Energy transfer by plasmon-induced local electromagnetic field in Au-based TiO2 plasmonic photocatalysts

Abstract

Although Au-based TiO2 plasmonic photocatalysts have received wide research attention as an effective strategy to extend the visible light response of TiO2, the energy transfer mode from plasmon-excited Au to TiO2 is still unclear. Herein, we synthesized Au@SiO2 core–shell structure and further constructed Au@SiO2-P25 (a commercial TiO2) thin film electrode to explore the plasmonic energy transfer mechanism from Au nanoparticles (NPs) to TiO2. The obtained samples were characterized by means of transmission electron microscopy, X-ray diffraction, UV–visible diffuse reflectance spectroscopy, and transient photocurrents. The result of transient photocurrents indicates that the SiO2 interlayer cannot inhibit the generation of electron–hole pairs in TiO2. Combining the finite difference time domain (FDTD) simulations, it was revealed that the photocurrents of Au@SiO2-P25 and Au-P25 are very dependent on the electromagnetic field intensity acting on TiO2. It can be deduced that the electron–hole pairs in TiO2 are excited by the local electromagnetic field induced by surface plasmon resonance (SPR) of Au NPs. Therefore, the energy transfer from Au to TiO2 is realized by the local electromagnetic field. This work provides solid evidence for the local electromagnetic field mechanism in a noble metal–semiconductor plasmonic system.