Study On Structural Color Enhancement Of Silica Based Photonic Crystals And Patterning Application

Compared to pigments and dyes,the structural color of creatures such as butterflies and beetles originates from the interaction of their micro-structure with light,which is more environmentally friendly and uneasy to fade.Structural colors can be divided into amorphous photonic crystal(APC)and crystalline photonic crystal(PC)structural colors.APCs display a single color and are mainly used for color display,while PCs exhibit angle-dependent color change and can be utilized for anti-counterfeiting in printing.At present,challenges in structural color materials include difficulty in large-scale production,low color saturation,and easily damaged ordered structures.This project focuses on the assembly of silicon dioxide-based amorphous and crystalline photonic crystals.On the one hand,acetylene carbon black(ACET)was added to improve color saturation,and acrylic resin was used to encapsulate and protect SiO2 APCs,then the large-scale fabrication and patterning applications of SiO2 APC pigments were explored.On the other hand,static settlement was used to obtain super monodispersed nano silica,then angle-dependent SiO2 PCs were obtained by gravity sedimentation method,and the application in anti-counterfeiting was explored.The main research results are as follows:(1)Fabrication of photonic crystal pigments.SiO2 APCs were prepared using vertical deposition and gravity deposition methods,with the gravity deposition process being simple and suitable for large-scale production.As an absorber,acetylene carbon black can improve the color saturation of photonic crystals.As its addition increased from 0.03 wt%to 0.12 wt%,the color saturation and uniformity continuously improved,with the best effect achieved at 0.09 wt%.The most uniform color was achieved at 40℃,and the coffee-ring phenomena appeared with increasing temperature.By cross-linking and curing into a film,acrylic resin can protect and isolate SiO2/ACET APC structures,significantly improving their abrasion resistance and liquid resistance.The SiO2/ACET APC microcapsules constructed can be used as pigments to prepare photonic crystal coatings or inks.(2)Large-area fabrication of amorphous photonic crystal and patterning applications.SiO2 APCs were prepared on PVC substrates using a spray coating method,and structural colors were obtained by controlling the size of SiO2 microsphere particles.The thickness of SiO2 APCs film increased with more layers of spray coatings,resulting in lighter and whitened structural color.The colors observed from 90°,60°,and 30° angles were basically consistent,revealing low angle dependency in the structural colors.Mixing two different sizes of SiO2 microspheres in a certain ratio produced an APC structure,and the reflection peak of the mixed APC moved between the reflection peaks of the two particle sizes.With mass ratios close to 1:1,the color saturation and structural ordering were relatively poor.When PVP was added into the assembly,SiO2/ACET/PVP APCs were obtained,with PVP distributed in the gaps between SiO2 microspheres.This caused the photonic crystal lattice spacing to increase and the photonic bandgap to redshift.PVP promoted the dispersion of SiO2 microspheres and carbon black,enhanced APC structural ordering,and increased color saturation.By using molds for spray coating and applying acrylic resin on top of APCs,protective and isolating films can be formed,enabling the rapid patterning application of structural colors.(3)Fabrication of visible light and liquid-responsive SiO2 PC structures.By increasing the concentration of SiO2 microspheres to 10 wt%,it can be used as photonic crystal ink for direct writing,and vivid color was presented.SiO2 PCs with red and green structural colors were prepared from 280 nm and 250 nm Si02 suspensions through rapid evaporation,displaying angle-dependent color change effects.After heat treatment,the orderliness and adhesion of the photonic crystals were improved,with SiO2 microspheres arranging more tightly.After a settling and layering treatment,the particle size of SiO2 microspheres became more uniform.Through gravity deposition,long-range ordered SiO2 PC structures can be formed,displaying bright colors and angle-dependent color variations.In some liquid,SiO2 PC powder transformed from white to brightly colored structural colors,and reverted to white when dried.This reversible property can be utilized in liquid sensing and anti-counterfeiting applications.