An interpretation of NO response kinetics for copper phthalocyanine-based binary Langmuir-Blodgett films in the context of the gas diffusion model

The effect of the introduction of arachidic acid into copper tetra-tert-butyl phthalocyanine (CuTTBPc) Langmuir-Blodgett films on their gas-sensing properties with respect to NO has been studied. It has been found that the electrical responses of the two-component films to NO are fully reversible at 40 degrees C, whereas the one-component ones made up of pure CuTTBPc have to be operated at about 150 degrees C to achieve the acceptable response kinetics. This advantage of the mixed films is offset by annealing at 150 degrees C for 3 h. The CuTTBPc:arachidic acid molar ratio lies in the range from 1:1 to 1:5 for the compromise between the response kinetics and the sensitivity of the NO sensors. Using the gas diffusion model, an interpretation of the response kinetics of the studied sensors is given. The most probable explanation is that hole-like defects, existing in the arachidic acid matrix, are responsible for drastic changes in the response kinetics of the sensors. (C) 1998 Elsevier Science S.A. All rights reserved.