Magnetochromatic Microspheres: Rotating Photonic Crystals
Magnetochromatic Microspheres: Rotating Photonic Crystals
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DOI：
10.1021/ja903626h
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发表时间：
2009-11-04
影响因子：
15
通讯作者：
Yin, Yadong
中科院分区：
文献类型：
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作者：
Ge, Jianping;Lee, Howon;Yin, Yadong
将超顺磁性（SPM）胶体颗粒瞬间组装在可紫外光固化树脂的乳液液滴内，然后进行快速紫外光固化，使液滴聚合并固定有序结构，制备了磁致色微球。当超顺磁性Fe3O4@SiO2核/壳粒子分散在液滴中，在排斥力和引力的平衡相互作用下自组织形成一维链，每个一维链中包含周期性排列的粒子，衍射可见光并显示场可调的颜色。紫外光引发的树脂低聚物聚合固定了微滴微球内部的周期性结构并保持了衍射特性。由于超顺磁链倾向于沿场方向排列，因此通过使用磁场改变晶格相对于入射光的方向，可以非常方便地控制这种光子微球的方向，从而控制它们的衍射颜色。出色的稳定性以及通过磁场快速开/关衍射的能力使该系统适用于彩色显示，可重写标牌和传感器等应用。作为一个简单的演示，我们通过将磁致色微球嵌入可以在固相和液相之间热切换的基质中，制造了一个具有开/关双稳态的显示单元。
Magnetochromatic microspheres have been fabricated through instant assembly of superparamagnetic (SPM) colloidal particles inside emulsion droplets of UV curable resin followed by an immediate UV curing process to polymerize the droplets and fix the ordered structures. When dispersed in the liquid droplets, superparamagnetic Fe3O4@SiO2 core/shell particles self-organize under the balanced interaction of repulsive and attractive forces to form one-dimensional chains, each of which contains periodically arranged particles diffracting visible light and displaying field-tunable colors. UV initiated polymerization of the oligomers of the resin fixes the periodic structures inside the droplet microspheres and retains the diffraction property. Because the superparamagnetic chains tend to align themselves along the field direction, it is very convenient to control the orientation of such photonic microspheres and, accordingly, their diffractive colors, by changing the orientation of the crystal lattice relative to the incident light using magnetic fields. The excellent stability together with the capability of fast on/off switching of the diffraction by magnetic fields makes the system suitable for applications such as color display, rewritable signage, and sensors. As a simple demonstration, we have fabricated a display unit that has on/off bistable states by embedding the magnetochromatic microspheres in a matrix that can thermally switch between solid and liquid phases.