iMdea Nanociencia, Campus Universitario de Cantoblanco, 28049 Madrid, Spain.
Nanoscale. 2017 Apr 20;9(16):5094-5101. doi: 10.1039/c7nr00810d.
Hysteresis losses in magnetic nanoparticles constitute the basis of magnetic hyperthermia for delivering a local thermal stress. Nevertheless, this therapeutic modality is only to be realised through a careful appraisal of the best possible intrinsic and extrinsic conditions to the nanoparticles for which they maximise and preserve their heating capabilities. Low frequency (100 kHz) hysteresis loops accurately probe the dynamical magnetic response of magnetic nanoparticles in a more reliable manner than calorimetry measurements, providing conclusive quantitative data under different experimental conditions. We consider here a set of iron oxide or cobalt ferrite nanocubes of different sizes, through which we experimentally and theoretically study the influence of the viscosity of the medium on the low frequency hysteresis loops of magnetic colloids, and hence their ability to produce and dissipate heat to the surroundings. We analyse the role of nanoparticle size, size distribution, chemical composition, and field intensity in making the magnetisation dynamics sensitive to viscosity. Numerical simulations using the stochastic Landau-Lifshitz-Gilbert equation model the experimental observations in excellent agreement. These results represent an important contribution towards predicting viscosity effects and hence to maximise heat dissipation from magnetic nanoparticles regardless of the environment.
磁滞损耗是磁热疗中利用局部热应力的基础。然而，这种治疗方法只有在仔细评估最佳内在和外在条件下才能实现，使纳米粒子能够最大化并保持其加热能力。低频（100 kHz）磁滞回线比量热测量更可靠地探测磁性纳米粒子的动态磁响应，在不同的实验条件下提供确凿的定量数据。我们在这里考虑了一组不同尺寸的氧化铁或钴铁氧体纳米立方体，通过实验和理论研究了介质粘度对磁性胶体低频磁滞回线的影响，以及它们向周围环境产生和耗散热量的能力。我们分析了纳米粒子尺寸、尺寸分布、化学成分和场强在使磁化动力学对粘度敏感方面的作用。使用随机朗之万-李-吉尔伯特方程的数值模拟与实验观察结果非常吻合。这些结果为预测粘度效应做出了重要贡献，从而最大限度地从磁性纳米粒子中耗散热量，无论环境如何。
