Low temperature synthesis of ZnO nanotubes based hydrogen sensors

A facile method has been developed to synthesize zinc oxide nanotubes (ZNTs) based hydrogen sensors at low temperature. ZnO nanorods (ZNRs) are first synthesized using the aqueous chemical process at 90 °C for 3 h, and then cooled down and maintained at 50 °C for a certain time (t = 6 h, 12 h and 18 h, respectively). ZNRs are transformed to ZNTs after the low temperature self-etching process. The ZNTs can provide a larger surface area than the pristine ZNRs for adsorbing additional gas ions, along with more oxygen vacancies to effectively sense gas ions with t increased from 6 h to 18 h. It is found that the hydrogen response of all ZNT hydrogen sensors, which is about 2 times higher than that of the pristine ZNR sensor (13.1%, at 500 ppm). It is noted that the ZNTs for t = 18 h possess the highest oxygen vacancies and the best response for hydrogen sensing (29.6%, at 500 ppm).