Open AccessMolecular mechanisms of mesoporous silica formation from colloid solution: Ripening-reactions arrest hollow network structures
Author(s) -
Bahanur Becit,
Patrick Duchstein,
Dirk Zahn
Publication year - 2019
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0212731
Subject(s) - nanoparticle , colloid , covalent bond , ostwald ripening , aqueous solution , chemical engineering , economies of agglomeration , colloidal silica , mesoporous silica , materials science , mesoporous material , molecular dynamics , solvent , nanotechnology , chemical physics , chemistry , catalysis , organic chemistry , computational chemistry , engineering , coating
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 SiO 2 /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.