Controlling Plasmon-Induced Resonance Energy Transfer and Hot Electron Injection Processes in Metal@TiO2 Core–Shell Nanoparticles

Plasmonic metals can excite charge carriers in semiconductors through plasmon-induced resonance energy transfer (PIRET) and hot electron injection processes. Transient absorption spectroscopy reveals that the presence of plasmon-induced charge separation mechanisms in metal@TiO2 core–shell nanoparticles can be controlled by tailoring the spectral overlap and the physical contact between the metal and the semiconductor. In Ag@SiO2@TiO2 sandwich nanoparticles, the localized surface plasmon resonance band is overlapped with the absorption band edge of TiO2, enabling PIRET, while the SiO2 barrier prevents hot electron transfer. In Au@TiO2, hot electron injection occurs, but the lack of spectral overlap disables PIRET. In Ag@TiO2, both hot electron transfer and PIRET take place. In Au@SiO2@TiO2, photoconversion in TiO2 is not enhanced by the plasmon despite strong light absorption by Au.