STUDIES WITH SOLID-STATE PHOSPHORESCENT COATINGS ON THEIR SENSITIVITYTO NITROGEN-OXIDES

Phosphorescent polymer film compositions and phosphorescent Langmuir-B lodgett coatings based on platinum and palladium porphyrins were teste d in the presence of nitrogen oxides (NOx). Dynamic quenching of phosp horescence by NOx was observed. It was accompanied by chemical interac tion of NOx with the dye molecules which caused persistent decrease of the phosphorescence signal and irreversible degradation of the sensor . Two modes of NOx quantitation based on measurement of either phospho rescence lifetime or time drift of intensity were examined. For the ph osphorescent polymer film compositions the analytical range of NOx was found to be 0-3.0% (m/m) with a detection limit of 0.1%. For the LB-f ilm coatings the sensitivity for NOx was about five times better: the range was 0-1.0% (m/m) with a detection limit of 0.02%. Although for b oth systems the analytical range of NOx covered was poor for practical purposes, the data obtained are useful for evaluation of possible int erferences by NOx in other applications, such as in oxygen and SO2 sen sors. The possibilities of the realization of a dual-sensing concept w ith a single phosphorescent probe is discussed with respect to simulta neous measurement of NOx/oxygen using polymer film compositions and NO x/SO2 using Langmuir-Blodgett coatings.