Studies On Preparation Of Nano TiO₂/SiO₂ Multilayer Film Via Layer-by-Layer Dipping And Their Structural Color Properties

Nano periodic structure of photonic crystal interacts with light can show a beautiful struture which is not easily influenced by environment and also not easily changes with the passage of time. One-dimensional(1D) photonic crystal can be made easily due to its simple struture and has the properties of 2D and 3D photonic crystals, so it is one of the important ways of building artificial structural color.This article, by means of using TiO2 nanoparticles and SiO2 nanoparticles instead of organic polymer, aseembled a series of TiO2/SiO2 photonic crystals via layer-by-layer self-assembly.First of all, TiO2 sol was prepared through hydrolysis reaction under acid condition. We investigated the influence of hydrolysis pH, reaction time, precursor adding time, the amount of deionized water on hydrolysis reaction. The results indicate that the average particle size of the prepared TiO2 sol is 9nm±nm, the dispersibility is high under the reaction condition of pH=1.5,2h as reaction time,30min as precursor adding time,20mL ethanol,200mL deionized water and 1mL acetic acid.Second, SiO2 sol was chemically modified by 3-aminopropyl triethoxysilane. After chemical modification, the size of SiO2 sol is uniform and the surface electrical changes from negative to positive under the reaction condition of pH=2.5,30℃.Afterwards, we investigated the influence of pH,concentration on the size and Zeta potential of TiO2 and SiO2 sol with the opposite charge. Then we aseembled the TiO2 films and SiO2 films by using different concentration of sol. When the TiO2 is 0.05wt%～0.1wt% and SiO2 is 0.1 wt%～0.3wt%, the films is smooth and uniform.Finally, a series of photonic crystals were prepared via layer-by-layer self-assembly dip-coating method.We also investigated the thickness and flatness of films, the reflective character and the angle dependent features of photonic crystal. The results show that with the increase of the incident angle, the first level reflection wavelength moves to shorter wavelength (blue shift) and proper optical thickness of the high and low refractive index region can assemble phonic crystals thin films with bright structural color. The series of photonic crystals made by using this process without organic polymer can shorten the period of preparation of photonic crystals so that it can reduce the time of preparation of photonic crystals.