Stability and Relaxation Mechanisms of Citric Acid Coated Magnetite Nanoparticles for Magnetic Hyperthermia

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• 作者：M. Elisa de Sousa ; Marcela B. Fern谩ndez van Raap ; Patricia C. Rivas ; Pedro Mendoza Z茅lis ; Pablo Girardin ; Gustavo A. Pasquevich ; Jose L. Alessandrini ; Diego Muraca ; Francisco H. S谩nchez
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 14, 2013
• 年：2013
• 卷：117
• 期：10
• 页码：5436-5445
• 全文大小：598K
• 年卷期：v.117,no.10(March 14, 2013)
• ISSN：1932-7455

文摘

Magnetite (Fe₃O₄) nanoparticles are proper materials for Magnetic Fluid Hyperthermia applications whenever these conjugate stability at physiological (neutral pH) medium and high specific dissipation power. Here, magnetite nanoparticles 9鈥?2 nm in size, electrostatically stabilized by citric acid coating, with hydrodynamic sizes in the range 17鈥?0 nm, and well dispersed in aqueous solution were prepared using a chemical route. The influence of media acidity during the adsorption of citric acid (CA) on the suspension鈥檚 long-term stability was systematically investigated. The highest content of nanoparticles in a stable suspension at neutral pH is obtained for coating performed at pH = 4.58, corresponding to the larger amount of CA molecules adsorbed by one carboxylate link. Specific absorption rates (SARs) of various magnetite colloids, determined calorimetrically at a radio frequency field of 265 kHz and field amplitude of 40.1 kA/m, are analyzed in terms of structural and magnetic colloid properties. Larger dipolar interactions lead to larger N茅el relaxation times, in some cases larger than Brown relaxation times, which in the present case enhanced magnetic radio frequency heating. The improvement of suspension stability results in a decrease of SAR values, and this decrease is even large in comparison with uncoated magnetite nanoparticles. This fact is related to interactions between particles.