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Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
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2014 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, 34-40 p.Article in journal (Refereed) Published
Abstract [en]

We report on the synthesis and decoration of high-aspect-ratio crystalline C-60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78 +/- 0.66 nm. In their pristine form, C-60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C-60 NRs. Bys measuring the electron mobility of different C-60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C-60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

Place, publisher, year, edition, pages
2014. Vol. 73, 34-40 p.
National Category
Physical Chemistry Nano Technology
Identifiers
URN: urn:nbn:se:umu:diva-97292DOI: 10.1016/j.carbon.2014.02.028ISI: 000335096300004OAI: oai:DiVA.org:umu-97292DiVA: diva2:771330
Available from: 2014-12-12 Created: 2014-12-12 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Fabricating designed fullerene nanostructures for functional electronic devices
Open this publication in new window or tab >>Fabricating designed fullerene nanostructures for functional electronic devices
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A long-term goal within the field of organic electronics has been to developflexible and functional devices, which can be processed and patterned withlow-cost and energy-efficient solution-based methods. This thesis presents anumber of functional paths towards the attainment of this goal via thedevelopment and demonstration of novel fabrication and patterningmethods involving the important organic-semiconductor family termedfullerenes.Fullerenes are soccer-shaped small molecules, with two often-employedexamples being the symmetric C60 molecule and its more soluble derivative[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We show that PCBM canbe photochemically transformed into a dimeric state in a bi-excited reactionprocess, and that the exposed material features a significantly reducedsolubility in common solvents as well as an effectively retained electronmobility. This attractive combination of material properties allows for adirect and resist-free lithographic patterning of electronic PCBM films downto a smallest feature size of 1 µm, using a simple and scalable two-stepprocess constituting light exposure and solution development. In a furtherdevelopment, it was shown that the two-step method was useful also in thearea-selective transformation of fullerene/conjugated-polymer blend films,as demonstrated through the realization of a functional complementary logiccircuit comprising a 5-stage ring oscillator.In another project, we have synthesized highly flexible, single-crystal C60nanorods with a solution-based self-assembly process termed liquid-liquidinterfacial precipitation. The 1-dimensional nanorods can be deposited fromtheir synthesis solution and employed as the active material in field-effecttransistor devices. Here, it was revealed that the as-fabricated nanorods canfeature an impressive electron mobility of 1.0 cm2 V-1 s-1, which is on par withthe performance of a work horse in the transistor field, viz. vacuumdeposited amorphous Si. We further demonstrated that the processability ofthe nanorods can be improved by a tuned light-exposure treatment, duringwhich the nanorod shell is polymerized while the high-mobility interior bulkis left intact. This has the desired consequence that stabile nanoroddispersions can be prepared in a wide range of solvents, and we anticipatethat functional electronic devices based on solution-processable nanorodscan be realized in a near future.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 71 p.
Keyword
Organic electronics, Organic field-effect transistor, Organic photovoltaics, Fullerene C60, PCBM, Photochemical transformation, Resist-free lithography, C60 Nanorod, Solution processable
National Category
Physical Chemistry Nano Technology
Research subject
nanomaterials; Physical Chemistry; Physics; Materials Science
Identifiers
urn:nbn:se:umu:diva-97294 (URN)978-91-7601-187-4 (ISBN)
Public defence
2015-01-20, N300, Naturvetarhuset, Umeå universitet, Universitetsvägen, 901 87 Umeå, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2014-12-19 Created: 2014-12-12 Last updated: 2014-12-18Bibliographically approved
2. Synthesis and Characterization of Carbon Based One-Dimensional Structures: Tuning Physical and Chemical Properties
Open this publication in new window or tab >>Synthesis and Characterization of Carbon Based One-Dimensional Structures: Tuning Physical and Chemical Properties
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Carbon nanostructures have been extensively used in different applications; ranging from electronic and optoelectronic devices to energy conversion. The interest stems from the fact that covalently bonded carbon atoms can form a wide variety of structures with zero-, one- and two-dimensional configuration with different physical properties. For instance, while fullerene molecules (zero-dimensional carbon structures) realize semiconductor behavior, two-dimensional graphene shows metallic behavior with exceptional electron mobility. Moreover the possibility to even further tune these fascinating properties by means of doping, chemical modification and combining carbon based sub-classes into new hybrid structures make the carbon nanostructure even more interesting for practical application. 

This thesis focuses on synthesizing SWCNT and different C60 one-dimensional structures as well as tuning their properties by means of different chemical and structural modification. The purpose of the study is to have better understanding of the synthesis and modification techniques, which opens for better control over the properties of the product for desired applications.

In this thesis carbon nanotubes (CNTs) are grown by chemical vapor deposition (CVD) on iron/cobalt catalyst particles. The effect of catalyst particle size on the diameter of the grown CNTs is systematically studied and in the case of SWCNTs it is shown that the chirality distribution of the grown SWCNTs can be tuned by altering the catalyst particle composition. In further experiments, incorporation of the nitrogen atoms in SWCNTs structures is examined. A correlation between experimental characterization techniques and theoretical calculation enable for precise analysis of different types of nitrogen configuration in SWCNTs structure and in particular their effect on growth termination and electronic properties of SWCNTs are studied.

C60 one-dimensional structures are grown through a solution based method known as Liquid-liquid interfacial precipitation (LLIP). By controlling the crystal seed formation at the early stage of the growth the morphology and size of the grown C60 one-dimensional structures where tuned from nanorods to large diameter rods and tubes. We further introduce a facile solution-based method to photo-polymerize the as-grown C60 nanorods, and show that such a method crates a polymeric C60 shell around the nanorods. The polymeric C60 shell exhibits high stability against common hydrophobic C60 solvents, which makes the photo-polymerized nanorods ideal for further solution-based processing. This is practically shown by decoration of both as grown and photo-polymerized nanorods by palladium nanoparticles and comparison between their electrochemical activities. The electrical properties of the C60 nanorods are also examined by utilizing a field effect transistor geometry comprising different C60 nanorods.

In the last part of the study a variant of CNT is synthesized in which large diameter, few-walled CNTs spontaneously transform to a collapsed ribbon shape structure, the so called collapsed carbon nanotube (CCNT). By inserting C60 molecules into the duct edges of CCNT a new hybrid structure comprising C60 molecules and CCNT is synthesized and characterized. A further C60 insertion lead to reinflation of CCNTs, which eventually form few-walled CNT completely filled with C60 molecules.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 71 p.
Keyword
Carbon Nanotube, single-walled carbon nanotube, nitrogen doped, chemical vapor deposition, fullerene, hybrid structures
National Category
Condensed Matter Physics
Research subject
nanomaterials
Identifiers
urn:nbn:se:umu:diva-97551 (URN)978-91-7601-191-1 (ISBN)
Public defence
2015-01-28, MA121, MIT Huset, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2015-01-07 Created: 2014-12-22 Last updated: 2015-01-04Bibliographically approved

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