Ammonia Detection Based on Core-Shell Nanoparticle ZnS/Co9S8 Composites

In this paper, the Co/Zn-based zeolite imidazole framework (Co/Zn-ZIF) was synthesized by an etching method. Then, a certain amount of sulfur powder was doped into it and annealed to synthesize ZnS/Co9S8 composites with a core-shell structure mechanism (CS-ZnS/Co9S8). Compared with the single-metal ZIF, which is more studied at present, the application of a bimetallic ZIF shows remarkable excellent performance in gas sensing. The test results show that the sensor with a CS-ZnS/Co9S8 film has ultrahigh sensitivity to ammonia. At its optimal operating temperature of 240 degrees C, the detection limit of ammonia concentration can be detected to be 0.2 ppm. At the same time, the response of the CS-ZnS/Co9S8 thin-film sensor to 5 ppm concentration of ammonia is 4.56, which is 2.85 times and 3.26 times that of the single ZnS and Co9S8 thin-film sensors. In addition, the CS-ZnS/Co9S8 thin-film sensor has a response/recovery time of 7 s/9 s and has excellent repeatability, long-term stability, selectivity, and antihumidity interference. In addition to the polyhedral core-shell mechanism formed by ZnS/Co9S8, the p-n heterojunction directly formed by ZnS and Co9S8 is also a very important factor for the substantial improvement of its sensing performance.