N-Triflyl Phosphoric Triamide: A High-Performance Purely Organic Trifurcate Quartz Crystal Microbalance Sensor for Chemical Warfare Agent

Detection of sulfur mustard simulant by trisaryl phosphoric triamide-based resin using a quartz crystal microbalance sensor

Chemical warfare agents (CWAs) pose a persistent threat to human safety, and bis(2-chloroethyl) sulfide, or sulfur mustard (SM) is one of the most dangerous substances and is able to cause serious harm. Detecting SM gas is vital, but current methods have high-temperature requirements and limited selectivity, mainly because of the lack of CWA receptor development, and this makes them challenging to use. To address this issue, we present a trisaryl phosphoric triamide-based resin receptor that preferentially interacts with a SM simulant 2-chloroethyl ethyl sulfide (2-CEES) through dipole interactions. The receptor was synthesized through a facile process using an amine and a triethyl phosphate and the properties of its coating were enhanced using epoxy chemistry. The receptor's superior triamide structure was evaluated using a quartz crystal microbalance and reactivity was confirmed by observing the variations in reactivity according to the number of phosphoramides. The receptor showed better reactivity to 2-CEES vapor than to the known poly(epichlorohydrin) and showed selectivity to other volatile organic compounds. Moreover, its durability was evident even 30 days post-coating. The applicability of this receptor extends to array sensors, sound acoustic wave sensors, and chemo-resistive and chemo-capacitive sensors, and it promises advances in chemical warfare agent detection.

Synergy of Two Intermolecular Hydrogen Bonds Promotes Highly Sensitive and Selective Room-Temperature Dimethyl Methylphosphonate Sensing: A Case of rGO-Based Gas Sensors

The development of room-temperature chemiresistive gas sensors with low limit of detection, high sensitivity, and selectivity for dimethyl methylphosphonate (DMMP) detection remains a challenge. Herein, a synergy of the two intermolecular hydrogen bond-promoted approach was proposed to fabricate a room-temperature DMMP sensor with enhanced performances. As a proof of concept, ternary p-hexafluoroisopropanol phenyl (HFIP) functionalized polypyrrole-reduced graphene oxide hybrids (HFIP-PPy-rGO) were rationally designed. During the sensing process, rGO serves as a conductive carrier, ensuring that the sensors operate at room temperature, and both HFIP and PPy act as adsorption sites for DMMP through hydrogen bonding interactions. As expected, the HFIP-PPy-rGO sensor exhibits high selectivity and sensitivity to DMMP. Besides, the HFIP-PPy-rGO sensor also possesses excellent linear response to DMMP and long-term stability. Experimental results and quartz crystal microbalance measurements prove that the specific recognition of DMMP is realized by forming two intermolecular hydrogen bonds between HFIP and DMMP, as well as PPy and DMMP. Additionally, the introduction of HFIP groups also contributes to adjusting device conductivity, enhancing signal conversion function. To put the DMMP sensor into potential practical application, the obvious sensing response to different DMMP concentrations in soil was confirmed, and a wireless detection system was built to realize real-time monitoring of DMMP concentrations in the surroundings. Overall, this study provides a facile and practical solution for improving the sensing performance of room-temperature sensors based on the hydrogen bond theory.

Hydrophobic Amplification Enabled High-Turnover Phosphazene Superbase Catalysis

β-Sulfido sulfonyl fluoride and its derivatives have been gaining attention recently in the fields of medicinal chemistry and material science. The conventional method for the synthesis of functionalized alkyl sulfonyl fluorides requires several chemical transformations. Therefore, a direct establishment of such chemical structures remains challenging, and an efficient catalytic approach is highly desired. Herein a significant "on-water" hydrophobic amplification was achieved, enabling a high-turnover catalytic thia-Michael addition to produce unprecedented β-arylated-β-sulfido sulfonyl fluorides. Amounts as low as 100 ppm (0.01 mol %) of the phosphazene superbase were sufficient to successfully catalyze the reaction with excellent chemo-/site-selectivity and with optimal functional group tolerance. Several β-arylated ethene sulfonyl fluorides were converted into thia-Michael adducts up to >99 % yields. The mild conditions, high turnover, neutral pH, and scalability of the sustainable catalytic process benefit the preparation of potential pharmaceuticals (e. g., polyisoprenylated methylated protein methyl esterase inhibitors) and organic materials (e. g., electrolyte additives).