On the physical limitations for radio frequency absorption in gold nanoparticle suspensions
On the physical limitations for radio frequency absorption in gold nanoparticle suspensions
复制标题
金纳米粒子悬浮液中射频吸收的物理限制
DOI：
10.1088/1361-6463/aa5a89
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Nordebo S
中科院分区：
文献类型：
--
作者：
Nordebo S
本文研究了金纳米颗粒悬浮液中射频吸收的物理限制。一个球形的几何形状被认为是由一个球形的胶体GNP悬浮液，其特征在于作为一个任意的被动介电材料，这是沉浸在一个任意的有损介质。考虑周围介质的趋肤效应，定义了相对加热系数和相应的最佳近场激励。经典的米氏理论的有损介质也被重新审视，它表明，最佳介电常数函数产生最大的吸收内的球形悬浮是一个共轭匹配相对于周围的有损材料。一个凸优化方法被用来调查的宽带可实现性的任意无源材料近似所需的共轭匹配在有限的带宽，类似于超材料的近似。窄带可实现性研究表明，对于由弱电解质溶液组成的周围介质，由于球形GNP悬浮液内部的电泳（等离子体）共振现象，电磁加热在微波制度中可以是显著的，只要相关的Drude参数可以被调谐到（或接近）共振。作为示范，一些现实的德鲁德参数进行了调查有关的GNP的体积分数，质量和摩擦常数。GNP可容纳的电荷量被确定为最重要的设计参数之一。然而，可靠地建模，测量和控制涂覆的GNP的电荷数的问题尚未完全理解，并且仍然是该领域中的一个开放的研究问题。所提出的理论和相关的物理限制为这一方向的进一步研究提供了有用的框架。未来的研究还旨在扩展到任意悬挂几何形状和列入的气动分析。
This paper presents a study of the physical limitations for radio frequency absorption in gold nanoparticle (GNP) suspensions. A spherical geometry is considered consisting of a spherical suspension of colloidal GNPs characterized as an arbitrary passive dielectric material which is immersed in an arbitrary lossy medium. A relative heating coefficient and a corresponding optimal near field excitation are defined, taking the skin effect of the surrounding medium into account. The classical Mie theory for lossy media is also revisited, and it is shown that the optimal permittivity function yielding a maximal absorption inside the spherical suspension is a conjugate match with respect to the surrounding lossy material. A convex optimization approach is used to investigate the broadband realizability of an arbitrary passive material to approximate the desired conjugate match over a finite bandwidth, similar to the approximation of a metamaterial. A narrowband realizability study shows that for a surrounding medium consisting of a weak electrolyte solution, the electromagnetic heating, due to the electrophoretic (plasmonic) resonance phenomena inside the spherical GNP suspension, can be significant in the microwave regime, provided that the related Drude parameters can be tuned into (or near to) resonance. As a demonstration, some realistic Drude parameters are investigated concerning the volume fraction, mass, and friction constant of the GNPs. The amount of charge that can be accommodated by the GNPs is identified as one of the most important design parameters. However, the problem of reliably modelling, measuring and controlling the charge number of coated GNPs is not yet fully understood, and is still an open research issue in this field. The presented theory and related physical limitations provide a useful framework for further research in this direction. Future research is also aimed at an expansion towards arbitrary suspension geometries and the inclusion of thermodynamical analysis.
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