Surface Acoustic Wave Sensor with Al–ZnO Sensitive Layer for Formaldehyde, Ammonia, and Sulfur Dioxide Gases Detection

Hazardous gases represent a significant threat to both the ecological environment and human health. Therefore, achieving rapid and precise detection of these harmful gases is of paramount importance for the environmental health and the safety of human life. Here, surface acoustic wave (SAW) sensing technology for formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2) gases was studied. A dual-channel mixed-signal SAW sensing system was proposed for the detection of target gases. The experimental results indicate that the sensitivity of the SAW sensor coated with an Al-doped zinc oxide (Al–ZnO) nanosheet layer is 2817, 3592, and 3927 Hz/ppm, respectively, which is approximately double that observed in the undoped ZnO sensitive layer. The SAW sensor coated with an Al–ZnO sensitive layer exhibits the greatest sensitivity to SO2 gas. Combined with density functional theory (DFT) analysis of adsorption energy and electron transfer, the results demonstrate that the Al–ZnO sensitive film exhibits a stronger adsorption capacity for SO2 gas molecules, which is basically consistent with the experimental conclusion. This work can provide a reliable theoretical foundation and technical support for the application of SAW sensors in industrial safety and environmental monitoring.