Highly sorbent films derived from Ni(SCN)2(4-picoline)4 for the detection of chlorinated and aromatic hydrocarbons with quartz crystal microbalance sensors

A quartz crystal microbalance (QCM) spray-coated with a Ni(SCN)(2)(4-picoline)(4) film is a sensitive detector for small aromatic (benzene, toluene) and chlorinated (trichloroethylene, perchloroethylene) vapors with a planar molecular geometry, Frequency changes during transient exposures to these vapors are rapid and reversible, In contrast, frequency changes during transient exposures to carbon tetrachloride vapor exhibit a very slow rise and decay, Impedance studies demonstrate that the QCMs are responding only to mass changes in the film, Calibration curves exhibit both linear and near-saturation responses, depending on the vapor and vapor concentration, Partition coefficients obtained from the linear response regimes of the calibration curves are in the 10 000-100 000 range, more than an order of magnitude larger than the partition coefficients for a prototypical soft polymer, poly(isobutylene), Despite the absence of evidence for crystallinity by optical or X-ray diffraction methods, the spray-coated films appear to be forming clathrates with the organic vapors, The Ni(SCN)(2)(4-picoline)(4) film is promising for the development of very sensitive and partially selective piezoelectric sensors for nonpolar or weakly polar organic vapors in air.