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Low-voltage voltammetric electrowetting of graphite surfaces by ion intercalation/deintercalation
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Zhang, Guohui, Walker, Marc and Unwin, Patrick R. (2016) Low-voltage voltammetric electrowetting of graphite surfaces by ion intercalation/deintercalation. Langmuir, 32 (30). pp. 7476-7484. doi:10.1021/acs.langmuir.6b01506 ISSN 0743-7463.
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Official URL: http://dx.doi.org/10.1021/acs.langmuir.6b01506
Abstract
We demonstrate low-voltage electrowetting at the surface of freshly cleaved highly oriented pyrolytic graphite (HOPG). Using cyclic voltammetry (CV), electrowetting of a droplet of a sodium perchlorate solution is observed at moderately positive potentials on high-quality (low step edge coverage) HOPG, leading to significant changes in the contact angle and relative contact diameter that are comparable to the results of the widely studied electrowetting on dielectric (EWOD) system, but over a much lower voltage range. The electrowetting behavior is found to be reasonably fast, reversible, and repeatable for at least 20 cyclic scans (maximum tested). In contrast to classical electrowetting, e.g., EWOD, the electrowetting of the droplet on HOPG occurs with the intercalation/deintercalation of anions between the graphene layers of graphite, driven by the applied potential, observed in the CV response, and detected by X-ray photoelectron spectroscopy. The electrowetting behavior is strongly influenced by those factors that affect the extent of the intercalation/deintercalation of ions on graphite, such as potential range scan rate, potential polarity, quality of the HOPG substrate (step edge density and step height), and type of anion in the solution. In addition to perchlorate, sulfate salts also promote electrowetting, but some other salts do not. Our findings suggest a new mechanism for electrowetting based on ion intercalation, and the results are important to fundamental electrochemistry as well as to diversifying the means by which electrowetting can be controlled and applied.
Item Type: | Journal Article | ||||||||||
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Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering | ||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||||||||
Library of Congress Subject Headings (LCSH): | Low voltage systems, Graphite intercalation compounds | ||||||||||
Journal or Publication Title: | Langmuir | ||||||||||
Publisher: | American Chemical Society | ||||||||||
ISSN: | 0743-7463 | ||||||||||
Official Date: | 2 August 2016 | ||||||||||
Dates: |
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Volume: | 32 | ||||||||||
Number: | 30 | ||||||||||
Number of Pages: | 9 | ||||||||||
Page Range: | pp. 7476-7484 | ||||||||||
DOI: | 10.1021/acs.langmuir.6b01506 | ||||||||||
Status: | Peer Reviewed | ||||||||||
Publication Status: | Published | ||||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||||
Description: | Document includes supporting information |
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Date of first compliant deposit: | 15 September 2016 | ||||||||||
Date of first compliant Open Access: | 12 July 2017 | ||||||||||
Funder: | European Research Council (ERC), University of Warwick, Advantage West Midlands (AWM), European Regional Development Fund (ERDF) | ||||||||||
Grant number: | 247143 (ERC) |
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