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Issue 35, 2018
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Absolute upconversion quantum yields of blue-emitting LiYF4:Yb3+,Tm3+ upconverting nanoparticles

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Abstract

The upconversion quantum yield (ΦUC) is an essential parameter for the characterization of the optical performance of lanthanoid-doped upconverting nanoparticles (UCNPs). Despite its nonlinear dependence on excitation power density (Pexc), it is typically reported only as a single number. Here, we present the first measurement of absolute upconversion quantum yields of the individual emission bands of blue light-emitting LiYF4:Yb3+,Tm3+ UCNPs in toluene. Reporting the quantum yields for the individual emission bands is required for assessing the usability of UCNPs in various applications that require upconverted light of different wavelengths, such as bioimaging, photocatalysis and phototherapy. Here, the reliability of the ΦUC measurements is demonstrated by studying the same batch of UCNPs in three different research groups. The results show that whereas the total upconversion quantum yield of these UCNPs is quite high—typically 0.02 at a power density of 5 W cm−2—most of the upconverted photon flux is emitted in the 794 nm upconversion band, while the blue emission band at 480 nm is very weak, with a much lower quantum yield of ∼6 × 10−5 at 5 W cm−2. Overall, although the total upconversion quantum yield of LiYF4:Yb3+,Tm3+ UCNPs seems satisfying, notably for NIR bioimaging, blue-light demanding phototherapy applications will require better-performing UCNPs with higher blue light upconversion quantum yields.

Graphical abstract: Absolute upconversion quantum yields of blue-emitting LiYF4:Yb3+,Tm3+ upconverting nanoparticles

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Publication details

The article was received on 21 Jun 2018, accepted on 16 Aug 2018 and first published on 17 Aug 2018


Article type: Paper
DOI: 10.1039/C8CP03935F
Citation: Phys. Chem. Chem. Phys., 2018,20, 22556-22562
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    Absolute upconversion quantum yields of blue-emitting LiYF4:Yb3+,Tm3+ upconverting nanoparticles

    M. S. Meijer, P. A. Rojas-Gutierrez, D. Busko, I. A. Howard, F. Frenzel, C. Würth, U. Resch-Genger, B. S. Richards, A. Turshatov, J. A. Capobianco and S. Bonnet, Phys. Chem. Chem. Phys., 2018, 20, 22556
    DOI: 10.1039/C8CP03935F

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