Submerged liquid plasma for the synchronized reduction and functionalization of graphene oxide

Formation of reduced and functionalized graphene oxide (r-FGO) at ambient temperature and pressure is demonstrated by generating liquid plasma submerged in acetonitrile and graphene oxide solution. The partial restoration of conjugation (sp(2) domain) and insertion of fluorophores such as nitrile and amine in r-FGO displays enhanced fluorescence property. Presence of nitrile and amine in r-FGO are confirmed by X-ray photoelectron spectroscopy and Fourier transforms infrared spectroscopy. Morphology and optical property of r-FGO are studied with transmission electron microscopy, scanning tunneling microscopy and Ultraviolet-visible spectroscopy measurements. The nitrile and amine present in r-FGO undergo a surface-controlled reversible redox reaction and sp(2)- enriched r-FGO acts as an electrical double layer, providing additional hybrid capacitance or pseudocapacitance. r-FGO shows high cyclic stability with a specific capacitance value of 349 F/g at the scan rate of 10 mV/s. Only marginal reduction of specific capacitance (<10% reduction) is observed at the end of 1000 cycles.