High Performance and Reusable SAW Sensor Coated with Thiourea-Decorated POSS with Different Functional Groups for DMMP Detection

A colorless, odorless G nerve agent, a type of chemical transfer agent (CWA) that causes significant loss of life, is being studied for quick and accurate detection. In this study, detection materials with different functional groups were synthesized based on thiourea (TU)-decorated polyhedral oligomeric silsesquioxane (POSS) to study the most suitable material for the detection of dimethyl methylphosphonate (DMMP), a simulant of neural agents. The sensing material was coated on a SAW sensor with a resonance frequency of 250 MHz based on ST-quartz, the DMMP exposure experiment was conducted, and the performance of the sensing material was compared through frequency shift before and after exposure. Coating materials with excellent reactivity with DMMP and appropriate coating concentration for each material were identified at a concentration of 10 ppm. Among them, POSS-TU with 3,5-bis(trifluoromethyl)phenyl as a functional group showed the largest frequency shift characteristics, and it was used in low concentration (1, 5, and 10 ppm) DMMP detection experiments to confirm linear frequency shift characteristics according to low concentration. Finally, through a selectivity experiment with other gases, it was confirmed that the amount of frequency shift in other gases except DMMP was small, making it an excellent DMMP sensing material.