Solution-processable method for producing high-quality reduced graphene oxide displaying 'self-catalytic healing’

Reduced graphene oxide (rGO) has potential as a mass-producible and cost-effective substitute for graphene, but displays poor crystal quality due to various types of structural defects. Though many attempts have been reported to improve the quality of rGO, most of them require sophisticated equipment or severe conditions such as toxic chemicals, high temperature, and electron beam or plasma treatment in ultra-high vacuum (UHV) conditions. Here, we report a mild and simple solution-based healing method for obtaining high-quality rGO, with this method involving the use of a simple camera flash light treatment and the nontoxic chemicals L-ascorbic acid and ethanol. Exposing a GO solution containing L-ascorbic acid and ethanol to the flash light irradiation for a short amount of time (<10 min) resulted in the formation of rGO displaying high quality both with respect to its chemical composition and its crystallinity. To elucidate the mechanism of the flash-light-induced healing of rGO, we acquired and analyzed the transient absorption spectrum for the healing reaction by using femtosecond pump-probe spectroscopy; this analysis revealed the photo-catalytic activity of GO by itself to repair chemical and topological defects, and we hence named this process 'self-catalytic healing’.