Wu Yuanting

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°C 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.