title: Modeling spontaneous formation of precursor nanoparticles in clear-solution zeolite synthesis.
abstract: We present a lattice model describing the formation of silica nanoparticles in the early stages of the clear-solution templated synthesis of silicalite-1 zeolite. Silica condensation/hydrolysis is modeled by a nearest-neighbor attraction, while the electrostatics are represented by an orientation-dependent, short-range interaction. Using this simplified model, we show excellent qualitative agreement with published experimental observations. The nanoparticles are identified as a metastable state, stabilized by electrostatic interactions between the negatively charged silica surface and a layer of organic cations. Nanoparticle size is controlled mainly by the solution pH, through nanoparticle surface charge. The size and concentration of the charge-balancing cation are found to have a negligible effect on nanoparticle size. Increasing the temperature allows for further particle growth by Ostwald ripening. We suggest that this mechanism may play a role in the growth of zeolite crystals.
authors.affiliation: Department of Chemical Engineering, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: M
authors.initials: M
authors.lastname: Jorge
authors.forename: Scott M
authors.initials: SM
authors.lastname: Auerbach
authors.forename: P A
authors.initials: PA
authors.lastname: Monson
mesh_terms: D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D017641:Zeolites / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D012996:Solutions; D017641:Zeolites; D012822:Silicon Dioxide