[Study of the fluorescent response for optical ammonia sensing film].

The characters of optical sensing films for ammonia were investigated based on a fluorescent indicator aminofluorescein (AF) immobilization. An organically modified silicates (ORMOSILSs) obtained by copolymerizing various proportions of methyltrimethoxysilane (Me-TriMOS) and tetramethoxysilane (TMOS) was applied. Compared with the fluorescent responses of fluorescein and fluorescein carboxylicate, the fluorescent intensity enhancement of AF for ammonia was found to be caused by the reaction of ammonia with the NH2 group on AF. The reaction may cause the reduction of the intermolecular self-quenching of AF, resulting in a fluorescence enhancement of sensing film in NH3 solution. Furthermore, the properties and the ammonia-sensing behavior of the film were investigated. The results presented here emphasized the significance of ormosil as a matrix for dissolved ammonia sensing. The detection limit for ammonia in water was 0.3 microg x mL(-1).