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Issue 17, 2016
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Unforeseen distance-dependent SERS spectroelectrochemistry from surface-tethered Nile Blue: the role of molecular orientation

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Abstract

Covalent immobilization of redox-active dyes is an important strategy to evaluate structure–activity relationships in nanoscale electrochemistry by using optical readouts such as surface-enhanced Raman scattering (SERS). Here we investigate the role of the tether length in the SERS spectroelectrochemistry of surface-attached Nile Blue. Differential pulse voltammetry and a potential-dependent SERS derivative analysis reveal that the Nile Blue molecules adopt a different orientation with respect to the electrode surface as the number of carbons in a carboxylic acid-terminated alkanethiol monolayer is varied, which leads to unique SERS spectroelectrochemical behaviors. We use the relative molecular orientations and spectral characteristics to propose a model in which tethers shorter than the length of the molecule limit molecular motion under electrochemical perturbation, but tethers longer than the length of the molecule allow dye intercalation into the hydrophobic self-assembled monolayer, producing an unexpected decrease in the SERS intensity when the molecule is in the oxidized form.

Graphical abstract: Unforeseen distance-dependent SERS spectroelectrochemistry from surface-tethered Nile Blue: the role of molecular orientation

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Supplementary files

Article information


Submitted
02 Jun 2016
Accepted
20 Jun 2016
First published
20 Jun 2016

Analyst, 2016,141, 5144-5151
Article type
Paper

Unforeseen distance-dependent SERS spectroelectrochemistry from surface-tethered Nile Blue: the role of molecular orientation

A. J. Wilson and K. A. Willets, Analyst, 2016, 141, 5144
DOI: 10.1039/C6AN01266C

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