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. •Tb(III) complexes doped into the silica nanoparticles display high luminescence.•Rate constants of energy transfer providing feeding of 5D4 level of Tb(III) were obtained.•Two different channels of energy transfer from singlet ligand level to 5D4 level are revealed.•Luminescence of silica coated Tb(III) complexes exhibits high thermo- and photo-stabilities.