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Formation of ω-Thiol Protected α,ω-Alkanedithiol Coated Gold Nanoparticles and Usage in Molecular Charge Transport Junctions
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Gold nanoparticles (AuNPs) coated with stabilizing molecular monolayers are applied in a range of different areas. The stabilizing molecules are often anchored to the AuNPs through thiol groups. Herein, we present a novel one-pot and one-phase (THF) synthetic route that for the first time allows preparation of stable, monodisperse AuNPs (~6 nm diameter, SEM) that are coated with α,ω-alkanedithiols and where the outer w-thiol group is protected by a triphenylmethyl (trityl) group which allows this thiol group to be exploited in later functionalizations. The ω-thiol group is activated (deprotected) under acidic conditions, and it can be deprotected first when the AuNP has been placed properly for a certain application. Using dielectrophoresis we trap 20 - 30 of the ω-thiol protected α,ω-alkanedithiol coated AuNPs in a 20 nm gold electrode nanogap. Subsequent deprotection leads to a three-orders of magnitude increase in the conductance, indicating that we fuse the isolated coated AuNPs into a network with covalent AuNP-molecule-AuNP as well as electrode-molecule-AuNP bonds. Furthermore, we were able to carry out a complete NMR spectroscopic characterization of the AuNP surface bonded alkanedithiols using a series of one- and two-dimensional NMR techniques. We can in particular deduce that there are no H-atoms bonded to the sulfurs of the Au-S-R linkages of our molecule coated AuNPs. Using the Stokes-Einstein equation and the translational diffusion coefficients derived by NMR we determined the AuNP diameters to be 5.6 nm, which agrees well with the value obtained from SEM.

Identifiers
URN: urn:nbn:se:uu:diva-122938OAI: oai:DiVA.org:uu-122938DiVA: diva2:311422
Available from: 2010-04-21 Created: 2010-04-21 Last updated: 2010-05-17
In thesis
1. Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles
Open this publication in new window or tab >>Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of new materials with novel properties plays an important role in improving our lives and welfare. Research in Nanotechnology can provide e.g. cheaper and smarter materials in applications such as energy storage and sensors. In order for this development to proceed, we need to be able to characterize the material properties at the nano-, and even the atomic scale. The ultimate goal is to be able to tailor them according to our needs.

One of the great challenges concerning the characterization of nano-sized objects is how to achieve the physical contact to them. This thesis is focused on the contacting of nanoobjects with the aim of electrically characterizing them and subsequently understanding their electrical properties. The analyzed nanoobjects are carbon nanosheets, nanotetrapods, nanoparticles and molecular systems.

Two contacting strategies were employed in this thesis. The first strategy involved the development of a focused ion beam (FIB) based nanocontact platform. The platform consists of gold nanoelectrodes, having nanogaps of 10-30 nm, on top of an insulating substrate. Gold nanoparticles, double-stranded DNA and cadmium telluride nanotetrapods have been trapped in the gaps by using dielectrophoresis. In certain studies, the gold electrodes have also been coated with conducting or non-conducting molecules, prior to the trapping of gold nanoparticles, in order to form molecular junctions. These junctions were subsequently electrically characterized to evaluate the conduction properties of these molecular systems. For the purpose of better controlling the attachment of molecules to the nanoelectrodes, a novel route to synthesize alkanedithiol coated gold nanoparticles was developed. The second contacting strategy was based on the versatility of the FIB instrument as a platform for in-situ manipulation and electrical characterization of non-functionalized and functionalized carbon nanosheets, where it was found that the functionalized samples had an increased conductivity by more than one order of magnitude.

Both contacting strategies proved to be valuable for building knowledge around contacting and electrical characterization of nanoobjects

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 88 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 745
Keyword
Focused Ion Beam, FIB, Scanning Electron Microscopy, SEM, Nanogap electrodes, Nanostructuring, Nanofabrication, Electron Beam Lithography, Electrical characterization, Dielectrophoresis
Identifiers
urn:nbn:se:uu:diva-122940 (URN)978-91-554-7809-4 (ISBN)
Public defence
2010-06-07, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, 75121, Uppsala, 10:15 (English)
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Supervisors
Available from: 2010-05-17 Created: 2010-04-21 Last updated: 2010-05-18Bibliographically approved

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