Recent studies chemical sensors based on phthalocyanines

Abstract

Phthalocyanines (Pcs) are organic compounds able to act as chemical recognition systems because of the various physical effects induced in them by interaction with a large number of gases. The gas response, stability and other sensing characteristics of the Pc films are affected by many factors, such as film morphology, molecular orientation and so on. The interaction between the Pc coatings and the gas molecules may be classified in terms of irreversible chemical affinity, reversible (usually charge transfer) chemical reaction or sorption. The nature of the interactions between the coating and vapor molecules determines the selectivity, sensitivity, signal kinetics, and the reversibility of the sensor. The magnitude of these interactions may be conveniently described in the frame of the linear sorption energy relationship (LSER) model that has been shown to be very efficient at predicting the behavior of polymer-based sensors. In this paper, the effect of coating parameters on sensing properties and sensing mechanism are reviewed. We have proposed an alternative way to achieve optimal sensor performance: liquid crystalline Pcs forming self-ordered thin films of defined area and thickness simply by heating the sample over the phase transition temperature and synthetized mesomorphic and functionalized phthalocyanines, to develop sensors based on mass-sensitive transducers (quartz crystal microbalance, QCM). Phthalocyanines used are discussed in terms of their physical and chemical properties, as well as their sensing properties: sensitivity, selectivity and reversibility. We showed our results with LSER and the results are in good agreement with this theory.