Soluble dodecylsulfanylphthalocyanines as sensitive coatings for chemical sensors in gas phase

In this study, a series of new soluble dodecylsulfanylphthalocyanines are investigated as sensitive coatings for organic vapors by utilizing modified and conventional electrode quartz crystal resonators (QCR) based on changes in dielectric properties (electrical loading) and the well-known mass loading effect. These sensing properties were investigated by measuring both series- and parallel-resonant frequencies (f_s and f_p). The results showed that the sensor signals are completely reversible and reproducible at room temperature. Differences between f_s and f_p were observed for all investigated analytes. The two sets of data appear to be linearly independent, thus providing the possibility of implementing chemical sensors with improved selectivity using pattern recognition. In addition, the interaction mechanisms between the volatile organic molecules and the investigated phthalocyanine (Pc) coatings are discussed utilizing the partition coefficients of the vapor molecules, and possible changes in the electrical properties of the coatings. In order to study all possible interaction mechanisms as well as the properties of the Pc materials, thin coatings of the Pcs are deposited on interdigital transducers on glass substrates and are being studied using impedance spectroscopy methods. The dc conductivities of the Pcs exposed to Cl₂ and Br₂ were also investigated.