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.

Novel electrochemical methods have been developed for determination of total hemoglobin, hematocrit, and detection of hemolysis in whole blood. Hemoglobin is measured through its peroxidase activity, a fluoride ion-selective electrode being used to monitor the rate of fluoride ion production from the oxidation of an organofluorine compound. Results agree well with those obtained with the cyanmethemoglobin method (r = 0.970). Hematocrit is determined from the ratio of the sodium ion concentrations measured with an ion-selective electrode before and after lysis of the erythrocytes. Results by this and the microhematocrit method correlated well (r = 0.987). Hemolysis in a whole-blood sample is detected by using an oxygen electrode to measure the oxygen released when hemoglobin in plasma is oxidized.

We report on the development of a technique for the rapid production of exfoliated graphite oxide, using an electrochemical oxidation and exfoliation method. Vitreous carbon foam (VCF) sheets were utilised as the anode in an electrolytic cell. VCF anodes were oxidized under a maximum applied electric field of 60V and a current of 2A in NaOH electrolyte solutions. The resulting solids, collected after separation of the electrolyte, were analysed using ultraviolet-visible spectroscopy, X-ray diffraction and scanning electron microscopy. The preliminary analysis shows that the solids collected were comprised of graphite oxide and partially reduced graphite oxide platelets. Quartz substrates coated in partially reduced graphite oxide solutions were thermally annealed to produce conductive layers.

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We report the fabrication and characterisation of the first graphene ring micro electrodes, formed by dip coating fibre optics with subsequently reduced graphite oxide. The behaviour of the so-formed Graphene RIng Micro Electrodes (GRIMEs) is studied using the ferricyanide probe redox system while electrode thicknesses is assessed using established electrochemical methods. A ring electrode of ∼73 nm thickness is produced on 220 μm diameter fibre optics, corresponding to an inner to outer radius ratio of >0.999, so allowing for use of extant analytical descriptions of very thin ring micro electrodes in data analysis. GRIMEs are highly reliable (current response invariant over >3000 scans) with the microring design allowing for efficient use of electrochemically active graphene edge sites. Further, the associated nA scale currents neatly obviate issues relating to the high resistivity of undoped graphene. Thus, the use of graphene in ring micro electrodes improves the reliability of existing micro electrode designs and expands the range of use of graphene-based electrochemical devices.