Energy Transfer from the Singlet Levels of Diketones and Dyes to Lanthanide Ions in Nanoparticles Consisting of Their Diketonate Complexes

摘要

The energy transfer from the S_1 levels of p-phenylbenzoyltrifluoroacetone (PhBTA) and dyes to different Ln~(3+) ions is studied in nanoparticles (NPs) composed of complexes of this diketone with Ln~(3+) and 1,10-phenanthroline (phen) and doped with dye molecules. The quenching rate constants in the NPs consisting from complexes of Pr~(3+), Nd~(3+), Sm~(3+), Eu~(3+), Ho~(3+), Er~(3+), and Tm~(3+) are determined from the data on the quenching of sensitized (cofluorescence) and ordinary fluorescence of coumarin 30 (C30) and rhodamine 6G (R6G). The quenching rate constants vary from ≤5 × 10~(11) to 10~(13) s~(-1) for the fluorescence quenching of PhBTA by different Ln~(3+) ions, while the quenching of dye fluorescence occurs at rates of the order of 10~9 s~(-1). In the case of complexes with the Pr~(3+) ions, the fluorescence quenching of PhBTA in NPs composed of its complexes is accompanied by sensitized luminescence of Pr~(3+). The quenching observed is due to a nonradiative energy transfer from the S_1 states of ligands and dyes to these ions. It is shown that in NPs composed of complexes with Eu~(3+), Yb~(3+), and Sm~(3+) the cofluorescence of C30 is quenched via the electron-transfer mechanism. The study of quenching of cofluorescence and fluorescence of dyes in NPs composed of mixed complexes of La~(3+) and Nd~(3+) (Ho~(3+)) shows that the observed quenching of fluorescence and cofluorescence is governed mainly by the quenching of the S_1 state of dyes when the Nd~(3+) (Ho~(3+)) content does not exceed 510% and by the quenching of the S_1 state of a ligand when the Nd~(3+) (Ho~(3+)) content exceeds 50%. It is assumed that the high rate constant of energy transfer from the S_1 level of ligands to ions Pr~(3+), Nd~(3+), Ho~(3+), Er~(3+), and Tm~(3+) in NPs composed of beta-diketonate complexes is caused by exchange interactions.