Controlled preparation of Au/Ag/SnO2 core–shell nanoparticles using a photochemical method and applications in LSPR based sensing

Abstract

A photochemical method for the controlled preparation of core–shell Au/Ag/SnO₂ nanorods (NRs) and nanospheres (NSs) has been developed based on photo-induced electron transfer processes in the plasmonic metal-semiconductor system. Au/AgNR/SnO₂ and Au/AgNS/SnO₂ were prepared by the UV irradiation of a mixture of mesoporous SnO₂ coated AuNRs, or AuNSs, and AgNO₃, in which AgNO₃ was reduced by electrons transferred from the photo-excited mesoporous SnO₂ (semiconductor) to the gold (metal). This method allows precise control over the composition and optical properties of the obtained nanoparticles. The LSPR refractive index sensitivity of the obtained Au/AgNR/SnO₂ nanoparticles has been optimized to obtain a refractive index sensitivity of ∼442 nm RIU⁻¹. The optimized nanoparticles were subsequently chosen for the LSPR based sensing of glutathione (GSH) with the limit of detection of ∼7.5 × 10⁻⁷ M. This photochemical method allows the controlled preparation of various Au/Ag/SnO₂ nanoparticles to adjust their LSPR to suit various applications.