Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications
Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications
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DOI：
10.1007/s11051-013-1613-6
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发表时间：
2013-05-01
影响因子：
2.5
通讯作者：
Sanchez, F. H.
中科院分区：
文献类型：
--
作者：
Mendoza Zelis, P.;Muraca, D.;Sanchez, F. H.
报道了通过物理交联制备的聚乙烯醇（PVA）聚合物基质中磁赤铁矿纳米粒子（NP）的磁性行为的研究。磁性纳米复合材料（铁凝胶）是通过在 PVA 聚合物存在下原位共沉淀铁盐获得的，然后进行冻融循环。将这些铁凝胶的磁性行为与使用戊二醛合成的类似系统的磁性行为进行了比较。由于凝胶中存在残留有毒分子，这种类型的化学交联剂存在一些缺点，这对于生物应用来说是不希望的。通过多种技术测定的特征粒径在 7.9-9.3 nm 范围内。通过X射线吸收光谱研究了纳米颗粒中铁的氧化态。穆斯堡尔测量表明，NP 磁矩呈现集体磁激发和超顺磁弛豫。铁凝胶中纳米粒子的阻断温度和不可逆温度以及磁各向异性常数是通过磁性测量获得的。使用包括两个磁性贡献（200 K 以下的大纳米粒子稍微偏离热力学平衡，以及处于热力学平衡的小纳米粒子）的经验模型来拟合实验磁化曲线。观察到与超顺磁状态的偏差。这种偏差是根据相互作用的超顺磁模型来解释的。从该模型中，可以获得相关的磁性和结构特性，例如偶极相互作用能的数量级、纳米颗粒磁矩以及每铁凝胶质量单位的纳米颗粒数量。这项研究有助于理解基于 PVA 的磁性铁凝胶可能出现的一类新型材料的基础物理学。
A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical cross-linking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing-thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical cross-linking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9-9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mossbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.