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carrier properties of graphene (and other two-dimensional materials) were found not only to be continuous, but to exhibit high crystal quality, in which importantly for graphene charge carriers can travel thousands of inter-atomic distances without scattering.4 These isolated graphene crystallites demonstrate exceptional electronic qualities, and graphene has exhibited the fastest electron mobilities when compared to all other possible materials, ‘theoretically’ meaning that in many applications graphene based electrodes react much faster.4 Advantages of using graphene as an electrode material Carbon materials have been widely utilised in both analytical and industrial electrochemistry, where in many areas they have out- performed the traditional noble metals. This diversity and success stems largely from carbons structural polymorphism, chemical stability, low cost, wide potential windows, relatively inert electrochemistry, rich surface chemistry and electro-cata- lytic activities for a variety of redox reactions.5 Most recently though the classical carbon materials based on graphite, glassy carbon, diamond and carbon black have been outperformed by the distinctive properties of micro-fabricated carbon structures, such as CNTs, enabling novel applications in sensing, electro- catalysis, and electronics. Until now CNTs have fore-fronted innovation and dominated the field, however, with the intro- duction of graphene, which is reported to offer more advanced properties and is likely to exhibit fewer of the weaknesses that plagued CNTs, enormous progress in this field is underway, led mainly because the relevant research concerning graphene can be built on the wealth of techniques and knowledge available from decades of research on graphite and CNTs, where it can possibly outperform them at each opportunity.5 Oxygenated species on graphene A major advantage of graphene that corresponds to determining its function is the presence of oxygen-containing groups at its edges or surface. These groups will greatly influence the elec- trochemical performance of graphene in terms of the heteroge- neous electron transfer rate as is observed for graphite electrodes and CNTs—which can be either advantageous or detrimental towards the sensing of a target analyte.20,21 Recently it has been shown that the voltammetric separation and sensitivity of uric and ascorbic acid can be achieved at graphitic oxide nano- platelets using a microwave-assisted hydrothermal elimination method. This method allows the density of oxygen-containing functional groups to be controlled, thus allowing the discrimi- nation of the peak separation of the target analytes which can commonly overlap on conventional graphite electrodes.22 When controlled attachment of functional elements are required, such as in the development of nano-architectonics, these sites provide convenient attachment sites, which are expected to be similar to that observed for CNTs.23 It has been reported for the case of CNTs that enediol groups on edge plane like-sites/defects are responsible for the enhancement of electron transfer for selected analytes through the withdrawal of two protons from the endiol groups, aiding the oxidation processes and giving rise to an observed reduction in overpotential voltages.2 We suggest that this might also be the case for graphene, but further research into this is required. The effects of oxygen-containing groups on graphene span much further, influencing the adsorption/desorption of mole- cules that takes place before and after an electrochemical reac- tion. In addition to this, specific groups can be introduced that play vital roles in electrochemical sensing and battery applica- tions.2 It is noteworthy that the electrochemical properties of graphene-based electrodes can hence be modified or tuned by chemical modification, and tailored to suit its application.6 It is heavily debatable, however, whether the presence of oxides upon its surface, in addition to the defect sites within graphene, may change its electronic and chemical properties for better or worse.24 These can possibly block the electrode activity; however, reports have shown that these can also enhance the performance of the electrode.10 Work on CNTs has shown that the oxygenated species may be ‘labelled’ and consequently identified with voltammetry and XPS. We expect that this methodology can be readily utilised in the case of graphene.25–27 The use of these oxygenated species can be used as ‘anchoring’ sites, for example the attachment of glucose oxidase (GOx) and diazonium species for a range of sensing applications.28–32 Graphene shows great electro- catalytic behaviour that is attributed to its unique physical and chemical properties, for example subtle electronic characteris- tics (attractive p–p interactions and its strong absorptive capability),24 suggesting a future in energy and molecule storage, mainly because of the extraordinary electronic prop- erties of graphene.24 Having considered each of graphenes unique electrochemical properties in turn, of which all are reported to be similar or slightly better than those of CNTs, it is apparent that graphene has one more significant advantage over CNTs: graphene generally does not contain metallic impurities.33,34 These impu- rities are commonly the ‘hidden’ origin of electrochemical activity for many analytes, which is inherent to the Chemical Vapour Deposition (CVD) fabrication process—with the amount of metallic impurities greatly varying between batches hindering exploitation, for example in the fabrication of reliable sensors and energy devices.35 Note, however, that there are some methods of fabricating graphene which involve CVD,12,36,37 and in these cases appropriate control experiments might need to be performed (within many CVD methods based around graphene production, however, non-metallic catalysts are used to over- come this issue). Industrial concepts also need to be considered; compared to CNTs and other electrode materials the production and pro- cessing of graphene appear to be simpler and more economic. Graphene can be produced on a much larger and cheaper scale than any of its counterparts and other electrode materials, meaning that the interest within it remains rife; rendering gra- phene an inexpensive alternative. However, at the present time (2010) because of the relative novelty of graphene and its little known manufacturing methods, corporate companies producing graphene are pricing very highly indeed. These prices are expected to drop with time as large-scale graphene production becomes easier and companies compete for customers. Note also, as with CNTs, reproducibility of fabrication and control of defects are likely to be problems common to graphene. 2770 | Analyst, 2010, 135, 2768–2778 This journal is a The Royal Society of Chemistry 2010 View Article Online Published on 04 October 2010. 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