Detection of organic vapors and NH3(g) using thin-film carbon black-metallophthalocyanine composite chemiresistors

Abstract

Thin-film chemiresistive vapor sensors have been fabricated using composites of carbon black (CB) and metallophthalocyanines. The resulting sensors exhibited large, rapid, and reversible relative differential resistance changes upon exposure to a series of test organic vapors. The individual sensor responses, and collective sensor array properties for classification of a series of test organic vapors, were comparable to those of chemiresistor arrays made from composites of conductors and insulating organic polymers. In addition to displaying resistance responses to volatile organic compounds, the CB/metallophthalocyanine composite sensors exhibited a high sensitivity towards trace levels of NH_3(g) under ambient temperature and pressure conditions. No degradation in sensor response was observed after nearly 12 h of repeated exposure to 30 parts per million of NH_3(g) in air. Chemiresistors formed from composites of CB and zinc phthalocyanines demonstrated responses that were comparable to those of commercial NH_3(g) sensors. The CB/metallophthalocyanine composites thus broaden the types of materials that can be used for this type of low-power chemiresistive gas sensing, and broaden the types of analytes that can be sensitively detected to include inorganic gases as well as organic vapors.