Direct Visualization of Molecule Deprotonation on an Insulating Surface

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• 作者：Markus Kittelmann ; Philipp Rahe ; Andr茅 Gourdon ; Angelika K眉hnle
• 刊名：ACS Nano
• 出版年：2012
• 出版时间：August 28, 2012
• 年：2012
• 卷：6
• 期：8
• 页码：7406-7411
• 全文大小：389K
• 年卷期：v.6,no.8(August 28, 2012)
• ISSN：1936-086X

文摘

Elucidating molecular-scale details of basic reaction steps on surfaces is decisive for a fundamental understanding of molecular reactivity within many fields, including catalysis and on-surface synthesis. Here, the deprotonation of 2,5-dihydroxybenzoic acid (DHBA) deposited onto calcite (101;4) held at room temperature is followed in situ by noncontact atomic force microscopy. After deposition, the molecules form two coexisting phases, a transient striped phase and a stable dense phase. A detailed analysis of high-resolution noncontact atomic force microscopy images indicates the transient striped phase being a bulk-like phase, which requires hydrogen bonds between the carboxylic acid moieties to be formed. With time, the striped phase transforms into the dense phase, which is explained by the deprotonation of the molecules. In the deprotonated state, the molecules can no longer form hydrogen bonds, but anchor to the surface calcium cations with their negatively charged carboxylate group. The deprotonation step is directly confirmed by Kelvin probe force microscopy images that unravel the change in the molecular charge.

Keywords:

deprotonation; insulating surface; noncontact atomic force microscopy; Kelvin probe force microscopy