Tuning the Electronic and Optical Properties of Graphene via Doping to Realize Nitrogen Dioxide Sensing: A Computational Study.

Recently, doped graphene has emerged as a promising material for gas sensing applications. In this study, we performed first-principles calculations to investigate the adsorption of nitrogen dioxide (NO) on pristine, nitrogen (N)-doped, ruthenium (Ru)-doped, and N-Ru--doped graphene surfaces. The adsorption energies, Mulliken charge distributions, differential charge densities, electronic density of states, and optical properties of NO on the graphene surfaces were evaluated. The adsorption energies follow the order N-Ru--doped > Ru-doped > N-doped > pristine graphene, suggesting that doped graphene has higher sensitivity to NO gas molecules than pristine graphene. Analysis of the charge transfer and differential charge densities indicated weak physisorption of NO on pristine and N-doped graphene, whereas stronger chemisorption of NO occurred on Ru-doped and N-Ru--doped graphene because of the formation of chemical bonds between NO and the doped surfaces. The peak absorption and reflection coefficients of NO adsorbed on N-Ru--doped graphene are approximately 2.88 and 7.75 times higher, respectively, than those of NO adsorbed on pristine graphene. The substantial changes of the electronic and optical properties of N-Ru--doped graphene upon interaction with NO can be exploited for the development of highly sensitive and selective NO gas sensors.