Ultrasensitive formaldehyde gas sensor based on Au-loaded ZnO nanorod arrays at low temperature

Au-loaded ZnO were successfully prepared by means of seed-assisted solvothermal methods. The vertically ordered nanorod arrays are uniformly grown on the Al2O3 substrate. The sensing properties of ZnO and Au-loaded ZnO sensors toward HCHO were investigated. Remarkably, the sensor based on 4 wt%Au-loaded ZnO nanorod arrays exhibits high response, short response and recover times, excellent selectivity, as well as low HCHO detection limit at 70 °C. After the incorporation of Au nanoparticle, the detection limit decreases from 10 ppm to 0.25 ppm, and the response increases more than 20 times under 100 ppm HCHO at 70 °C. Moreover, the mechanism of HCHO sensing with Au-loaded ZnO was explored by the calculations obtained from the first-principle studies.