Effects of Support and Ligand on the Photoluminescence Properties of Siliceous Grafted Europium Complexes

Abstract

Europium ions were introduced in SiO 2 and MCM-41 via two different pathways: (1) grafting the europium complexes with two alkoxide structures, 3-(2-imidazolin-1-yl)-propyl-triethoxysilane (IPTES) and aminopropyl-trimethoxysilane (APTMS), and (2) functionalization of the SiO 2 support with silicon 4-carboxylbutyltriethoxide followed by subsequent addition of the europium ions. The new materials were characterized using nitrogen adsorption isotherms at −196 °C, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared, NMR, DR−UV−vis, steady-state emission and excitation, and time-resolved photoluminescence spectroscopy. Spectral changes found in the time-resolved photoluminscence spectra strongly point to the distribution of europium ions on a range of environments in both SiO 2 and MCM-41 supports. The average europium photoluminescence lifetimes decrease within the order: Eu 3+ -IPTES/SiO 2 (550 μs) > Eu 3+ -APTMS/ SiO 2 (425 μs) > Eu 3+ -APTMS/MCM-41 (370 μs) > Eu 3+ -IPTES/MCM-41 (320 μs) > Eu 3+ -CABES/SiO 2 (240 μs). The photoluminescence quantum efficiency has the largest value, of 22%, for Eu 3+ -IPTES/SiO 2, while the most reduced value, of 9%, was measured for Eu 3+ -CABES/SiO 2 .