The effect of atmospheric tarnishing on the optical and structural properties of silver nanoparticles

We investigate the optical and morphological effects of silver island films exposed to atmosphere. Silver nanoparticles with an average radius below 5 nm were highly tarnished after one week, showing significant morphological changes. Using x-ray photoelectron spectroscopy we demonstrate that the tarnishing is predominantly caused by oxidation and not sulfidation for exposed silver nanostructures under normal conditions. Post-deposition annealing of tarnished nanoparticle films results in further morphological changes which are highly dependent on the exposure time and nominal film thickness. Our results suggest that the size and density of the nanoparticles can be pre-designed by controlling the deposition thickness, tarnishing and annealing. The processing causes a red-shift in the localized surface plasmon resonance due to reduced particle interactions.