Cadmium sulfide activated zinc oxide coatings deposited by liquid plasma spray for room temperature nitrogen dioxide detection under visible light illumination

Zinc oxide (ZnO) is well-known to be used as a gas sensing material. However, due to its high operation temperature, the chemical and thermal stability of ZnO based gas sensors are relatively low. In recent years, some researchers adopt light illumination as activated source to replace heating and obtain high gas sensing performance at low temperature. The study that follows is an attempt to use cadmium sulfide (CdS) as sensitizer to activate ZnO at room temperature with assistance of visible-light illumination. CdS-ZnO coatings were deposited by liquid plasma spray with aqueous solution containing zinc acetate and cadmium sulfide as precursors. The crystal structure of as-sprayed CdS-ZnO coatings was characterized by X-ray diffractometer (XRD) and field-emission scanning electron microscopy (FE-SEM). The sensing performance of sensors based on CdS-ZnO coatings were tested with 1 ppm nitrogen dioxide (NO2) at room temperature illuminated under various visible lights. The results demonstrated that the LPS process was a straightforward method for deposition of high performance CdS-ZnO sensitive layers and the obtained sensors showed high responses to NO2 at room temperature.