Electric field driven protonation/deprotonation of self-assembled monolayers of acid-terminated thiols

Langmuir : the ACS Journal of Surfaces and Colloids
Ian BurgessR Bruce Lennox

Abstract

Using electrochemical impedance spectroscopy (EIS), we provide an explanation for the pH dependence of the voltammetric peak height for the electric-field-driven protonation and deprotonation of carboxylic acid-terminated thiol self-assembled monolayers (SAMs). The current flowing through the interface can be divided into a purely capacitive current and a protonation/deprotonation current that is directly related to the rate of change of the SAM's protonation (or deprotonation). We demonstrate that at applied potentials close to those corresponding to half-ionization of the SAM and pHs near the pK(1/2), the equivalent circuit describing the interface consists of a Helmholtz film capacity in parallel with a "protonation/deprotonation" impedance which is further shown to be a series combination of a resistor, Rp, and capacitor Cp. Explicit expressions for Rp and Cp are derived in terms of the rate constants for the forward (protonation) and reverse (deprotonation) reactions. Simulated EIS data demonstrate the agreement between our model of the interface and experimental impedance and voltammetric data.

Citations

Jun 7, 2012·Analytical Chemistry·Antonio M LuqueRafael Andreu
Mar 29, 2013·Analytical Chemistry·Juan José CalventeJosé Luis Olloqui-Sariego
Aug 24, 2011·Langmuir : the ACS Journal of Surfaces and Colloids·Fernanda Camacho-AlanisNathan S Swami
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Jan 24, 2012·Langmuir : the ACS Journal of Surfaces and Colloids·Chaoxiong Ma, Joel M Harris
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Jan 8, 2008·Electroanalysis·Jonathan S Daniels, Nader Pourmand
Nov 26, 2010·Physical Chemistry Chemical Physics : PCCP·Wenbin Zhang, Ian J Burgess
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Feb 7, 2008·Langmuir : the ACS Journal of Surfaces and Colloids·Mario TagliazucchiIgal Szleifer
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Jun 30, 2021·Physical Chemistry Chemical Physics : PCCP·Elisabeth HenggeRoland Würschum
Jul 14, 2021·Journal of the American Chemical Society·Murielle F DelleyJames M Mayer
Feb 27, 2018·Langmuir : the ACS Journal of Surfaces and Colloids·Catherine AdamThomas Doneux
Jun 24, 2020·Journal of the American Chemical Society·Aimin GeAndrew A Peterson
Jan 24, 2007·Langmuir : the ACS Journal of Surfaces and Colloids·Burke C Barlow, Ian J Burgess

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