Electric Field-Induced Ordering of Reduced Graphene Oxide Particles in Colloid

We demonstrated that the alignment of reduced graphene oxide (rGO) particles in dimethylformamide dispersions was electrically controlled. The field-induced alignment of the rGO particles imparted an optical anisotropy of both the birefringence and dichroism, simultaneously. The optical transmittance with crossed polarizers is determined by the combination of both birefringence and dichroism, and hence, it is somewhat difficult and inaccurate to calculate the degree of the ordering of rGO particles. On the other hand, by using parallel polarizers in the measurement, the birefringence effect could be eliminated, and we measured the order parameter of the rGO. Interestingly, the order parameter of rGO particles was high and comparable to that in GO dispersion. The saturated S order parameter at high electric fields decreased, as the rGO concentration increased. The field-induced rGO ordering will be useful for various applications such as flexible electronics and energy storage devices.