Site-Selective and High-Density Gold Nanoparticle Photodeposition on the Edges of ZnO Nanowires.

Selective modification of chemically active sites on supports, such as steps, edges, and corners, with metal nanoparticles (NPs) is a challenging topic in the fields of catalysis and photocatalysis. However, the formation of site-selective, high-density metal NPs on a support has not yet been achieved. Radial ZnO mesocrystals composed of hexagonal nanowires (NWs) with {101̅0} sidewalls were synthesized by a simple solution-phase method. Here, we show that Au NPs are densely aligned along the edges of ZnO NWs by photodeposition from an O2-free aqueous methanol solution of HAuCl4, even though the Au complexes are uniformly adsorbed across the entire surface of the ZnO NWs. On the basis of the results of experiments and density functional theory calculations, we proposed a reaction mechanism of site-selective photodeposition involving the reduction of the Au complex by the excited electrons instantly relaxed at the edge sites followed by crystal growth. This study encourages us to apply site-selective photodeposition to other faceted semiconductor nanocrystals and to contribute to the improvement in their catalytic and photocatalytic activities.