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3D Electron crystallography: Real space reconstruction and reciprocal space tomography
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). (Professor Xiaodong Zou)
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electron crystallography is an important technique for studying micro- and nano-sized materials. It has two important advantages over X-ray crystallography for structural studies: 1) crystals millions of times smaller than those needed for X-ray diffraction can be studied; 2) it is possible to; focus the electrons to form an image. The local atomic arrangement can be seen directly by high-resolution transmission electron microscopy (HRTEM). The crystallographic structure factor phases, which are lost in recording diffraction patterns, are present in HRTEM images and can be determined experimentally. The main disadvantages of electron crystallography compared to X-ray diffraction are that the data are difficult to collect, often incomplete and suffer from dynamic scattering. New methods need to be developed to overcome these problems. In this work, structure determination of several unique and complex porous materials including zeolites and mesoporous silica is demonstrated. None of the structures of these materials could be solved by X-ray crystallography. New techniques are also developed in order to overcome the disadvantages of electron crystallography. The new techniques include a digital sampling method for collecting precession electron diffraction data and a rotation method for automatic collection of complete 3D electron diffraction data. A number of practical issues concerning data collection and data processing are described and the data quality is analysed.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University , 2010. , 72 p.
Keyword [en]
Electron crystallography, Electron microscopy, Porous materials
National Category
Chemical Sciences
Research subject
Structural Chemistry
Identifiers
URN: urn:nbn:se:su:diva-39034ISBN: 978-91-7447-044-4 (print)OAI: oai:DiVA.org:su-39034DiVA: diva2:318051
Public defence
2010-06-08, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted.Available from: 2010-05-17 Created: 2010-05-06 Last updated: 2010-05-14Bibliographically approved
List of papers
1. Synthesis and structure of polymorph B of zeolite Beta
Open this publication in new window or tab >>Synthesis and structure of polymorph B of zeolite Beta
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2008 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, no 9, 3218-3223 p.Article in journal (Refereed) Published
Abstract [en]

It was found that either polymorph B or polymorph C of zeolite beta can be obtained from the same structure directing agent: 4,4-dimethyl-4-azonia-tricyclo[5.2.2.02,6]undec-8-ene hydroxide. The synthesis occurs through a consecutive process where polymorph B is first formed and then transformed into polymorph C. It is possible to produce a zeolite highly enriched in polymorph B, provided that the transformation of this phase into polymorph C is slowed down up to the point where polymorph C is only detected at trace levels. The structure of polymorph B was determined for the first time by electron crystallography with SAED and HRTEM from areas of unfaulted polymorph B crystals.

Identifiers
urn:nbn:se:su:diva-15423 (URN)10.1021/cm8002244 (DOI)000255623400061 ()
Available from: 2008-12-02 Created: 2008-12-02 Last updated: 2017-12-13Bibliographically approved
2. A tri-continuous mesoporous material IBN-9 with the silica pore wall following a hexagonal minimal surface
Open this publication in new window or tab >>A tri-continuous mesoporous material IBN-9 with the silica pore wall following a hexagonal minimal surface
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2009 (English)In: Nature Chemistry, ISSN 1755-4349, Vol. 1, 123-127 p.Article in journal (Refereed) Published
Abstract [en]

Ordered porous materials with unique pore structures and pore sizes in the mesoporous range (2–50 nm) have many applications in catalysis, separation and drug delivery. Extensive research has resulted in mesoporous materials with onedimensional, cage-like and bi-continuous pore structures. Three families of bi-continuous mesoporous materials have been made, with two interwoven but unconnected channels, corresponding to the liquid crystal phases used as templates. Here we report a three-dimensional hexagonal mesoporous silica, IBN-9, with a tri-continuous pore structure that is synthesized using a specially designed cationic surfactant template. IBN-9 consists of three identical continuous interpenetrating channels, which are separated by a silica wall that follows a hexagonal minimal surface. Such a tri-continuous mesostructure was predicted mathematically, but until now has not been observed in real materials.

Keywords: mesoporous structure, electron microscopy, self-assembly

Identifiers
urn:nbn:se:su:diva-36770 (URN)10.1038/nchem.166 (DOI)000268996400014 ()
Available from: 2010-01-26 Created: 2010-01-26 Last updated: 2010-05-14Bibliographically approved
3. The ITQ-37 mesoporous chiral zeolite
Open this publication in new window or tab >>The ITQ-37 mesoporous chiral zeolite
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2009 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 458, no 7242, 1154-1157 p.Article in journal (Refereed) Published
Abstract [en]

The synthesis of crystalline molecular sieves with pore dimensions that fill the gap between microporous and mesoporous materials is a matter of fundamental and industrial interest(1-3). The preparation of zeolitic materials with extralarge pores and chiral frameworks would permit many new applications. Two important steps in this direction include the synthesis(4) of ITQ-33, a stable zeolite with 18 x 10 x 10 ring windows, and the synthesis(5) of SU-32, which has an intrinsically chiral zeolite structure and where each crystal exhibits only one handedness. Here we present a germanosilicate zeolite (ITQ-37) with extralarge 30-ring windows. Its structure was determined by combining selected area electron diffraction ( SAED) and powder X-ray diffraction (PXRD) in a charge-flipping algorithm(6). The framework follows the SrSi2 (srs) minimal net(7) and forms two unique cavities, each of which is connected to three other cavities to form a gyroidal channel system. These cavities comprise the enantiomorphous srs net of the framework. ITQ-37 is the first chiral zeolite with one single gyroidal channel. It has the lowest framework density (10.3 T atoms per 1,000 angstrom(3)) of all existing 4-coordinated crystalline oxide frameworks, and the pore volume of the corresponding silica polymorph would be 0.38 cm(3) g(-1).

Identifiers
urn:nbn:se:su:diva-31943 (URN)10.1038/nature07957 (DOI)000265754600044 ()0028-0836 (ISBN)
Available from: 2009-12-01 Created: 2009-12-01 Last updated: 2017-12-12Bibliographically approved
4. Precession Electron Diffraction Using a Digital Sampling Method
Open this publication in new window or tab >>Precession Electron Diffraction Using a Digital Sampling Method
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2010 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 211, no 1, 47-55 p.Article in journal (Refereed) Published
Abstract [en]

A software-based method for collecting precession electron diffraction (PED) patterns isdescribed. The PED patterns are obtained on a computer controlled transmission electronmicroscope. A series of electron diffraction (ED) patterns are collected as still ED frames atequal intervals while the electron beam is precessed by one period (360°) around the opticalaxis. A PED pattern is obtained by combining the different ED frames, which resembles thesampling of a conventional PED pattern. Since intermediate ED frames are collected, it ispossible to perform different post-processing strategies on the ED data. This can be used forgeometric corrections to obtain accurate integrated intensities. The alignments and datacollection are fully automated and controlled by software. The data quality is comparable towhat can be achieved using specialized hardware for precession. The PED data can be usedfor structure solution and refinement with reasonably good R-values.

Place, publisher, year, edition, pages
Elsevier B.V., 2010
Keyword
Precession electron diffraction; crystallography; data processing; crystal structure; TEM control; Lorentz correction
National Category
Environmental Sciences
Identifiers
urn:nbn:se:su:diva-39241 (URN)10.1016/j.ultramic.2010.09.008 (DOI)
Available from: 2010-05-14 Created: 2010-05-14 Last updated: 2017-12-12Bibliographically approved
5. Collecting 3D electron diffraction data by the rotation method
Open this publication in new window or tab >>Collecting 3D electron diffraction data by the rotation method
2010 (English)In: Zeitschrift fur Kristallographie, ISSN 0044-2968, Vol. 225, no 2-3, 94-102 p.Article in journal (Refereed) Published
Abstract [en]

A new method for collecting complete three-dimensional electron diffraction data is described. Diffraction data is collected by combining electron beam tilt at many very small steps, with rotation of the crystal in a few but large steps. A number of practical considerations are discussed, as well as advantages and disadvantages compared to other methods of collecting electron diffraction data.

Keyword
Electron diffraction, data collection, 3D diffraction data
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-31968 (URN)10.1524/zkri.2010.1202 (DOI)000276505200007 ()
Available from: 2009-12-01 Created: 2009-12-01 Last updated: 2017-12-12Bibliographically approved

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