Novel luminescent terbium molecular-based hybrids with modified meta-aminobenzoic acid covalently bonded with silica

Abstract

A novel type of sol–gel-derived organic–inorganic molecular-based hybrid material with the two parts covalently linked together via Tb–O and Si–O bonds was synthesized. The organic component was obtained from a derivative of meta-aminobenzoic acid (MAB) which is modified by 3-(triethoxysilyl)-propyl isocyanate, and then the precursor is applied to coordinate to Tb³⁺ with the carboxyl group and its triethoxysilyl moiety is capable of undergoing polymerization or cross-linking reactions with TEOS (tetraethoxysilane). Accordingly, the final hybrid material is formed by a combination of hydrolysis and polycondensation processes of two ethoxy groups (both MAB-Si and TEOS). Ultraviolet absorption, phosphorescent and fluorescent spectra were used to investigate the photophysical properties of the hybrid material, which reveal that the triplet energy of modified meta-aminobenzoic acid matches with the emissive energy level of Tb³⁺. In this way, the intramolecular energy transfer process took place within this molecular-based hybrid and a strong green emission of Tb³⁺ was achieved.