From Self-Affine Ag to Mounded Ag@Ag2O Core−Shell Nanoplasmonic Surfaces By Sonochemistry

Abstract

A controllable ultrasound-assisted synthetic approach has been developed that allows deposition of elemental silver and core−shell Ag@Ag2O nanoparticles, close-packed in thin-film form on glass substrates, suitable for a wide range of applications. Ultrasonic irradiation modifies the reaction mechanism, allowing precise control over the composition of the nanoparticles and their packing in the form of thin films. The crystal radii of the synthesized materials fall within the nano range (∼9 nm in the case of bare Ag, 5 nm for the Ag core, and 9 nm for the Ag2O shell in the case of Ag@Ag2O films). Nanostructured Ag films exhibit self-affine, while the films built up by Ag@Ag2O core−shell nanocrystals exhibit a mounded morphology. The interface width and the mean roughness are significantly smaller for sonochemically synthesized surfaces. The observed trends in the localized surface plasmon resonance (LSPR) absorptions in the case of bare Ag plasmonic surfaces are dominated by the particle size, inhomogeneous broadening induced by the size dispersion of the nanoparticles, interparticle plasmon coupling, and nanocrystal−substrate interaction. The notable red shift of the LSPR absorption maximum in the case of films built up by Ag@Ag2O core−shell nanoparticles is governed by the influence of the dielectric shell.