Fiber optic ammonia sensor using Bromocresol Green pH indicator

We report a fiber optic sensor for low levels of ammonia gas detection based on the use a Bromocresol Green (BCG) pH indicator attached to the optical fiber employing hydrophobic and gas permeable polyurethane film named Tecoflex® as attraping matrix. Highly reproducible and reversible fiber optical sensors have been achieved employing simple and short fabrication processes. The advantage for employ a BCG pH indicator is to take advantage of the basicity of ammonia exhibiting a wide spectral response (500 nm-750 nm) and shows recovery times of less than 15 s. The Tecoflex® film provides additional advantages to be measured to the sensitive area of the sensor, such as operation even in extremely dry environments, efficient transport and prevent leakage or detachment of the BCG pH indicator. The combination of the BCG pH indicator and Tecoflex® film provides a reliable and robust fiber optic ammonia gas sensor.