Luminescent Monodisperse Nanocrystals of Lanthanide Oxyfluorides Synthesized from Trifluoroacetate Precursors in High-Boiling Solvents

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• 作者：Ya-Ping Du ; Ya-Wen Zhang ; Ling-Dong Sun ; Chun-Hua Yan
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：January 17, 2008
• 年：2008
• 卷：112
• 期：2
• 页码：405 - 415
• 全文大小：1515K
• 年卷期：v.112,no.2(January 17, 2008)
• ISSN：1932-7455

文摘

Monodisperse lanthanide oxyfluoride nanocrystals (LaOF:Ce and/or Tb, LaOF:Eu, LaOF:Eu/LaOF (core/shell), GdOF:Ce,Tb, GdOF:Eu, GdOF:Yb,Er) with cubic structure were prepared by codecomposing thelanthanide trifluoroacetate precursors (Ln(CF₃COO)₃) in oleic acid/oleylamine. The nanocrystals show controlledsize (2-7 nm) and shape (nanopolyhedra and elongated nanocrystals) and can form a large-area superlatticeon copper grids via self-assembly. They were characterized by means of X-ray diffraction (XRD), X-rayphotoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and photoluminescence (PL)and upconversion (UC) spectroscopies, along with PL lifetime measurement. The formation of well-dopedLnOF nanocrystals has been demonstrated by the combined results of XRD, XPS, and luminescencemeasurements. The luminescent behaviors of differently sized and shaped nanocrystals have been revealed tobe largely dependent upon the small size effect in terms of surface-to-volume ratio and the surface-structureeffects in terms of the surface site of the luminescent ions and surface bonding of the capping ligands. Itseems that LaOF is a better host material for the energy transfer from Ce³⁺ to Tb³⁺ ions in emitting greenlight than GdOF, whereas GdOF is a better host material for the red emissions from Eu³⁺ ions than LaOF.Under a 980 nm near-IR laser excitation, the GdOF:Yb,Er nanocrystals can emit UC green light through atwo-photon process.