Computer Chemie Centrum, Lehrstuhl für Theoretische Chemie, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
PLoS One. 2019 Mar 7;14(3):e0212731. doi: 10.1371/journal.pone.0212731. eCollection 2019.
The agglomeration of silica nanoparticles in aqueous solution is investigated from molecular simulations. Mimicking destabilization of colloidal solutions by full removal of protective moieties or surface charge, association of SiO2/Si(OH)4 core/shell particles leads to rapid proton transfer reactions that account for local silanole → silica ripening reactions. Yet, such virtually barrier-less binding is only observed within a limited contact zone. Agglomeration hence leads to the formation of oligomers of nanoparticles, whilst full merging into a compact precipitate is hampered by the need for extended structural reorganisation. Implementing sufficiently fast supply from colloidal solution, our simulations show the development of silica networks comprised of covalently bound, yet not fully merged nanoparticles. Within the oligomerized nanoparticle network, coordination numbers range from 2 to 5 -which is far below closest packing. Our simulations hence rationalize the formation of covalently bound network structures hosting extended pores. The resulting interfaces to the solvent show water immobilization only for the immediate contact layers, whilst the inner pores exhibit solvent mobility akin to bulk water.
从分子模拟角度研究了硅纳米粒子在水溶液中的团聚。通过完全去除胶体溶液的保护基团或表面电荷来模拟胶体的不稳定性，SiO2/Si(OH)4 核/壳粒子的缔合导致快速质子转移反应，从而解释了局部硅醇→硅颗粒的熟化反应。然而，只有在有限的接触区域内才会观察到这种实际上没有障碍的结合。团聚导致纳米粒子的低聚物的形成，而由于需要扩展结构重组，完全合并成紧密的沉淀物受到阻碍。通过从胶体溶液中实现足够快的供应，我们的模拟表明由共价键合但未完全合并的纳米粒子组成的二氧化硅网络的发展。在寡聚纳米粒子网络中，配位数范围从 2 到 5-远低于最紧密堆积。因此，我们的模拟可以解释形成具有扩展孔的共价键合网络结构。与溶剂的界面仅在最接近的接触层中表现出水的固定化，而内部孔则表现出与本体水相似的溶剂流动性。
