Enhanced Plasmonic Electron Transfer from Gold Nanoparticles to TiO2 Nanorods via Electrochemical Surface Reduction

The transport of charge carriers across the heterojunction of an optoelectronic device plays a crucial role in the performance of the device. This issue is particularly important in the area of heterogeneous metal-semiconducting photocatalysis in terms of harvesting the hot carriers generated under plasmonic resonance. This paper presents the results of a case study on the impact of electrochemical surface reduction on the transport properties of plasmonic electrons, which are generated on gold nanoparticles (Au NPs) under visible light irradiation to TiO 2 nanorods (TiO 2 NRs). Based on microscopic and spectroscopic characterizations, this study examined the subtle changes in the structural and the optical properties of the Au NPs/TiO 2 NRs upon surface reduction of the oxygen layer which is ubiquitous on TiO 2 NRs. These results suggest that the oxygen layer works as a blocking layer that limits the charge transfer efficiency of plasmonic electrons from Au to TiO 2 and, consequently, reduces the device performance. The main thesis was verified directly by comparing the photocatalytic activities of pristine Au NPs/TiO2 NRs and Au NPs/reduced TiO 2 NRs with methylene blue as a reference. The photocatalytic performance of the Au NPs/reduced TiO 2 NRs was two times higher than that of the pristine one owing to the efficient charge transfer across the Au/TiO 2 interface. This simple surface treatment can be employed widely to enhance the charge transport efficiency of various optoelectronic materials and devices derived from metal-semiconducting heterostructures.