THE CHEMICAL DEGRADATION OF GAS-SENSING MESO-TETRA-ARYLPORPHIN THIN-FILMS BY HIGH-LEVELS OF DINITROGEN TETROXIDE

Thin solid films of free base meso-tetra-arylporphins and their zinc, copper, platinum and palladium complexes have been exposed to high levels of dinitrogen tetroxide (NOX). The optical spectra (300-850 nm) were recorded in transmission before and after exposure to NOX. On the basis of the foregoing spectroscopic evidence, films resistant to permanent chemical damage by high levels of NOX ( greater than 10,000 ppm) are identified. Reaction schemes are presented for those molecules that can be regenerated after chemical attack by NOX. The relevance of these observations to the selection of solid organic films suitable as industrial gas sensors is highlighted.