Comparative Gas Sensing in Cobalt, Nickel, Copper, Zinc, and Metal-Free Phthalocyanine Chemiresistors

The sensitivities of metallophthalocyanine (MPcs: M = Co, Ni, Cu, Zn, and H-2) chemiresistors to vapor phase electron donors were examined using 50 nm MPc: films deposited on interdigitated electrodes. Sensor responses were measured as changes in current at constant voltage. Analytes were chosen to span a broad range of Lewis base and hydrogen bond base strengths. The MPc sensor responses were correlated exponentially with binding enthalpy. These exponential fits were consistent with the van't Hoff equation and standard free energy relationships. Sensor recovery times were found to depend exponentially on binding enthalpy, in agreement with the Arrhenius; equation. Relative sensitivities of all MPcs were compared via two-way ANOVA analysis. Array response patterns were differentiated via linear discriminant analysis, and analyte identification was achieved over a range of concentrations with 95.1% classification accuracy for the strong binding analytes. The ability to distinguish among different analytes, regardless of their concentration, through normalization of the responses to a reference sensor is particularly noteworthy.