Particle Technology Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, CH-8092 Zurich, Switzerland.
Particles-Biology Interactions Laboratory, Department of Materials Meet Life, Swiss Federal Laboratories for Materials Science and Technology (Empa), Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland.
J Colloid Interface Sci. 2017 Dec 1;507:95-106. doi: 10.1016/j.jcis.2017.07.096. Epub 2017 Jul 27.
The surface chemistry of synthetic amorphous silicas is essential for their applicational performance and for understanding their interactions with biological matter. Synthesis of silica by flame spray pyrolysis (FSP) allows to control the content and type of hydroxyl groups which also affects the cytolytic activity.
By controlling the FSP process variables, silica nanoparticles with the same specific surface area but different surface chemistry and content of internal silanols are prepared by combustion of hexamethyldisiloxane sprays, as characterized by Raman and infrared spectroscopy, thermogravimetric analysis, and titration with lithium alanate. Cytolytic activity is assessed in terms of membrane damage in human blood monocytes in vitro.
Unlike commercial fumed silica, FSP-made silicas contain a significant amount of internal silanol groups and a high surface hydroxyl density, up to ∼8OH/nm, similar to silicas made by wet-chemistry. Increasing the residence time of particles at high temperature during their synthesis reduces the internal and surface hydroxyl content and increases the relative amount of isolated silanols. This suggests incomplete oxidation of the silica matrix especially in short and "cold" flames and indicates that the silica particle formation pathway involves Si(OH). The surface chemistry differences translate into lower cytolytic activity for "cold-" than "hot-flame" silicas.
合成无定形硅的表面化学性质对其应用性能以及理解其与生物物质的相互作用至关重要。通过火焰喷雾热解（FSP）合成硅，可以控制羟基的含量和类型，这也会影响细胞溶解活性。
通过控制 FSP 工艺变量，用六甲基二硅氧烷喷雾燃烧制备出比表面积相同但表面化学性质和内部硅醇含量不同的纳米硅，通过拉曼和红外光谱、热重分析和与锂铝酸盐滴定进行表征。细胞溶解活性通过体外人血单核细胞的膜损伤来评估。
与商业气相法二氧化硅不同，FSP 法制备的硅含有大量的内部硅醇基团和高表面羟基密度，高达约 8OH/nm，类似于湿法化学制备的硅。在合成过程中增加颗粒在高温下的停留时间会降低内部和表面羟基的含量，并增加孤立硅醇的相对含量。这表明硅基质的氧化不完全，尤其是在短而“冷”的火焰中，这表明硅颗粒的形成途径涉及 Si(OH)。表面化学性质的差异导致“冷火焰”硅比“热火焰”硅的细胞溶解活性更低。
