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Potential dependent orientation of sulfanylbenzonitrile monolayers monitored by SERS

Potential dependent orientation of sulfanylbenzonitrile monolayers monitored by SERS
Potential dependent orientation of sulfanylbenzonitrile monolayers monitored by SERS

The change in orientation of 2-, 3-, and 4-sulfanylbenzonitrile (SBN) self assembled monolayers (SAMs) with respect to electrochemical potential was studied using surface-enhanced Raman spectroscopy (SERS). Being able to understand monolayer orientation under potential control has important applications in both sensors and molecular electronics, where orientation can affect sensitivity and electron transfer respectively. We characterise the vibrations of all three monolayers using a combination of experimental and density function theory (DFT) calculated spectra. The results reveal that the SERS intensities of both in plane (IP) and out of plane (OOP) modes of the aromatic ring and nitrile group are reversibly changed by potential, indicating an orientation change via variations in the tilt and/or twist angles. At more negative potentials the nitrile group of all three SAMs is more perpendicular to the electrode surface and at more positive potentials it is more parallel, governed by an electrostatic interaction between the nitrile group and the electrode surface. Additional effects of the applied potential are observed for the orientation of the ring with respect to the electrode surface through aromatic ring-surface π interactions, confirmed by examination of the effects of the applied potential on the peak width of the C–C ring breathing mode.

Orientation, Self-assembled monolayers, SERS, Surface interactions
0013-4686
378-387
Keeler, Alexander J.
5994294a-4164-4606-be61-4aab969a37fb
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169
Keeler, Alexander J.
5994294a-4164-4606-be61-4aab969a37fb
Russell, Andrea E.
b6b7c748-efc1-4d5d-8a7a-8e4b69396169

Keeler, Alexander J. and Russell, Andrea E. (2019) Potential dependent orientation of sulfanylbenzonitrile monolayers monitored by SERS. Electrochimica Acta, 305, 378-387. (doi:10.1016/j.electacta.2019.03.044).

Record type: Article

Abstract

The change in orientation of 2-, 3-, and 4-sulfanylbenzonitrile (SBN) self assembled monolayers (SAMs) with respect to electrochemical potential was studied using surface-enhanced Raman spectroscopy (SERS). Being able to understand monolayer orientation under potential control has important applications in both sensors and molecular electronics, where orientation can affect sensitivity and electron transfer respectively. We characterise the vibrations of all three monolayers using a combination of experimental and density function theory (DFT) calculated spectra. The results reveal that the SERS intensities of both in plane (IP) and out of plane (OOP) modes of the aromatic ring and nitrile group are reversibly changed by potential, indicating an orientation change via variations in the tilt and/or twist angles. At more negative potentials the nitrile group of all three SAMs is more perpendicular to the electrode surface and at more positive potentials it is more parallel, governed by an electrostatic interaction between the nitrile group and the electrode surface. Additional effects of the applied potential are observed for the orientation of the ring with respect to the electrode surface through aromatic ring-surface π interactions, confirmed by examination of the effects of the applied potential on the peak width of the C–C ring breathing mode.

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More information

Accepted/In Press date: 6 March 2019
e-pub ahead of print date: 9 March 2019
Published date: 10 May 2019
Keywords: Orientation, Self-assembled monolayers, SERS, Surface interactions

Identifiers

Local EPrints ID: 432831
URI: http://eprints.soton.ac.uk/id/eprint/432831
ISSN: 0013-4686
PURE UUID: a97c7a20-ba2f-4c66-b789-1f9bbf46ee4f
ORCID for Andrea E. Russell: ORCID iD orcid.org/0000-0002-8382-6443

Catalogue record

Date deposited: 26 Jul 2019 16:30
Last modified: 26 Nov 2021 02:40

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Contributors

Author: Alexander J. Keeler

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