We have found that liquid gallium exhibits as a good graphitizing catalyst for a large area graphene sheet. While gallium and carbon are known to be an insoluble system, however, we have found that the catalytic reaction occurs at a very narrow interfacial region between amorphous carbon and liquid gallium. Amorphous carbon film was transformed into graphite layer composed of a few layers of graphene sheet. These thin graphene film can be easily transferred into silicon substrate through the intermediation of PDMS rubber stamping.

For the development of biofunctional carbon nanotubes for biosensors, drug carriers, and nanobiocatalysts, their aggregation and biofouling in aqueous solutions are crucial problems because this behavior leads to a reduction of their excellent optical and electrical properties and nanoscale size effects. This paper presents a new method for enhancing the dispersibility of protein-carbon nanotube conjugates and for exfoliating the protein from the carbon nanotube sidewalls through controlling the concentration of guanidine hydrochloride (Gdn·HCl) in the solution. In medium concentrations (2-3 M) of Gdn·HCl, the dispersibility of protein-carbon nanotube conjugates was found to be substantially increased without denaturation or aggregation of the proteins. At higher concentrations (>6 M) of Gdn·HCl, pristine carbon nanotubes were precipitated instantly as a result of dissociation of the protein. These phenomena indicate that Gdn·HCl functions not only as a dispersion adjuvant for biofunctional protein-carbon nanotube conjugates, but also as a cleaning agent for the purification of biofouled carbon nanotubes. The dissociation concentrations of Gdn·HCl were higher than the midpoint of protein denaturation, suggesting that protein adsorption on carbon nanotubes is more stable than protein folding toward Gdn·HCl.