Issue 4, 2019

A code with a twist: supraparticle microrod composites with direction dependent optical properties as anti-counterfeit labels

Abstract

Superparamagnetic iron oxide nanoparticles can be assembled to form anisotropic microrod supraparticles with the assistance of a magnetic field during synthesis. Optionally, these iron oxide microrods can furthermore be coated with a thin silica shell. Due to their anisotropic structure, both microrod types can be aligned in a magnetic field while being dispersed in a matrix material which can be cured during the alignment of the microrods. In this way, an anisotropic magnetic composite is obtained. Interestingly, it was observed that the optical extinction properties for visible light in such a composite are direction dependent, which can be explained by using appropriate models based on Maxwell equations. Based on the understanding of this principle, a clever approach for a hidden code could be proposed which is obtained from mixing pure iron oxide and silica coated microrod supraparticles in such an anisotropic composite. The hidden code, which comes down to obtaining a single value eventually, can only be revealed when knowing that the system needs to be measured with a certain “twist”.

Graphical abstract: A code with a twist: supraparticle microrod composites with direction dependent optical properties as anti-counterfeit labels

Supplementary files

Article information

Article type
Paper
Submitted
09 Nov 2018
Accepted
31 Jan 2019
First published
31 Jan 2019
This article is Open Access
Creative Commons BY license

Nanoscale Adv., 2019,1, 1510-1515

A code with a twist: supraparticle microrod composites with direction dependent optical properties as anti-counterfeit labels

S. Wintzheimer, T. Granath, A. Eppinger, M. R. Goncalves and K. Mandel, Nanoscale Adv., 2019, 1, 1510 DOI: 10.1039/C8NA00334C

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