Article abstract
Nature Materials 5, 400 - 408 (2006)
doi:10.1038/nmat1636
Subject Categories: Separation materials | Nanoscale materials | Porous materials
Mechanistic principles of nanoparticle evolution to zeolite crystals
Tracy M. Davis1, Timothy O. Drews1, Harikrishnan Ramanan1,2, Chuan He1, Jingshan Dong1, Heimo Schnablegger3, Markos A. Katsoulakis4, Efrosini Kokkoli1, Alon V. McCormick1, R. Lee Penn2 and Michael Tsapatsis1
Abstract
Precursor nanoparticles that form spontaneously on hydrolysis of tetraethylorthosilicate in aqueous solutions of tetrapropylammonium (TPA) hydroxide evolve to TPA-silicalite-1, a molecular-sieve crystal that serves as a model for the self-assembly of porous inorganic materials in the presence of organic structure-directing agents. The structure and role of these nanoparticles are of practical significance for the fabrication of hierarchically ordered porous materials and molecular-sieve films, but still remain elusive. Here we show experimental findings of nanoparticle and crystal evolution during room-temperature ageing of the aqueous suspensions that suggest growth by aggregation of nanoparticles. A kinetic mechanism suggests that the precursor nanoparticle population is distributed, and that the 5-nm building units contributing most to aggregation only exist as an intermediate small fraction. The proposed oriented-aggregation mechanism should lead to strategies for isolating or enhancing the concentration of crystal-like nanoparticles.
- University of Minnesota, Department of Chemical Engineering and Materials Science, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, USA
- University of Minnesota, Department of Chemistry, B-4, 139 Smith Hall, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA
- Anton Paar GmbH, Anton-Paar-Str. 20, A-8054 Graz, Austria
- University of Massachusetts, Department of Mathematics and Statistics, 710 North Pleasant Street, Amherst, Massachusetts 01003, USA
Correspondence to: Michael Tsapatsis1 e-mail: tsapatsi@cems.umn.edu
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