Rate and mechanistic investigation of Eu(OTf)₂-mediated reduction of graphene oxide at room temperature

We describe a fast, efficient, and mild approach to prepare chemically reduced graphene oxide (rGO) at room temperature using divalent europium triflate {Eu(OTf)₂}. The characterization of solution-processable reduced graphene oxide has been carried out by various spectroscopic (FT-IR, UV-visible absorption, and Raman), microscopic (TEM and AFM), and powder X-ray diffraction (XRD) techniques. Kinetic study indicates that the bimolecular rate constants for the reduction of graphene oxide are 13.7 ± 0.7 and 5.3 ± 0.1 M^-1 s^-1 in tetrahydrofuran (THF)-water and acetonitrile (ACN)-water mixtures, respectively. The reduction rate constants are two orders of magnitude higher compared to the values obtained in the case of commonly used reducing agents such as the hydrazine derivative, sodium borohydride, and a glucose-ammonia mixture. The present work introduces a feasible reduction process for preparing reduced graphene oxide at ambient conditions, which is important for bulk production of GO. More importantly, the study explores the possibilities of utilizing the unique chemistry of divalent lanthanide complexes for chemical modifications of graphene oxide.