Fabrication and photoluminescence of thin films of lanthanide–polyoxometalates grafted on colloid silica sphere

In this paper, two lanthanide–polyoxometalates Na9LnW10O36 (Ln=Eu, Dy, LnW10) were grafted on 400 nm amine-functionalized spherical Stöber silica. The monolayer thin films of hybrid particles were fabricated on quartz by spin-coating method. The hybrid particles and thin films obtained were characterized by IR, UV–vis spectra, scanning electron microscopy, transmission electron microscope and luminescent spectra, respectively. The hybrid particles show strong luminescence which could be seen by naked eyes. The excitation spectra of hybrid particles and thin films show both abroad ligand to metal charge band and the excitation lines of rare earth ions. The transition 5D0→7F0 could be seen in the emission of hybrid EuW10/SiO2 spheres and thin films, which could not be found in spectrum of EuW10 solid. It is noticed that the intensity ratio of red (5D0→7F2) to orange (5D0→7F1) of Eu3+ and the yellow to blue (4F9/2→6H13/2: 4F9/2→6H15/2) of Dy3+ in LnW10/SiO2 particles and thin films are quite different from those of LnW10 solids. The different shapes and ratios between characteristic emissions of hybrid particles and thin films indicated the various symmetry of sites occupied by Ln3+ ions.