Emission enhancement of Eu(III) and/or Tb(III) ions entrapped in silica xerogels with ZnO nanoparticles by energy transfer

Luminescent materials consisting of Eu(III) and/or Tb(III) ions and quantum dots of the ZnO semiconductor were immobilized in oxide xerogels by the impregnation method. The material’s excitation spectra showed the characteristic absorption bands of lanthanide(III) ions and sharp bands at low wavelengths attributed to excitons in the semiconductor nanoparticles. The luminescence emission of Ln(III) ions (Ln = Tb and/or Eu) showed very low intensity when typical excitation wavelengths for both ions were used (λ_exc = 394 for Eu(III), 350 nm for Tb(III)). In three-component materials (ZnO quantum dots and Ln(III) ions in oxide xerogels) only the Tb(III) emission could be improved by using an excitation wavelength corresponding to the position of one of the exciton absorption bands. The energy transfer enhancing the Eu(III) emission was possible in the four-component system (ZnO quantum dots plus Tb(III) and Eu(III) incorporated into the oxide matrix). The best results of the Eu(III) emission intensity were obtained when the silica xerogel served as the matrix of the four-component material thermally treated at 80 °C.