In this letter, experimental results on the capability of a tin dioxide (SnO2)-based silica optical fiber (SOF) sensor to detect sub-ppm ammonia concentrations in water environments, at room temperature, are presented. SnO2 sensitive layers have been deposited on the fiber end by using the simple and low cost electrostatic spray pyrolysis deposition technique. The surface morphology of the deposited SnO2 layers as well as its influence on the near field profile of the emergent electromagnetic field from the fiber coating have been investigated by means of atomic force microscopy and scanning near field optical microscopy. The room temperature adsorption measurements reveal the excellent sensor resolution of 80 ppb, good recovery features, high repeatability, and fast response times (a few minutes). The results obtained demonstrate the strong potentiality of the proposed SnO2-based SOF sensor to be employed for water quality monitoring applications. (c) 2006 American Institute of Physics.
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