Preparation of an NH3 sensor based on CeO2/Zn2SnO4 with abundant oxygen vacancies and its application in monitoring beef freshness

A CeO 2 /Zn 2 SnO 4 ammonia (NH 3 ) sensor with excellent sensing performance was prepared by a one-step hydrothermal method, and the effect of surface oxygen vacancies on the performance of the sensor was analyzed by density functional theory (DFT). Experimental results show that the construction of CeO 2 /Zn 2 SnO 4 heterojunction can improves the content of oxygen vacancies on the surface of Zn 2 SnO 4 , which provides more adsorption active sites for NH 3 molecules and effectively improves the gas sensing performance of the sensor. DFT results indicate that surface oxygen vacancies facilitate the charge transfer caused by the adsorption of NH 3 molecules by CeO 2 , thereby increasing the binding energy of NH 3 molecules. Additionally, the surface oxygen vacancies can cause the structure of Zn 2 SnO 4 to deform during the adsorption of NH 3 , leading to significant electron hybridization and thereby increasing the binding energy of NH 3 molecules. In addition, CeO 2 /Zn 2 SnO 4 sensor was successfully applied to detect the NH 3 gas concentration released by different levels of freshness of beef, providing an effective method for monitoring the freshness of high-protein foods.