Interference enhanced SPR-mediated visible-light responsive photocatalysis of periodically ordered ZnO nanorod arrays decorated with Au nanoparticles

Abstract

Periodically ordered ZnO nanorod arrays were epitaxially grown on GaN(0001) substrates by polystyrene (PS) nanosphere lithography combined with following hydrothermal growth. The periodicity of ZnO nanorod arrays was varied by choosing PS nanospheres of different diameters. Then Au nanoparticles (NPs) were deposited on the ZnO nanorods to form Au–ZnO nanorod arrays samples. The PATP-to-DMAB model reaction was applied to detect the influence of ZnO nanorods periodicity on the surface plasmon resonance (SPR)-mediated photocatalytic performance of Au–ZnO nanorod arrays samples under 633 nm irradiation. The Au–ZnO nanorod array sample of 800 period presented inferior photocatalytic activities relative to those of individual Au NPs. However, the photocatalytic activities on the Au–ZnO nanorod array sample of 500 nm period were superior relative to those of individual Au NPs. The surface plasmon polaritons (SPP) of plasmonic NPs can change the propagation path of incident light to vertical direction after scattering on them. The Au–ZnO nanorod array sample of 500 nm period possessed the distance between neighbor ZnO rods smaller than the wavelength of irradiation light, and thus the scattered light interfered with each other after the incident light was scattered by the Au NPs on the neighbor ZnO rods. Then the electric field (E-field) intensities near Au NPs were elevated due to the interference effect. Since the SPR-mediated photocatalytic activity is proportional to the square value of local E-field intensity (E²), thus the photocatalytic activities on Au NPs were enhanced. This work might provide a new route to elevate SPR-mediated photocatalytic performance based on the deposition of plasmonic metals on periodically ordered arrays.