Characteristics of dye-impregnated tetraethylorthosilane (TEOS) derived sol-gel coatings

An investigation has been carried out on a cross-comparison study into several sol-gel coatings, impregnated with a pH-sensitive fluorescent dye, to determine their optimum characteristics, with the aim of their application as thin film sensor elements in fibre optic chemical sensors. In this test of the coatings, they were applied to standard, cleaned microscope slides and several characteristics, such as the ability of the sol to wet the glass substrate and the optical clarity of the subsequent coating were investigated and found to depend mainly on the water: tetraethylorthosilane (H₂O: TEOS) ratio used in their preparation but also on the extent of aging and the level of catalyst used. It was found that thicker coatings could be created through the use of suitable chemical additives in the preparation process.