Energy migration toward a dye in nanoparticles from complexes with short fluorescent state lifetimes

• Published in: Optics and spectroscopy 2012-12, Vol.113 (6), p.607-615
• Main Authors: Sveshnikova, E. B., Mironov, L. Yu, Dudar’, S. S., 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/S0030400X12120089

We have studied regular features of the fluorescence sensitization (cofluorescence) of coumarin 30 and rhodamine 6G introduced into nanoparticles from complexes Ln(PhBTA) 3 phen, where PhBTA is p -phenylbenzoyltrifluoroacetone and Ln is a triply charged Pr, Nd, Sm, Eu, Er, or Yb ion, which absorbs in the fluorescence range of ligands of complexes and dyes. We show that both the cofluorescence intensities ( I cofl ) of rhodamine 6G in nanoparticles from Sm and Eu complexes and the behavior of intensity I cofl on the content of rhodamine 6G coincide with the corresponding data obtained for nanoparticles from La and Lu complexes doped with rhodamine 6G molecules. A considerable decrease in I cofl of rhodamine 6G is observed only in nanoparticles from complexes Nd(PhBTA) 3 phen. In nanoparticles from Pr, Nd, Sm, Eu, Er, and Yb complexes doped with coumarin 30, it has been observed that, depending on the choice of the central ion, I cofl of coumarin 30 is 2 to 80 times lower compared to I cofl of the dye in nanoparticles from La and Lu complexes. A separate analysis of the influence of these ions on the energy transfer from complexes to coumarin 30 and on the fluorescence intensity of coumarin 30 incorporated into nanoparticles from these ions showed that a decrease in I cofl of coumarin 30 by a factor of 2–20 occurs due to the reduction of τ fl of ligands of complexes under the influence of the interaction with Pr, Nd, Sm, Eu, Er, and Yb ions. Since τ fl of complexes La(PhBTA)3phen is ∼2 ps, while that of complexes Gd(PhBTA)3phen is ∼1 ps, then, in nanoparticles with a maximal decrease in I cofl of coumarin 30, τ fl of complexes is reduced to ∼0.1 ps. It has been found that, in nanoparticles from complexes with this τ fl , energy migration over complexes takes place. However, as distinct from nanoparticles from La, Lu, and Y complexes, the free path length of singlet excitons in nanoparticles from complexes of absorbing ions is smaller than the nanoparticle size.