Fabrication of Ag-Doped ZnO Nanoparticle Gas Sensor and Its Application in Detection of CO

Online monitoring of dissolving carbon monoxide (CO) gas in transformer oil allowed prompt detection of aging, overheat, and discharge faults, which could timely diagnosis of equipment malfunction. In this paper, CO sensor were fabricated by pure and Ag-doped ZnO nanoparticles respectively, and the sensor performances were evaluated through a series of tests on the aspects of working temperature, sensing response, detection limit, linearity, and stability. In addition, the sensing mechanism was also discussed. The results showed that the 11.7 wt% Ag-doped ZnO sensor exhibited the excellent gas sensing performance. The optimum working temperature of ZnO could be decreased from 340 °C to 300 °C after Ag doping, and a linear relationship between the gas response and the concentration of CO detection from 1 to μ500 L/L was obtained. Furthermore, the sensing response of 11.7 wt% Ag-doped ZnO had higher sensing response for CO than that of un-doped ZnO. This could be attributed to the introduction of impurity level, which facilitated the mobility of charge carrier into the conduction band of the semiconductor during the gas sensing reaction.