title: Phase- and size-controllable synthesis of hexagonal upconversion rare-earth fluoride nanocrystals through an oleic acid/ionic liquid two-phase system.
abstract: Herein, we introduce a facile, user- and environmentally friendly (n-octanol-induced) oleic acid (OA)/ionic liquid (IL) two-phase system for the phase- and size-controllable synthesis of water-soluble hexagonal rare earth (RE = La, Gd, and Y) fluoride nanocrystals with uniform morphologies (mainly spheres and elongated particles) and small sizes (<50 nm). The unique role of the IL 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)) and n-octanol in modulating the phase structure and particle size are discussed in detail. More importantly, the mechanism of the (n-octanol-induced) OA/IL two-phase system, the formation of the RE fluoride nanocrystals, and the distinctive size- and morphology-controlling capacity of the system are presented. BmimPF(6) is versatile in term of crystal-phase manipulation, size and shape maintenance, and providing water solubility in a one-step reaction. The luminescent properties of Er(3+)-, Ho(3+)-, and Tm(3+)-doped LaF(3), NaGdF(4), and NaYF(4) nanocrystals were also studied. It is worth noting that the as-prepared products can be directly dispersed in water due to the hydrophilic property of Bmim(+) (cationic part of the IL) as a capping agent. This advantageous feature has made the IL-capped products favorable in facile surface modifications, such as the classic Stober method. Finally, the cytotoxicity evaluation of NaYF(4):Yb,Er nanocrystals before and after silica coating was conducted for further biological applications.
authors.affiliation: Department of Bio-Nano Science and Engineering, National Key Laboratory of Nano/Micro Fabrication Technology, Institute of Micro-Nano Science and Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China.
authors.forename: Meng
authors.initials: M
authors.lastname: He
authors.forename: Peng
authors.initials: P
authors.lastname: Huang
authors.forename: Chunlei
authors.initials: C
authors.lastname: Zhang
authors.forename: Jiebing
authors.initials: J
authors.lastname: Ma
authors.forename: Rong
authors.initials: R
authors.lastname: He
authors.forename: Daxiang
authors.initials: D
authors.lastname: Cui
mesh_terms: D020003:1-Octanol / Q000737:chemistry; D000465:Algorithms; D005459:Fluorides / Q000138:chemical synthesis / Q000737:chemistry*; D006801:Humans; D052578:Ionic Liquids / Q000737:chemistry; D049449:Luminescence; D008674:Metals, Rare Earth / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D019301:Oleic Acid / Q000737:chemistry*; D012995:Solubility; D014867:Water / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry
chemical_list: D052578:Ionic Liquids; D008674:Metals, Rare Earth; D014867:Water; D019301:Oleic Acid; D015019:Yttrium; D020003:1-Octanol; D005459:Fluorides