Self-assembly and Local Functionality at Au/Electrolyte Interfaces: An in-situ Scanning Tunneling Microscopy Approach

Li, Zhihai

Dissertation / PhD Thesis/Book

Self-assembly and Local Functionality at Au/Electrolyte Interfaces: An in-situ Scanning Tunneling Microscopy Approach

Li, Z. (Corresponding author)FZJ*

2007
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-482-4

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Reihe Informationstechnik / Information Technology 16, VIII, 135 S. (2007) = RWTH Aachen, Diss., 2007

Please use a persistent id in citations: http://hdl.handle.net/2128/2599

Abstract: The integration of molecular structures in electronic circuits is currently an active field of fundamental research inspired by the visionary concepts of moleculebased electronics. The bottom-up approach, based on the self-assembly of functional molecular building blocks into more complex architectures, represents an attractive alternative to silicon-based nanoelectronics. Basic concepts and strategies of twodimensional self-assembly and electron transport in tailored nanostructures can be also addressed and explored at electrified solid/liquid interfaces employing the electrolyte as an “electrochemical gate”. In this dissertation, we applied electrochemical $\underline{S}$canning $\underline{T}$unneling $\underline{M}$icroscopy and $\underline{S}$pectroscopy (STM and STS) in combination with $\underline{C}$yclic $\underline{V}$oltammetry (CV) and $\underline{S}$urface $\underline{E}$nhanced $\underline{I}$nfrared $\underline{R}$eflection $\underline{A}$bsorption $\underline{S}$pectroscopy (SEIRAS) to investigated the two-dimensional (2D) assembly of aromatic carboxylic acids triggered by directional hydrogen bond and substrate–adsorbate coordination, and structure as well as electron transfer properties of redox-active thioalkylviologen derivatives at electrified gold/aqueous electrolyte interfaces. First, the steady state and kinetic processes of self-assembled adlayers of carboxylic acids were investigated on Au(111)/electrolyte interfaces. The target molecules include trimesic acid (TMA), isophthalic acid (IA), terephthalic acid (TA) and benzoic acid (BA). Five distinctly different 2D self-assembled nanostructures of TMA were created by tuning the applied electrode potential. The properties of these adlayers have been elucidated at the molecular level by in situ STM. Four different ordered adlayers of planar-oriented molecules, which are labeled as honeycomb structures, a ribbon-type phase, a herringbone-type phase and hydrogen-bonded dimers were found in the potential range -0.250 V ≤ E ≤ 0.400 V, i.e. at an uncharged or slightly negatively charged Au(111) electrode. The structure transitions are in all cases triggered by increasing the electrode potential. Further increase of the electrode potential to positive charge densities, i.e. E > 0.400 V, causes an orientation change from planar to upright. An initially disordered [...]

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