Ammonia sensing performance of thin films of cobalt(II) phthalocyanine bearing fluorinated substituents

Abstract

In this work, a new cobalt phthalocyanine derivative bearing 5-(trifluoromethyl)-2-mercaptopyridine substituents (CoPc) was synthesized and characterized. The redox properties of CoPc were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV) methods. The sensing performance of CoPc thin films deposited by spin coating of its solution in ethylacetate was studied against low concentrations of ammonia (0.3 to 50ppm) by measuring changes in the films' conductivity at different humidity. It has been shown that the CoPc-based sensor displays an improved ammonia sensing performance in terms of sensitivity, response and recovery times. Ammonia can be detected in the presence of volatile organic vapors, and its detection limit was found to be 0.3ppm. At the same time, low concentrations of CO2 comparable with the concentrations of ammonia do not influence on the sensitivity of CoPc film to ammonia, however the sensor response noticeably distorts in the presence of high CO2 concentrations in the gas mixture.