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A lesson from the unusual morphology of silica mesoporous crystals: Growth and close packing of spherical micelles with multiple twinning
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2006 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 45, no 39, 6516-6519 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2006. Vol. 45, no 39, 6516-6519 p.
Keyword [en]
crystal growth, electron microscopy, mesoporous materials, silica, surfactants
Identifiers
URN: urn:nbn:se:su:diva-25028DOI: 10.1002/anie.200601451OAI: oai:DiVA.org:su-25028DiVA: diva2:198759
Note
Part of urn:nbn:se:su:diva-7651Available from: 2008-05-12 Created: 2008-05-09 Last updated: 2010-04-14Bibliographically approved
In thesis
1. A structural study into the boundary surface and associated curvature of three-dimensional mesoporous silica crystals
Open this publication in new window or tab >>A structural study into the boundary surface and associated curvature of three-dimensional mesoporous silica crystals
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Since their first discovery in the early 1990s, mesoporous crystals (MCs) have fascinated researchers in various fields because of their interesting structures and their potential uses. Electron crystallography (EC) gives the direct three-dimensional (3D) realization of a crystal as a reconstructed electrostatic potential map (EPM). Various 3D-EPMs of silica MCs with cubic symmetry have been previously obtained by EC.

The main task in this thesis is the development of structural analyses focusing on MCs and thus to evaluate the properties of periodic mesopores within EC data. How MC structures can be described and solved by EC is discussed in terms of the interpretation of the reconstructed 3D-EPM. Assuming a regime of an equi-potential surface (EPS), a structural description for MCs is suggested as a surface that optimizes the curvature elasticity evaluated on every EPS. The geometric properties of cubic MCs so far already reconstructed by EC, are then analyzed on the basis of the optimized EPSs. The analysis provides the property of the mesopores independently from gas adsorption measurements. A large cage-like MC is further studied by in-situ synchrotron powder X-ray diffraction to help understand the nitrogen adsorption process onto the mesopore wall.

As an additional study, a silica MC showing its crystal morphologies of icosahedron, decahedron, etc. is studied. Results by EC suggest that the spherical uni-modal cages form the cubic close packing. The morphologies observed are explained in terms of the multiple twinning, which is analogous to metal nanoparticles. The occurrence of multiple twinning in MCs is discussed in light of the synthesis condition and the shape of micelles.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2008. 109 p.
Keyword
mesoporous crystal, electron crystallography, electrostatic potential map, equi-potential surface, curvature, multiplly-twinned particle
National Category
Other Basic Medicine
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-7651 (URN)978-91-7155-672-1 (ISBN)
Public defence
2008-06-02, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:30
Opponent
Supervisors
Available from: 2008-05-12 Created: 2008-05-09 Last updated: 2011-03-01Bibliographically approved
2. Synthesis and Characterization of Functionalized Silica Mesoporous Crystals: Cationic Surfactant and Co-structure Directing Agent System
Open this publication in new window or tab >>Synthesis and Characterization of Functionalized Silica Mesoporous Crystals: Cationic Surfactant and Co-structure Directing Agent System
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This dissertation has been focused on the synthesis and characterization of novel functionalized silica mesoporous crystals by using cationic surfactant and co–structure directing agents (CSDA), the central concept of the synthesis method is to build proper organic/inorganic interactions by introducing CSDA into the synthesis system.

By using cationic surfactant as template and anionic CSDA, carboxylic group functionalized mesoporous silicas were successfully synthesized. Well ordered 2D p6mm, cubic Fm-3m, mixture of CCP (Fm-3m) and HCP (P63/mmc), and cubic Fd-3m with uniform carboxylic group distribution have been obtained. Besides, we have investigated the Fm-3m/Fd-3m type intergrowth and new type defects observed in the Fd-3m structure using transmission electron microscopy (TEM) and proposed a “polyhedron packing” model.

New amphoteric, inorganic amino acid with highly ordered mesopores were synthesized. Uniform distribution of acid and base organic groups on the mesopore surfaces were formed by interactions between the counter charged surfactant head groups and ionic parts of CSDAs. It has been demonstrated that organic (–NH2 and –COOH) pairs incorporated in the mesopore walls behave as natural amino acids, collectively exhibiting an isoelectric point of ~6.0. Moreover, we have demonstrated that the inorganic amino acid is an efficient catalyst for the reaction between aldehydes and carbon nucleophiles.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2010. 82 p.
Keyword
Mesoporous silica, Template synthesis, Functionalization, Electron microscopy, Defects, Crystal growth, Catalysis
National Category
Inorganic Chemistry
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-38398 (URN)978-91-7447-029-1 (ISBN)
Public defence
2010-05-18, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2010-04-26 Created: 2010-04-13 Last updated: 2010-04-14Bibliographically approved

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