High-Quality Sodium Rare-Earth Fluoride Nanocrystals:  Controlled Synthesis and Optical Properties

• Published in: Journal of the American Chemical Society Vol. 128; no. 19; pp. 6426 - 6436
• Main Authors: Mai, Hao-Xin, Zhang, Ya-Wen, Si, Rui, Yan, Zheng-Guang, Sun, Ling-dong, You, Li-Ping, Yan, Chun-Hua
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 17.05.2006
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Nanocrystalline materials; Nanocrystals and nanoparticles; Nanoscale materials and structures: fabrication and characterization; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Rare earths Fluorides; Fluorescence spectroscopy; Crystalline phase; Transmission electron microscopy; Ternary compounds; Optical properties; Photoluminescence; Nanostructured materials; Alkali metals Compounds; Nanocrystal; Sodium fluorides
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja060212h

We report a general synthesis of high-quality cubic (α-phase) and hexagonal (β-phase) NaREF4 (RE:  Pr to Lu, Y) nanocrystals (nanopolyhedra, nanorods, nanoplates, and nanospheres) and NaYF4: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 α → β 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 I 610/I 590 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.