A novel gas microsensor combining SnO2 submicron/nanostructured porous sensitive film with Micro-Electro-Mechanical systems (MEMS) microheater was successfully fabricated. The film was made of hierarchically mixed Pd/SnO2 (HM-PTO) composites composed of Pd/SnO2 hollow submicrospheres (Pd/SnO2-HSs) and Pd/SnO2 nanoparticles (Pd/SnO2-NPs) deposited on the microheater platform using the microdispensing method. The as-prepared HM-PTO sensors exhibited high sensitivities, fast response/recovery rates, good selectivity, reliable reversibility, and relevant stability towards ethanol at low power consumption. The resulting superior sensing performances were attributed to the unique hierarchical structure. The internal void architecture of Pd/SnO2-HSs provided large specific surface areas, proper mesopore size distribution, large number of active adsorption/interaction sites, as well as promoted the chemisorption and dissociation of gas molecules due Pd-doping to yield superior gas response. In particular, the nano-sized SnO2 particles ensured the uniform deposition of the materials to yield enhanced local conductivities, and possibly faster phase transfer reactions responsible for the extremely good response/recovery performance. This simple fabrication procedure combined with high sensing performances look promising for the development of hierarchical morphologies of novel materials for gas sensing applications.
