Enhanced Ag@SnO₂ Plasmonic Nanoparticles for Boosting Photoluminescence and Photocurrent Response of ZnO Nanorod UV Photodetectors

Ag@SnO₂ nanoparticles (NPs) have been prepared by varying the concentration of sodium stannate trihydrate coated onto ZnO nanorods as the photoanode for photoelectrochemical self-powered ultraviolet photodetectors (UVPDs). Their structure, morphology, and optical properties were investigated. Compared with ZnO nanorods (NRs), the Ag@SnO₂-coated ZnO NRs exhibited ultraviolet photoluminescence enhanced by nearly six orders of magnitude when 2 mL 40 mM sodium stannate trihydrate was used. This enhanced photoluminescence intensity is ascribed to the localized surface plasmon resonance of Ag in Ag@SnO₂. Moreover, when varying the sodium stannate trihydrate concentration in the Ag@SnO₂ NPs, the UVPD with 2 mL 40 mM sodium stannate trihydrate exhibited a high photocurrent density (J_sc) of 5.81 mA cm⁻² compared with 2.34 mA cm⁻² for the ZnO UVPD. This boost in J_sc is attributed to enhanced UV light harvesting and reduced charge recombination. Furthermore, this device also reached a high on/off ratio of 3885 and fast response time compared with the ZnO UVPD. Finally, such photoanodes formed from Ag@SnO₂ nanoparticles coated on ZnO NRs are promising for use in photoelectrochemical-type self-powered UV photodetectors.