A facile, coverage controlled deposition of Au nanoparticles on ZnO nanorods by sonochemical reaction for enhancement of photocatalytic activity

This study reports the synthesis of Au/ZnO heterostructured nanorods by a facile sonochemical method and their improved photocatalytic activity. A simple and fast deposition of gold nanoparticles on ZnO nanorods was performed without any surfactants or additives. Through various analyses (SEM, XRD, TEM, and EELS), we confirmed the formation of a highly crystalline Au/ZnO nanostructure; several tens of nanometer-sized polycrystalline Au nanoparticles were uniformly deposited on the surface of ZnO nanorods. The size and the density of Au nanoparticles could be controlled by the modulation of the concentration of the gold ion precursor and the solvent compositions. Formation of smaller Au nanoparticles with a lower surface coverage was induced at a lower concentration of the gold ion source with a solvent composition ratio of 1:4 of D.I. water to ethanol. Compared with bare ZnO nanorods, Au/ZnO heterostructures exhibited enhanced photocatalytic activity in the photodegradation of an organic dye, which is caused by the Au nanoparticles acting as an electron sink and lowering the local work function.