Surface-enhanced Raman spectroscopy investigation of the potential-dependent acid-base chemistry of silver-immobilized 2-mercaptobenzoic acid
The acid-base chemistry of 2-mercaptobenzoic acid (2-MBA) immobilized on a polycrystalline silver surface was investigated by surface-enhanced Raman spectroscopy under potential control. The COO(-) bending mode of the benzoate form and the C-COOH stretching mode of the benzoic acid form of 2-MBA wer...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1992. - 27(2011), 7 vom: 05. Apr., Seite 3527-33 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2011
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article |
| Zusammenfassung: | The acid-base chemistry of 2-mercaptobenzoic acid (2-MBA) immobilized on a polycrystalline silver surface was investigated by surface-enhanced Raman spectroscopy under potential control. The COO(-) bending mode of the benzoate form and the C-COOH stretching mode of the benzoic acid form of 2-MBA were used to determine the relative deprotonated and protonated populations of the bound ligand, respectively. In addition, shifts in the symmetric carboxylate stretching mode of 2-MBA reveal interactions between the benzoate group and the silver surface, interactions which could be displaced by acetate and other buffer anions from solution. It was found that the applied potential has a significant effect on the proton dissociation equilibrium of immobilized 2-MBA. This effect arises from the surface potential governing the activity of protons at the interface, which changes the interfacial pH relative to bulk solution. The results are fit to a Poisson-Boltzmann model, corrected for potential distribution across the monolayer and interactions between adjacent immobilized ligands. The results show a significant increase in the intrinsic pK(a) of the immobilized ligand compared to 2-MBA in free solution, which is likely due to an increase in electron density on the benzoic acid group that occurs upon binding of the thiol group to the silver surface |
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| Beschreibung: | Date Completed 13.07.2011 Date Revised 30.03.2011 published: Print-Electronic Citation Status PubMed-not-MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/la1044859 |