EFFECTS OF MORPHOLOGY ON NO2 DETECTION IN AIR AT ROOM-TEMPERATURE WITH PHTHALOCYANINE THIN-FILMS

Lead phthalocyanine films freshly deposited on alumina and glass were found to consist of disordered phases and fine particles with mean diameter below 0.2μm. Following annealing at 300 ° C, a transition to a crystalline form is obtained. The crystal size in the films annealed at 300 ° C or above is affected by the nature of the substrate, ambient atmosphere and annealing time. Following an optimized preparation procedure, the films exhibit response times of less than 20 sec and recovery times of the order of several minutes, independently of N02 concentration or exposure time, at room temperature. They consist of fine crystals with mean diameters of the order of 0.2μm and amorphous phases are not observed. For zinc, copper, cobalt and nickel phthalocyanine films, some improvements in the response and recovery times are achieved by annealing but not sufficient to allow No2 detection at room temperature. For films of these phthalocyanines, fine crystals of the type formed in leadphthalocyanine films were not produced in the conductive paths when the films were annealed at 300 ° C in air. © 1990 Chapman and Hall Ltd.