http://www.nature.com/nchem/reshigh/2008/1108/full/nchem.88.html
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Graphene synthesis: Chemical peel
Anne Pichon
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Abstract
Large graphene sheets can be prepared by reduction of graphite oxide in pure hydrazine
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Introduction
© 2008 NPG
Graphene, a single layer of carbon atoms in a honeycomb lattice, is the building block of graphitic materials (fullerenes, carbon nanotubes and graphite). Despite a flurry of investigations prompted by the recent discovery of its unusual physical properties, however, graphene sheets are still difficult to prepare. The reduction of silicon carbide at high temperature is a laborious, low-yield procedure. Mechanical methods to separate graphite sheets with adhesive tape are hard to scale up, and chemical processes — where graphite oxide sheets are separated before being reduced by hydrazine — have been hindered by their re-aggregation in aqueous solution.
Now, Yang Yang, Richard Kaner and co-workers at the University of California, Los Angeles, have successfully avoided re-aggregation1 by using pure hydrazine as a solvent. Colloids were formed in which each two-dimensional sheet was surrounded by hydrazinium counter-ions. This enabled a good dispersion as well as a complete reduction, thereby producing single- or few-layer graphene on deposition onto a surface. Observation of the sheets by microscopy and computer-generated molecular models of the structure both suggest that the planar structure of graphene is re-established by the removal of alcohol and acid functional groups on reduction.
The morphology and surface coverage can be controlled by the concentration and composition of the dispersion, and the large graphene sheets prepared are easily processed and characterized. They also display better electrical properties than those of other chemically converted graphene sheets, displaying performances close to peeled graphite when deposited on silica and incorporated as the semiconducting layer in field-effect transistors.
Top of pageReference
Tung V. C., Allen M. J., Yang Y. & Kaner R. B. High-throughput solution processing of large-scale graphene. Nature Nanotech. doi:10.1038/nnano.2008.329 (2008). | Article |
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