Characteristics of the substituted metal phthalocyanine NO 2 sensor

Abstract

Substituted phthalocyanines, netal tetra-tertiary-butylphthalocyanines, are applied to a thin-film nitrogen dioxide sensor, and response curves are measured. Although faster diffusion of the gas in the substituted phthalocyanene films is expected, the films are presupposed to be unstable. Some substituted phthalocyanines are decomposed at high temperature. Neither metal tetra-carboxyphthalocyanines nor metal tetra-aminophthalocyanines can be sublimited. Stable metal tetra-tertiary-butylphthalocyanines evaporate at about 400 °C. Copper tetra-tertiarybutylphthalocyanine is sublimated under vacuum on the quartz substrate, on which an interdigitated platinum electrode is formed. Vanadium-oxide-substituted phthalocyanines are also tested. Resistivity is measured in a heat-controlled quartz chamber under dry mixed gases. X-ray diffraction spectra are also measured. These films made from substituted phthalocyanines show higher resistivity and quicker recovery. SEM images show that the structure of these thin films is the same as that of films from a simple metal phthalocyanine. Higher resistivity and higher recovery could originate from the wider stacking space and the weaker nitrogen dioxide affinity of those phthalocyanines.