Preparation and Characterization of Near-Infrared Luminescent Bifunctional Core/Shell Nanocomposites

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• 作者：Maofeng Zhang ; Songjun Shi ; Jianxin Meng ; Xiaoqing Wang ; Hai Fan ; Yongchun Zhu ; Xuyang Wang ; Yitai Qian
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：February 28, 2008
• 年：2008
• 卷：112
• 期：8
• 页码：2825 - 2830
• 全文大小：223K
• 年卷期：v.112,no.8(February 28, 2008)
• ISSN：1932-7455

文摘

Bifunctional nanocomposites with superparamagnetic and NIR luminescent properties were synthesized by alayer-by-layer and a modified Stöber method. Fe₃O₄ nanoparticles as the core were coated with NaYF₄:Ln³⁺(Ln = Nd, Er, Pr, or Ho) to form the first layer. Then, the second layer was coated with silica to improve thechemical stability and photostability. The X-ray diffraction patterns showed that a cubic spinel structure ofFe₃O₄ and the coexistence of a cubic and hexagonal structure of NaYF₄ were obtained. Energy dispersiveX-ray (EDX) spectroscopy analysis confirmed the core/shell structure of Fe₃O₄@NaYF₄:Ln³⁺. Transmissionelectron microscopy images revealed that the bifunctional nanocomposites consisted of crystalline Fe₃O₄@NaYF₄:Ln³⁺ cores and amorphous SiO₂ shells, in a spherical shape with a narrow size distribution. Magneticmeasurements showed that the obtained bifunctional nanocomposites exhibited superparamagnetic behavior.Emission spectra indicated that the bifunctional nanocomposites possessed a high near-infrared (NIR)luminescent intensity. Moreover, the hexagonal phase NaYF₄:Ln³⁺ showed NIR emission 10 to 15 timesstronger than the cubic phase.