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

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.

[1]  I. Grigorieva,et al.  Unimpeded Permeation of Water Through Helium-Leak–Tight Graphene-Based Membranes , 2011, Science.

[2]  T Matsumoto,et al.  A long-term lifetime amperometric glucose sensor with a perfluorocarbon polymer coating. , 2001, Biosensors & bioelectronics.

[3]  D. J. Harrison,et al.  Prevention of the rapid degradation of subcutaneously implanted Ag/AgCl reference electrodes using polymer coatings. , 1994, Analytical chemistry.

[4]  Chang Auck Choi,et al.  An iridium oxide reference electrode for use in microfabricated biosensors and biochips. , 2004, Lab on a chip.

[5]  Samuel P. Kounaves,et al.  Fabrication and Characterization of a Solid State Reference Electrode for Electroanalysis of Natural Waters with Ultramicroelectrodes , 1997 .

[6]  H. S. Wolff,et al.  iRun: Horizontal and Vertical Shape of a Region-Based Graph Compression , 2022, Sensors.

[7]  Hui Xu,et al.  Electrochemical Sensors for Clinic Analysis , 2008, Sensors.

[8]  J. Zemel,et al.  pH-sensitive sputtered iridium oxide films , 1981 .

[9]  Sejin Park,et al.  Nanoporous platinum solid-state reference electrode with layer-by-layer polyelectrolyte junction for pH sensing chip. , 2011, Lab on a chip.

[10]  Michael J. Tarlov,et al.  Sputtered thin-film pH electrodes of platinum, palladium, ruthenium, and iridium oxides , 1995 .

[11]  Sung Yang,et al.  Fabrication method and characterization of electrodeposited and heat-treated iridium oxide films for pH sensing , 2014 .

[12]  Michael Gaitan,et al.  AgCl microelectrodes with improved stability for microfluidics , 2006 .

[13]  Marcin Majda,et al.  Effects of Electrodeposition Conditions and Protocol on the Properties of Iridium Oxide pH Sensor Electrodes , 2009 .

[14]  Isao Karube,et al.  Microfabricated Liquid Junction Ag/AgCl Reference Electrode and Its Application to a One-Chip Potentiometric Sensor , 1999 .

[15]  Min Wang,et al.  Fabrication and characterization of planar reference electrode for on-chip electroanalysis , 2006 .

[16]  N. Ito,et al.  Development of a micro-planar Ag/AgCl quasi-reference electrode with long-term stability for an amperometric glucose sensor , 2002 .

[17]  Byoung-Ho Kang,et al.  Enhancement of physical and chemical properties of thin film Ag/AgCl reference electrode using a Ni buffer layer , 2004 .

[18]  Sami Hietala,et al.  Sorption and diffusion of methanol and water in PVDF-g-PSSA and Nafion® 117 polymer electrolyte membranes , 2000 .

[19]  Mi-Sook Won,et al.  An all-solid-state reference electrode based on the layer-by-layer polymer coating. , 2007, The Analyst.

[20]  Patrick J. Kinlen,et al.  A solid-state pH sensor based on a Nafion-coated iridium oxide indicator electrode and a polymer-based silver chloride reference electrode , 1994 .

[21]  S. Cogan,et al.  Sputtered iridium oxide films for neural stimulation electrodes. , 2009, Journal of biomedical materials research. Part B, Applied biomaterials.

[22]  Isao Karube,et al.  Problems associated with the thin-film Ag/AgCl reference electrode and a novel structure with improved durability , 1998 .

[23]  R. Ruoff,et al.  The chemistry of graphene oxide. , 2010, Chemical Society reviews.

[24]  Joseph Wang,et al.  A „Hybrid“ Thin-Film pH Sensor with Integrated Thick-Film Reference , 2001 .

[25]  Cecilia Jiménez-Jorquera,et al.  Fabrication Process of Ag/AgCl Reference Pseudo-Electrode Based on Electrodeposition of Au on Pt Surfaces from Formaldehyde Baths: Chemical Stability and Adherence , 2009 .

[26]  M. Jamal Deen,et al.  Microfabricated Reference Electrodes and their Biosensing Applications , 2010, Sensors.

[27]  William A. MacCrehan,et al.  Ag/AgCl microelectrodes with improved stability for microfluidics , 2006 .

[28]  Craig E. Banks,et al.  Characterization and fabrication of disposable screen printed microelectrodes , 2009 .

[29]  P. Kurzweil,et al.  Metal Oxides and Ion-Exchanging Surfaces as pH Sensors in Liquids: State-of-the-Art and Outlook , 2009, Sensors.

[30]  Yuzuru Takamura,et al.  Fabrication and Characterization of Planar Screen-Printed Ag/AgCl Reference Electrode for Disposable Sensor Strip , 2010 .

[31]  John Atkinson,et al.  Thick film silver-silver chloride reference electrodes , 1998 .