Particle motion artifacts in equilibrium magnetization measurements of large iron oxide nanoparticles
Particle motion artifacts in equilibrium magnetization measurements of large iron oxide nanoparticles
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DOI：
10.1016/j.jmmm.2021.168889
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发表时间：
2022-04-01
影响因子：
2.7
通讯作者：
Rinaldi-Ramos, Carlos M.
中科院分区：
文献类型：
--
作者：
Savliwala, Shehaab;Liu, Sitong;Rinaldi-Ramos, Carlos M.
氧化铁纳米粒子发现许多应用，由于它们的响应时，受到外部施加的磁场。平衡磁化测量（通常称为磁化曲线）是评估颗粒是否显示磁滞以及获得磁特性（例如饱和磁化强度）的基本表征工具。对于超顺磁性颗粒，可以通过将数据拟合到理论模型（例如Langevin函数）来获得磁性尺寸分布，这被称为磁性粒度分析。如果希望使用所得的尺寸估计作为应用中的颗粒性能的预测器，则必须在捕获具有最小伪影的颗粒的响应的条件下获得磁化数据。在本文中，我们使用选定的氧化铁纳米粒子批次的物理尺寸范围从20到45 nm，以证明样品制备方法对所获得的磁化数据的影响。我们表明，在粉末形式和液体溶剂中的测量显示不同程度的颗粒相互作用的文物在低场，强烈依赖于颗粒大小和表面涂层的厚度。此外，在“固体”含蜡烃基质中的测量结果表明，大颗粒尺寸的颗粒旋转伪影是敏感的。硬交联的聚合物矩阵示出完全限制粒子运动，导致磁化强度数据，遵循朗之万函数，如果进行测量以上的阻塞温度的粒子。最后，我们讨论了矩阵相关的测量伪影的存在如何影响使用magnetogranulometry获得的磁直径拟合，以及如何测量以上和以下的阻塞温度可以影响拟合结果。
Iron oxide nanoparticles find many applications due to their response when subjected to externally applied magnetic fields. Equilibrium magnetization measurements (commonly known as magnetization curves) are an essential characterization tool to evaluate if particles display hysteresis, and to obtain magnetic properties such as the saturation magnetization. For superparamagnetic particles, one can obtain a magnetic size distribution by fitting the data to a theoretical model, such as the Langevin function, in what is called magnetogranulometric analysis. If one wishes to use the resulting size estimates as a predictor of particle performance in applications, magnetization data must be obtained under conditions that capture the response of the particles with minimal artifacts. In this paper, we used selected iron oxide nanoparticle batches with physical size ranging from 20 to 45 nm to demonstrate the influence of sample preparation methods on the magnetization data obtained. We show that measurements in powder form and in liquid solvents display varying degrees of particle interaction artifacts at low fields, depending strongly on particle size and on the thickness of the surface coating. In addition, measurements in 'solid' waxy hydrocarbon matrices are shown to be susceptible to particle rotation artifacts for large particle sizes. Hard crosslinked polymer matrices are shown to restrict particle motion completely, resulting in magnetization data that follows the Langevin function if the measurement is performed above the blocking temperature of the particles. We end with a discussion of how the presence of matrix-dependent measurement artifacts influence the magnetic diameter fits obtained using magnetogranulometry, and how measuring above and below the blocking temperature can affect fit results.