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Issue 40, 2018
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Modified surface states of NaGdF4:Yb3+/Tm3+ up-conversion nanoparticles via a post-chemical annealing process

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Abstract

An amorphous layer acting as a quenching center at the surface of oleic acid-capped NaGdF4:Yb3+/Tm3+ nanoparticles is observed directly, which can be reconstructed via a novel post-chemical annealing process. The amorphous phase of the surface layer of NaGdF4:Yb3+/Tm3+ nanoparticles gradually crystallizes as the post-chemical annealing temperature increases; meanwhile, the good dispersibility of the as-obtained nanoparticles is maintained. The reduction of surface defects and higher local symmetry of the crystal field environment around the doped rare-earth ions contribute to drastically increased up-conversion (UC) emission intensity of the NaGdF4:Yb3+/Tm3+ nanoparticles. In particular, the blue emission of Tm3+ at 450 nm enhances 10-fold after the post-chemical annealing process at 250 °C compared with the counterpart without further surface-state treatments. The color gamut of well-crystallized NaGdF4:Yb3+/Tm3+ with a modified surface covers the blue to yellow region in CIE chromaticity coordinates via a non-steady-state UC process. The results indicate that the surface states of these UC nanoparticles can be feasibly improved via the post-chemical annealing process without encouraging agglomeration, which further optimizes their UC properties for practical applications.

Graphical abstract: Modified surface states of NaGdF4:Yb3+/Tm3+ up-conversion nanoparticles via a post-chemical annealing process

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Publication details

The article was received on 21 Jun 2018, accepted on 11 Sep 2018 and first published on 12 Sep 2018


Article type: Paper
DOI: 10.1039/C8NR05021J
Citation: Nanoscale, 2018,10, 19031-19038
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    Modified surface states of NaGdF4:Yb3+/Tm3+ up-conversion nanoparticles via a post-chemical annealing process

    Q. Min, L. Zhao, Y. Qi, J. Lei, W. Chen, X. Xu, D. Zhou, J. Qiu and X. Yu, Nanoscale, 2018, 10, 19031
    DOI: 10.1039/C8NR05021J

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