Modeling of gas adsorption on graphene nanoribbons

Abstract

We present a theory to study gas molecules adsorption on armchair graphene nanoribbons (AGNRs) by applying the results of ab initio calculations to the single-band tight-binding approximation. In addition, the effect of edge states on the electronic properties of AGNR is included in the calculations. Under the assumption that the gas molecules adsorb on the ribbon sites with uniform probability distribution, the applicability of the method is examined for finite concentrations of adsorption of several simple gas molecules (CO, NO, CO2, NH3) on 10-AGNR. We show that the states contributed by the adsorbed CO and NO molecules are quite localized near the center of original band gap and suggest that the charge transport in such systems cannot be enhanced considerably, while CO2 and NH3 molecules adsorption acts as acceptor and donor, respectively. The results of this theory at low gas concentration are in good agreement with those obtained by density-functional theory calculations.

Electronic Structure Calculation of Adsorbate Gas Molecules on an Armchair Graphene Nanoribbon

“…The adsorption of NH 3 molecule converts the electronic structure of 6-AGNR as a degenerate semiconductor. These results are consistent with those obtained by Huang et al [22] and Saffarzadeh [24].…”

“…However DFT calculations show that AGNRs are semiconducting with a finite band gap and the value of the gap depends on their width [19][20][21]. Theoretical and ab initio studies of GNRs sensing properties have been reported already, showing that absorption of CO 2 or O 2 molecules changes the AGNR to p-type semiconductor, while NH 3 adsorption changes it to a n-type semiconductor [22][23][24].…”

BN-C Hybrid Nanoribbons as Gas Sensors

“…6b) for A 7 GNR, the CO (NH 3 ) adsorbed molecule induces quasi-localized state in the band gap, which is located near and above the Fermi level (near the conduction band) without any changing in the position of the HOMO and LUMO states in good agreement with previous study. 14 The decreasing of the concentration of gas leads to decreasing the intensity of the induced states (see Fig. 6).…”

“…For the center region by N S atoms and N G molecule adsorption, the gas concentration is determined as c ¼ N G N s . 14 In this study we suppose N G = 1. The possibility weight of each configuration can be attributed to the adsorption energy [E ads = E adsorbed À (E pristine + E molecule )] with the linear relation.…”

“…23 The electronic properties of the system including semi-infinite regions can be investigated by using of surface Green's function and transfer matrix approach. 24 For the nonmagnetic system, in the tight-binding approximation, the Hamiltonian of supercells is defined as 14 :…”