1. Effects of Phonon Confinement on Anomalous Thermalization, Energy Transfer, and Upconversion in Ln3+-Doped Gd2O3Nanotubes
- Author
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Mario S. Reis, Rute A. S. Ferreira, Duarte Ananias, Vitor S. Amaral, Andreia G. Macedo, João Rocha, and Luís D. Carlos
- Subjects
Lanthanide ,Photoluminescence ,Materials science ,Condensed matter physics ,Phonon ,Doping ,Condensed Matter Physics ,Photon upconversion ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Thermalisation ,Quantum dot ,Electrochemistry ,Luminescence - Abstract
There is a growing interest in understanding how size-dependent quantum confinement affects the photoluminescence efficiency, excited-state dynamics, energy-transfer and thermalization phenomena in nanophosphors. For lanthanide (Ln 3+ )-doped nanocrystals, despite the localized 4f states, confinement effects are induced mostly via electron-phonon interactions. In particular, the anomalous thermalization reported so far for a handful of Ln 3+ -doped nanocrystals has been rationalized by the absence of low-frequency phonon modes. This nanoconfinement may further impact on the Ln 3+ luminescence dynamics, such as phonon-assisted energy transfer or upconversion processes. Here, intriguing and unprecedented anomalous thermalization in Gd 2 O 3 :Eu 3+ and Gd 2 O 3 :Yb 3+ ,Er 3+ nanotubes, exhibiting up to one order of magnitude larger than previously reported for similar materials, is reported. This anomalous thermalization induces unexpected energy transfer from Eu 3+ C 2 to S 6 crystallographic sites, at 11 K, and 2 H 11/2 → 4 I 15/2 Er 3+ upconversion emission; it is interpreted on the basis of the discretization of the phonon density of states, easily tuned by varying the annealing temperature (923-1123 K) in the synthesis procedure, and/or the Ln 3+ concentration (0.16-6.60%).
- Published
- 2010
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