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arXiv 1903.04877cond-mat.soft
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二维Polymer纳米复合薄膜中长磁偶极链的零场组装

Zero Field Assembly of Long Magnetic Dipolar Chains in 2D Polymer Nanocomposite Films

Christian Appel, Björn Kuttich, Lukas Stühn, Robert W. Stark, Bernd Stühn

摘要:

几十年来,人们一直在理论上预测零场下磁偶极纳米颗粒链的存在,但这些结构很少在实验上观察到。一个先决条件是形成链的颗粒上的永久磁矩。在这里,我们报告的磁性偶极链的球形氧化铁纳米粒子的直径为\SI{12.8}{\nano\meter}的观察。纳米颗粒嵌入在聚合物薄膜中。由于聚合物基质的高粘度,主要聚集机制由偶极相互作用驱动。较小的氧化铁纳米颗粒(\SI{9.4}{\nano\meter})不显示永久磁矩,不形成链,但紧凑的聚集体。不同的氧化铁纳米粒子和聚合物在空气-水界面的混合单分子膜的特征在于朗缪尔等温线和原位X射线反射仪(XRR)。颗粒与聚合物的组合导致在空气-水界面处的稳定的聚合物纳米复合膜。XRR实验表明,纳米颗粒浸没在\SI{3}{\nano\meter}的薄聚合物基质中。使用原子力显微镜(AFM)的LB膜,我们测量的横向分布的粒子在膜中。转移膜内的单个结构的分析结果在分形维数,是在良好的协议与2D模拟。

英文摘要:

The existence of magnetic dipolar nanoparticle chains at zero field has been predicted theoretically for decades, but these structures are rarely observed experimentally. A prerequisite is a permanent magnetic moment on the particles forming the chain. Here we report on the observation of magnetic dipolar chains of spherical iron oxide nanoparticles with a diameter of \SI{12.8}{\nano\meter}. The nanoparticles are embedded in an ultrathin polymer film. Due to the high viscosity of the polymer matrix, the dominating aggregation mechanism is driven by dipolar interactions. Smaller iron oxide nanoparticles (\SI{9.4}{\nano\meter}) show no permanent magnetic moment and do not form chains but compact aggregates. Mixed monolayers of different iron oxide nanoparticles and polymer at the air-water interface are characterized by Langmuir isotherms and in-situ X-ray reflectometry (XRR). The combination of the particles with a polymer leads to a stable polymer nanocomposite film at the air-water interface. XRR experiments show that nanoparticles are immersed in a thin polymer matrix of \SI{3}{\nano\meter}. Using atomic force microscopy (AFM) on Langmuir-Blodgett films, we measure the lateral distribution of particles in the film. An analysis of single structures within transferred films results in fractal dimensions that are in excellent agreement with 2D simulations.

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