Synthesis of Core-Shell Ferrite Nanoparticles for Ferrofluids: Chemical and Magnetic Analysis

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• 作者：Juliano de A. Gomes ; Marcelo H. Sousa ; Francisco A. Tourinho ; Renata Aquino ; Geraldo J. da Silva ; Jé ; rô ; me Depeyrot ; Emmanuelle Dubois ; Ré ; gine Perzynski
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：April 24, 2008
• 年：2008
• 卷：112
• 期：16
• 页码：6220 - 6227
• 全文大小：130K
• 年卷期：v.112,no.16(April 24, 2008)
• ISSN：1932-7455

文摘

A chemical core-shell strategy is developed here for the synthesis of ferrofluids based on nanoparticles ofdifferent ferrites with different mean sizes. A heterogeneity of chemical composition, associated with asuperficial enrichment of iron, allows to obtain chemically stable ionic colloids. We propose here a core-shell model to describe the synthesized nanoparticles, which is tested by chemical and magnetic measurementsperformed at the various steps of the synthesis. The thickness of the superficial layer, rich in iron, is rangingbetween 0.4 and 1.3 nm, depending on the nanoparticle size and on the underlying ferrite. Its density is foundclose to that of maghemite, and its magnetization depends on the core ferrite. It is low with a cobalt ferritecore and larger for the three other ferrites investigated here (NiFe₂O₄, CuFe₂O₄, and ZnFe₂O₄). Magneticmeasurements prove that there is a strong redistribution of Zn²⁺ ions inside the core of the synthesizednanoparticles based on ZnFe₂O₄.