Energy transfer from the singlet levels of diketones and dyes to lanthanide ions in nanoparticles consisting of their diketonate complexes

• Published in: Optics and spectroscopy 2014-06, Vol.116 (6), p.933-940
• Main Authors: Mironov, L. Yu, Sveshnikova, E. B., Ermolaev, V. L.
• Format: Article
• Language: English
• Subjects: Condensed-Matter Spectroscopy; Lasers; Optical Devices; Optics; Photonics; Physics; Physics and Astronomy
• ISSN: 0030-400X; 1562-6911
• DOI: 10.1134/S0030400X14060162

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 5–10% 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.