A Novel Way to Prepare Luminescent Terbium Molecular-Scale Hybrid Materials: Modified Heterocyclic Ligands Covalently Bonded with Silica

Abstract

The syntheses of modified nicotinic and picolinic acid by (3-aminopropyl)triethoxysilane and the preparation of their corresponding organic−inorganic molecular-based hybrid materials with the two components equipped with covalent bonds are described. The organic part is a derivative of heterocyclic compounds which is used to coordinate to Tb3+ and further introduced into silica matrixes by Si−O bonds after hydrolysis and polycondensation processes. According to the Judd-Ofelt theory, covalency increases with the increasing reciprocal energy difference between the 4fN and 4fN-15d1 configurations. Infrared, ultraviolet absorption, phosphorescence spectra, and luminescence spectra were applied to characterize the photophysical properties of the obtained hybrid material, and the above spectroscopic data revealed that the triplet energy of modified heterocyclic acid especially the modified nicotinic acid matched the emissive energy level of Tb3+. In this way, an intramolecular energy transfer process took place within these molecular-based hybrids and strong green emission of Tb3+ was achieved.