Adsorption of sulfur containing molecules on monoatomic Au, Ag, and binary Au-Ag nanowires: Size and composition dependence

Abstract

The self-assembly of monoatomic nanowires have shown rich properties that can be controlled by their size and composition. This first principles study investigates the electronic structures of monoatomic Aum, Agn, and binary Aum-Agn nanowires with m + n = 2–6. Binding energies are calculated and the nature of chemical bonds for the pure wires and energetically low-lying isomers of alloy nanowires are compared. Our results show that the formation of linear atomic chains is plausible for both Ag and Au. However, the stability enhancement is observed by increasing the Au content. For pure and alloy nanowires a dimer-growth route are observed which may be the result of Peierls distortion. We also study the adsorption of H2S on the considered nanowires and explain the effect of size and composition of the nanowire upon the adsorption. In order to monitor the selectivity of nanowires toward sulfide species, first the adsorption behaviors of nanowires configuration, upon the adsorption of H2S, are compared with the nanoclusters structures having the same number of atoms. Next, adsorptions of other sulfur containing molecules such as HS and cysteine over a given size of nanowire having different Au and Ag compositions are investigated. It is found that the adsorption strength of H2S over pure silver or Ag-rich nanowires is close to the cysteine, but the adsorption strength of HS is substantially higher. Thus, pure silver or Ag-rich nanostructures are suggested as highly selective sensor for detection of HS from H2S and cysteine.