Nizam M El-Ashgar, Ahmed I El-Basioni, Issa M El-Nahhal, Shehata M Zourob, Taher M El-Agez, Sofyan A Taya
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 pKa 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.
أ.د نظام محمود الأشقر | Prof. Nizam M. El-Ashgar | 13613