Detailed mechanism of the ligand-to-metal energy transfer of silica-coated Tb(III) complex with p-sulfonatothiacalix[4]arene

The energy transfer mechanism, which provides the feeding of the excited 5D4 level of Tb(III), has been studied by photoluminescence spectroscopy in the Tb(III) complex with p-sulfonato-thiacalix[4]arene doped into the silica nanoparticles. The quantitative evaluation of the rate constants of each energy transfer step highlights two channels of the energy transfer from the singlet ligand-centered level to the 5D4 level. The channel one occurs via the triplet ligand level S1→T1→5D4, the second channel comes about via the higher levels of Tb(III) S1→5D3→5D4. The latter channel determines the rate of the luminescence decay of the 5D4 level. The high luminescence efficiency and enhanced thermo- and photo-stabilities make the Tb(III) complexes doped into the silica nanoparticles a promising nanomaterial for medical and bioanalytical applications.