Paramagnetism and improved upconversion luminescence properties of NaYF4：Yb,Er/NaGdF4 nanocomposites synthesized by a boiling water seed-mediated route  

作　　者：Chao-Qing YANG Ao-Ju LI Wei GUO Peng-Hua TIAN Xiao-Long YU Zhong-Xin LIU Yang CAO Zhong-Liang SUN 

机构地区：[1]Key Laboratory of Ministry of Education for Advanced Materials in Tropical Island Resources, Hainan University, Haikou 570228, China

出　　处：《Frontiers of Materials Science》2016年第1期38-44,共7页材料学前沿（英文版）

基　　金：Acknowledgements Authors would like to acknowledge the National Natural Science Foundation of China （NSFC, Grant No. 51361009）, the International Joint Project of Hainan Province （Grant No. KJHZ2014-19）, the Postgraduate Innovative Project of Hainan Province in 2015 （Grant No. Hys2015-24） and the Postgraduate Practice ＆ Innovation Projects of Hainan University in 2015 for financial support. The Instrumental Analysis Center of Hainan University is also acknowledged here.

摘　　要：In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4：Yb, Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4：Yb,ErlNaGdF4 core-shell structured upconversion nanoparticles （CSUCNPs） have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4：Yb,Er to 350℃ and increases its upconversion （UC） luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln^3＋-doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging （MRI）o The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW.cm-2. A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance （EPR） spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4：Yb, Er nuclei. Then prepared sample is heated at elevated temperature to improve the fluorescence intensity, and next a NaGdF4 shell grows on the surface of NaYF4 nuclei. NaYF4：Yb,ErlNaGdF4 core-shell structured upconversion nanoparticles （CSUCNPs） have been successfully synthesized by above route. The use of boiling water decreases the cubic-to-hexagonal phase transition temperature of NaYF4：Yb,Er to 350℃ and increases its upconversion （UC） luminescence intensity. A heterogeneous NaGdF4 epitaxially growing on the surface of Ln^3＋-doped NaYF4 not only improves UC luminescence, but also creates a paramagnetic shell, which can be used as contrast agents in magnetic resonance imaging （MRI）o The solution of CSUCNPs shows bright green UC fluorescence under the excitation at 980 nm in a power density only about 50 mW.cm-2. A broad spectrum with a dominant resonance at g of about 2 is observed by the electron paramagnetic resonance （EPR） spectrum of CSUCNPs. Above properties suggest that the obtained CSUCNPs could be potential candidates for dual-mode optical/magnetic bioapplications.

关 键 词：boiling water UPCONVERSION nanoparticle fluorescence imaging PARAMAGNETISM 

分 类 号：TQ171.112[化学工程—玻璃工业] TN104.3[化学工程—硅酸盐工业]