Visible-Light-Assisted HCHO Gas Sensing Based on Fe-Doped Flowerlike ZnO at Room Temperature

In this work, Fe-doped flowerlike ZnO powders with various doping contents were successfully fabricated by a hydrothermal method. The results of X-ray diffraction and UV-vis DRS spectra revealed that the Fe ions have been successfully doped into the crystal lattice of the ZnO host structure, and the optical absorption response of Fe-doped ZnO was extended into the visible region for the incorporation of Fe ions. The room-temperature photoelectric gas sensing of formaldehyde (HCHO) based on the Fe-doped ZnO was also studied under 532 nm light irradiation provided by a green laser pointer. It was found that the as-prepared Fe-doped ZnO samples showed excellent sensitivity, in which the gas response to 5 and 100 ppm formaldehyde can reach to 22% and 28796 under 532 nm light irradiation at room temperature, respectively. The sensing mechanism of the obvious visible-light-induced photoelectric gas sensing was discussed with the help of surface photovoltage measurement. Our results demonstrated that visible light irradiation was a promising approach to achieving a large response for gas sensors at room temperature. This work will pave a way for the development of a low-cost practical gas sensor.