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Issue 20, 2018
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Absolute up-conversion quantum efficiency reaching 4% in β-NaYF4:Yb3+,Er3+ micro-cylinders achieved by Li+/Na+ ion-exchange

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Abstract

Absolute quantum efficiency (QE) of up-conversion (UC) materials is still limited to ∼3%, which strongly limits their applications in many areas. Herein, we report highly efficient UC β-NaYF4:Yb3+,Er3+ micro-cylinders prepared via a newly developed Li+/Na+ ion exchange method (IEM) with absolute QE as high as ∼4.0%. A small amount of Li+ is interstitially incorporated in β-NaYF4:Yb3+,Er3+, which not only maintains well the micro-cylindrical morphology but also enhances the emission intensity by ∼40%, doubles absolute UCQE (∼3.0% under a fixed excitation power density of 15 W cm−2), and prolongs the lifetime. The UC excitation profile is composed of a sharp peak at 976 nm and a weak shoulder at 935 nm. The absolute UCQE of Li+/Na+ IEM β-NaYF4:Yb3+,Er3+ is systemically studied over a wide excitation power density of 0.4–100 W cm−2, and we obtained impressively high UCQE of 4.0% under 60 W cm−2 power density, which is among the highest values in the literature. The application of two green UC emissions of Li+/Na+ IEM β-NaYF4:Yb3+,Er3+ in ratiometric thermometers is successfully demonstrated. The high relative temperature sensitivity (SR) of 1113/T2 and excellent repeatability as indicated by three heating–cooling cycles (293–753 K) suggest their promising application as a temperature sensor.

Graphical abstract: Absolute up-conversion quantum efficiency reaching 4% in β-NaYF4:Yb3+,Er3+ micro-cylinders achieved by Li+/Na+ ion-exchange

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Publication details

The article was received on 17 Apr 2018, accepted on 27 Apr 2018 and first published on 27 Apr 2018


Article type: Paper
DOI: 10.1039/C8TC01806E
Citation: J. Mater. Chem. C, 2018,6, 5453-5461
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    Absolute up-conversion quantum efficiency reaching 4% in β-NaYF4:Yb3+,Er3+ micro-cylinders achieved by Li+/Na+ ion-exchange

    S. Fan, G. Gao, S. Sun, S. Fan, H. Sun and L. Hu, J. Mater. Chem. C, 2018, 6, 5453
    DOI: 10.1039/C8TC01806E

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