Magnetic Nanocomposite Particles and Hollow Spheres Constructed by a Sequential Layering Approach

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• 作者：Frank Caruso ; Marina Spasova ; Andrei Susha ; Michael Giersig ; and Rachel A. Caruso
• 刊名：Chemistry of Materials
• 出版年：2001
• 出版时间：January 2001
• 年：2001
• 卷：13
• 期：1
• 页码：109 - 116
• 全文大小：610K
• 年卷期：v.13,no.1(January 2001)
• ISSN：1520-5002

文摘

The fabrication of magnetic composite core-shell particles and hollow spheres with tailoreddimensions and compositions has been accomplished by a multistep (layer-by-layer) strategy.Composite particles were prepared by coating submicrometer-sized anionic polystyrene (PS)latices with magnetite (Fe₃O₄) nanoparticle layers alternately adsorbed with polyelectrolytefrom aqueous solution. The thickness of the deposited multilayers could be finely tuned withnanoscale precision, either by selection of the number of adsorption cycles performed or bythe number of polyelectrolyte layers deposited between each nanoparticle layer (i.e.,interlayer). As demonstrated by transmission electron microscopy, a marked improvementin the growth, uniformity, and regularity of the composite multilayers was achieved whenthe number of polyelectrolyte interlayers was increased from one [(poly(diallyldimethylammonium chloride) (PDADMAC)] to three [(PDADMAC/poly(styrenesulfonate) (PSS)/PDADMAC)]. Hollow, intact magnetic spheres were obtained by calcination of the core-shellparticles at elevated temperature. Furthermore, composite hollow spheres were preparedby calcination of PS latices coated with multilayers of silica and Fe₃O₄ nanoparticles. Thesenanoengineered colloidal particles may potentially find applications as delivery systems, orin diagnostics, where the particles can be directed by application of an external magneticfield.