The preparation of solution-processable graphene from graphite oxide typically involves a hydrazine reduction step, but the use of such a reagent in the large-scale implementation of this approach is not desirable due to its high toxicity. Here, we compare the deoxygenation efficiency of graphene oxide suspensions by different reductants (sodium borohydride, pyrogallol, and vitamin C, in addition to hydrazine), as well as by heating the suspensions under alkaline conditions. In almost all cases, the degree of reduction attainable and the subsequent restoration of relevant properties (e.g., electrical conductivity) lag significantly behind those achieved with hydrazine. Only vitamin C is found to yield highly reduced suspensions in a way comparable to those provided by hydrazine. Stable suspensions of vitamin C-reduced graphene oxide can be prepared not only in water but also in common organic solvents, such as N,N-dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP). These results open the perspective of replacing hydrazine in the reduction of graphene oxide suspensions by an innocuous and safe reductant of similar efficacy, thus facilitating the use of graphene-based materials for large-scale applications.

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Graphene has attracted a great deal of scientific interest in latter years owing to its unique properties, with many prospective applications being actively investigated at present. However, the actual implementation of graphene in technological uses will depend critically on the development of appropriate methodologies for its mass production. In this regard, one of the most promising approaches is based on the exfoliation and reduction of graphite oxide. Graphenes derived from graphite oxide can be prepared at low cost and high throughput, can be further processed in a number of solvents, and are chemically versatile, among other attractive features. In an environment-conscious world, the availability of green approaches toward graphene production would also constitute an added advantage. During the last year, different environmentally friendly methods for the production of graphene from graphite oxide have emerged, which we highlight here. These are based on solvothermal and electrochemical processes, as well as on the use of green reductants. Several open questions and possible future directions for this research topic are also discussed. L: GuardiaLaura Guardia graduated in Chemistry from University of Buenos Aires (Argentina) and received a PhD degree from the University of Oviedo on molecular recognition of antibiotics. Currently, she is a post-doctoral researcher at INCAR, working on the synthesis and applications of graphene.

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Chemical reduction of exfoliated graphite oxide (graphene oxide) has become one of the most promising routes for the mass production of graphene sheets. Nonetheless, the material obtained by this method exhibits considerable structural disorder and residual oxygen groups, and reports on their microscopic structure are quite scarce. We have investigated the structure and chemistry of graphene oxide samples reduced to different degrees using atomic force and scanning tunneling microscopy (AFM/STM) as well as X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD), respectively. TPD and XPS results indicate that reduction proceeds mainly by eliminating the most labile oxygen groups, which are ascribed to epoxides and hydroxyls on basal positions of the graphene plane. AFM/STM shows that the sheets are composed of buckled oxidized regions intermingled with flatter, non-oxidized ones, with the relative area of the latter increasing with the reduction degree.