Single-atom nanozymes possessing robust multienzyme-mimetic catalytic properties for sensing of volatile alkaline gas

Volatile alkaline gases (VAGs) emitted from various sources, such as the food or chemical industry, pose potential harm to the natural environment and human health. Therefore, the development of a real-time, rapid, and costeffective detection method is crucial. In this study, the enzyme-like catalytic types and activities of four different metal-based single-atom enzymes (Ga, Cu, Mn, and Zn SAzymes) were selected and evaluated. Among them, Ga SAzyme exhibited the most promising catalytic properties. Furthermore, the multienzyme catalytic properties of Ga SAzyme were utilized for the detection of ammonia, and it was found that its peroxidase-like (POD-like) activity showed a strong affinity for ammonia (Km = 0.05 mM). This detection strategy demonstrated high sensitivity, with a limit of detection (LOD) of 3.0 mM in the linear range of 0.01-0.05 M and 7.0 mM in the linear range of 0.075-0.25 M. Additionally, the method was characterized by fast response time (15 s) and low cost ($0.035 per sample). The proposed method holds great potential for the detection of VAGs from various sources in the future.