[Synthesis and property of nano-fumed silica derivative with quaternary ammonium group].

Nano-fumed silica derivative with quaternary ammonium group was synthesized and the antimicrobial activity was investigated. The nano-fumed silica derivative was investigated by Fourier-transform infrared spectroscopy (FTIR). The zeta potential and the size of the nano-fumed silica derivative were measured. The antimicrobial properties of the nano-fumed silica derivative against selected microorganisms were tested by the quantitative suspension method. The zeta potential showed that the isoelectric points of nano-fumed silica and modified nano-fumed silica are pH=4. 8 and pH =10.5-10.8, respectively, and the shift of the isoelectric point is due to the quaternary ammonium salt. The obtained nano-fumed silica derivative inhibited the growth of Gram-negative (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and fungus (Candida albicans). The inhibiting effect of nano-fumed silica derivative on the microorganisms varied with the time of exposure. The bacteriostatic rates were noted to be 99.99%, 99.99% and 94.12% after 15 minutes' exposure, respectively. Thus the results indicate that nano-fumed silica derivative with quaternary ammonium group has significant inhibitory effect on the growth of bacteria.