Recently, metal nanomaterials with novel plasmonic properties have been found to enhance the photocurrent of metal oxides (MO). The mechanism behind is not well established. Several explanations have been proposed, including hot electron injection, local field enhancement, and enhanced light absorption of bandgap states in the MO due to enhanced light scattering by the metal nanostructures. Metal nanomaterials have also been used in conjunction with dyes or quantum dots (QDs) to improve the photoresponse, in which one or more than one of the different mechanisms mentioned above could be in operation. In this work, we employ ultrafast laser techniques to directly study the hot electron dynamics in Au/ZnO nanocomposite structure to look for possible evidence of direct charge injection from Au nanoparticles to ZnO. We also conducted PEC studies of related metal-metal oxide systems to understand the mechanism behind enhanced photocurrent in the visible and UV regions. Based on these studuies, it appears that metal nanoparticles can enhance light scattering and thereby light absorption by sensitizers such as QDs or bandgap states of metal oxides directly through far field effect. We found little evidence of direct hot electron injection from metal nanoparticles to metal oxides. There is also no evidence for enhancement due to near field effect. It is very possible that different mechanisms may be in operation under different experimental conditions. Thus, further study is necessary to achieve a more complete understanding of the plasmonic enhancement of observed photocurrent in metal-metal oxide system composite structures.

Mechanism behind plasmonic enhancement of photocurrent of metal oxide nanostructures

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.