Visible optical sensing of ammonia based polyaniline film

Optical sensors have been used in new technologies for detecting small amounts of chemical, gaseous species. In this work, a new optical gas sensor using thin polymer layers was developed. We selected a polymer for the gas sensing material. Polymers were synthesized and chemically polymerized by using distilled aniline. The optical property of the polymer as a sensing material was analyzed by using UV-Vis-NIR. These layers were prepared by using centrifugal force. The polymer layer was uniformly deposited on an inner glass pillar The light source was a red-LED with 655 nm wavelength. The light power transmitted through the guide cell was measured with a photodiode. The variation of light power transmitted was detected when the gas was absorbed in the polymer layer The transmitted light intensity was decreased because gas molecules were absorbed into the polymer layer. NH₃ gas is used as the evaluating gas. This optical sensor showed a good sensitivity to NH₃ gas.