Journal
JOURNAL OF NON-CRYSTALLINE SOLIDS
Volume 353, Issue 3, Pages 286-294Publisher
ELSEVIER
DOI: 10.1016/j.jnoncrysol.2006.12.006
Keywords
sol-gel, aerogel and solution chemistry; sol-gels (xerogels); adsorption
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The sensing of a chemical environment is achieved mainly in the surface by interactions of the sensor material with its chemical surroundings. Therefore, porous structure control is key in developing good chemical sensors. The aim of this work was to obtain materials of tailored porosity to be used as support matrix for optical chemical sensors. We studied the simultaneous effect of pH, temperature, ethanol:TEOS, and water:TEOS molar ratios on gelation time, and textural and structural properties. We used a 2(4) factorial design that evaluates the effect of each independent variable and their interactions. Samples were characterized by XRD, SEM, FTIR, and gas adsorption (N-2 at 77 K and CO2 at 273 K). The gelation time decreased with increasing temperature, water:TEOS molar ratio, and pH; and with decreasing ethanol:TEOS molar ratios. Synthesis conditions also affected the xerogels porous textures. Xerogels obtained at pH 2.5 were ultramicroporous. In general, samples synthesized at pH 4.5 and ethanol:TEOS molar ratio of 2.25:1 were mesoporous, but the material is not appropriate for use as support in fiber optical sensors. (c) 2006 Elsevier B.V. All rights reserved.
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