A V2O5/MWCNTs composite thin film gas sensor for the fast detection of ammonia

In the present study, we develop a new ammonia gas sensor by using sol-gel method and post annealing process. The structure, morphology, and composition of the gas sensor have been characterized by SEM, XRD, XPS, and Raman. The results prove that the V2O5/MWCNTs (multi-walled carbon nanotubes) composite thin film was successfully deposited on alumina substrate. By comparing the responses of the gas sensor to ammonia gas at different temperatures, we find out that the sensor shows good response and excellent response time to ammonia gas at 200 ℃. At this temperature, the sensor exhibits a response of 20% for 100 ppm of ammonia gas with a response time of only 8 s. We find its response time is better than that of ammonia sensors based on single V2O5 or MWCNTs materials. The outstanding sensitivity and unique response curve can be mainly attributed to the semiconductor properties of the two materials and the formation of P-N heterojunction at their interface.