Synthesis and characterization of ordered arrays of topological defects in mesoporous silica films

H. W. Hillhouse, J. W. Van Egmond, M. Tsapatsis, J. C. Hanson, J. Z. Larese

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

Abstract

Defects are commonly found throughout crystalline solids and often have a pronounced effect on mechanical, optical, chemical, and transport properties.1 Liquid-crystalline materials also contain defects resulting in topologies where the director field is undefined at a point or on a curve at the defect core.2 In both the crystalline and liquid-crystalline state, defects typically disrupt long-range order, rendering the material isotropic at large length scales. Acid synthesis of mesoporous silica proceeds through a liquid-crystalline stage3 in which defects determine the channel orientation of the resulting porous material. Previously, hexagonal phase mesoporous silica films have been grown with channels dominantly oriented parallel to the substrate.4-6 Here, we report that ordered arrays of topological defects can be generated leading to mesoporous silica films with long-range orientation and rotational order with approximately half of the channels oriented perpendicular to the substrate by growing the films epitaxially on a crystalline substrate in a shear flow field. Two-dimensional X-ray diffraction patterns recorded from films grown on mica are 'single-crystal-like,' exhibiting 6-fold symmetry that is rotationally invariant over the entire film.

Original languageEnglish (US)
Pages (from-to)2888-2893
Number of pages6
JournalChemistry of Materials
Volume12
Issue number10
DOIs
StatePublished - Nov 2 2000

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