title: Microwave-assisted solvothermal synthesis and upconversion luminescence of CaF2:Yb3+/Er3+ nanocrystals.
abstract: Water-dispersible CaF2 and Yb(3+)/Er(3+) codoped CaF2 (CaF2:Yb(3+)/Er(3+)) nanocrystals with different sizes and different Yb(3+) and Er(3+) dopant concentrations were synthesized using ionic liquid 1-n-butyl-3-methyl imidazolium tetrafluoroborate as a fluorine source by the rapid microwave-assisted solvothermal method. It was found that the morphology, size and crystallinity of CaF2:Yb(3+)/Er(3+) nanocrystals could be adjusted by using adenosine 5'-triphosphate disodium salt (ATP). Yb(3+) and Er(3+) ions were doped into CaF2 nanocrystals to enable upconversion luminescence emission, and the as-prepared CaF2:Yb(3+)/Er(3+) samples exhibited upconversion luminescence upon excitation at 980 nm. Confocal laser scanning microscopy images showed that the CaF2:Yb(3+)/Er(3+) nanocrystals could be used for efficient labeling of human gastric carcinoma cells. Moreover, in vitro cytotoxicity experiments indicated that the as-prepared CaF2:Yb(3+)/Er(3+) nanocrystals had essentially little cytotoxicity. These results indicate that the as-prepared CaF2:Yb(3+)/Er(3+) nanocrystals are promising for the application as a luminescent label material in biological imaging.
authors.affiliation: State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China. Electronic address: y.j.zhu@mail.sic.ac.cn.
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China.
authors.forename: Jin
authors.initials: J
authors.lastname: Wu
authors.affiliation: State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, PR China.
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
keywords: Fluorides; Microwave; Nanostructures; Rare earths; Upconversion