Ultraviolet light activated ultrahigh frequency surface acoustic wave DMMP gas sensor with 10 ppb detection limit at room temperature

Dimethyl methylphosphonate (DMMP) is commonly used as a simulant for sarin in calibrating organophosphorus detectors. Among various DMMP sensors, surface acoustic wave (SAW) sensors are gaining significant attention for their attributes of wireless monitoring, digital outputs, and cost-effectiveness. However, there is a significant challenge remained as it is difficult to simultaneously improve sensitivity and reduce limit of detection (LOD) when monitoring the DMMP at room temperature. In this study, a comprehensive strategy was developed by applying Cu ion-doped ZrO2 (Cu-ZrO2) nanocomposite as a high-performance sensitive layer coated onto an ultrahigh frequency (4.98 GHz) SAW sensor for detecting low concentration DMMP at room temperature under ultraviolet (UV) light activation. The developed ultrahigh frequency SAW DMMP sensor demonstrated an exceptional sensitivity of 1198.2 kHz/ppm, similar to 1198 times higher than that of a conventional SAW sensor operated at a frequency of 162.4 MHz. It showed an ultralow LOD of 10 ppb, rapid response/recovery times of 39 s/25 s, and a long-term stability up to 30 days. Such the exceptional performance is primarily attributed to the Cu-ZrO2 sensitive layer, of which the doped Cu ions lead to the formation of more unsaturated Zr4 + ions, increasing the Lewis acid sites and promoting the effective interactions between Lewis sites and DMMP molecules. In addition, attributed to the ultrahigh resonant frequency of the SAW device, a giant elastic loading effect was identified to significantly enhance the sensing performance. This study provides a promising and versatile methodology for achieving ultrahigh sensitivity DMMP detection based on the SAW technology.