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

pH-responsive polymers enable the dyeless optical detection of acidic or ba sic pollutants in air. The characterization of the sorption process and the optimization of the response time of the sensitive layers were highlighted . The swelling of a pH-responsive polysiloxane induced by sorption of gaseo us ammonia was investigated by measurement techniques such as spectroscopic ellipsometry (SE) and infrared spectroscopy (IR). Furthermore, the pH-resp onsive polymer was applied for the detection of gaseous ammonia using the L ED-based reflectometric interference spectroscopy set-up (RIfS(4 lambda)). A limit of detection of 0.30 mg/m(3) ammonia and a response time (t(90%)) o f 35 s could be verified. The application of pH-responsive polymers can be a powerful alternative to dye-based optical sensing, since photobleaching o r leaching of the sensitive functional unit cannot occur applying this appr oach, and since the properties of the sensitive layer proved to be very pro mising.