Real-time tracking of optical and structural properties of Ag-based bimetallic nanoparticles

The Localized Surface Plasmon resonance (LSPR) of metallic nanoparticles (NPs) is strongly dependent on their local environment and on their constituent-material dielectric functions. Thus, chemical modifications occurring at their vicinity, or directly within the NPs may be optically monitored. Moreover, Ag-based NPs may display a well-defined LSPR strongly sensitive to small variations of the surrounding. In this respect, Ag-based NPs (produced by laser vaporization) containing another reactive metal have been investigated. The first illustration deals with iron-silver NPs investigated through TEM observations, in situ optical spectroscopy and Monte Carlo simulations, leading us to conclude that iron and silver initially adopt a segregated configuration with a silver-enriched surface. During oxidation, iron likely diffuses throughout the silver shell, leading to an Ag@Fe3O4 configuration, while an inverse process may occur during annealing under a reducing atmosphere [1].We also performed optical and environmental TEM characterizations on In-Ag NPs. Optical spectra show LSPRs in the UV range down to 310 nm for as prepared NPs. A NP deposition at elevated temperatures even results in an LSPR