Preparation And H₂S Gas Sensing Properties Of ZnS Decorated ZnO Nanorods-based Sensors

H2S is a neurotoxic and asphyxiant gas in living environment, which is also related tosome diseases such as Alzheimer’s disease, Down syndrome, Liver cirrhosis and so on. Hence,it is significant to detect low concentration of H2S effectively for human health. As a typicalreducing gas, H2S can be monitored by sensors based on semiconducting metal oxides at theirworking temperature. However, it is dangerous to detect H2S at high temperature for itsflammability. Therefore, explotation a new type of sensor for detecting H2S at roomtemperature is a great challenge in the present reseaches. In this dissertation, a lot of studieshave been carried out to realize stable detection of H2S at room tempertature on ZnOnanorods-based sensors.The sensing property of ZnO nanorods, grown on different substrates, to H2S was testedusing a CGS-1TP intelligent gas sensing analysis system. We found that ZnO naorods grownon interdigital electrode substrate displays excellent sensing property to H2S at roomtemperature. Its sensitivity is as high as218.2to1ppm H2S, and the value is3.06even in thecase of10ppb. The sensor also showed perfect selective detection to H2S. However, a poorrepeatability was found on this type of sensors. The sensing property of ZnO nanorods-basedsensor to H2S was studied and an improved method was proposed to realize the repeatabilityof ZnO nanorods-based sensors.A protective cover of ZnS on ZnO nanorod was designed to improve the repeatability fordetection of H2S. The target gas, H2S, was used as passivating agent to form a ZnS layer onthe surface of ZnO nanorods. We studied the effects of passivator concentration andpassivation time on the sensing property of ZnO nanorods-based sensors for H2S detection.Experiment results displayed that a repeatable detection of H2S was achieved with ZnOnanorods-based sensors by passivating in10ppm H2S for200s. A further anneal process wascarried out to elevated the stability of the above-mentioned sensitive devices, which havepotential application in the detection of H2S without auxiliary heating.A detailed characterization of passivated ZnO nanorods was performed by XRD、SEM、TEM、EDS et. al.. The relationship between thickness of ZnS layer and the sensing propertyof ZnO nanorods-based sensor was discussed. Furthermore, the sensing mechanism ofZnO@ZnS core/shell structure to H2S at room temperature was proposed to understand itsoutstanding response performance.