Seki Toya, Seki Yutaro, Iwata Naoto, Furumi Seiichi
Department of Chemistry, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
Materials (Basel). 2022 Jul 15;15(14):4943. doi: 10.3390/ma15144943.
Colloidal crystals (CCs) are periodic arrays of monodisperse microparticles. Such CCs are very attractive as they can be potentially applicable as versatile photonic devices such as reflective displays, sensors, lasers, and so forth. In this article, we describe a promising methodology for synthesizing monodisperse magnetite microparticles whose diameters are controllable in the range of 100-200 nm only by adjusting the base concentration of the reaction solution. Moreover, monodisperse magnetite microparticles in aqueous suspensions spontaneously form the CC structures under an external magnetic field, leading to the appearance of Bragg reflection colors. The reflection peak can be blue-shifted from 730 nm to 570 nm by the increase in the external magnetic field from 28 mT to 220 mT. Moreover, the reflection properties of CCs in suspension depend on the microparticle concentration in suspension and the diameter of the magnetite microparticles. Both fine-control of microparticle diameter and investigation of magneto-optical properties of CCs would contribute to the technological developments in full-color reflective displays and sensors by utilizing these monodisperse magnetite microparticles.
胶体晶体（CCs）是单分散微粒的周期性阵列。这类胶体晶体极具吸引力，因为它们有可能用作多种光子器件，如反射式显示器、传感器、激光器等等。在本文中，我们描述了一种很有前景的合成单分散磁铁矿微粒的方法，通过仅调节反应溶液的碱浓度，其直径可控制在100 - 200纳米范围内。此外，水悬浮液中的单分散磁铁矿微粒在外部磁场作用下会自发形成CC结构，从而产生布拉格反射颜色。随着外部磁场从28毫特斯拉增加到220毫特斯拉，反射峰可从730纳米蓝移至570纳米。而且，悬浮液中CCs的反射特性取决于悬浮液中的微粒浓度以及磁铁矿微粒的直径。通过利用这些单分散磁铁矿微粒，对微粒直径的精细控制以及对CCs磁光特性的研究都将有助于全彩反射式显示器和传感器的技术发展。
