title: Energy Migration Upconversion in Manganese(II)-Doped Nanoparticles.
abstract: We report the synthesis and characterization of cubic NaGdF4:Yb/Tm@NaGdF4:Mn core-shell structures. By taking advantage of energy transfer through Yb→Tm→Gd→Mn in these core-shell nanoparticles, we have realized upconversion emission of Mn(2+) at room temperature in lanthanide tetrafluoride based host lattices. The upconverted Mn(2+) emission, enabled by trapping the excitation energy through a Gd(3+) lattice, was validated by the observation of a decreased lifetime from 941 to 532 μs in the emission of Gd(3+) at 310 nm ((6)P(7/2)→(8)S(7/2)). This multiphoton upconversion process can be further enhanced under pulsed laser excitation at high power densities. Both experimental and theoretical studies provide evidence for Mn(2+) doping in the lanthanide-based host lattice arising from the formation of F(-) vacancies around Mn(2+) ions to maintain charge neutrality in the shell layer.
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore).
authors.forename: Xiyan
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore).
authors.forename: Xiaowang
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J3 (Canada).
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Chevrier
authors.affiliation: Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602 (Singapore).
authors.forename: Xian
authors.initials: X
authors.lastname: Qin
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore).
authors.forename: Xiaoji
authors.initials: X
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (P. R. China).
authors.forename: Shuyan
authors.initials: S
authors.lastname: Song
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (P. R. China). hongjie@ciac.ac.cn.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J3 (Canada). peng.zhang@dal.ca.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543 (Singapore). chmlx@nus.edu.sg.|Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602 (Singapore). chmlx@nus.edu.sg.
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Liu
keywords: doping; lanthanides; nanoparticles; transition metals; upconversion