Rare earth hybrid materials of organically modified silica covalently bonded to a GaN matrix: multicomponent assembly and multi-color luminescence

Abstract

Three kinds of rare earth hybrid materials with enhanced thermostability and photoluminescence properties have been prepared for the first time by using a functionalized GaN matrix as one of the building blocks. A number of silane coupling agents (isocyanate triethoxysilane (ICTES), 3-chloropropyl triethoxysilane (CPTES) and 3-aminopropyl triethoxysilane (APTES)) behave as the covalent linkages for modification by both hydroxylation of GaN and functionalized photoactive ligands (4-mercaptobenzoic acid (MBA), 4-hydroxybenzoic acid (HBA) and nitrobenzoyl chloride (NBC)), resulting in the precursors (MBA–ICTES–GaN, HBA–CPTES–GaN and NBC–APTES–GaN). Subsequently, multicomponent photofunctional rare earth hybrid materials with the three precursors and 1,10-phenanthroline (Phen) are assembled and characterized by their FTIR spectra, UV–vis diffuse reflectance spectra, XRD patterns, and photoluminescent behaviour (luminescence, lifetime, quantum efficiency, and energy transfer). These results reveal that the Eu³⁺ hybrids with the MBA–ICTES–GaN unit have a better luminescence intensity ratio, higher quantum efficiency and longer lifetime than those with the HBA–CPTES–GaN and NBC–APTES–GaN units. Meanwhile the hybrid Phen–Tb–HBA–CPTES–GaN possesses a stronger characteristic emission of Tb³⁺ ions than the other two hybrids (Phen–Tb–MBA–ICTES–GaN and Phen–Tb–NBC–APTES–GaN). Moreover, two-color-based hybrid materials are fabricated by combining different molar ratios of Eu³⁺ and Tb³⁺ in the same system (Phen–RE–MBA–ICTES–GaN) with emission at a wavelength of 331 nm (RE = Eu, Tb) and yellow luminescence can be achieved.