Dyeless optical detection of ammonia in the gaseous phase using a pH-responsive polymer-characterization of the sorption process

摘要

pH-responsive polymers enable the dyeless op- tical detection of acidic or basic pollutants in air. The characterization of the sorption process and the optimiza- tion of the response time of the sensitive layers were high- lighted. The swelling of a pH-responsive polysiloxane in- duced by sorption of gaseous ammonia was investigated by measurement techniques such as spectroscopic ellip- sometry (SE) and infrared spectroscopy (IR). Furthermore, the pH-responsive polymer was applied for the detection of gaseous ammonia using the LEO-based reflectometric interference spectroscopy set-up (RIfS4A). A limit of de- tection of 0.30 mg/m3 ammonia and a response time (t9O%) of 35 s could be verified. THe application of pH-respon- sive polymers can be a powerful alternative to dye-based optical sensing, since photob.leaching or leaching of the sensitive functional unit cannot occur applying this ap- proach, and since the properties of the sensitive layer proved to be very promising.