We report the fabrication and characterisation of the first graphene ring micro electrodes with the addition of a miniature concentric Ag/AgCl reference electrode. The graphene ring electrode is formed by dip coating fibre optics with graphene produced by a modified Hummers method. The reference electrode is formed using an established photocatalytically initiated electroless deposition (PIED) plating method. The performance of the so-formed graphene ring micro electrodes (GRiMEs) and associated reference electrode is studied using the probe redox system ferricyanide and electrode thicknesses assessed using established electrochemical methods. Using 220 μm diameter fibre optics, a ~15 nm thick graphene ring electrode is obtained corresponding to an inner to outer radius ratio of >0.999, so allowing for use of extant analytical descriptions of very thin ring microelectrodes in data analysis. GRiMEs are highly reliable (current response invariant over >3,000 scans), with the concentric reference electrode showing comparable stability (current response invariant over >300 scans). Furthermore the micro-ring design allows for efficient use of electrochemically active graphene edge sites and the associated nA scale currents obtained neatly obviate issues relating to the high resistivity of undoped graphene. Thus, the use of graphene in ring microelectrodes improves the reliability of existing micro-electrode designs and expands the range of use of graphene-based electrochemical devices.
References
[1]
Smith, C.P.; White, H.S. Theory of the voltammetric response of electrodes of submicron dimensions. Anal. Chem. 1993, 65, 3343–3353.
[2]
Henstridge, M.C.; Dickinson, E.J.F. On the estimation of the diffuse double layer of carbon nanotubes using classical theory: Curvature effects on the Gouy-Chapman limit. Chem. Phys. Lett. 2010, 485, 167–170.
[3]
Liu, Y.; He, R. Theory of electrochemistry for nanometer-sized disk electrodes. J. Phys. Chem. C 2010, 114, 10812–10822.
[4]
Watkins, J.J.; Zhang, B. Electrochemistry at nano-scaled electrodes. J. Chem. 2005, 82, 712–719.
[5]
Kou, R.; Shao, Y. Stabilization of electrocatalytic metal nanoparticles at metal-metal oxide- graphene triple junction points. J. Am. Chem. Soc. 2011, 133, 2541–2547.
[6]
Stoller, M.D.; Park, S. Graphene-based ultracapacitors. Nano Lett. 2008, 8, 3498–3502.
[7]
Keeley, P.A.; McEvoy, N. Thin film pyrolytic carbon electrodes: A new class of carbon electrode for electroanalytical sensing applications. Electrochem. Comm. 2010, 12, 1034–1036.
[8]
Wang, Y.; Velmurugan, J. Kinetics of charge-transfer reactions at nanoscopic electrochemical interfaces. Isr. J. Chem. 2010, 50, 291–305.
[9]
Arrigan, D.W.M. Nanoelectrodes, nanoelectrode arrays and their applications. Analyst 2004, 129, 1157–1165.
[10]
Sanchez, V.C.; Jachak, A. Biological interactions of graphene-family nanomaterials: An interdisciplinary review. Chem. Res. Toxicol. 2011, 25, 15–34.
[11]
Shao, Y.; Wang, J. Graphene based electrochemical sensors and biosensors: A review. Electroanalysis 2010, 22, 1027–1036.
[12]
Wang, J.; Lu, D. Voltammetric sensor for uranium based on the propyl gallate-modified carbon paste electrode. Electroanalysis 1995, 7, 247–250.
[13]
Ni, Z.H.; Wang, H.M. Graphene thickness determination using reflection and contrast spectroscopy. Nano Lett. 2007, 7, 2758–2763.
[14]
Ambrosi, A.; Sasaki, T. Platelet graphite nanofibers for electrochemical sensing and biosensing: The influence of graphene sheet orientation. Chem. Asian J. 2010, 5, 266–271.
[15]
Xu, X.; Weber, S.G. Carbon fiber/epoxy composite ring-disk electrode: Fabrication, characterization and application to electrochemical detection in capillary high performance liquid chromatography. Electroanal. Chem. 2009, 630, 75–80.
[16]
Xu, K.; Ding, M.S. A better quantification of electrochemical stability limits for electrolytes in double layer capacitors. Electrochim. Acta 2001, 46, 1823–1827.
[17]
Shang, N.G.; Papakonstantinou, P. Catalyst-free efficient growth, orientation and biosensing properties of multilayer graphene nanoflake films with sharp edge planes. Adv. Funct. Mater. 2008, 18, 3506–3514.
[18]
Diekmann, C.; Cammann, D. Disposable reference electrode. Sens. Actuators B Chem. 1995, 24, 276–278.
[19]
Pedrotti, J.J.; Angnes, L. Miniaturized reference electrodes with microporous polymer junctions. Electroanalysis 1996, 8, 673–675.
[20]
Desmond, D.; Lane, B. Evaluation of miniaturised solid state reference electrodes on a silicon based component. Sens. Actuators 1997, 44, 389–396.
[21]
Hassel, W.A.; Fushimi, K. An agar-based silver/silver chloride reference electrode for use in micro-electrochemistry. Electrochem. Commun. 1999, 1, 180–183.
[22]
Suzuki, H.; Shiroishi, H. Microfabricated liquid junction Ag/AgCl reference electrode and its application to a one-chip potentiometric sensor. Anal. Chem. 1999, 71, 5069–5075.
[23]
Huang, R.S.; Huang, I.Y. Fabrication and characterisation of a new planer solid-state reference electrode for ISFET sensors. Thin Solid Films 2002, 406, 255–261.
[24]
Zhou, J.; Ren, K. Fabrication of a microfluidic Ag/AgCl reference electrode and its application for portable and disposable electrochemical microchips. Electrophoresis 2010, 31, 3083–3089.
[25]
Becerril, H.A.; Mao, J. Evaluation of solution-processed reduced graphene oxide films as transparent conductors. Am. Chem. Soc. 2008, 2, 463–470.
[26]
Hummers, W.S.; Offeman, R.E. Preparation of graphitic oxide. J. Am. Chem. Soc. 1958, 80, 1339–1339.
[27]
Goss, C.A.; Charych, D.H. Application of (3-mercaptopropyl)trimethoxysilane as a molecular adhesive in the fabrication of vapor-deposited gold electrodes on glass substrates. Anal. Chem. 1991, 63, 85–88.
[28]
Bromley, M.A.; Boxall, C. Photocatalytic initiation of electroless deposition. J. Photochem. Photobiol. A Chem. 2010, 216, 228–237.
[29]
Yu, J.C.; Ho, W. Light-induced super-hydrophilicity and photocatalytic activity of mesoporous TiO2 thin films. J. Photochem. Photobiol. A Chem. 2001, 148, 331–339.
[30]
Blake, P.; Hill, E.W. Making graphene visible. Appl. Phys. Lett. 2007, 91, 063124.
[31]
Stankovich, S.; Dikin, D.A. Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide. Carbon 2007, 45, 1558–1565.
[32]
Willemse, C.M.; Tlhomelang, K. Metallo-graphene nanocomposite electrocayalytic platform for the determination of toxic metal ions. Sensors 2011, 11, 3970–3987.
[33]
Goncalves, E.S.; Rezende, M.C. Dynamics of defects and surface structure formation in reticulated vitreous carbon. Braz. J. Phys. 2006, 36, 264–266.
[34]
Choucair, M.; Thordarson, P. Gram-scale production of graphene based on solvothermal synthesis and sonication. Nat. Nanotechnol. 2009, 4, 30–33.
[35]
Pimenta, M.A.; Dresselhaus, G. Studying disorder in graphite-based systems by Raman spectroscopy. Phys. Chem. Chem. Phys. 2007, 9, 1276–1291.
[36]
Ferrari, A.C.; Meyer, J.C. Raman spectrum of graphene and graphene layers. Phys. Rev. Lett. 2006, 97, 187401.
[37]
Radovic, L.R. Chemistry and Physics of Carbon: A Series of Advances; Marcel Dekker: New York, NY, USA, 2001; Volume 27, pp. 382–393.
[38]
Kharissova, O.V.; Kharisov, B.I. Graphenes, one of the hottest areas in the nanotechnology: Attention of chemists is needed. Open Inorg. Chem. J. 2008, 2, 39–49.
[39]
Biniak, S.; Pakula, M. Effect of activated carbon surface oxygen- and/or nitrogen- containing groups on adsorption of copper(II) ions from aqueous solution. Langmuir 1999, 15, 6117–6122.
[40]
Bard, A.J.; Faulkner, L.R. Electrochemical Methods, 2nd ed. ed.; John Wiley & Sons Inc: New York, NY, USA, 2001; pp. 808–809.
[41]
Szabo, A. Theory of the current at microelectrodes: Application to ring electrodes. J. Phys. Chem. 1987, 91, 3108–3111.
[42]
Smythe, W.R. The capacitance of a circular annulus. J. Appl. Phys. 1951, 22, 1499–1502.
