Preparation of ZnO nanoparticles/Ag nanowires nanocomposites as plasmonic photocatalysts and investigation of the effect of concentration and diameter size of Ag nanowires on their photocatalytic performance

In this work the plasmonic photocatalytic activity of ZnO/noble metals nanocomposites has been investigated. Ag nanowires and Au nanospheres were prepared and mixed with ZnO in order to prepare the nanocomposites. It was demonstrated that the composites containing the plasmonic Ag nanowires and ZnO nanoparticles showed a significant photocatalytic activity enhancement compared to the pure ZnO in decomposition of methylene blue (MB). By investigation of mechanisms governing the performance of plasmonic photocatalysts, it was found that the photocatalytic activity enhancement can be attributed to the energy transfer from Ag nanowires to the ZnO nanoparticles induced by the surface plasmonic resonance (SPR). Such energy transfer is due to increasing the average path length of the photons in the composite and the SPR-induced local electromagnetic field near the surface of Ag nanowires. This mechanism predicts an enhancement in the concentration of charge carriers at the semiconductor surface by which the photocatalytic activity improves. The results showed that the photocatalytic activity enhancement was depended on the diameter size and concentration of Ag nanowires in the composites. Our studies showed that the composite containing 4.5 wt % of Ag nanowires with mean diameter size of 280 nm exhibited the highest photocatalytic activity enhancement compared to the pure ZnO nanoparticles. Furthermore, ZnO/Au nanospheres composite presented a little enhancement in photocatalytic activity compared to the composites containing Ag nanowires.