Masud Aurangzeb Rashid, Hong Seung-Ho, Shen Tian-Zi, Shahzad Amir, Song Jang-Kun
School of Electronics & Electrical Engineering, Sungkyunkwan University Suwon Gyeonggi-do 16419 South Korea
College of Information & Communication Engineering, Sungkyunkwan University Suwon Gyeonggi-do 16419 South Korea.
RSC Adv. 2018 May 4;8(30):16549-16556. doi: 10.1039/c8ra02186d. eCollection 2018 May 3.
Two-dimensional (2D) nanoparticles in an oligomer-tethered alpha zirconium phosphate (αZrP) colloid self-assemble to form a cofacial lamellar structure with regular spacing parallel to the surface and exhibit high reflectance and vivid structural colors within the visible frequency spectrum. Here, we demonstrate electrical switching of the structural color reflection by electrical control of the liquid crystalline phase of the αZrP colloid. At low frequency (less than 15 Hz, optimally at 1 Hz), electrohydrodynamic flow in the colloid destroys the photonic crystalline lamellar phase and creates an apparently disordered dynamic state with local nematic orientation. The method using electrohydrodynamic flow is a better approach to erase the photonic crystalline ordering of nanoparticles, than application of a high-frequency field, which has been proposed previously, in terms of the required voltage and color uniformity. The field-induced disordered particle orientation can be spontaneously recovered to the initial photonic crystal state by removing the applied voltage, but this method requires quite a long time and does not work in materials with a high nanoplatelet concentration. On the other hand, by applying a horizontal high-frequency field (approximately 10 kHz), the initial lamellar ordering can be forcibly recovered. In this way, the structural color in the 2D nanoparticle colloid can be repeatedly erased or rewritten by switching the frequency of the applied voltage from 10 kHz to 1 Hz and , respectively. Our method of switching a 2D colloid using both electrohydrodynamic flow and frequency modulation is expected to be a promising approach to control the photonic crystallinity of colloidal photonic crystals.
在由低聚物连接的α-磷酸锆（αZrP）胶体中的二维（2D）纳米颗粒自组装形成与表面平行且具有规则间距的共面层状结构，并在可见光谱范围内表现出高反射率和鲜艳的结构色。在此，我们通过对αZrP胶体的液晶相进行电控制来演示结构色反射的电切换。在低频（小于15Hz，最佳为1Hz）下，胶体中的电流体动力学流动会破坏光子晶体层状相，并产生具有局部向列取向的明显无序动态状态。就所需电压和颜色均匀性而言，与先前提出的施加高频场相比，使用电流体动力学流动的方法是消除纳米颗粒光子晶体有序性的更好方法。通过去除施加的电压，场诱导的无序颗粒取向可以自发恢复到初始光子晶体状态，但这种方法需要相当长的时间，并且在高纳米片浓度的材料中不起作用。另一方面，通过施加水平高频场（约10kHz），可以强制恢复初始层状有序性。通过这种方式，通过分别将施加电压的频率从10kHz切换到1Hz，可以反复擦除或重写二维纳米颗粒胶体中的结构色。我们使用电流体动力学流动和频率调制来切换二维胶体的方法有望成为控制胶体光子晶体光子结晶度的一种有前途的方法。
