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

Abstract

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.

Hydrogen-Bond Acidic Materials in Acoustic Wave Sensors for Nerve Chemical Warfare Agents’ Detection

“…Materials based on POSS continue to attract significant interest to this day [ 91 , 92 ]. In 2020, Kim et al [ 91 ] described a material functionalized with substituents containing 4-(trifluoromethyl)phenol groups at the corners of the POSS cage (the structure of this material is presented in Figure 5 g as POSS-4-(trifluoromethyl)phenol).…”

“…In 2023, Bae et al [ 92 ] described the synthesis and investigation of thiourea-decorated POSS with fluorinated substituents that increase acidity, named PSS-TU3 (its structure is presented in Figure 5 h). Unlike most previously used materials, in this case, there were no hydroxyl groups, but hydrogen atoms bonded to the nitrogen atoms in secondary amines of the thiourea substituent.…”

“…The sensors' responses to DMMP at a concentration of 0.5 mg/m 3 and a temperature of 28 °C were tested. The highest response values were obtained for the BSP3 analog (3629 Hz) and the PMPS analog Materials based on POSS continue to attract significant interest to this day [91,92]. In 2020, Kim et al [91] described a material functionalized with substituents containing 4-(trifluoromethyl)phenol groups at the corners of the POSS cage (the structure of this material is presented in Figure 5g as POSS-4-(trifluoromethyl)phenol).…”