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Magnetic Hyperthermia Experiments with Magnetic Nanoparticles in Clarified Butter Oil and Paraffin: A Thermodynamic Analysis
The Journal of Physical Chemistry C ( IF 3.7 ) Pub Date : 2020-12-02 , DOI: 10.1021/acs.jpcc.0c06843
Adriele A. de Almeida 1 , Emilio De Biasi 1, 2 , Marcelo Vasquez Mansilla 1 , Daniela P. Valdés 1, 2 , Horacio E. Troiani 2, 3 , Guillermina Urretavizcaya 4 , Teobaldo E. Torres 1 , Luis M. Rodríguez 1 , Daniel E. Fregenal 5 , Guillermo C. Bernardi 1 , Elin L. Winkler 1, 2 , Gerardo F. Goya 6, 7 , Roberto D. Zysler 1, 2 , Enio Lima 1
Affiliation  

In specific power absorption models for magnetic fluid hyperthermia (MFH) experiments, the magnetic relaxation time of nanoparticles (NPs) is known to be a fundamental descriptor of the heating mechanisms. The relaxation time is mainly determined by the interplay between the magnetic properties of NPs and the rheological properties of NPs’ environment. Although the role of magnetism in MFH has been extensively studied, the thermal properties of the NP medium and their changes during MFH experiments have been underrated so far. Herein, we show that ZnxFe3–xO4 NPs dispersed through different media with phase transition in the temperature range of experiment as clarified butter oil (CBO) and paraffin. These systems show nonlinear behavior of the heating rate within the temperature range of MFH experiments. For CBO, a fast increase at ∼306 K is associated with changes in the viscosity (η(T)) and specific heat (cp(T)) of the medium at its melting temperature. This increment in the heating rate takes place around 318 K for paraffin. The magnetic and morphological characterization of NPs together with the observed agglomeration of NPs above 306 and 318 K for CBO and paraffin, respectively, indicate that the fast increase in MFH curves could not be associated with the change in the magnetic relaxation mechanism, with Néel relaxation being dominant. In fact, successive experimental runs performed up to temperatures below and above the CBO and paraffin melting points resulted in different MFH curves due to agglomeration of NPs driven by magnetic field inhomogeneity during the experiments. Our results highlight the relevance of the thermodynamic properties of the system NP-medium for an accurate measurement of the heating efficiency for in vitro and in vivo environments, where the thermal properties are largely variable within the temperature window of MFH experiments.

中文翻译:

澄清的黄油油和石蜡中的磁性纳米粒子的磁热实验:热力学分析

在用于磁流体高温(MFH)实验的特定功率吸收模型中,已知纳米粒子(NPs)的磁弛豫时间是加热机制的基本描述。弛豫时间主要由NPs的磁性和NPs环境的流变特性之间的相互作用决定。尽管已经广泛研究了磁性在MFH中的作用,但到目前为止,NP介质的热性质及其在MFH实验中的变化都被低估了。在这里,我们表明Zn x Fe 3– x O 4在实验温度范围内,澄清的黄油(CBO)和石蜡将NP分散在不同的介质中,并发生相变。这些系统显示了在MFH实验温度范围内加热速率的非线性行为。对于CBO,约306 K处的快速增加与粘度(η(T))和比热(c pT))介质在其熔化温度下的温度。对于石蜡,加热速率的这种增加发生在318 K左右。NPs的磁性和形态学特征,以及观察到的CBO和石蜡分别高于306和318 K的NPs的团聚,表明MFH曲线的快速增加与Nelel弛豫的磁弛豫机制的变化无关。占主导地位。实际上,由于在实验期间磁场不均匀性驱动的NP的团聚作用下,连续实验运行直到CBO之上和之下的温度,石蜡熔点导致了不同的MFH曲线。
更新日期:2020-12-17
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