ZnO Nanoparticle-Based MEMS Sensors for H₂S Detection

The development of microelectromechanical system (MEMS)-based sensors with ZnO nanoparticles as sensitive materials for detecting a low concentration of H2S has recently attracted extensive attention because of their small size and easy integration. In this study, undecorated ZnO nanoparticles were synthesized by a facile coprecipitation method with the regulation of ammonia water. The phase structure, nanostructure, specific area, surface basicity, and oxygen species of the synthesized ZnO nanoparticles were systematically investigated. Then, preferred ZnO-1 nanoparticles were deposited on the MEMS microhotplate chips as a sensitive material, and the corresponding gas-sensing performances were characterized for various gases at an optimal operating temperature of 220 °C. The MEMS-based sensors with ZnO-1 showed good sensitivity to 1 ppm H2S at 220 °C with response/recovery times of 72 and 29 s, respectively. Furthermore, the sensor presented a wide linear range from 50 ppb to 15 ppm, good repeatability, and high selectivity. Such enhanced sensing performance to H2S was mainly attributed to the large surface area and the high surface basicity of prepared ZnO-1 nanoparticles. Moreover, a plausible reason for the enhanced sensing performance was also proposed.