Publication detail

Structure and stability of 7-mercapto-4-methylcoumarin self-assembled monolayers on gold: an experimental and computational analysis

Marchi, D Cara, E Lupi, F. F. Hoenicke, P. Kayser, Y Beckhoff, B Castellino, M Klapetek, P. Zoccante, A Laus, M Cossi, M

Original Title

Structure and stability of 7-mercapto-4-methylcoumarin self-assembled monolayers on gold: an experimental and computational analysis

Type

journal article in Web of Science

Language

English

Original Abstract

Self-assembled monolayers (SAM) of 7-mercapto-4-methylcoumarin (MMC) on a flat gold surface were studied by molecular dynamics (MD) simulations, reference-free grazing incidence X-ray fluorescence (GIXRF) and X-ray photoelectron spectroscopy (XPS), to determine the maximum monolayer density and to investigate the nature of the molecule/surface interface. In particular, the protonation state of the sulfur atom upon adsorption was analyzed, since some recent literature presented evidence for physisorbed thiols (preserving the S-H bond), unlike the common picture of chemisorbed thiyls (losing the hydrogen). MD with a specifically tailored force field was used to simulate either thiol or thiyl monolayers with increasing number of molecules, to determine the maximum dynamically stable densities. This result was refined by computing the monolayer chemical potential as a function of the density with the bennet acceptance ratio method, based again on MD simulations. The monolayer density was also measured with GIXRF, which provided the absolute quantification of the number of sulfur atoms in a dense self-assembled monolayer (SAM) on flat gold surfaces. The sulfur core level binding energies in the same monolayers were measured by XPS, fitting the recorded spectra with the binding energies proposed in the literature for free or adsorbed thiols and thiyls, to get insight on the nature of the molecular species present in the layer. The comparison of theoretical and experimental SAM densities, and the XPS analysis strongly support the picture of a monolayer formed by chemisorbed, dissociated thiyls.

Keywords

self-assebled monoalyers;MMC dimer;modelling;atomic force microscopy;GIXRF;XPS

Authors

Marchi, D; Cara, E; Lupi, F. F.; Hoenicke, P.; Kayser, Y; Beckhoff, B; Castellino, M; Klapetek, P.; Zoccante, A; Laus, M; Cossi, M

Released

5. 9. 2022

Publisher

ROYAL SOC CHEMISTRY

Location

CAMBRIDGE

ISBN

1463-9084

Periodical

Physical Chemistry Chemical Physics

Year of study

24

Number

36

State

United Kingdom of Great Britain and Northern Ireland

Pages from

22083

Pages to

22090

Pages count

8

URL

https://www.researchgate.net/publication/363285531_Structure_and_Stability_of_7-mercapto-4-methylcoumarin_Self-Assembled_Monolayers_on_Gold_an_Experiment_and_Computational_analysis

BibTex

@article{BUT182644,
  author="Marchi, D and Cara, E and Lupi, F. F. and Hoenicke, P. and Kayser, Y and Beckhoff, B and Castellino, M and Klapetek, P. and Zoccante, A and Laus, M and Cossi, M",
  title="Structure and stability of 7-mercapto-4-methylcoumarin self-assembled monolayers on gold: an experimental and computational analysis",
  journal="Physical Chemistry Chemical Physics",
  year="2022",
  volume="24",
  number="36",
  pages="22083--22090",
  doi="10.1039/d2cp03103e",
  issn="1463-9084",
  url="https://www.researchgate.net/publication/363285531_Structure_and_Stability_of_7-mercapto-4-methylcoumarin_Self-Assembled_Monolayers_on_Gold_an_Experiment_and_Computational_analysis"
}