(269d) Development of a Gas Sensor Array for Detecting Toxic VOCs Using Metalated Gold Monolayer Protected Clusters

Gas sensor arrays are a promising means of detecting toxic volatile organic compounds (VOCs) in environmental air. Among different airborne VOCs, benzene, toluene, ethylbenzene, xylene (BTEX), and trichloroethylene (TCE) are the most abundant and toxic VOCs. These VOCs induce cardiovascular metabolic syndrome and lung cancer, etc. Detection of these VOCs in environmental air by current gas sensors is very challenging because of sensitivity, selectivity and air matrix interference issues. Thiol-functionalized gold nanoparticle-based chemiresistors provide an advantage over other gas sensors, such as lower fabrication cost, room-temperature operation, and higher sensitivity and selectivity. This is achieved by tailoring the composition of the thiolate monolayers. The present work demonstrates development of alkali metal ion-carboxylate functionalized gold monolayer protected clusters (Au MPCs) as a sensing material for highly sensitive and selective detection of BTEX and TCE.

A gas sensor array has been fabricated using micro-electromechanical system (MEMS) technology. The sensor array features four circularly shaped sensing areas containing interdigitated electrodes that can perform simultaneously testing four different sensing materials. Lithium, sodium, potassium, and cesium carboxylate-linked Au MPCs were synthesized and tested for sensing vapors of BTEX, TCE as well as some non-aromatic and chlorinated VOCs. The results demonstrate that the responses of metalated Au MPCs are rapid, reversible, and linear for all the tested analytes. Cation-linked Au MPCs improve sensitivity and selectivity toward sensing BTEX due to cation–π interactions and the relative strength of the sensitivity follows the order of K⁺ > Na⁺ > Li⁺. Furthermore, Cs⁺-functionalized Au MPCs respond highly to chlorinated compounds, which helps to detect TCE in air. These metalated Au MPCs sensors show much promise for developing a sensor array for real-time measurements of toxic airborne VOCs.