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