Eu3+ based mesoporous hybrid material with tunable multicolor emission modulated by fluoride ion: application for selective sensing toward fluoride ion

A novel Eu-containing SBA-15 mesoporous hybrid material with multicolor emission modulated by fluoride ion was synthesized. First, the organic ligand 1-(2-naphthoyl)-3,3,3-trifluoroacetonate (NTA) was modified by the silane coupling agent 3-(triethoxysilyl)propylisocyanate to form an alkene precursor (NTA-Si), which was covalently grafted onto a mesoporous SBA-15 backbone through co-hydrolysis and co-condensation reactions; as a result, mesoporous hybrid NTA-S15 was obtained. 2-(2-Carboxylphenyl)-imidazo[4,5-f]-1,10-phenanthroline (L) was used as the second ligand, whose two pyridine N atoms coordinate with europium ions and sensitize the luminescence of Eu3+, and the NH group of the imidazole ring and –COOH group formed hydrogen bonds with fluoride ions. Finally, after the coordination reaction between Eu3+ and the organic ligands (NTA-S15 and L), the mesoporous hybrid material Eu(NTA-S15)3L was obtained. Fourier transform infrared, small-angle X-ray diffraction, N2 adsorption measurements, transmission electron microscopy, and scanning electron microscopy were performed, and photoluminescence spectra and thermogravimetric plots were characterized. The results show that Eu(NTA-S15)3L displays a high surface area, uniform mesostructure, good thermal stability, and excellent photophysical properties. Furthermore, Eu(NTA-S15)3L exhibits a highly sensitive sensing function toward the fluoride ion. More importantly, tunable multicolor emissions, which cover nearly the entire visible region, can be readily achieved by varying fluoride ion concentrations under a single-wavelength excitation.