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Modified Surface States of NaGdF4:Yb3+/Tm3+ Up-conversion Nanoparticles via a Post-chemical Annealing Process

Abstract

Amorphous layer acting as quenching centers at the surface of oleic acid capped NaGdF4:Yb3+/Tm3+ nanoparticles is observed directly, which could 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 well dispersibility of the as-obtained nanoparticles is reserved. The reduction of surface defects and a higher local symmetry of the crystal field environment around the doped rare-earth ions contribute to the drastically increased up-conversion (UC) emission intensity of NaGdF4:Yb3+/Tm3+ nanoparticles. Especially, 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 suffering further surface-states treatment. The color gamut of the well crystallized NaGdF4:Yb3+/Tm3+ with modified surface covers 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 could be feasible improved via the post-chemical annealing process without encouraging agglomeration, which further optimizes their UC properties for practical application.

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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, Accepted Manuscript
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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, X. Yu and J. Qiu, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR05021J

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