Mechanism of trace-level detection of dibutyl sulfide (DBS) at room temperature using UV-activated MoO3 coated quartz crystal microbalance (QCM) sensor

Use of chemical warfare agents (CWAs) by terrorists poses significant challenges for law enforcement, emergency responders, and public health authorities. Timely detection of CWAs assumes importance for enhancing preparedness, response, and recovery capabilities. Mustard gas, or sulfur mustard, is a highly dangerous CWA due to its high toxicity, persistence, potential for secondary contamination, and weaponization. Simulants are essential in developing sensors for detecting CWAs, as handling real agents is dangerous outside controlled conditions. One simulant for mustard gas is dibutyl sulfide (DBS). The present study describes the development of a highly efficient MoO3 thin film-based gas sensor for the trace-level detection of DBS at room temperature. A thin film of MoO3 was coated on Quartz Crystal Microbalance (QCM) using the RF magnetron sputtering technique. In the presence of ultraviolet light (~ 355nm), the sensor exhibited a high sensitivity of 0.4Hz/ppm in the range of 2 – 400 ppm DBS with a quick response time (~7s) and recovery time (~15s) towards 2 ppm DBS at room temperature. The MoO3 sensor also demonstrated high selectivity and stable reproducibility. Hence in the current investigation, the detailed DBS sensing mechanism for RF sputtered MoO3 thin film is also discussed.