and as the temperature is further increased, the thermal conductivity decreases with temperature. Moreover, the thermal conductivity in SiGeNR, SiNR, and GeNR increases as the length is being increased. Predicting new features of SiGeNR, SiNR and GeNR open new possibilities for nanoelectronic device applications of group IV two-dimensional materials.

A Platform for Large-Scale Graphene Electronics - CVD Growth of Single-Layer Graphene on CVD-Grown Hexagonal Boron Nitride

2013 ◽  
Vol 25 (19) ◽  
pp. 2746-2752 ◽  
Author(s):  
Min Wang ◽  
Sung Kyu Jang ◽  
Won-Jun Jang ◽  
Minwoo Kim ◽  
Seong-Yong Park ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Large Scale ◽  
Hexagonal Boron Nitride ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Layer Graphene ◽  
Cvd Growth
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