Gas molecule adsorption on silicene nanoribbons: Conductance modulation and contact effects*

We investigate the effects of adsorption of gas molecules on the quantum conduction of silicene nanoribbons with and without silver contacts, using ab initio methods and Green's function formalism. The adsorption positions and orientations are determined through energy calculations and structure optimizations for NO$_2$,CO$_2$, and CO gas molecules. The conduction change upon gas molecules adsorption is studied for isolated silicene nanoribbons and for silicene nanoribbons on silver side contacts for potential applications as ultrasensitive nanoelectrochemical sensors.