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Issue 43, 2013
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The role of defects in the reaction of chlorine atoms with alkanethiol self-assembled monolayers

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Abstract

Scanning tunneling microscopy (STM) in ultra-high-vacuum is used to investigate the reaction of gas-phase atomic chlorine with octanethiolate self-assembled-monolayers on Au(111). Exposure to Cl atoms results in the formation of a variety of surface defects, and eventually leads to a complete loss of order within the alkanethiolate monolayer. X-ray photoelectron spectroscopy and thermal desorption mass spectrometry show that these morphological changes are accompanied by significant chlorination of the monolayer as well as a ∼30% decrease in the amount of adsorbed sulfur. The rate of reaction is measured through the analysis of sequences of STM images, and coverage-vs.-exposure data shows that the average reactivity of any given molecule within the monolayer decreases as the reaction progresses. Working with the assumption that monolayer defects created by Cl-atom reaction will affect the reactivity of neighboring molecules, a kinetic Monte Carlo simulation shows the data are consistent with defect sites inhibiting reaction rate by a factor of 5 or more. This behavior is opposite to that found for hydrogen-atom reactions, where edge and defect sites were far more reactive. The dynamics of chlorine-atom reactivity are described primarily in terms of the formation and subsequent reaction of surface-adsorbed radicals, with surface defects providing sites where these radicals can be quenched.

Graphical abstract: The role of defects in the reaction of chlorine atoms with alkanethiol self-assembled monolayers

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Publication details

The article was received on 13 May 2013, accepted on 10 Jul 2013 and first published on 10 Jul 2013


Article type: Paper
DOI: 10.1039/C3CP52023D
Citation: Phys. Chem. Chem. Phys., 2013,15, 18844-18854
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    The role of defects in the reaction of chlorine atoms with alkanethiol self-assembled monolayers

    D. Y. Lee, M. M. Jobbins, A. R. Gans and S. A. Kandel, Phys. Chem. Chem. Phys., 2013, 15, 18844
    DOI: 10.1039/C3CP52023D

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