title: Revisiting the optimized doping ratio in core/shell nanostructured upconversion particles.
abstract: The development of rare-earth doped upconversion nanoparticles (RE-UCNPs) in various applications is fuelling the demand for nanoparticles with highly enhanced upconversion luminescence (UCL). Although the core/shell structure is proved to enhance the UCL effectively, there is still plenty of room to further improve the UCL by optimizing the doping ratio of the materials. In this article, a general strategy is demonstrated to achieve highly-enhanced visible UCL in core/shell nanostructured NaREF4by increasing the doping ratio of Yb3+in the core region. The energy transfer from RE-UCNPs to surface quenching sites through Yb3+-Yb3+energy migration is demonstrated to be the main reason for restricting the doping ratio of Yb3+. Notable UCL enhancement (ca. 15 times) of core/shell structured α-NaYF4:Yb,Er@CaF2nanoparticles is observed by increasing the concentration of Yb3+to 98 mol%. The highly-enhanced visible UCL signal is used to guide the lymphatic vessel resection with the naked eye.
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Bin
authors.initials: B
authors.lastname: Shen
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Shengming
authors.initials: S
authors.lastname: Cheng
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Gu
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Danrui
authors.initials: D
authors.lastname: Ni
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Su
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Wei
authors.identifier: http://orcid.org/0000-0002-8096-2212
authors.initials: W
authors.lastname: Feng
authors.affiliation: Department of Chemistry and The State Key Laboratory of Molecular Engineering of Polymers and Institute of Biomedicine Science and Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai, 200433, P. R. China. fyli@fudan.edu.cn fengweifd@fudan.edu.cn.
authors.forename: Fuyou
authors.initials: F
authors.lastname: Li