▎ 摘　　要

Graphene nanoflakes (GNFs) have a great potential for use in future nanoelectronic applications. One promising application of this structure is usage as a nanosensor for various gas molecules. The main purpose of the current study is to exploit the potential applicability of using GNFs as a nanosensor for small gas molecules (CO2, NO2, N-2, O-2, CO, and NO). For this reason, the interactions between these molecules in the horizontal and vertical directions with GNFs have been investigated by means of the density functional theory (DFT) method at the B3LYP/3-21 G level with the Gaussian 09 program. The band gaps, density of states (DOS), dipole moments, total energies, HOMO and LUMO energies, and Fermi level energies are calculated for GNFs with and without the above gas molecules. We found that GNFs are very sensitive to these gas molecules in the horizontal direction. The band gap was affected and reduced its value with these gas molecules. All the systems became unstable with gas molecules due to the total energies being reduced with gas molecules in the two types of directions,. An important result is that the interactions of these gas molecules in the horizontal direction results in fairly large alteration of the dipole moments of the GNFs and slight changes in the vertical directions in comparison with the pristine case of GNFs. The strong interactions between the O-2 and the GNFs induce dramatic changes to the GNF's electronic properties and lead to a large reduction in the energy gap of the GNFs. However, the results of this work open a way for the development of new and effective nanosensors for gas molecules based on functionalized GNFs. (C) 2017 The Physical Society of the Republic of China (Taiwan). Published by Elsevier B.V. All rights reserved.