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Formation and NMR Spectroscopy of ω-Thiol Protected α,ω-Alkanedithiol Coated Gold Nanoparticles and Their Usage in Molecular Charge Transport Junctions
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Physical Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.ORCID iD: 0000-0002-9092-261X
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2011 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 14, 9057-9067 p.Article in journal (Refereed) Published
Abstract [en]

Gold nanoparticles (AuNPs) coated with stabilizing molecular monolayers are utilized in areas ranging from life sciences to nanoelectronics. Here we present a novel and facile one-pot single phase procedure for the preparation of stable AuNPs with good dispersity, which are coated with α,ω-alkanedithiols whose outer ω-thiol is protected by a triphenylmethyl group. Using dielectrophoresis we were able to trap these AuNPs, coated with ω-thiol protecting groups, in a 20 nm gold electrode nanogap. The ω-thiol group was then deprotected under acidic conditions in situ once the AuNPs were correctly positioned in the device. The subsequent deprotection resulted in an increase of conductance by three orders of magnitude, indicating that the isolated dithiol coated AuNPs were fused into a covalently bonded network with AuNP-molecule-AuNP as well as electrode-molecule-AuNP linkages. Furthermore, complete characterization of the AuNP surface-bonded alkanedithiols was achieved using a series of one- and two-dimensional NMR spectroscopy techniques. Our spectra of the molecule-coated AuNPs show well resolved signals, only slightly broader than for free molecules in solution, in contrast to many earlier reported NMR spectral data of molecules attached to AuNPs. Complementary diffusion NMR spectroscopic experiments were performed to prove that the observed alkanedithiols are definitely surface bonded species and do not exist in free and unattached form.

Place, publisher, year, edition, pages
2011. Vol. 27, no 14, 9057-9067 p.
Keyword [en]
Chemistry, Materials Science
National Category
Chemical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-154968DOI: 10.1021/la2019007ISI: 000292617800056OAI: oai:DiVA.org:uu-154968DiVA: diva2:422851
Projects
KoF U3MEC
Funder
Swedish Research Council
Available from: 2011-06-14 Created: 2011-06-14 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Building Systems for Electronic Probing of Single Low Dimensional Nano-objects: Application to Molecular Electronics and Defect Induced Graphene
Open this publication in new window or tab >>Building Systems for Electronic Probing of Single Low Dimensional Nano-objects: Application to Molecular Electronics and Defect Induced Graphene
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nano-objects have unique properties due to their sizes, shapes and structure. When electronic properties of such nano-objects are used to build devices, the control of interfaces at atomic level is required.

In this thesis, systems were built that can not only electrically characterize nano-objects, but also allow to analyze a large number of individual nano-objects statistically at the example of graphene and nanoparticle-molecule-nanoelectrode junctions.

An in-situ electrical characterization system was developed for the analysis of free standing graphene sheets containing defects created by an acid treatment. The electrical characterization of several hundred sheets revealed that the resistance in acid treated graphene sheets decreased by 50 times as compared to pristine graphene and is explained by the presence of di-vacancy defects. However, the mechanism of defect insertion into graphene is different when graphene is bombarded with a focused ion beam and in this case, the resistance of graphene increases upon defect insertion. The defect insertion becomes even stronger at liquid N2 temperature.

A molecular electronics platform with excellent junction properties was fabricated where nanoparticle-molecule chains bridge 15-30nm nanoelectrodes. This approach enabled a systematic evaluation of junctions that were assembled by functionalizing electrode surfaces with alkanethiols and biphenyldithiol. The variations in the molecular device resistance were several orders of magnitude and explained by variations in attachment geometries of molecules. 

The spread of resistance values of different devices was drastically reduced by using a new functionalization technique that relies on coating of gold nanoparticles with trityl protected alkanedithiols, where the trityl group was removed after trapping of nanoparticles in the electrode gap. This establishment of a reproducible molecular electronics platform enabled the observation of vibrations of a few molecules by inelastic tunneling spectroscopy. Thus this system can be used extensively to characterize molecules as well as build devices based on molecules and nanoparticles. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 109 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 877
Keyword
Graphene, defect induced graphene, molecular electronics, nanoelectrodes, nanoparticles, conductivity, junction, nanomaterial, focused ion beam, surface functionalization, electrical characterization
National Category
Nano Technology Engineering and Technology
Research subject
Engineering Science with specialization in Materials Analysis
Identifiers
urn:nbn:se:uu:diva-160630 (URN)978-91-554-8212-1 (ISBN)
Public defence
2011-12-12, Häggsalen, Ångströmlab, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2011-11-21 Created: 2011-10-27 Last updated: 2011-11-23Bibliographically approved

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Publisher's full texthttp://pubs.acs.org/doi/abs/10.1021/la2019007

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Jafri, S. Hassan M.Blom, TobiasGogoll, AdolfLeifer, KlausOttosson, Henrik

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