Programme

P.16 -- Poster, VCTP-45

Date: Tuesday, 13 October 2020

Time: 08:30 - 10:00

A DFT Study of Some VOCs Adsorption on the Pristine Graphene

Viet Bac T. Phung (1), Van An Dinh (2, 3)

(1) Institute of Sustainability Science, VNU Vietnam Japan University, Luu Huu Phuoc street, My Dinh, Nam Tu Lien, Hanoi, Vietnam (2, 3) Nanotechnology Program, VNU Vietnam Japan University, Luu Huu Phuoc street, My Dinh, Nam Tu Lien, Hanoi, Vietnam 3. Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

In this study, the adsorption properties of two volatile organic compounds (VOCs) - acetone (CH3)2CO and dicchlomethane CH2Cl2 - in human breath on the surface of pristine graphene are investigated using the density functional theory (DFT) method. The most favourable adsorption configurations of considered VOC molecules on the graphene surface are obtained first from scanning method [1], and then the adsorption energy profiles are calculated in framework of three van der Waals functionals: revPBE-vdW, optPBE-vdW, and vdW-DF2. All of these VOCs are found to orient parallel to the graphene surface at the distance of approximately 3.00 Å. We found that the highest occupied molecular orbitals (HOMO) of the considered VOCs shift backward the Fermi level during adsorption. The HOMO orbitals of VOCs interact with p orbitals of graphene’s C and a tunnelling band gap occurs at the Dirac cone. These results suggest the charge donation tendency of VOC molecules to graphene. Bader charge analysis shows that these VOCs act as donors on graphene and 0.03e and 0.075e of charge was transferred from dicchlomethane and acetone, respectively, to graphene surface. The larger charge transfer, the larger the change in electrical conductance, which indicates the stronger effect to the sensor response towards VOCs. Recomendations on the enhancement of the selectivity of graphene-based sensing materials have also been made by other methods such as introducing a vacancy or doping transition metal molecules on the graphene surface. Reference: [1] Computational DFT-based Nanoscope developed by Van An Dinh, Vietnam Japan University (2018).

Presenter: Phung T. V. Bac