Reserch On Liquid Colloidal Crystals And Electronic Controlled Optical Properties Based On Electrode Induced Assembly

Responsive colloidal crystal is an intelligent optical material that can adjust the optical band gap structure under external chemical or physical stimulation,so as to change the light reflection signal and structural color.It has broad application prospects in the fields of display,anti-counterfeiting,stealth,sensing and so on.Among them,the electric field response liquid colloidal crystals have attracted extensive attention because of its high stability,fine control and short response time.Throughout the research progress of colloidal crystals,most of the current research focuses on the dynamic regulation of their color hue(i.e.reflection wavelength),and there are few studies on the regulation of color brightness(i.e.reflection intensity)or purity(i.e.reflection half peak width).However,nowadays,people not only pay attention to the diversity of colors,but also increasingly pursue brighter or brighter colors.At present,only by controlling the self-assembly process and doping luminescent materials to improve its brightness,but the two methods are mainly for static thin film materials.Therefore,it is urgent to develop a simple,universal and efficient new method to regulate its brightness.Based on the induced effect of electrode surface charge on colloidal particle self-assembly,this paper constructs a multi-color high brightness device with high stability and fast response,and shows the application research of this device.The specific contents and conclusions are as follows:First,prepare Fe₃O₄@C colloidal particles and characterize the static and dynamic optical properties of their electrical response devices.Prepared by hydrothermal solvent method Fe₃O₄@C colloidal particles were tested by SEM,TEM and zeta potential,Fe₃O₄@C colloidal particles are spherical particles with core-shell structure with superparamagnetism and negative surface charge.The liquid colloidal crystals were prepared by evaporation induced supersaturation precipitation.The electrical response devices with different initial colors were constructed according to different concentrations.It was found that the 25wt%device can realize the full color change of visible light under the driving of low voltage(-1.3 V to 0.8 V),and its response time and cycle stability were explored.Secondly,the surface of the electrode was treated by O₂ plasma and polydiallyl dimethyl ammonium chloride(PDDA)adsorption to realize high brightness devices and explore its mechanism.By adjusting the plasma treatment time and PDDA treatment time,electrodes with different surface charge states can be obtained.Through the characterization of the optical properties of devices assembled with different electrodes,it is found that the uniform positive charge electrode effectively improves the lattice size of short-range ordered particles through the induction of particle assembly,increases its reflection intensity by 110%,and significantly improves its brightness and saturation.The potential distribution of surface charge is simulated by COMSOL software.The results show that the surface negative charge of the original ITO electrode is uneven,and the uneven potential distribution leads to the maximum disorder of colloidal particle arrangement;The treated electrode surface has uniform positive charge,uniform potential distribution,and due to the existence of Coulomb gravity,a uniform and more ordered colloidal crystal array is formed,which increases the reflection intensity.Finally,the dynamic optical performance of the display device assembled by positive charge electrode under electric field is tested.The display device assembled by positive charge electrode realizes the full color change of visible light driven by-1.3 V to 0.8 V.It displays the same color as the traditional display device at the same voltage,but the reflection intensity is increased by 100%,the response time is shortened by 50%,and 1000 reversible cycle tests can be achieved.Based on its excellent performance of multi-color and high brightness,three kinds of patterned display devices with variable background color,fixed background color and dual electrode control are prepared by charge patterning design of the electrode.