Studies On Preparation Of TiO₂/SiO₂Photonic Crystals Via Layer-by-Layer Self-Assembly And Their Structural Color Properties

Photonic crystals can control the movement of photons to manipulate the transmission of electromagnetic wave and then to produce bright saturate structural color because of the characteristics of the photonic band gap and the photon localization. Structural color displayed by photonic crystals is generated by light interacting with nano periodic structure. The bright strucrural color is not easily influenced by environment and also not easily changes with the passage of time. The research of structural color of photonic crystals is comprehensive. The preparation of one-dimensional heterostructure photonic crystals is relatively simple and their structural color is gorgeous so it’s one of the important ways of building artificial structural color.This article uses TiO2nanoparticles and SiO2nanoparticles as assembly building block. We assembled a series of heterostructure TiO2/SiO2photonic crystals via layer-by-layer self-assembly dipping-pulling method.First of all, TiO2sol was prepared through hydrolyzing n-Butyl titanate under acid condition. We investigated the influence of hydrolysis pH, reaction time, precursor adding time, aging time and the amount of precursor on the particle size and Zeta potential of the prepared TiO2sol. The results indicate that the average particle size of the prepared TiO2sol is8nm±1nm, the dispersibility is high and Zeta potential is larger than25mV under the reaction condition of pH=1.5,2h as reaction time,25min-45min as precursor adding time,4d as aging time and the relative volumn concentration of precursor less than3.0%.Second, SiO2sol was physically modified by polyvinylamine and tetraethylenepentamine and chemically modified by3-aminopropyl triethoxysilane respectively. The average size and Zeta potential of the sol before and after modification were measured by DLS. The results show that the simple physical modification can’t get stable SiO2sol whose particle size has little change, Zeta potential is positive and dispersibility is good. While after chemical modification, the size of SiO2sol has little change, PDI is lower than0.20and Zeta potential is28mV±3mV. That is to say, chemical modification can get stable SiO2sol whose particle size has little change, Zeta potential is positive and dispersibility is high. Afterwards, we investigated the influence of alternate repetition times, the concentration of SiO2sol, using AP-SiO2sol or not, the pH value of SiO2sol and the pulling rate on the assembled thin films. The more the alternating repetition times is, the thicker the film is. The smaller the concentration of SiO2sol is, the thicker the film is. The thickness of the film assembled by AP-SiO2and SiO2sol is thicker than that assembled by cationic reagent PVAm and SiO2sol. With the increase of pH value of SiO2sol, the adsorption quantity decreases. Under the same conditions, the thickness and the regularity degree of the film pulled with250μm/s are higher than that pulled with500μm/s.Our research finds that the assembled thin film increases by a lateral expansion mode.Finally, a series of photonic crystals were prepared via layer-by-layer self-assembly dipping-pulling method. The results show that proper optical thickness of the high and low refractive index region can assemble phonic crystals thin films with bright structural color. With the increase of the number of Bragg stacks, the reflectance increases. With the increase of the incident angle, the first level reflection wavelength moves to shorter wavelength (blue shift).