Plasmonic-enhanced self-cleaning activity on asymmetric Ag/ZnO surface-enhanced Raman scattering substrates under UV and visible light irradiation

Two different asymmetric Ag/ZnO composite nanoarrays were fabricated. These nanoarrays are proposed as highly sensitive and uniform surface-enhanced Raman scattering (SERS) substrates with plasmonic-enhanced UV-visible photocatalytic properties for self-cleaning. The asymmetric nanostructures are composed of Ag nanoparticles hanging inside or capping on the top of ZnO hollow nanospheres, which allows the generation of a strong local electric field near the contact area owing to the asymmetric dielectric environment. Experimental and simulation results showed that these asymmetric structures are favorable for achieving high photocatalytic activity under UV and visible light irradiation, in addition to improving the SERS performance. The electron transfer model based on band gap alignment was employed to further illustrate the mechanisms of the photocatalytic activity, which was dependent on the wavelength of the irradiation. Given the dramatically improved photocatalytic performance, together with the reproducible and uniform SERS signals verified by the Raman mapping results, the large area ordered asymmetric metal/semiconductor nanoarrays have been demonstrated to be suitable for further applications in multifunctional photoelectrochemical chips.