A chemiresistive sensor is described for the detection of methane (CH4), a potent greenhouse gas that also poses an explosion hazard in air. The chemiresistor allows for the low-power, low-cost, and distributed sensing of CH4 at room temperature in air with environmental implications for gas leak detection in homes, production facilities, and pipelines. Specifically, the chemiresistors are based on single-walled carbon nanotubes (SWCNTs) noncovalently functionalized with poly(4-vinylpyridine) (P4VP) that enables the incorporation of a platinum-polyoxometalate (Pt-POM) CH4 oxidation precatalyst into the sensor by P4VP coordination. The resulting SWCNT-P4VP-Pt-POM composite showed ppm-level sensitivity to CH4 and good stability to air as well as time, wherein the generation of a high-valent platinum intermediate during CH4 oxidation is proposed as the origin of the observed chemiresistive response. The chemiresistor was found to exhibit selectivity for CH4 over heavier hydrocarbons such as n-hexane, benzene, toluene, and o-xylene, as well as gases, including carbon dioxide and hydrogen. The utility of the sensor in detecting CH4 using a simple handheld multimeter was also demonstrated.
Keywords: catalysis; chemiresistors; methane; selectors; sensor.