Visible optical sensing of ammonia based on polyaniline film

In this work, a new optical gas sensor using thin polymer layers was developed. The polymer sensing layers were synthesized by chemical polymerization using the distilled aniline. The optical property of a polymer as a sensing material was analyzed using UV-Vis-NIR. These layers were prepared using centrifugal force. The polymer layer was uniformly deposited on inner glass pillar. The light source was red-light emitting diode (LED) with a 655nm wavelength. The light power transmitted through the guide cell was measured with a photodiode. Variation of the light power transmitted was detected when the gas was absorbed into the polymer layer. The transmitted light intensity decreased because gas molecules were absorbed into the polymer layer. This optical sensor showed a good sensitivity to NH₃ gas.