AC-impedance-based chemical sensors for organic solvent vapors

A type of chemical sensor based on impedance spectroscopy (IS) measurements utilizing an interdigital transducer structure on a glass substrate is investigated for the detection of organic solvent molecules, such as chloronated hydrocarbons, in the gas phase. The IDT structures were coated with sensitive materials such as soluble tetrakis-t-butyl phthalocyaninatonickel(II), ethylcellulose, poly(ethyl, acrylate), and poly(etherurethane). The target organic solvent molecules are dichloromethane, chloroform, trichloroethene, tetrachloroethene, toluene, and ethanol. The sensor responses were monitored by measuring changes in the transducer/coating composite properties upon exposure to the organic solvent molecules. The sensor parameters of interest include the electrostatic capacitance, the resistance of the composite and the relaxation time, which will lead to the implementation of a multi-information sensor. Results are presented and compared for selected samples with completely reversible sensor signals at room temperature. Based on the measurements, use of metal complexes can improve sensitivity and increase the signal-to-noise ratio.