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Transmission Electron Microscopy of Graphene and Hydrated Biomaterial Nanostructures: Novel Techniques and Analysis
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Electron Microscopy and Nanoengineering)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transmission Electron Microscopy (TEM) on light element materials and soft matters is problematic due to electron irradiation damage and low contrast. In this doctoral thesis techniques were developed to address some of those issues and successfully characterize these materials at high resolution. These techniques were demonstrated on graphene flakes, DNA/magnetic beads and a number of water containing biomaterials. The details of these studies are given below.

A TEM based method was presented for thickness characterization of graphene flakes. For the thickness characterization, the dynamical theory of electron diffraction is used to obtain an analytical expression for the intensity of the transmitted electron beam as a function of thickness. From JEMS simulations (experiments) the absorption constant λ in a low symmetry orientation was found to be ~ 208 nm (225 ± 9 nm). When compared to standard techniques for thickness determination of graphene/graphite, the method has the advantage of being relatively simple, fast and requiring only the acquisition of bright-field (BF) images. Using the proposed method, it is possible to measure the thickness change due to one monolayer of graphene if the flake has uniform thickness over a larger area.

A real-space TEM study on magnetic bead-DNA coil interaction was conducted and a statistical analysis of the number of beads attached to the DNA-coils was performed. The average number of beads per DNA coil was calculated around 6 and slightly above 2 for samples with 40 nm and 130 nm beads, respectively. These results are in good agreement with magnetic measurements. In addition, the TEM analysis supported an earlier hypothesis that 40 nm beads are preferably attached interior of the DNA-coils while 130 nm beads closer to the exterior of the coils.

A focused ion-beam in-situ lift-out technique for hydrated biological specimens was developed for cryo-TEM. The technique was demonstrated on frozen Aspergillus niger spores which were frozen with liquid nitrogen to preserve their cellular structures. A thin lamella was prepared, lifted out and welded to a TEM grid. Once the lamella was thinned to electron transparency, the grid was cryogenically transferred to the TEM using a cryo-transfer bath. The structure of the cells was revealed by BF imaging. Also, a series of energy filtered images was acquired and C, N and Mn elemental maps were produced. Furthermore, 3 Å lattice fringes of the underlying Al support were successfully resolved by high resolution imaging, confirming that the technique has the potential to extract structural information down to the atomic scale. The experimental protocol is ready now to be employed on a large variety of samples e.g. soft/hard matter interfaces.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , 124 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 917
Keyword [en]
Graphene flakes, magnetic beads/DNA coils, hydrated biomaterials, transmission electron microscopy, focused ion beam/scanning electron microscopy, bright-field/dark-field imaging, high resolution imaging, electron diffraction and cryogenic temperatures
National Category
Engineering and Technology
Research subject
Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-171991ISBN: 978-91-554-8333-3 (print)OAI: oai:DiVA.org:uu-171991DiVA: diva2:513322
Public defence
2012-05-21, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-04-26 Created: 2012-03-30 Last updated: 2012-08-01Bibliographically approved
List of papers
1. A simple TEM method for fast thickness characterization of suspendedgraphene flakes
Open this publication in new window or tab >>A simple TEM method for fast thickness characterization of suspendedgraphene flakes
(English)Manuscript (preprint) (Other academic)
National Category
Nano Technology Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-171983 (URN)
Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2012-08-01
2. Mild sonochemical exfoliation of bromine-intercalated graphite a new route towards graphene
Open this publication in new window or tab >>Mild sonochemical exfoliation of bromine-intercalated graphite a new route towards graphene
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2009 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 42, no 11, 112003- p.Article in journal (Refereed) Published
Abstract [en]

A method to produce suspensions of graphene sheets by combining solution-based bromine intercalation and mild sonochemical exfoliation is presented. Ultrasonic treatment of graphite in water leads to the formation of suspensions of graphite flakes. The delamination is dramatically improved by intercalation of bromine into the graphite before sonication. The bromine intercalation was verified by Raman spectroscopy as well as by x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations show an almost ten times lower interlayer binding energy after introducing Br2 into the graphite. Analysis of the suspended material by transmission and scanning electron microscopy (TEM and SEM) revealed a significant content of few-layer graphene with sizes up to 30 µm, corresponding to the grain size of the starting material

Place, publisher, year, edition, pages
IOP Publishing Ltd, 2009
Keyword
Graphene
National Category
Physical Sciences Organic Chemistry Engineering and Technology
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-111654 (URN)10.1088/0022-3727/42/11/112003 (DOI)000266250300003 ()
Available from: 2009-12-18 Created: 2009-12-18 Last updated: 2016-04-14Bibliographically approved
3. Graphene Formation by Sonochemical Exfoliation of Bromine-intercalated Graphite.Influence of Solvent Properties on Exfoliation Yield and Deposition Outcome
Open this publication in new window or tab >>Graphene Formation by Sonochemical Exfoliation of Bromine-intercalated Graphite.Influence of Solvent Properties on Exfoliation Yield and Deposition Outcome
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-171988 (URN)
Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2012-09-18
4. Real-Space Transmission Electron Microscopy Investigations of Attachment of Functionalized Magnetic Nanoparticles to DNA-Coils Acting as a Biosensor
Open this publication in new window or tab >>Real-Space Transmission Electron Microscopy Investigations of Attachment of Functionalized Magnetic Nanoparticles to DNA-Coils Acting as a Biosensor
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2010 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 41, 13255-13262 p.Article in journal (Refereed) Published
Abstract [en]

The present work provides the first real-space analysis of nanobead-DNA coil interactions. Immobilization of oligonucleotide-functionalized magnetic nanobeads in rolling circle amplified DNA-coils was studied by complex magnetization measurements and transmission electron microscopy (TEM), and a statistical analysis of the number of beads hybridized to the DNA-coils was performed. The average number of beads per DNAcoil using the results from both methods was found to be around 6 and slightly above 2 for samples with 40 and 130 nm beads, respectively. The TEM analysis supported an earlier hypothesis that 40 nm beads are preferably immobilized in the interior of DNA-coils whereas 130 nm beads, to a larger extent, are immobilized closer to the exterior of the coils. The methodology demonstrated in the present work should open up new possibilities for characterization of interactions of a large variety of functionalized nanoparticles with macromolecules, useful for gaining more fundamental understanding of such interactions as well as for optimizing a number of biosensor applications.

National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-132261 (URN)10.1021/jp105756b (DOI)000282855100028 ()
Available from: 2010-10-18 Created: 2010-10-18 Last updated: 2016-12-01Bibliographically approved
5. Impact of matrix properties on survival of freeze-dried bacteria
Open this publication in new window or tab >>Impact of matrix properties on survival of freeze-dried bacteria
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2011 (English)In: Journal of the Science of Food and Agriculture, ISSN 0022-5142, E-ISSN 1097-0010, Vol. 91, no 14, 2518-2528 p.Article in journal (Refereed) Published
Abstract [en]

Background:

Disaccharides are in general first choice as formulation compounds when freezedrying microorganisms. Although polysaccharides and other biopolymers are considered too large to stabilize and interact with cell components in the same beneficial way as disaccharides, polymers have been reported to support cell survival. In the present study we compare the efficiency of sucrose, the polymers Ficoll, hydroxyethylcellulose, hydroxypropylmethylcellulose and polyvinylalcohol to support survival of three bacterial strains during freeze-drying. The initial osmotic conditions were adjusted to be similar for all formulations. Formulation characterization was used to interpret the impact that different compound properties had on cell survival.

Results:

Despite differences in molecular size, both sucrose and the sucrose based polymer Ficoll supported cell survival after freeze-drying equally well. All formulations became amorphous upon dehydration. Scanning electron microscopy and X-ray diffraction data showed that the discerned differences in structure of the dry formulations had little impact on the survival rates. The capability of the polymers to support cell survival correlated with the surface activity of the polymers in a similar way for all investigated bacterial strains.

Conclusion:

Polymer-based formulations can support cell survival as effectively as disaccharides if formulation properties of importance for maintaining cell viability are identified and controlled.

Keyword
formulation, freeze-drying, biopolymer, sucrose, bacteria, surface
National Category
Food Science Engineering and Technology
Research subject
Biology with specialization in Microbiology; Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-138967 (URN)10.1002/jsfa.4343 (DOI)000296385900004 ()
Available from: 2010-12-22 Created: 2010-12-21 Last updated: 2017-12-11Bibliographically approved
6. Direct ”Click” Synthesis of Hybrid Bisphosphonate-Hyaluronic Acid Hydrogel in Aqueous Solution for Biomineralization
Open this publication in new window or tab >>Direct ”Click” Synthesis of Hybrid Bisphosphonate-Hyaluronic Acid Hydrogel in Aqueous Solution for Biomineralization
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2012 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 24, no 9, 1690-1697 p.Article in journal (Refereed) Published
Abstract [en]

We report the synthesis of injectable in situ forming hybrid hydrogel material and investigate its ability to support the mineralization process under mild conditions. To achieve this, we have prepared a hyaluronic acid (HA) derivative that is dually functionalized with cross-linkable hydrazide groups and bisphosphonate ligands (HA-hy-BP). The hybrid hydrogel can be formed by simple mixing of two solutions: the solution of HA-hy-BP and the Ca2+ ions containing solution of aldehyde-derivatized HA (HA-al). We found that the conjugation of BP, a P-C-P analogue of pyrophosphate, to the hydrogel matrix promotes an efficient and fast mineralization of the matrix. The mineralization is facilitated by the strong interaction between BP residues and Ca2+ ions that serve as nanometer-sized nucleation points for further calcium phosphate deposition within the HA hydrogel. Compared with previously reported hydrogel template-driven mineralization techniques, the present approach is maximally adapted for clinical settings since the formation of the hybrid takes place during quick mixing of the sterilized solutions. Moreover, the hybrid hydrogel is formed from in vivo degradable components of the extracellular matrix and therefore can be remodeled in vivo through concerted HA degradation and calcium phosphate mineralization.

Keyword
hybrid organic-inorganic materials, injectable materials, hydrogels, hyaluronic acid, mineralization
National Category
Biochemistry and Molecular Biology Materials Engineering Polymer Chemistry
Research subject
Engineering Science with specialization in Materials Science; Chemistry with specialization in Polymer Chemistry
Identifiers
urn:nbn:se:uu:diva-171989 (URN)10.1021/cm300298n (DOI)000303628100019 ()
Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2017-12-07Bibliographically approved
7. A site-specific focused-ion-beam lift-out method for cryo transmission electron microscopy
Open this publication in new window or tab >>A site-specific focused-ion-beam lift-out method for cryo transmission electron microscopy
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Structural Biology Engineering and Technology Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-171990 (URN)
Available from: 2012-03-30 Created: 2012-03-30 Last updated: 2012-08-01

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