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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Uniform and water stable magnetite nanoparticles with diameters around the monodomain-multidomain limit
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Uniform and water stable magnetite nanoparticles with diameters around the monodomain-multidomain limit

机译：直径约单畴-多畴极限的均匀且水稳定的磁铁矿纳米颗粒

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摘要

A direct method for the preparation of uniform magnetite nanoparticles with sizes around 30 nm and stable in aqueous media at pH 7 has been developed. This method is based on the precipitation of an iron ( II) salt ( FeSO4) in the presence of a base ( NaOH) and a mild oxidant ( KNO3). Reaction rate seems to be controlled by the iron salt concentration and the presence of ethanol in the media. Thus lower iron concentration and a water/ethanol ratio equal to one lead to the formation of the smallest particles, 30 nm in diameter. Colloidal suspensions of these particles were directly obtained by simple ultrasonic treatment of the powders leading to very stable ferrofluids at pH 7. Sulphate anions present at the particle surface seem to be responsible for the colloidal stability, providing a biocompatible character to the suspensions. The structural, morphological and magnetic characterization of the nanoparticles is also described and suggests that the smallest particles have a diameter close to the limit between monodomain-multidomain magnetic structure, which could account for the high powder absorption of magnetic fields. According to this calorimetric experiments resulted in specific power absorption rates of ca 80-95 W g(-1), which are among the highest values reported in the literature and make these nanoparticles very interesting for hyperthermia.
机译：已经开发了一种直接的方法来制备均匀的磁铁矿纳米颗粒，该纳米颗粒尺寸约为30 nm，并且在pH 7的水性介质中稳定。该方法基于在碱（NaOH）和弱氧化剂（KNO3）存在下铁（II）盐（FeSO4）的沉淀。反应速率似乎受铁盐浓度和培养基中乙醇的存在控制。因此较低的铁浓度和等于一的水/乙醇比导致形成直径为30 nm的最小颗粒。这些颗粒的胶体悬浮液是通过对粉末进行简单的超声处理直接得到的，从而在pH 7下产生非常稳定的铁磁流体。颗粒表面存在的硫酸根阴离子似乎是胶体稳定性的原因，为悬浮液提供了生物相容性。还描述了纳米颗粒的结构，形态和磁性特征，并表明最小的颗粒的直径接近单畴-多畴磁性结构之间的极限，这可以解释磁场对粉末的高吸收。根据该量热实验，得出的比功率吸收率约为80-95 W g（-1），这是文献报道的最高值之​​一，这些纳米粒子对于热疗非常有趣。

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