Greatly enhanced size-tunable ultraviolet upconversion luminescence of monodisperse β-NaYF4:Yb,Tm nanocrystals
- 8 August 2011
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry
- Vol. 21 (35), 13413-13421
- https://doi.org/10.1039/c1jm11480h
Abstract
Monodisperse β-NaYF4:Yb,Tm nanocrystals (nanospheres and nanoplates) with a uniform size were successfully synthesized. By tuning the ratios of solvent, reaction temperature, and reaction time, we manipulated their phase, shape, and size in the range of 30–400 nm. As a chelating agent and shape modifier, oleic acid (OA) was introduced into the reaction mixtures and played a key role in fine-tuning the nanocrystals. Possible mechanisms were proposed for forming the products with various architectures. Spectral analysis showed that the β-NaYF4:Yb,Tm nanocrystals were excellent materials for intense ultraviolet and blue upconversion luminescence. Here, we demonstrate that, under 980 nm excitation, the intense 5-photon upconversion fluorescence (290 nm and 345 nm) from the 1I6 level of Tm3+ ions is much stronger than the 4-photon upconversion fluorescence (361 nm and 451 nm) from the 1D2 level and the 3-photon upconversion fluorescence (474 nm) from the 1G4 level. The analysis of the temporal evolution of UC luminescence suggests that long lifetimes benefit the intense ultraviolet upconversion luminescence.Keywords
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