Biological Physics, Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
Applied Surface Chemistry, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
Adv Colloid Interface Sci. 2017 Sep;247:426-434. doi: 10.1016/j.cis.2017.03.002. Epub 2017 Mar 11.
We review the use of various types of emulsions as media for synthesis of porous silica particles. The use of high internal phase emulsions, i.e. emulsions with a high ratio of dispersed to continuous phase, is an approach that has attracted considerable attention. Polymerization of the continuous phase followed by removal of the dispersed phase leads to a material with an even distribution of pores if the emulsion droplets are uniform in size. Another route is to use particle stabilized emulsions as template. This will lead to either hydrophilic or hydrophobic porous silica particles depending on whether the templating emulsion is oil-in-water or water-in-oil, respectively. Use of double emulsions as templates is a way to obtain porous particles with hierarchical porosity, usually both macropores and mesopores. Templating amphiphiles, which are often polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymers, are needed in order to obtain materials with highly ordered pore structure. Non-ordered mesoporous silica with small particle size and relatively large pores can be obtained by emulsifying a silica precursor together with an inert solvent in water and allowing the silica to gel within the drops. Hollow silica spheres, i.e. spherical particles with a void in the middle, can be prepared by using emulsion drops as templates around which silica polymerizes. The particles have nanometer-sized pores penetrating the shell.
我们回顾了各种类型的乳液作为合成多孔硅粒子的介质的用途。使用高内相比乳液（即分散相与连续相之比高的乳液）是一种引起了相当多关注的方法。如果乳液液滴大小均匀，则聚合连续相并除去分散相后，会得到具有均匀孔分布的材料。另一种途径是使用颗粒稳定乳液作为模板。根据乳化液是油包水还是水包油，这将导致得到亲水或疏水多孔硅粒子。使用双重乳液作为模板是一种获得具有分级孔结构的多孔粒子的方法，通常是大孔和中孔。为了获得具有高度有序孔结构的材料，需要使用两亲性模板剂，其通常是聚氧乙烯-聚氧丙烯-聚氧乙烯嵌段共聚物。通过将硅前驱体与惰性溶剂一起乳化在水中并使硅在液滴内凝胶化，可以得到具有小粒径和相对大孔的无序介孔硅。可以使用乳液滴作为模板，在其周围聚合硅，制备中空硅球，即中间有空腔的球形粒子。这些粒子具有贯穿壳层的纳米级孔。
