Sandwiched CdS/Au/ZnO Nanorods with Enhanced Ultraviolet and Visible Photochemical and Photoelectrochemical Properties via Semiconductor and Metal Cosensitizing

Sandwich-structured CdS/Au/ZnO nanorods were prepared by embedding Au nanoparticles in CdS coating-covered ZnO nanorods for high photochemical and photoelectrochemical activities via semiconductor and metal cosensitizing. The photoelectrochemical and photochemical properties were evaluated for the CdS/Au/ZnO nanorods to be used as a photoanode in a photo-electrochemical process and as a photocatalyst to photo-degrade organic methylene blue molecules. The CdS coatings serve as a semiconductor sensitizer to improve the photogeneration of electron-hole pairs and promote the separation and transfer of photogenerated electrons and holes by extending the photoresponse range, increasing light absorption and suppressing the recombination of electrons and holes. The Au nanoparticles act as a metal sensitizer to further increase the light absorption because of the local surface plasmon resonance effect and the increased effective optical path length and promote the transfer of photogenerated electrons from the conduction band of CdS to that of ZnO as an electron relay. The cosensitizing by CdS coatings and Au nanoparticles offers the CdS/Au/ZnO nanorods high photochemical and photoelectrochemical activities.