On the physical limitations for radio frequency absorption in gold nanoparticle suspensions

Nordebo, Sven and Dalarsson, Mariana and Ivanenko, Yevhen and Sjoeberg, Daniel and Bayford, Richard (2017) On the physical limitations for radio frequency absorption in gold nanoparticle suspensions. Journal of Physics D: Applied Physics, 50 (15). ISSN 0022-3727

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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 to reliably model, measure and control 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 aiming at an expansion towards arbitrary suspension geometries and the inclusion of thermodynamical analysis.

Item Type: Article
Additional Information: Article number = 155401
Research Areas: A. > School of Science and Technology
Item ID: 21291
Notes on copyright: This is an author-created, un-copyedited version of an article accepted published in Journal of Physics D: Applied Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6463/aa5a89
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Depositing User: Richard Bayford
Date Deposited: 14 Feb 2017 16:46
Last Modified: 07 Dec 2018 08:22
URI: http://eprints.mdx.ac.uk/id/eprint/21291

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