Novel europium complexes covalently bonded to MCM-41 and SBA-15: spatial confinement effects on photoluminescence behavior

Abstract

Novel organic–inorganic luminescent mesoporous hybrid materials were assembled through the coordination reaction between europium nitrate with chelated quinoline-amide type ligands immobilized in mesoporous materials (MCM-41 and SBA-15). The mesoporous hybrid materials were characterized by elemental analysis, Fourier-transform infrared spectra, powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and nitrogen (N₂) adsorption–desorption. The results demonstrated that the highly ordered mesoporous structures were retained after the complexes covalently bonded to the channels of the matrices. The SBA-15-type hybrid materials, with pore sizes twice that of MCM-41, display more efficient emission due to the spatial confinement of the nanochannels of the mesoporous matrix. This deduction is strengthened by the fact that the influences are more obvious for complexes including rigid end group ligands. In addition, the Eu³⁺ complexes coordinated with ligands containing rigid end groups in MCM-41 matrices exhibit better photoluminescence stability upon exposure to ultraviolet light.