AC-IMPEDANCE-BASED CHEMICAL SENSORS FOR ORGANIC-SOLVENT VAPORS

A type of chemical sensor based on impedance spectroscopy (IS) measure ments utilizing an interdigital transducer structure on a glass substr ate is investigated for the detection of organic solvent molecules, su ch as chloronated hydrocarbons, in the gas phase. The IDT structures w ere coated with sensitive materials such as soluble tetrakis-t-butyl p hthalocyaninatonickel(II), ethylcellulose, poly(ethyl, acrylate), and poly(etherurethane). The target organic solvent molecules are dichloro methane, chloroform, trichloroethene, tetrachloroethene, toluene, and ethanol. The sensor responses were monitored by measuring changes in t he transducer/coating composite properties upon exposure to the organi c solvent molecules. The sensor parameters of interest include the ele ctrostatic capacitance, the resistance of the composite and the relaxa tion time, which will lead to the implementation of a multi-informatio n sensor. Results are presented and compared for selected samples with completely reversible sensor signals at room temperature. Based on th e measurements, use of metal complexes can improve sensitivity and inc rease the signal-to-noise ratio.