Hierarchical Assembly of ZnO Nanostructures on SnO₂ Backbone Nanowires: Low-Temperature Hydrothermal Preparation and Optical Properties

Hierarchical nanostructures with SnO(2) backbones and ZnO branches are successfully prepared in a large scale by combining the vapor transport and deposition process (for SnO(2) nanowires) and a hydrothermal growth (for ZnO). The ZnO nanorods grow epitaxially on the SnO(2) nanowire side faces mainly with a four-fold symmetry. The number density and morphology of the secondary ZnO can be tailored by changing the precursor concentration, reaction time, and by adding surfactants. Photoluminescence (PL) properties are studied as a function of temperature and pumping power. Such hybrid SnO(2)-ZnO nanostructures show an enhanced near-band gap emission compared with the primary SnO(2) nanowires. Under the optical excitation, a UV random lasing is observed which originates from the hierarchically assembled ZnO branches. These three-dimensional nanostructures may have application potentials as chemical sensors, battery electrodes, and optoelectronic devices.