Enhanced Luminescence Characteristics of Mesophase Silica Thin Films Doped with In-Situ-Formed Rare Earth Complexes

Abstract

Several rare earth ions with sharp emission lines, which are caused by f-f electronic transitions, have received much attention as potential materials for phosphors. In particular, rare earth complexes exhibit high luminescent intensities when excited by visible or UV wavelengths because of the intramolecular energy transfer from the ligands to the rare earth ions. In this study, mesophase silica thin films doped with in-situ-formed Tb or Eu complexes were synthesized by adding the ligands, rare earth chloride, and a surfactant to hydrolyzed tetramethyl orthosilicate (TMOS). The structure of the mesophase thin films was characterized with X-ray diffraction and transmission electron microscopy, and they were found to have a 2D hexagonal structure. The UV-Vis absorption and emission spectra indicated that the Tb and Eu complexes were formed in situ during the formation of the mesophase film. Compared to typical inorganic sol gel silica thin films doped with the same rare earth complexes, the mesophase thin films of this study exhibited higher emission intensities and longer luminescence lifetimes with only one luminescent center because of the effective prevention of dopant aggregation