Structurally stressed PT09SBA: A close look at the properties of large pore photoluminescent, redox active mesoporous hybrid silica

Abstract

A thien-2-yl substituted, electron-rich phenothiazine has been converted over several steps into a redox active sol–gel precursor. Following a fluoride-catalyzed synthesis, a phenothiazine-based mesoporous hybrid organosilica was obtained. The electrochemical behavior and the luminescence properties of the immobilized chromophore have been studied using solid state fluorescence spectroscopy, electron paramagnetic resonance spectroscopy (EPR) and solid state voltammetry (CV and DPV). The influence of both the presence of fluoride anions and the acidic pH during the material synthesis were explored by means of scanning and transmission electron microscopy (SEM and TEM), X-ray powder diffraction (XRD) and nitrogen physisorption measurements. While a combination of acidic pH and fluoride was found necessary for the material formation, partial cleavage of the precursor was observed. Data obtained from both the chemical as well as the electrochemical oxidation/reduction of the immobilized PT dye indicates the formation of an organic layer containing several species inside the pore channels.