Double Layer Effects at Molecular Films Containing Acid/Base Groups

Fawcett, W. Ronald; Fedurco, Milan; Kováčová, Zuzana

doi:10.1021/la00019a062

Cited by 81 publications

(88 citation statements)

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“…These results can be classified into two groups. The first group [8][9][10][11][12][13] displays an increase of the monolayer acidity as the potential is made more positive (in agreement with predictions from electrostatic models [17][18][19]), whereas the second group [14][15][16] shows the opposite trend (which has been rationalized in terms of a cation-exchange model [14][15]). The potential-induced ionization of 11-mercaptoundecanoic acid (MUA) monolayers has been reported to display both of these opposite trends, under the scrutiny of different experimental techniques and in the presence of different electrolyte solutions.…”

Section: Introductionsupporting

confidence: 73%

Potentiostatic infrared titration of 11-mercaptoundecanoic acid monolayers

Luque¹,

Cuesta²,

Calvente³

et al. 2014

Electrochemistry Communications

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In situ IR difference spectra of 11-mercaptoundecanoic acid (MUA) monolayers deposited on gold, and in the presence of a NaF solution in deuterated water, have been recorded as a function of both solution pH * and substrate's potential. IR spectra recorded under voltammetric conditions indicate that the potential-induced ionization of the monolayer is a slow process, involving a simultaneous rearrangement of the hydrocarbon chains, and that a significant population of carboxylic groups are not dissociated at positive potentials, even in the presence of a pH * 9 solution. Steep potentiostatic IR titration curves, consistent with a monolayer pKa = 4.3, are obtained at negative potentials. As the potential is made more positive, titration curves become lower, broader and are shifted towards more basic pHs, as would be expected when only a fraction of the carboxylic groups become ionized in the presence of less favorable interactions. Rather than acting directly on the electrostatic energy of the carboxylate groups, the electrode potential seems to control the ionization of the monolayer by attracting (or repelling) cations from the electrolyte and by reorienting the thiol head groups inside and outside the low permittivity layer of methylene chains.

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Section: Introductionsupporting

confidence: 73%

Potentiostatic infrared titration of 11-mercaptoundecanoic acid monolayers

Luque¹,

Cuesta²,

Calvente³

et al. 2014

Electrochemistry Communications

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“…The MPPA/Au electrode shows a pair of small peaks with a midpoint potential (E 0 ' = (E pa + E pc )/2) of À335 mV (Figure 3 a), which could be attributed to the electric-field-induced protonation/ deprotonation peak of PO 3 H 2 groups in the MPPA SAM, as in the case of COOH-terminated SAMs. [24] After Hb adsorption, the Hb/MPPA/Au electrode (Figure 3 b) shows a significant pair of well-defined and nearly symmetrical reduction/ oxidation peaks, attributable to the characteristics of the Fe III /Fe II redox couple of the immobilized Hb. The formal potential E 0 ', defined as the average of E pa and E pc , is about À343 AE 5 mV, which is close to the values reported by others for similar experimental conditions.…”

Section: Resultsmentioning

confidence: 97%

Hemoglobin on Phosphonic Acid Terminated Self‐Assembled Monolayers at a Gold Electrode: Immobilization, Direct Electrochemistry, and Electrocatalysis

Chen

Jin

Guo

et al. 2008

Chemistry A European J

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Phosphonic acid (--PO(3)H(2)) terminated self-assembled monolayers (SAMs) on a gold surface were used as a functional interface to immobilize hemoglobin (Hb). In situ surface-enhanced infrared absorption spectroscopy (SEIRAS) measurements show that Hb immobilization is a sluggish process due to formation of multilayer Hb structures on the PO(3)H(2)-terminated SAMs, as revealed by ellipsometry, atomic force microscopy (AFM), and cyclic voltammetry (CV). In the multilayered Hb film, the innermost Hb molecules can directly exchange electrons with the electrode, whereas Hb beyond this layer communicates electronically with the electrode via protein-protein electron exchange. In addition, electrochemical measurements indicate that immobilization of Hb on the PO(3)H(2)-terminated SAMs is not driven by the electrostatic interaction, but likely by hydrogen-bonding interaction. The immobilized Hb molecules show excellent bioelectrocatalytic activity towards hydrogen peroxide, that is, the PO(3)H(2)-terminated SAMs are promising for construction of third-generation biosensors.

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“…Another area of interest was double layer effects at self-assembled monolayers. In 1994, we described a model for the ionization of acidic head groups in self-assembled monolayers which took into consideration discreteness-of-charge effects [60]. The cutoff disc model described by Levine [61] was used to estimate these effects.…”

Section: The 1990smentioning

confidence: 99%

Fifty years of studies of double layer effects in electrode kinetics—a personal view

Fawcett

2011

J Solid State Electrochem

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Developments in the treatment of double layer effects in electrode kinetics are outlined. These include discreteness-of-charge effects in the presence of specific adsorption, solvent effects in electron transfer reactions, and effects related to the distribution of charge in polyatomic reactants. The importance of studies at single crystal electrodes is emphasized, and the development of a single crystal ultramicroelectrode described. Finally, a method of improving the estimate of the diffuse layer potential drop on the basis of Monte Carlo simulations is presented.

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Double Layer Effects at Molecular Films Containing Acid/Base Groups

Cited by 81 publications

References 0 publications

Potentiostatic infrared titration of 11-mercaptoundecanoic acid monolayers

Potentiostatic infrared titration of 11-mercaptoundecanoic acid monolayers

Hemoglobin on Phosphonic Acid Terminated Self‐Assembled Monolayers at a Gold Electrode: Immobilization, Direct Electrochemistry, and Electrocatalysis

Fifty years of studies of double layer effects in electrode kinetics—a personal view

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