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On the quality and structural characteristics of oligo(ethylene glycol) assemblies on gold: An experimental and theoretical study
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
Bogolyubov Institute for Theoretical Physics.
Bogolyubov Institute for Theoretical Physics.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
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2009 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, Vol. 172, no 1-3, 9-20 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents results of several years of experimental and theoretical work on a library of oligo(ethylene glycol)-containing self-assembled monolayers (OEG SAMs) on gold. The library consists of 15 different thiol compounds, which all contain alkyl and OEG portions of different length, as well as amide moieties forming a stabilizing lateral hydrogen bonding network. We have investigated the quality, conformation, orientation, defect structure and infrared (IR) signatures of these OEG SAMs prepared by spontaneous adsorption from dilute solutions. It is shown that solution concentration and incubation time are important factors to obtain high quality SAMs, in particular for those containing long OEG chains. Further on, the thiol compounds should contain a sufficiently long alkyl spacer to provide in plane van der Waals interactions strong enough to govern the formation of a densely packed alkylthiolate overlayer on the Au(1 1 1) surface. Such a highly ordered alkyl support, which is additionally stabilized by the lateral hydrogen bonds, enables us to vary the length of the terminal OEG portion from 1 to at least 12, without affecting the integrity and conformational characteristics of the supporting (alkyl) part of the SAM. Also, we discuss the importance of appropriate modeling tools to advance the understanding of IR signatures of the OEG SAMs. Finally, we demonstrate the generality of our "modular approach" by analyzing the structure of OEG SAMs formed by compounds extended with an additional terminal amide and an alkyl tail. Thus, the SAMs discussed herein provide an attractive platform for construction of advanced nanoarchitectures on surfaces, not only limited to biomaterials and fouling applications.

Place, publisher, year, edition, pages
2009. Vol. 172, no 1-3, 9-20 p.
Keyword [en]
Ab initio modeling; Hydrogen bonding; Infrared spectroscopy; Oligo(ethylene glycol); Self-assembled monolayers; X-ray photoelectron spectroscopy
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-18753DOI: 10.1016/j.elspec.2009.03.016OAI: oai:DiVA.org:liu-18753DiVA: diva2:221294
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2015-05-29
In thesis
1. Structural Studies of Oligo(ethylene glycol)-Containing Assemblies on Gold
Open this publication in new window or tab >>Structural Studies of Oligo(ethylene glycol)-Containing Assemblies on Gold
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work presents in this thesis has been focused on structural  characterization of a series of selected well-defined molecular architectures for the application as biomimetic membranes. The molecular architectures were prepared by self-assembly from dilute solution onto gold substrates, so called self-assembled monolayers (SAMs).

Biological membranes are essential components for all living systems; their molecular organizations and interactions with intra- and extracellular networks are key factors of cell functions. Many important biological processes are regulated at membrane interfaces via interactions between membrane proteins. Therefore, identification of the cell structures and understanding of the processes associated with membranes are crucial. However, the intrinsic complexity of the cell membrane systems makes direct investigation extra difficult. Based on this reason, artificial model membranes have become a useful strategy. Especially, solid supported tethered lipid membranes on SAMs allow for controlling the composition and geometry of biomimetic assemblies on molecular scale. However, the underlying mechanisms of lipid vesicle fusion on SAMs remain unclear. In this thesis, a series of thiolate SAMs containing alkyl chains and oligo(ethylene glycol) (OEG) portions of different length as well as amide linking groups were prepared and characterized in detail by employing a number of surface analyzing methods. In parallel, a set of ab initio modeling was undertaken for the best interpretation of the experimental infrared spectra. Investigation of small unilamellar vesicles interact with such SAMs is included as well.

The results show this type of assemblies forms highly ordered and oriented SAMs regardless of the length of the extended alkyl chains. The two layers of lateral hydrogen bonding networks through the two amide linking groups improve further the structural robustness of the assemblies. Furthermore, the use of deuterated terminal alkyl chains enables a direct relation between the surface density of the anchor molecules and the properties of the lipidbilayers. IRRAS data and ab initio modeling confirm that orientation of the helical OEG is affected by the second hydrogen bonding layer rather than the extended alkyl tails. Nanopatterns consisting of such SAMs with different extended alkyl chains can be employed as supports for the assembly of artificial cell membranes.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 62 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1446
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-77056 (URN)978-91-7519-898-9 (ISBN)
Public defence
2012-05-31, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
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Available from: 2012-05-03 Created: 2012-05-03 Last updated: 2012-06-29Bibliographically approved

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Valiokas, RamunasLee, Hung-HsunLiedberg, Bo

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