Three-dimensional hierarchical SnO2 dodecahedral nanocrystals with enhanced humidity sensing properties

One-step hydrothermal method was adopted to synthesize tin dioxide (SnO2) nanostructures with different morphologies, i.e., three-dimensional (3D) hierarchical SnO2 dodecahedral nanocrystals (DNCs), 3D hierarchical SnO2 nanorods (NRs), and SnO2 nanoparticles (NPs). The humidity sensors based on the as-synthesized nanostructures were produced to investigate the relationship between morphology and humidity sensing property. The nanosensor based on 3D hierarchical SnO2 DNCs exhibited superior humidity sensing properties compared to those based on 3D hierarchical SnO2 NRs and SnO2 NPs. The enhanced sensing properties for SnO2 DNCs are attributed to the peculiar 3D open nanostructures and high chemical activity of the exposed {101} facets. The 3D open nanostructures can promote the penetration and diffusion of water molecules, and the exposed {101} facets can improve the adsorption ability of water molecules. Furthermore, density functional theory (DFT) calculations were performed to further confirm that {101} facets can adsorb more water molecules than {110} facets. Our results demonstrate that morphology and surface engineering is an effective strategy to enhance the humidity sensing properties of nanomaterials.