myU OneStop


Kokkoli Research GroupDepartment of Chemical Engineering and Materials Science (CEMS)

Mechanistic Principles of Nanoparticle Evolution to Zeolite Crystals

Davis, T.M., Drews, T.O., Ramanan, H., He, C., Dong, J., Schnablegger, H., Katsoulakis, M.A., Kokkoli, E., McCormick, A.V., Penn, R.L., and Tsapatsis, M.

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.

Citation
Davis, T.M., Drews, T.O., Ramanan, H., He, C., Dong, J., Schnablegger, H., Katsoulakis, M.A., Kokkoli, E., McCormick, A.V., Penn, R.L., and Tsapatsis, M. "Mechanistic Principles of Nanoparticle Evolution to Zeolite Crystals", Nature Materials, 2006, 5 (5): 400-408.
Publisher's Link
PDF