C. Preininger et al., Effect of the sol-gel matrix on the performance of ammonia fluorosensors based on energy transfer, J FLUORESC, 8(3), 1998, pp. 199-205
We report on the effect of organomodified sol-gel materials on fluorosensor
s for ammonia. The fluorosensors are based on ion pairs composed of an iner
t fluorophore and a pH-sensitive absorber dye and are embedded in sol-gel g
lass. Upon exposure to ammonia, deprotonation of the pH-sensitive dye bromo
phenolblue occurrs, and consequently, energy is transferred from the fluoro
phore rhodamine B or tetramethylrhodamine ethyl ester to the absorber. The
response of the fluorosensors using different ratios of precursors, such as
tetramethoxysilane and phenyltrimethoxysilane, is investigated. Detection
limits for sol-gel layers composed of 50% tetramethoxysilane and 50% phenyl
trimethoxysilane are as low as 0.1 mg/L of aqueous ammonia. Response times
are of the order of 3 to 6 min for forward response. The reversibility of t
he sensor is related to the composition of the organically modified sol-gel
glasses and is fastest for sensor layers composed of pure phenyltrimethoxy
silane. Conditioning, regeneration, and storage of the layers are shown to
be of vital importance for the performance of the sensor layers.