Incorporation of luminescent lanthanide complex inside the channels of organically modified mesoporous silica via template-ion exchange method

Abstract

Luminescent lanthanide complex, Eu(phen)₂Cl₃·2H₂O (Euphen, phen = 1,10-phenanthroline) has been incorporated inside the channels of mesoporous silica MCM-41 with its external surface modified by phenyltriethoxysilane (Ph-Si(OEt)₃) via a simple template-ion exchange method. The passivation of active groups such as silanols in the external surface ensures that the ion exchange reaction occurs between the surfactant cations and the lanthanide complex ions inside the channels of the modified MCM-41. The passivation result is confirmed by ²⁹Si MAS NMR spectroscopy. FT-IR demonstrates that the cationic surfactants are completely removed. XRD and N₂ adsorption–desorption measurements are employed to characterize the mesostructure of Euphen-Ph-MCM-41. Luminescence and stability studies on the materials of Euphen and Euphen-Ph-MCM-41 show that the resultant hybrid material Euphen-Ph-MCM-41 exhibits the characteristic emission of Eu³⁺ ions under UV irradiation with higher ⁵D₀ luminescence quantum efficiency, longer lifetime and better thermal stability than the corresponding pure complex Euphen. Moreover, the characterization results show that the local symmetry and the first coordination shell of Eu³⁺ ions are changed after the complex ions become incorporated into the MCM-41 channels and that a more symmetric environment is occupied by the Eu³⁺ ions in Euphen-Ph-MCM-41 than in Euphen. There is also a more efficient ligand-to-Eu(III) intramolecular energy transfer process in Euphen-Ph-MCM-41.