Author/Authors :
El-Nahhal، Issa M. نويسنده , , Zourab، Shehata M. نويسنده Chemistry Department, Al–Azhar University of Gaza, Gaza, 1277, Palestine , , Kodeh، Fawzi S. نويسنده Chemistry Department, Al–Azhar University of Gaza, Gaza, 1277, Palestine , , Qudaih، Alaa I. نويسنده Chemistry Department, Al–Azhar University of Gaza, Gaza, 1277, Palestine ,
Abstract :
Bromothymol blue (BTB) thin films were prepared by depositing a thin layer of a sol containing tetraorthosilicate (TEOS) and bromothymol blue (BTB) pH-indicator in the presence of surfactants, namely cetyltrimethylammonium bromide C19H42BrN (CTAB) or dodecyldimethyl amino-oxide C14H31NO (69%), C16H35NO (11%), Genaminox LA, (GLA) onto a glass slide substrate. CTAB or GLA surfactants were used to improve the mesostructure of the host material and to increase its porosity. Optical BTB thin films were found to be sensitive against pH, and behave as free BTB. This provides evidence for weak interactions between the BTB molecules and the host silica matrix. The effects of the sol mixture on the stability and reproducibility and the colourmetric response to solutions of different pH were examined and pKa values were determined. The BTB thin film sensors showed an advantage over the encapsulated monolithic sensors in which the thin film sensors exhibit a faster response time than the monolithic discs. These pH sensors showed reproducibility and high stability behavior.
