Source:http://linkedlifedata.com/resource/pubmed/id/20644777
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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
6
|
| pubmed:dateCreated |
2010-7-20
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| pubmed:abstractText |
Monodisperse beta-NaYF4:Yb,Tm nanocrystals with controlled size (25-150 nm), shape (sphere, hexagonal prism, and hexagonal plate), and composition (Yb: 20-40%, Tm: 0.2-5%) were synthesized from the thermolysis of metal trifluoroacetates in hot surfactant solutions. The upconversion (UC) of near-infrared light (980 nm) to ultra-violet (360 nm), blue (450 and 475 nm), red (650 and 695 nm) and infrared (800 nm) light in the beta-NaYF4:Yb,Tm nanocrystals has been studied by UC spectroscopy. Both the total intensity of UC emissions and the relative intensities of emissions at different wavelengths have shown a strong dependence on different particle sizes and different Tm3+ and Yb3+ concentrations. As a result, different overall output colors of UC emissions can be achieved by altering sizes and Yb3+/Tm3+ doping concentrations of the beta-NaYF4:Yb,Tm nanocrystals. The intensity-power curves of a series of samples have proved that emissions at 360 and 450 nm can be ascribed to four-photon process (1D2 to 3H6 and 1D2 to 3H4, respectively), while emissions at 475 and 650 nm are three-photon processes (1G4 to 3H6 and 1G4 to 3H4, respectively) and emissions at 695 and 800 nm are two-photon ones (3F2 to 3H6 and 3F4 to 3H6, respectively). A UC saturation effect would occur under a certain excitation intensity of the 980 nm CW diode laser for the as-obtained beta-NaYF4:Yb,Tm nanocrystals, leading to the decrease of the slopes of the I-P curves. The results of our study also revealed that the successive transfer model instead of the cooperative sensitization model can be applied to explain the UC behaviors of the beta-NaYF4:Yb,Tm nanocrystals. Further, an unexpected stronger emissions of four-photon process at 360 and 450 nm for approximately 50 nm beta-NaYF4:Yb,Tm nanocrystals than those for the bigger (approximately 150 nm) nanocrystals was observed and explained in terms of the effects of crystallite size, surface-to-volume ratio and homogeneity of the doping cations.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:status |
PubMed-not-MEDLINE
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| pubmed:month |
Jun
|
| pubmed:issn |
2040-3372
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| pubmed:author | |
| pubmed:issnType |
Electronic
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| pubmed:volume |
2
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
953-9
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| pubmed:dateRevised |
2011-6-22
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| pubmed:year |
2010
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| pubmed:articleTitle |
Colloidal synthesis and blue based multicolor upconversion emissions of size and composition controlled monodisperse hexagonal NaYF4:Yb,Tm nanocrystals.
|
| pubmed:affiliation |
Beijing National Laboratory for Molecular Sciences, Peking University, Beijing, 100871, China.
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| pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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