Sol-Gel Thin Films Immobilized with Bromocresol Purple pH-Sensitive Indicator in Presence of Surfactants

Abstract

Preparation of transparent sol-gel thin film immobilized with bromocresol purple (BCP) pH-sensitive indicator was made via the acid catalyzed sol-gel reaction of tetraethylorthosilicate and the bromocresol purple indicator (BCP). Different surfactants include cationic cetyl trimethyl ammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS), and nonionic Triton X-100 (TX-100) were used to improve the mesostructure of the host material and to increase its porosity. The color change behavior of the immobilized bromocresol purple indicator affected significantly in presence of SDS comparing with its free counterpart in aqueous solution. In presence of CTAB and Triton-X 100, the immobilized bromocresol purple indicator shows similar behavior as its free counterpart in aqueous solution. The BCP retains its structure during the sol-gel reactions in terms of response to pH. Different parameters including concentration of indicator and surfactant, temperature, number of layers, response time, life time, and the number of measurements were investigated. The pK a values of the different prepared BCP immobilized thin films were determined. The BCP thin film sensor showed stability, repeatability, reproducibility, fast response, and long life time behavior. The polarized light microscopy indicated that the bromocresol purple indicator molecules are distributed uniformly within the host silica network.

Optical sensing system based on wireless paired emitter detector diode device and ionogels for lab-on-a-disc water quality analysis

“…The pKa of BCP in the ionogel was determined using standard buffer solutions ( comparison to a pK a of 6.3 reported in literature 55 . It was previously demonstrated that when pH indicator dyes are immobilised within solid gels, the micro-environment of the matrix shifts the pK a of the dye slightly, on occasions by over 0.5 pH unit 56 .…”

Micro- and nanostructured sol-gel-based materials for optical chemical sensing (2005–2015)

“…The same group also reported on TEOSbased films doped with chlorophenol red which was used to monitor the acidity around stained glass windows in Madrid [95]. The influence of the surfactants on sol-gel-based pH sensor response was also investigated [96,97]. The TEOSbased sol was doped with bromocresol red and three different surfactants, namely cationic cetyl trimethyl ammonium bromide, anionic sodium dodecyl sulfate (SDS) and non-ionic Triton X-100.…”

Sol–gel based optically active phenolphthalein encapsulated nanomatrices for sensing application

“…Even though significant advances in technologies based on sol-gel thin film processing have been reported [1][2][3][4][5][6][7], still relatively little efforts are directed toward understanding the different pH-sensing dyes' immobilization behavior into sol-gelbased silica matrices without leaching problem [8][9][10]. These can be used for designing photocatalysts, for water detection, and also for developing the novel chemical sensor materials [11].…”

“…To solve this issue, in this study, we propose two types of matrices, titania and silica-titania by sol-gel method at low temperature. There are three methods to immobilize indicator into sol-gel matrix: covalent binding, impregnation, and chemical doping [1]. The chemical doping sol-gel method allows fast application of the coating solution without damaging film and is quite attractive to prepare nanomaterials by hydrolysis and polycondensation of different precursors in liquid and to immobilize the dyes (guests) into fabricated nanomaterials host network for photocatalysis and sensing applications.…”