Sol–gel entrapment of bromothymol blue (BTB) indicator in the presence of cationic 16E1Q and 16E1QS surfactants

Abstract

Sol–gel entrapment method was used to entrap bromothymol blue (BTB) pH indicator into mesoporous silica materials in the presence of cationic surfactants: 2-(hexadecyloxy)-2-oxoethyl-N,N,N-triethyl ammonium iodide (16E1Q) and 2-(hexadecyloxy)-2-oxoethanaminium-p-toluene sulfonate (16E1QS). The use of this new family of surfactants has modified the morphology and porosity of silica host matrix for better sensing capability and for faster response toward pH change. The physical interactions between BTB molecules and host mesoporous silica network were based on the nature of the surfactant. The presence of surfactants has shifted pKa values of more basic in comparison with that of BTB-entrapped silica system.