Sensitization of Eu3+ Luminescence in Eu:YPO4 Nanocrystals

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• 作者：Jiangchao Chen ; Qingguo Meng ; P. Stanley May ; Mary T. Berry ; Cuikun Lin
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 21, 2013
• 年：2013
• 卷：117
• 期：11
• 页码：5953-5962
• 全文大小：444K
• 年卷期：v.117,no.11(March 21, 2013)
• ISSN：1932-7455

文摘

Eu:YPO₄路xH₂O (x = 0.5鈥?) nanocrystals were synthesized by a liquid鈥搒olid鈥搒olution (LSS) solvothermal method and dispersed in chloroform. In order to sensitize the emission from the Eu³⁺ ions, 2-thenoyltrifluoroacetone (HTTFA) was used to replace a significant fraction of the oleate capping ligand on the as-prepared Eu:YPO₄路xH₂O (x = 0.5鈥?) nanocrystals. During the ligand exchange, HTTFA reacts with oleate, forming oleic acid and 2-thenoyltrifluoroacetonate, TTFA. The negatively charged TTFA then displaces the neutral oleic acid ligand from the surface of the nanoparticles. The resulting surface-modified samples were less dispersible in chloroform than were the as-prepared, oleate-capped nanoparticles but were easily dispersed in pyridine, forming very clear mixtures. The resulting surface-modified nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), UV鈥搗is absorption spectroscopy, photoluminescence (PL) spectroscopy, and time-resolved luminescence spectroscopy. XRD analysis indicates that the samples are crystalline with a hexagonal phase. The oleate-capped Eu:YPO₄路xH₂O (x = 0.5鈥?) nanocrystals have a zeolite structure with a porous surface. The morphology and quality of the nanoparticles remained unchanged upon ligand exchange. The FTIR spectrum of the surface-modified (TTFA-sensitized) Eu:YPO₄路xH₂O (x = 0.5鈥?) nanocrystals shows signals for both 2-thenoyltrifluoroacetate and oleate. Using UV鈥搗is absorbance and elemental analysis, it is estimated that approximately half of the native oleate capping ligands are replaced with TTFA. Colloidal dispersions in pyridine show characteristic emission of Eu³⁺⁵D₀ 鈫?⁷F_J (J = 0鈥?) when excited at the TTFA absorbance band at 350 nm. Ligand excitation at 350 nm results in an enhancement of external quantum efficiency of Eu³⁺ emission of up to 4700脳 relative to direct Eu³⁺ excitation at 464 nm. The ability to sensitize emission from these nanocrystals greatly increases their potential for application in display and lighting fields.