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Cooperative and non-cooperative sensitization upconversion in lanthanide-doped LiYbF4 nanoparticles

Abstract

Lanthanide (Ln3+)-doped upconversion nanoparticles (UCNPs) have attracted tremendous interest for their potential bioapplications. However, the intrinsic photophysics responsible for upconversion (UC) especially the cooperative sensitization UC (CSU) in colloidal Ln3+-doped UCNPs remains untouched so far. Herein, we report a unique strategy for the synthesis of high-quality LiYbF4:Ln3+ core-only and core/shell UCNPs with tunable particle size and shell thickness. Energy transfer UC from Er3+, Ho3+ and Tm3+ and CSU from Tb3+ were comprehensively surveyed under 980-nm excitation. Through surface passivation, we achieved efficient non-cooperative sensitization UC with absolute UC quantum yield (QY) of 3.36%, 0.69% and 0.81% for Er3+, Ho3+ and Tm3+, respectively. Particularly, we for the first time quantitatively determined the CSU efficiency for Tb3+ with an absolute QY of 0.0085% under excitation at a power density of 70 W·cm-2. By means of temperature-dependent steady-state and transient UC spectroscopy, we unraveled the dominant mechanisms of phonon-assisted cooperative energy transfer (T > 100 K) and sequential dimer ground-state absorption/excited-state absorption (T < 100 K) for the CSU process in LiYbF4:Tb3+ UCNPs.

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Supplementary files

Publication details

The article was accepted on 06 Apr 2017 and first published on 11 Apr 2017


Article type: Paper
DOI: 10.1039/C7NR02124K
Citation: Nanoscale, 2017, Accepted Manuscript
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    Cooperative and non-cooperative sensitization upconversion in lanthanide-doped LiYbF4 nanoparticles

    Q. Zou, P. Huang, W. Zheng, W. You, R. Li, D. Tu, J. Xu and X. Chen, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR02124K

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