Application And Research Of Structural Color Fabricated By Electrostatic Self-assembly

Structural color is derived from light reflected from nano-scale structure of surface without pigment,and it has attracted growing interest due to its high brightness,high saturation,iridescence and never fading characteristics.As is well known,there is dyeing pollution in the textile industry.If structural color would be used in the textiles,the realization of fabric color will become diversified,safety and durable.Photonic crystals are materials patterned with a periodicity in dielectric constant,which can create a range of forbidden frequencies called a photonic band gap(PBG).Photons with energies existing in PBG cannot propagate through the medium and the incident light will be totally reflected and diffracted,then we can see the structural color.To definite the relation between photonic crystal and structural color,and to direct our further experiments,the theoretical model of photonic crystal was studied firstly.In this paper,we took 3-dimensional photonic crystal with face-centered-cubic(FCC)structure as the sample investigating its optical properties including reflectivity,PBG and related possible influencing factors.FCC Structure was considered into 1-D photonic crystal under the formalism of equivalent layers based on the principle of volume invariably.The influence of the microsphere size,the crystal stack thickness and the incident angle on optical properties was analyzed.The results showed that the optimum particle size range of SiO2 was 200nm-350nm,and with the microsphere size increasing,the positions of PBG moved to the right.With crystal stack thickness increasing,the reflectivity became higher and PBG was more narrow and close.With the incident angle larger,the reflectivity changed slightly while the positions of PBG moved to the left.As the reflectivity of photonic crystals with different structure parameters has been known,we can get their structural color in chromaticity diagram visually through CIE chromatic system.The structural color of silica photonic crystals with 200nm,250nm,300nm,350nm SiO2 particles were blue,green,yellow and red respectively.For silica photonic crystals with the same particle size,with crystal stack thickness increasing,the saturation of structural color changed but the hue was the same.For silica photonic crystals with the same particle size and crystal stack thickness,the wavelength of the structural color got shorter when the incident angle became larger,but when the incident angle increased to some values,the wavelength began longer and the chromaticity coordinates moved closer to the center position of the CIE chromaticity diagram.Electrostatic self-assembly technology is based on electrostatic adsorption and has many advantages such as easy operation,good stability,and rich film forming material.Multilayer structure can be developed on the charged substrate by adsorbing oppositely charged polyelectrolytes layer-by-layer.The premise of making multilayer structure is to make charged nanoparticles with good monodispersity.We determined SiO2 sol-solution preparation method firstly.Then we made SiO2 sol-solution with different particle-size and good monodispersity through controlling the volume of ammonium hydroxide.The key to realize structural color is to make the nanoparticles arrange orderly.Through the experiments,we knew that when the concentration of PDDA was 2.0%,the concentration of SiO2 sol solution was 0.8%and the assembly cycle was 15,the Si02 nanoparticles were close and orderly.The influence of substrate's hydrophily and roughness on Si02 nanoparticles' arrangement was compared.It was found that SiO2 nanoparticles arrange better on the substrate with stronger hydrophilic and lower roughness.Besides,no matter on which substrate,the samples could show different colors under different angles.In this paper,we studied the theoretical model of photonic crystal with different structural parameters and researched the experimental conditions of electrostatic self-assembly technology to make PDDA/SiO2 multilayer structure which can generate structural color.All of those provide a reference for the structural color realization on fabric,and have some theoretical and practical significance.