Adsorption of gas molecules on ultra-thin pristine and doped graphene nanoribbons

We have investigated the adsorption of CO, NO, CO₂, and NO₂ gas molecules on ultra-thin graphene nanoribbons (GNRs) using density functional theory-based calculations. In both armchair and zigzag GNR, the gas molecules stabilize at the center of hexagonal ring and interact weakly with GNR with adsorption energy in the range of -0.06 to -0.56 eV. The change in the electron density of states near fermi level on adsorption of gas molecules show that pristine GNR is more sensitive for NO₂ in comparison to CO, NO and CO₂. When dopant (B & N) and vacancy defect are introduced in the GNR surface, the adsorption of gas molecules is enhanced with higher interaction energy in the range -0.19 to -0.87 eV. The electronic properties of GNR shows strong dependence with width upto 5 layers and shows no change in the electronic properties with further increase in the width. The adsorption of gas molecules changes Electronic density of states (DOS) of GNRs near fermi level due to charge transfer and rearrangement. CO, CO₂, and NO₂ molecules behave as charge acceptor whereas NO molecule act as a charge donor. The result can be explained based on number of size dependent electronic properties of GNRs and nature of dopants/defects.