Abstract
The hydroquinone/quinone (H2Q/Q) redox system was tethered to glassy carbon surfaces using first an electrochemical pre-oxidation treatment to afford carboxylic acid functionalities followed by immobilizing the H2Q precursor, n-(2,5-dimethoxyphenyl)alkan-1-amine (general structure: H2N-(CH2)n-C6H3(OCH3)2, n = 1, 2, 4, 8, and 12), by carbodiimide chemistry and a final demethylation reaction. The resultant surfaces exhibited the expected chemical reversibility in aqueous solution with a pH-sensitive position of the formal potential (∼55 mV/pH unit), and an increase in the peak potential separation going from 0.02 V for n = 1 to 0.21 V for n = 12. The films were very robust and could withstand prolonged sonication and relatively large potential excursions. While the films followed the expected kinetic distance dependence for up to 4 methylene units the electrode kinetics was faster than expected for longer alkyl spacers. We suggest that film disorder, electrode-mediating effects, and a roughened electrode material could account for these apparent inconsistencies. To further understand such effects, two complementary electrode modification strategies leading to better film ordering on carbon were adapted; immobilizing a thin layer of benzoic acid by oxidative deposition of 4-aminobenzoic acid or employing a plasma deposition process to tether an acid analogue. Analysis of the various electrodes was accomplished by electrochemical methods, atomic force microscopy, and X-ray photoelectron spectroscopy.
| Original language | English |
|---|---|
| Pages (from-to) | 1680-1688 |
| Number of pages | 9 |
| Journal | Electrochimica Acta |
| Volume | 53 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - 2007 Dec 31 |
| Externally published | Yes |
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Keywords
- Distance-dependent electrochemical properties
- Hydroquinone
- Modified electrodes
- pH sensor
ASJC Scopus subject areas
- Chemical Engineering(all)
- Analytical Chemistry
- Electrochemistry
Cite this
Evaluation of various strategies to formation of pH responsive hydroquinone-terminated films on carbon electrodes. / Holm, Allan Hjarbæk; Vase, Karina Højrup; Winther Jensen, Bjorn; Pedersen, Steen Uttrup; Daasbjerg, Kim.
In: Electrochimica Acta, Vol. 53, No. 4, 31.12.2007, p. 1680-1688.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Evaluation of various strategies to formation of pH responsive hydroquinone-terminated films on carbon electrodes
AU - Holm, Allan Hjarbæk
AU - Vase, Karina Højrup
AU - Winther Jensen, Bjorn
AU - Pedersen, Steen Uttrup
AU - Daasbjerg, Kim
PY - 2007/12/31
Y1 - 2007/12/31
N2 - The hydroquinone/quinone (H2Q/Q) redox system was tethered to glassy carbon surfaces using first an electrochemical pre-oxidation treatment to afford carboxylic acid functionalities followed by immobilizing the H2Q precursor, n-(2,5-dimethoxyphenyl)alkan-1-amine (general structure: H2N-(CH2)n-C6H3(OCH3)2, n = 1, 2, 4, 8, and 12), by carbodiimide chemistry and a final demethylation reaction. The resultant surfaces exhibited the expected chemical reversibility in aqueous solution with a pH-sensitive position of the formal potential (∼55 mV/pH unit), and an increase in the peak potential separation going from 0.02 V for n = 1 to 0.21 V for n = 12. The films were very robust and could withstand prolonged sonication and relatively large potential excursions. While the films followed the expected kinetic distance dependence for up to 4 methylene units the electrode kinetics was faster than expected for longer alkyl spacers. We suggest that film disorder, electrode-mediating effects, and a roughened electrode material could account for these apparent inconsistencies. To further understand such effects, two complementary electrode modification strategies leading to better film ordering on carbon were adapted; immobilizing a thin layer of benzoic acid by oxidative deposition of 4-aminobenzoic acid or employing a plasma deposition process to tether an acid analogue. Analysis of the various electrodes was accomplished by electrochemical methods, atomic force microscopy, and X-ray photoelectron spectroscopy.
AB - The hydroquinone/quinone (H2Q/Q) redox system was tethered to glassy carbon surfaces using first an electrochemical pre-oxidation treatment to afford carboxylic acid functionalities followed by immobilizing the H2Q precursor, n-(2,5-dimethoxyphenyl)alkan-1-amine (general structure: H2N-(CH2)n-C6H3(OCH3)2, n = 1, 2, 4, 8, and 12), by carbodiimide chemistry and a final demethylation reaction. The resultant surfaces exhibited the expected chemical reversibility in aqueous solution with a pH-sensitive position of the formal potential (∼55 mV/pH unit), and an increase in the peak potential separation going from 0.02 V for n = 1 to 0.21 V for n = 12. The films were very robust and could withstand prolonged sonication and relatively large potential excursions. While the films followed the expected kinetic distance dependence for up to 4 methylene units the electrode kinetics was faster than expected for longer alkyl spacers. We suggest that film disorder, electrode-mediating effects, and a roughened electrode material could account for these apparent inconsistencies. To further understand such effects, two complementary electrode modification strategies leading to better film ordering on carbon were adapted; immobilizing a thin layer of benzoic acid by oxidative deposition of 4-aminobenzoic acid or employing a plasma deposition process to tether an acid analogue. Analysis of the various electrodes was accomplished by electrochemical methods, atomic force microscopy, and X-ray photoelectron spectroscopy.
KW - Distance-dependent electrochemical properties
KW - Hydroquinone
KW - Modified electrodes
KW - pH sensor
UR - http://www.scopus.com/inward/record.url?scp=35548942204&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=35548942204&partnerID=8YFLogxK
U2 - 10.1016/j.electacta.2007.08.018
DO - 10.1016/j.electacta.2007.08.018
M3 - Article
VL - 53
SP - 1680
EP - 1688
JO - Electrochimica Acta
JF - Electrochimica Acta
SN - 0013-4686
IS - 4
ER -