Optimized design of multi-shell ZnO/TiO2/ZnSe nanowires decorated with Ag nanoparticles for photocatalytic applications

Composite nanomaterials consisting of semiconductor sensitizers and noble metal nanoparticles (NPs) exhibit great potential for high-efficiency photocatalytic applications. However, the differences in structure can significantly affect the light utilization efficiency and photocatalytic performance. In this study, we report the structural design of multi-shell coaxial nanowires (NWs) for their applications in photocatalytic degradation. Two types of multi-shell coaxial NWs, namely, ZnO/TiO2/ZnSe/Ag(NPs) and ZnO/TiO2/Ag(NPs)/ZnSe NWs, were successfully fabricated. Experimental and theoretical results revealed that surface structures and the position of Ag NPs in coaxial NWs significantly influenced the intensity of localized surface plasmon resonance, light absorption, and photocatalytic performance. The photocatalytic activity of the ZnO/TiO2/Ag(NPs)/ZnSe NWs was significantly enhanced under UV and visible light irradiation compared with that of the ZnO/TiO2/ZnSe/Ag(NPs) NWs. The improved performance was explained by electron transfer models combined with band structure alignment. Furthermore, an optimal NW structure was proposed on the basis of the analysis of photocatalytic mechanisms. This study provides guidance to the design of composite materials for high-efficiency photocatalytic applications.