Ultrasensitive room-temperature chemical sensors by Ag-decorated ultraporous ZnO nanoparticle networks

Highly sensitive room temperature gas sensors consisting of ultraporous ZnO nanoparticle networks decorated with Ag nanoparticles (NPs) were fabricated by nanoparticle aerosol self-assembly and sequential sputtering. Optimization of the AgNPs loading and the thickness of ultraporous ZnO networks lead to a sensor response, defined as the ratio of resistance change, of 1.8 and 7.4 at 0.1 and 1 ppm ethanol concentrations, respectively, at room temperature under light irradiation. This is ~10 times higher than that of pure ultraporous ZnO film under the same experimental conditions. Furthermore, the optimal AgNPs-decorated ultraporous ZnO films can detect as low as 5 ppb of ethanol gas at room temperature under light illumination. The high sensitivity of AgNPs-decorated ZnO film can be ascribed to the synergistic effects of the ultraporous nanoparticle network morphology, AgNPs sensitization and light-assisted photo-excited gas-sensing process. These provide directions for the design of high sensitive metal-oxide semiconductor-based gas sensors capable to operate at room temperature.