Synthesis and luminescence properties of spherical bridged polysilsequioxanes activated by lanthanide ions

Luminescent microspherical bridged polysilsequioxane were prepared by heating the mixture of lanthanide ions (EuCl₃ or TbCl₃) and bis-silylated bipyridine having dual roles, i.e. the bipyridine moieties can sensitize the luminescence of Eu³⁺ (or Tb³⁺) ions and the alkoxysilane substituent can be hydrolyzed and condensed via sol–gel process to create inorganic silica framework. The obtained microspheres were systematically investigated by IR spectroscopy, scanning electron microscopy, absorption spectroscopy, PL excitation and emission spectroscopy. IR spectra indicate that the silylated bipyridine has been hydrolyzed under the reaction conditions. SEM images show the microspherical morphology of the luminescent materials. It has been confirmed that the strong luminescence of the spherical bridged polysilsequioxanes is due to the effective energy transfer from the silylated bipyridine to the chelated lanthanide ions.