Fluorescent silica hybrid materials containing benzimidazole dyes obtained by sol–gel method and high pressure processing

Abstract

New silica hybrid materials were obtained by incorporation of two benzimidazole dyes in the silica network by sol–gel technique, using tetraethylorthosilicate (TEOS) as inorganic precursor. Several syntheses were performed with two catalysts (HF and NaF) producing powders and monoliths with different characteristics. The dye 2-(2′-hydroxy-5′-aminophenyl)benzimidazole was dispersed and physically adsorbed in the matrix, and the dye 2′(5′-N-(3-triethoxysilyl)propylurea-2′-hydroxyphenyl)benzimidazole was silylated, becoming chemically bonded to the silica network. High pressure technique was used to produce fluorescent and transparent silica compacts with the silylated and incorporated dye, at 6.0 GPa and room temperature. The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. The influence of the syntheses conditions was investigated by textural analysis using nitrogen adsorption isotherms.