Formic acid an efficient solvent to prepare polyaniline/silicate glass composite using sol–gel technique

In this work an efficient method to prepare silicate glass and hybrid inorganic–organic material composed of polyaniline (PANi) and silica gel network has been developed using the sol–gel technique. The method consists in mixing tetraethoxysilane (TEOS) and PANi in formic acid, which acts as solvent and catalyst simultaneously. This process is based on the facts that PANi is souble in formic acid and the acid is an efficient catalyst to form polysilicate network. Transparent and monolithic hybird glass doped with PANi has been obtained. The extent of the polysilicate network development was investigated by 29Si nuclear magnetic resonance spectroscopy. Spectroscopic analysis in the ultraviolet–visible (UV–Vis) region as a function of the pH shows that this composite can be used as an efficient pH sensor, since PANi remains optically active.