Preparation of SiO2 microspheres with sodium ions and self-assembly of photonic crystals

SiO2 microspheres were prepared via a novel co-precipitation process.The Na + ions were introduced by adding sodium chloride and metal sodium in solution systems for improving surface charge of the SiO2 microspheres.And then SiO2 photonic crystals were fabricated by the vertical deposition method.The electrical properties,micromorphology and optical properties were characterized by zeta potential instrument,scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy and Uv-Vis-Nir spectrophotometer.Zeta potential of the SiO2 microspheres modified by sodium chloride and metal sodium were averagely heightened 11.39 mV and 13.52 mV respectively in ethanol solution.EDS spectra showed that there was Na element in the SiO2 microspheres.SEM images showed that the average size of the SiO2 microspheres modified by sodium chloride and metal sodium were 380 nm and 354 nm respectively,larger than that of the unmodified ones,and their distribution standard deviation was less than 5%,and the sample of SiO2 photonic crystals was face-centered cubic structure with their (111) planes parallel to the substrate.In addition,absorption spectra showed that photonic band gap of the SiO2 photonic crystals was modified by sodium chloride and metal sodium located in 856 nm and 798 nm respectively.Meanwhile,their absorption peaks became narrower and higher and exhibited a red-shift phenomenon.