Itzhaik Alkotzer Yafit, Grzegorzewski Franziska, Belausov Eduard, Zelinger Einat, Mechrez Guy
Department of Food Sciences, Institute of Postharvest and Food Sciences, Agricultural Research Organization (ARO), Volcani Center 68 HaMaccabim Road Rishon Letzion 7505101 Israel
Agro-Nanotechnology and Advanced Materials Center, Agricultural Research Organization (ARO), Volcani Center 68 HaMaccabim Road Rishon Letzion 7505101 Israel.
RSC Adv. 2019 Dec 2;9(68):39611-39621. doi: 10.1039/c9ra07597f.
Oil-in-water Pickering emulsions are stabilized by functionalization of hydrophilic silica nanoparticles with two organosilane precursors of opposite polarity, dodecyltriethoxysilane (DTES) and 3-(aminopropyl)triethoxysilane (APTES), in a two-step emulsification procedure. The modification of the silica nanoparticles is verified by Fourier transform infrared (FTIR) spectroscopy analysis. The stabilization of the oil droplets by silica is confirmed by tracing the localization of the colloidal silica nanoparticles at the oil-water interface, as observed by confocal fluorescence microscopy. In comparison to modification of the silica nanoparticles prior to the emulsification, functionalization of silica with both organosilanes achieves enhanced emulsion stability and homogeneity, by forming a polysiloxane network between the silica nanoparticles, through polymerization of the organosilanes in the presence of water. The polysiloxane network fixes the silica in place as solid shells around the emulsion droplets, in structures called colloidosomes. These colloidosome shell structures are visualized using confocal microscopy and cryogenic scanning electron microscopy, the latter method successfully enables the direct observation of the silica nanoparticles embedded in the polysiloxane matrix around the oil droplets. Stabilizing the Pickering emulsion droplets and forming silica-based colloidosome shells is dependent on the extent of the hydrolysis and polycondensation reaction of the two organosilanes.
水包油型Pickering乳液通过两步乳化程序，用两种极性相反的有机硅烷前驱体——十二烷基三乙氧基硅烷（DTES）和3-(氨丙基)三乙氧基硅烷（APTES）对亲水性二氧化硅纳米颗粒进行功能化处理来实现稳定。通过傅里叶变换红外（FTIR）光谱分析验证了二氧化硅纳米颗粒的改性。通过共聚焦荧光显微镜观察追踪胶体二氧化硅纳米颗粒在油水界面的定位，证实了二氧化硅对油滴的稳定作用。与乳化前对二氧化硅纳米颗粒进行改性相比，用两种有机硅烷对二氧化硅进行功能化处理，通过在水存在下有机硅烷的聚合，在二氧化硅纳米颗粒之间形成聚硅氧烷网络，从而提高了乳液的稳定性和均匀性。聚硅氧烷网络将二氧化硅固定在乳液滴周围形成固体壳层，这种结构称为胶体囊泡。使用共聚焦显微镜和低温扫描电子显微镜对这些胶体囊泡壳结构进行了可视化，后一种方法成功地实现了对嵌入油滴周围聚硅氧烷基质中的二氧化硅纳米颗粒的直接观察。稳定Pickering乳液滴并形成基于二氧化硅的胶体囊泡壳取决于两种有机硅烷的水解和缩聚反应程度。
