Molecular assembly and photophysical properties of a novel luminescent terbium hybrid material with modified carboxyl group of p-aminobenzoic acid as a functional bridge

A new kind of sol-gel derived organic–inorganic molecular-based hybrid material with the two components covalently linked together via Tb–O and Si–O bonds was prepared. The organic part is a derivative of p-aminobenzoic acid (PAB) which is grafted by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) through the hydrogen transfer addition reaction between COOH of PAB and internal ester (isocyanate) of TESPIC, then the bifunctional precursor is used to coordinate to rare earth ions (Tb3+) with carboxyl group and its triethoxysilyl moiety is capable of undergoing polymerization or cross-linking reactions with TEOS (tetraethoxysilane). Therefore, the final hybrid materials are formed by a combination of hydrolysis and polycondensation processes of two ethoxy groups (both PAB–Si and TEOS). In this way, the effective intramolecular energy transfer process took place within these molecular-based hybrids and a strong green emission of Tb3+ was achieved.