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Dodecagonal tiling in mesoporous silica
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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2012 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 487, no 7407, 349-353 p.Article in journal (Refereed) Published
Abstract [en]

Recent advances in the fabrication of quasicrystals in soft matter systems have increased the length scales for quasicrystals(1) into the mesoscale range (20 to 500 angstroms). Thus far, dendritic liquid crystals(2), ABC-star polymers(3), colloids(4) and inorganic nanoparticles(5) have been reported to yield quasicrystals. These quasicrystals offer larger length scales than intermetallic quasicrystals (a few angstroms)(1,6), thus potentially leading to optical applications through the realization of a complete photonic bandgap induced via multiple scattering of light waves in virtually all directions(7-9). However, the materials remain far from structurally ideal, in contrast to their intermetallic counterparts, and fine control over the structure through a self-organization process has yet to be attained. Here we use the well-established self-assembly of surfactant micelles to produce a new class of mesoporous silicas, which exhibit 12-fold (dodecagonal) symmetry in both electron diffraction and morphology. Each particle reveals, in the 12-fold cross-section, an analogue of dodecagonal quasicrystals in the centre surrounded by 12 fans of crystalline domains in the peripheral part. The quasicrystallinity has been verified by selected-area electron diffraction and quantitative phason strain analyses on transmission electron microscope images obtained from the central region. We argue that the structure forms through a non-equilibrium growth process, wherein the competition between different micellar configurations has a central role in tuning the structure. A simple theoretical model successfully reproduces the observed features and thus establishes a link between the formation process and the resulting structure.

Place, publisher, year, edition, pages
2012. Vol. 487, no 7407, 349-353 p.
National Category
Chemical Sciences
Research subject
Structural Chemistry
Identifiers
URN: urn:nbn:se:su:diva-80284DOI: 10.1038/nature11230ISI: 000306506500039OAI: oai:DiVA.org:su-80284DiVA: diva2:556847
Note

AuthorCount:5;

Available from: 2012-09-26 Created: 2012-09-17 Last updated: 2017-12-07Bibliographically approved
In thesis
1. A structural investigation into the complexity of mesoporous silica crystals: From a view of curvature and micellar interaction to quasicrystallinity
Open this publication in new window or tab >>A structural investigation into the complexity of mesoporous silica crystals: From a view of curvature and micellar interaction to quasicrystallinity
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mesoporous silica crystals have a large variety of structures mainly due to the versatility of their structure template. The configuration and the chemical state of the templating micellar surfactants, together with the kinetic process of silica will determine the final outcome of the synthesis. Increasing the understanding of the complex formation processes involved will enable a possibilityto fine tune the material for specific uses, today focused into the fields of photoniccrystals, drug delivery, catalysis and separation technology.

In this thesis emphasis is put on (1) increasing the understanding the formation mechanism yielding the different species of mesoporous silica crystals through an in depth study of quasicrystallinity (2) Characterization and description of the structural complexity through various characterization techniquesand also by studying the kinetic structural transformation phenomenon related to the minimal G- and D-surfaces. (3) The structural studies of the versatile surfactant liquid crystals for establishing a thermodynamically stable basis to evaluate the kinetic mesoporous silica growth processes. Furthermorethe thesis both enlightens the possibilities of and contributes to the developmentof electron microscopy characterization techniques.

In these studies, electron microscopy is largely employed in the characterization to give a thorough picture of the mesoporous structures. This is combined with the sample preparation techniques cross-section polishing and ionslicing. Low voltage scanning electron microscopy is utilized for studying the surfaces and cross-sections of various materials at the limit of the resolution. Here, a deep understanding of the electron beam-material interaction is used for a better interpretation of the detected signals. Transmission electron microscopyis combined with electron crystallographic reconstruction to yield a three dimensional structural model. For determination of the quasicrystallinity level for a structure of dodecagonal tiling, revealed in the scope of this study,a phason strain analysis was made.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2012. 110 p.
Keyword
electron microscopy, mesoporous silica, quasicrystal, minimal surface
National Category
Chemical Sciences
Research subject
Structural Chemistry
Identifiers
urn:nbn:se:su:diva-82382 (URN)978-91-7447-602-6 (ISBN)
Public defence
2012-12-21, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:30 (English)
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Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 7: Manuscript.

Available from: 2012-11-29 Created: 2012-11-13 Last updated: 2012-11-20Bibliographically approved

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