title: Impact of high ytterbium(III) concentration in the shell on upconversion luminescence of core-shell nanocrystals.
abstract: After coating 20 Yb/2 Er:NaGdF4 core nanocrystals with a NaYbF4 shell, upconversion emission of the rare earth ions weakens. So far, the exact reason for this phenomenon is still unclear due to lack of the direct evidence. In this report, a core@shell@shell sandwich-like structure is designed and fabricated to investigate this phenomenon. We find that high Yb(3+) concentration in the shell has mainly two adverse impacts: it promotes not only the deleterious back energy transfer from Er(3+) in the core to Yb(3+) in the shell but also the energy transfer from Yb(3+) in the core to Yb(3+) in the shell. To obtain nanocrystals with high upconversion efficency, appropriate Yb(3+) concentration should be introduced into the shell or the transition layer.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Fuzhou, Fujian, 350002 (P. R. China), Fax: (+86) 571-87713542, Fax: (+86) 591-83705402.
authors.forename: Lei
authors.initials: L
authors.lastname: Lei
authors.forename: Daqin
authors.initials: D
authors.lastname: Chen
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Zhu
authors.forename: Ju
authors.initials: J
authors.lastname: Xu
authors.forename: Yuansheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D018360:Crystallography, X-Ray; D049449:Luminescence; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles; D015018:Ytterbium / Q000737:chemistry*
chemical_list: D015018:Ytterbium
keywords: core-shell; energy transfer; nanostructures; upconversion; ytterbium