Optical ammonia gas sensor based on nanostructure dye-doped polypyrrole

Design and fabrication of an optical gas sensor based on ammonia vapor sensing system are described. A dye-doped nanostructure polypyrrole (PPy) film, as sensitive layer, has been synthesized by chemical processing. The dye-doped PPy gas sensor was prepared by the doping of eriochrome cyanine R (ECR) in polypyrrole (PPy–ECR) and used for selective optical ammonia gas sensor. The sensing properties of the optical PPy–ECR and morphology of the polymer film was studied by UV–vis spectroscopy and scanning electron microscopy (SEM) respectively. The change in optical absorption of thin polymer layers in the presence of ammonia gas is used as a sensor signal. Sensing tests performed under exposition to calibrated amounts of ammonia reveal that these simple and inexpensive sensors are able to detect ammonia gas at room temperature in a fast reliable way, with a sensitivity linearly related to concentration in the range between 15 μg L−1 and 260 μg L−1. Optical PPy–ECR gas sensor presents low detection limit (5 μg L−1) and good reproducibility in construction (RSDs < 5%). The sensor is highly selective to ammonia gas over diverse amine gases, water and organic solvents. The method was applied for determination of ammonia in environmental real samples with satisfactory recovery.