Modification of mesostructure base on composition of silica materials and their applications to pH sensing

Abstract

AbstractThis study induced a chemical combination of fluoresceinamine (FA) and (3‐chloropropyl)triethoxysilane (CP‐TEOS) in the presence of tetraethyl orthosilicate (TEOS) which is able to maintain the shape of the mesostructure without prior removal of the surfactant. The sol‐gel derived silica films were controlled by the reaction time and molar ratios of TEOS and CP‐TEOS, and characterized in terms of response to pH, pKa values, effects of oxidation number, leaching, and scanning electron microscopy (SEM) imaging. The conclusions include the effect on molar ratios and the choice of reaction time. The results of this study are summarized as follows: (1) increasing the molar ratio of TEOS, the mesostructure of these films exhibited not only perfect single‐crystal morphology but also a hexagonal morphology; (2) the most suitable molar ration in this synthesis is the ratio of 1:1 (the molar ratio of TEOS and CP‐TEOS); (3) the reaction time for this system should be controlled at least to over 6 hr in order to maintain high intensity absorbance against a minimum of indicator quantity. Leaching‐out is more pronounced for films used directly after preparation and varies for different molar ratios. The long‐term implication of leaching‐out on sol‐gel based pH sensors is discussed. Copyright © 2006 John Wiley & Sons, Ltd.