Preparation of modified SiO2 colloidal spheres with succinic acid and the assembly of colloidal crystals

SiO₂ colloidal spheres were synthesized by Stöber method. In order to enhance surface charge of the SiO₂ spheres, they were modified with succinic acid. Scanning electron microscope (SEM) shows that the average size of modified SiO₂ spheres is 473 nm, and its distribution standard deviation is less than 5%; Fourier-transform infrared spectra (FT-IR) and X-ray photoelectron spectrometer (XPS) results indicate that one end of succinic acid is chemically bonded to the SiO₂ spheres through esterification; Zeta potential of the modified SiO₂ spheres in water solution is improved from -53.72 to -67.46 mV, and surface charge density of the modified SiO₂ spheres is enhanced from 0.19 to 0.94 μC/cm². SiO₂ colloidal crystal was fabricated from aqueous colloidal solution by the vertical deposition method at 40℃ and 60% relative humidity. SEM images show that the sample of SiO₂ colloidal crystal is face-centered cubic (fcc) structure with its (111) planes parallel to the substrate. Transmission measurement shows the existence of photonic band gap at 1047 nm.