Luminescent lanthanide-polyoxometalates assembling zirconia–alumina–titania hybrid xerogels through task-specified ionic liquid linkage

Abstract

This paper is focused on the preparation and characterization of luminescent hybrid materials of zirconia (alumina, titania) xerogels encapsulated with high luminescent lanthanide polyoxometalates via a sol–gel process. Firstly, liquid compound 1-methyl-3-propionyloxy imidazolium bromide (IM⁺Br⁻) is assembled with lanthanide polyoxometalates (NaLnW₁₀O₃₆·32H₂O, abbreviated as LnW10, Ln = Eu, Tb, Sm, Dy) through the ion exchange reaction, resulting in Ln-IL, Then Ln-IL is connected to zirconia (alumina/titania) by the chelating reaction between a propionyloxy group of the IM⁺ component and metallic alkoxides (Zr(OCH₂CH₂CH₂CH₃)₄, Ti(OCH(CH₃)₂)₄, Al(OCH(CH₃)₂)₃) under mild conditions after hydrolysis and condensation. These hybrid materials are characterized by Fourier transform infrared spectroscopy, wide angle X-ray diffraction, thermogravimetric analysis, as well as luminescence. The above measurements indicate that they possess high thermal-stability, amorphous structure features and especially favorable luminescent performances such as long luminescent decay lifetime, high quantum yield. It is found that alumina and zirconia are superior matrices to titania for the luminescence of lanthanide polyoxometalates, and close white-light integration can be realized for hybrids of titania gels.