Abstract: SiO₂ nanoparticles were activated by octylamine modified sodium alginate via two ways,physical mixing and chemical grafting.The activated SiO₂ nanoparticles were characterized by FTIR,¹HNMR and DLS,et al.Then Pickering emulsions were prepared with the activated SiO₂ nanoparticles under assistance of ultrasonic wave,and morphology of the emulsions was observed.Experimental results showed that octylamine side chain was successfully grafted onto the sodium alginate.The particle size of activated SiO₂ nanoparticles via both physical mixing and chemical grafting ways is larger than that of unactivated SiO₂ nanoparticles,and increases to 467.0 and 414.4 nm respectively.Surface potential of activated SiO₂ nanoparticles changes to -43.9 and -35.2 mV respectively,which is lower than that of unactivated SiO₂ nanoparticles,which shows a surface potential of -17.0 mV.Meanwhile,the activated SiO₂ nanoparticles reveal better emulsifying properties,especially the nanoparticles activated by chemical grafting way could produce a more stable Pickering emulsion with better droplet dispersion,uniform size and with average particle diameter of 5 μm.

Key words: alginate derivative, SiO₂ nanoparticles, physical mixing, chemical grafting, Pickering emulsions