Institut für Polymerchemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
J Colloid Interface Sci. 2011 Aug 15;360(2):408-14. doi: 10.1016/j.jcis.2011.04.062. Epub 2011 Apr 27.
Aquasols containing silica nanoparticles with diameters of 75 to 95 nm were obtained directly by hydrolysis of 2 wt.% tetraethoxysilane (TEOS) in water in the presence of a non-ionic surfactant. The reaction was catalyzed by hydrochloric acid, ammonia, or sodium hydroxide. The particle size, which mainly depends on the concentration of TEOS in water, was determined by dynamic light scattering (DLS). Whereas the catalysts have almost no influence on the particle size, they very strongly affect the morphology of the silica particles formed. The dried SiO(2) particles obtained via the HCl-catalyzed reaction have film-forming properties and show no measurable BET surface area. SiO(2) particles prepared with ammonia as catalyst form nanoporous films on glass, and the BET surface area of the freeze-dried particles is 540 m(2)/g. Using sodium hydroxide as catalyst results in some agglomeration of uniform spherical particles with a BET surface area of 237 m(2)/g. (29)Si MAS NMR investigations of the freeze-dried particles provide information about the degree of condensation and the ratio of "free" hydroxyl groups. The silica aquasols described have a surprisingly high hydrophilizing effect on hydrophobic fibers (PP, PET). Silica nanoparticles of comparable diameters, prepared by the "Stöber method", dispersed in alcohol do not show any hydrophilizing properties worth to mention.
直接在非离子表面活性剂存在下，通过水解 2wt.%四乙氧基硅烷（TEOS）在水中获得含有直径为 75 至 95nm 的二氧化硅纳米颗粒的水溶胶。该反应由盐酸、氨水或氢氧化钠催化。粒径主要取决于水中 TEOS 的浓度，通过动态光散射（DLS）确定。虽然催化剂对粒径几乎没有影响，但它们对形成的二氧化硅颗粒的形态有很强的影响。通过 HCl 催化反应得到的干燥 SiO(2)颗粒具有成膜性能，并且没有可测量的 BET 比表面积。用氨作为催化剂制备的 SiO(2)颗粒在玻璃上形成纳米多孔膜，并且冷冻干燥颗粒的 BET 表面积为 540m(2)/g。使用氢氧化钠作为催化剂会导致具有 BET 表面积为 237m(2)/g 的均匀球形颗粒的一些团聚。（29）Si MAS NMR 研究冷冻干燥颗粒提供了关于缩合程度和“游离”羟基比例的信息。所描述的水溶胶对疏水性纤维（PP、PET）具有惊人的高亲水化效果。分散在酒精中的具有可比直径的通过“Stöber 方法”制备的二氧化硅纳米颗粒没有表现出任何值得一提的亲水化性质。
