Mesoporous TiO₂ as a nanostructured inorganic polymer thin film applied for a wide range ammonia concentration analyzer based on photoelectrochemical reaction

Mesoporous TiO₂ as a nanostructured inorganic polymer thin film was applied for a wide range ammonia concentration analyzer in combination with an O₂-reducing Pt cathode based on photocurrent generation from ammonia induced by UV-light irradiation. Various structured sensor units were fabricated comprised of a TiO₂ photoanode, a Pt cathode, and an ultraviolet light-emitting diode (UV-LED) light source, and the photocurrent behavior was investigated as a function of ammonia concentration in water under stirring. Among the sensor units fabricated, the Type 4 sensor for which both the electrode surfaces are located perpendicular to the stirring direction gave the best characteristics, which was interpreted by the effective supply of ammonia and O₂ onto the electrode surfaces. It was successfully demonstrated that this new type ammonia concentration analyzer gives a linear correlation of photocurrents against logarithmic ammonia concentration in the wide range of five orders of magnitude from 1 mM to nearly 10 M. Copyright © 2011 John Wiley & Sons, Ltd.