Synthesis of unique ZnO/SnO ₂ core-shell structural microspheres and their gas-sensing properties

Nanomaterials with unusual architectures or morphologies often exhibit novel functional properties. Here, we apply a simple two-step solution method to synthesize the ZnO/SnO ₂ microspheres with an average size of 1-2 μm, which exhibit a unique core-shell architecture with a uniform dispersion of SnO ₂ nanoparticles on surfaces of spherical ZnO cores. We further investigate in detail the morphology evolution with reaction time, based upon which a likely growth mechanism is proposed. In property, the prepared core-shell structural ZnO/SnO ₂ microspheres show excellent gas-sensing functions to ethanol gas of 50 ppm at an optimal temperature as low as 250 °C, rendering the hybrid microspheres a promising gas-sensing material for the on-site detection of ethanol.