Chemical Spacer Design for Engineering the Relaxometric Properties of Core鈥揝hell Structured Rare Earth Nanoparticles

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• 作者：Jiayi Huang ; Yi Hou ; Chunyan Liu ; Lihong Jing ; Tiancong Ma ; Xiaodan Sun ; Mingyuan Gao
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：December 8, 2015
• 年：2015
• 卷：27
• 期：23
• 页码：7918-7925
• 全文大小：486K
• ISSN：1520-5002

文摘

The development of T₁/T₂ dual-modality contrast agents for magnetic resonance imaging (MRI) is beneficial for eliminating artifacts. However, T₁ and T₂ agents in the case of direct contact will interfere with each other, and the intrinsic mechanism remains unclear yet. Gadolinium(III) is widely used as T₁ contrast agents, while dysprosium(III) exhibits the strongest magnetic moment among rare earth (RE) elements due to the spin鈥搊rbital coupling and can potentially be used as T₂ contrast agents. The very similar chemical properties of RE elements allow integration of Gd(III) and Dy(III) within single nanocrystals for investigating the interactions between T₁ and T₂ components so as to achieve T₁/T₂ dual-modality contrast agents with optimized performance. Therefore, core鈥搒hell鈥搒hell structured NaDyF₄@NaREF₄@NaGdF₄:Yb,Er nanocrystals were prepared via a seed-mediated growth approach and Gd(III), Er(III), and Y(III) were chosen to construct NaREF₄ spacer layer for mediating the interactions between Dy(III) and Gd(III) ions. It was found out that, with the decrease of the electron cloud distortion ability from Gd(III) to Y(III), the PEGylated core鈥搒hell鈥搒hell particles present increasing longitudinal relaxivity values from 0.50 to 1.82 mM^鈥? s^鈥?. On the basis of the longitudinal relaxivity theory and polarizability of different RE elements, the above tendency can be interpreted by the distortion tendency of the electron cloud of RE(III) in the spacer layer which strongly mediates the interactions between electron clouds of Dy(III) and Gd(III) ions. Further upconversion luminescence spectroscopy study in combination with the relaxivity measurements on nanocrystals with thicker spacer (3.5 vs 1.9 nm) also supported the above explanation.