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Issue 12, 2017
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Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents

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Abstract

The rational design of brighter upconversion nanoparticles (UCNPs) requires a better understanding of the radiationless deactivation pathways in these materials. Here, we demonstrate the potential of excitation power density (P)-dependent studies of upconversion (UC) luminescence intensities, slope factors, and absolute quantum yields (ΦUC) of popular β-NaYF4:20% Yb3+,2% Er3+ UCNPs of different surface chemistries in organic solvents, D2O, and water as a tool to gain deeper insight into the UC mechanism including population and deactivation pathways particularly of the red emission. Our measurements, covering a P regime of three orders of magnitude, reveal a strong difference of the P-dependence of the ratio of the green and red luminescence bands (Ig/r) in water and organic solvents and P-dependent population pathways of the different emissive energy levels of Er3+. In summary, we provide experimental evidence for three photon processes in UCNPs, particularly for the red emission. Moreover, we demonstrate changes in the excited population dynamics via bi- and triphotonic processes dependent on the environment, surface chemistry, and P, and validate our findings theoretically.

Graphical abstract: Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents

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Publication details

The article was received on 04 Jan 2017, accepted on 28 Feb 2017 and first published on 28 Feb 2017


Article type: Paper
DOI: 10.1039/C7NR00092H
Citation: Nanoscale, 2017,9, 4283-4294
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    Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents

    C. Würth, M. Kaiser, S. Wilhelm, B. Grauel, T. Hirsch and U. Resch-Genger, Nanoscale, 2017, 9, 4283
    DOI: 10.1039/C7NR00092H

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