title: High-quality sodium rare-earth fluoride nanocrystals: controlled synthesis and optical properties.
abstract: We report a general synthesis of high-quality cubic (alpha-phase) and hexagonal (beta-phase) NaREF4 (RE: Pr to Lu, Y) nanocrystals (nanopolyhedra, nanorods, nanoplates, and nanospheres) and NaYF(4):Yb,Er/Tm nanocrystals (nanopolyhedra and nanoplates) via the co-thermolysis of Na(CF3COO) and RE(CF3COO)3 in oleic acid/oleylamine/1-octadecene. By tuning the ratio of Na/RE, solvent composition, reaction temperature and time, we can manipulate phase, shape, and size of the nanocrystals. On the basis of its alpha --> beta phase transition behavior, along the rare-earth series, NaREF4 can be divided into three groups (I: Pr and Nd; II: Sm to Tb; III: Dy to Lu, Y). The whole controlled-synthesis mechanism can be explained from the point of view of free energy. Photoluminescent measurements indicate that the value of I610/I590 and the overall emission intensity of the NaEuF4 nanocrystals are highly correlative with the symmetries of the Eu3+ ions in both the lattice and the surface.
authors: Beijing National Laboratory for Molecular Sciences, State Key Lab of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, China.
authors: Hao-Xin
authors: HX
authors: Mai
authors: Ya-Wen
authors: YW
authors: Zhang
authors: Rui
authors: R
authors: Si
authors: Zheng-Guang
authors: ZG
authors: Yan
authors: Ling-dong
authors: LD
authors: Sun
authors: Li-Ping
authors: LP
authors: You
authors: Chun-Hua
authors: CH
authors: Yan