Studies On Preparation Of ZrO₂/SiO₂ Photonic Crystals Structural Color Via Layer-by-layer Self-Assembly

There are many examples of colors that are not chemical but rather physical in nature. Compared to pigment color, structural color has the characteristics of high brightness, high saturation and resistances. Artificial photonic crystals are the main source of artificial structural color. Photonic crystals can be divided into one-, two- and three-dimensional photonic crystals. Compared to two- and three-dimensional photonic crystals, one-dimensional photonic crystals have simpler structures and they are readily to be prepared.In this thesis, nano-ZrO₂ sol and nano-SiO₂ sol were chosen to fabricate one-dimentional photonic crystals by spin coating.Firstly, ZrO₂ sol with small diameter and narrow size distribution was synthesized by a one-step hydrothermal method. In the preparation process, ZrO?NO3?2·8H2O is used as the precursor and NH3H2O as precipitant. The influence of reaction temperature, reaction pH, reaction time and aging time on the properties of the products were investigated. The optimum reaction condition were obtained as follow:T=160?, pH= 3.5, t= 11 h. The product is clear, stable and light blue opalescent sol with particle diameter of 29.65nm, PDI of 0.251, Zeta potential of 27.9 mV.Secondly, the influences of concentration of SiO₂ sol and pH to its size, PDI and Zeta potential were examined. The uniform films were prepared by ZrO₂ sol and SiO₂ sol. The influences of sol concentration, coating speed and times on the thickness of the oxide film were studied as well.Thirdly, ZrO₂ and SiO₂ sols were used to assemble 1D photonic crystals with layer-by layer spin coating procedure. In the fabrication, the influences of the concentration of sol, spinning speed and stack numbers on the thickness of the films were investigated. The optical properties of the ID photonic crystals were investigated. The results are as follows:the photonic band gap turns blue when the angle of the incident light increases, which proves the angular dependence of 1D photonic crystals; the photonic band gap turns red when the period of Bragg stack is wider; the reflection peak becomes stronger as the numbers of Bragg stack increase. 1D photonic crystals with different structural color were prepared by adjusting the thickness of high and low refractive index films, the mechanism of layer-by-layer ?LbL? assembly of thin films was studied as well.