The translucency, high porosity and high surface area of silica aerogels make them attractive as platforms for optical sensors. In this study, oxygen-sensitive aerogels were made using a tetraethyl orthosilicate (TEOS)-based sol-gel precursor recipe and processed via rapid supercritical extraction (RSCE). In earlier work in our group, tetramethyl orthosilicate (TMOS) was used as the silica precursor for aerogel-platform luminescent sensors. Using a recipe with TEOS and ethanol, rather than TMOS and methanol, rendered the process more cost effective but also produced cloudy aerogels that were unsuitable for sensor applications. Employing methanol (rather than ethanol) as a solvent increased the translucency of TEOS-based aerogels significantly (60%T at 650nm). The precursor mixture (1:22:3.5:3.5 molar ratio of TEOS : methanol : acidic water : basic water) was doped with ruthenium(II) 4,7-diphenyl-1,10-phenanthroline [Ru(dpp)32+]. The luminescence of Ru(dpp)32+ is quenched by oxygen; hence, observed emission intensity can be related to the concentration of oxygen. Transmittance of the probe-doped aerogels decreased (to 40% at 650nm), but remained adequate for measurement in a fluorometer. The color and excitation and emission spectra of the aerogels demonstrate that Ru(dpp)32+ is physically entrapped in the aerogel matrix. The fluorescent responses of the Ru(dpp)32+-doped aerogels to a nitrogen atmosphere were measured quantitatively with respect to fluorescence under ambient conditions (ca. 21% oxygen). Signal increases of up to 6 times were observed within seconds. The results of studies of sensor response to varying percent oxygen and of sensor reversibility will be presented.

Luminescent-probe-doped TEOS-based silica aerogels for oxygen sensor applications

247th National Meeting (2014)

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