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Sensors 2015, 15(3), 6469-6482; doi:10.3390/s150306469

A Solid-State Thin-Film Ag/AgCl Reference Electrode Coated with Graphene Oxide and Its Use in a pH Sensor

1
Department of Medical System Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea
2
School of Mechatronics, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Korea
*
Author to whom correspondence should be addressed.
Academic Editor: W. Rudolf Seitz
Received: 12 February 2015 / Revised: 10 March 2015 / Accepted: 12 March 2015 / Published: 17 March 2015
(This article belongs to the Section Chemical Sensors)
View Full-Text   |   Download PDF [1345 KB, uploaded 24 March 2015]   |  

Abstract

In this study, we describe a novel solid-state thin-film Ag/AgCl reference electrode (SSRE) that was coated with a protective layer of graphene oxide (GO). This layer was prepared by drop casting a solution of GO on the Ag/AgCl thin film. The potential differences exhibited by the SSRE were less than 2 mV for 26 days. The cyclic voltammograms of the SSRE were almost similar to those of a commercial reference electrode, while the diffusion coefficient of Fe(CN)63− as calculated from the cathodic peaks of the SSRE was 6.48 × 10−6 cm2/s. The SSRE was used in conjunction with a laboratory-made working electrode to determine its suitability for practical use. The average pH sensitivity of this combined sensor was 58.5 mV/pH in the acid-to-base direction; the correlation coefficient was greater than 0.99. In addition, an integrated pH sensor that included the SSRE was packaged in a secure digital (SD) card and tested. The average sensitivity of the chip was 56.8 mV/pH, with the correlation coefficient being greater than 0.99. In addition, a pH sensing test was also performed by using a laboratory-made potentiometer, which showed a sensitivity of 55.4 mV/pH, with the correlation coefficient being greater than 0.99. View Full-Text
Keywords: Ag/AgCl; reference electrode; pH sensor; graphene oxide; iridium oxide pH working electrode; potentiometer Ag/AgCl; reference electrode; pH sensor; graphene oxide; iridium oxide pH working electrode; potentiometer
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Kim, T.Y.; Hong, S.A.; Yang, S. A Solid-State Thin-Film Ag/AgCl Reference Electrode Coated with Graphene Oxide and Its Use in a pH Sensor. Sensors 2015, 15, 6469-6482.

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