Surface-plasmon-enhanced ultraviolet emission of Au-decorated ZnO structures for gas sensing and photocatalytic devices

Pure and Au-decorated sub-micrometer ZnO spheres were successfully grown on glass substrates by simple chemical bath deposition and photoreduction methods. The analysis of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, energy-dispersive X-ray spectroscopy (EDS), UV-vis absorption, and photoluminescence (PL) spectra results were used to verify the incorporation of plasmonic Au nanoparticles (NPs) on the ZnO film. Time-resolved photoluminescence (TRPL) spectra indicated that a surface plasmonic effect exists with a fast rate of charge transfer from Au nanoparticles to the sub-micrometer ZnO sphere, which suggested the strong possibility of the use of the material for the design of efficient catalytic devices. The NO2 sensing ability of as-deposited ZnO films was investigated with different gas concentrations at an optimized sensing temperature of 120 degrees C. Surface decoration of plasmonic Au nanoparticles provided an enhanced sensitivity (141 times) with improved response (tau(Res) = 9 s) and recovery time (tau(Rec) = 39 s). The enhanced gas sensing performance and photocatalytic degradation processes are suggested to be attributed to not only the surface plasmon resonance effect, but also due to a Schottky barrier between plasmonic Au and ZnO structures.