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

• Published in: Frontiers of materials science Vol. 10; no. 1; pp. 38 - 44
• Main Authors: Yang, Chao-Qing, Li, Ao-Ju, Guo, Wei, Tian, Peng-Hua, Yu, Xiao-Long, Liu, Zhong-Xin, Cao, Yang, Sun, Zhong-Liang
• Format: Journal Article
• Language: English
• Published: Beijing Higher Education Press 01-03-2016
• Subjects: Chemistry and Materials Science; Materials Science; Research Article; 上转换发光特性; 合成; 异质外延生长; 沸水; 纳米复合材料; 路线; 顺磁性; upconversion; nanoparticle; boiling water; fluorescence imaging; paramagnetism
• ISSN: 2095-025X; 2095-0268
• DOI: 10.1007/s11706-016-0318-z

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.