Effect of centrifugal cleaning on the electro-optic response in the preparation of aqueous graphene-oxide dispersions

The quality of aqueous graphene oxide (GO) dispersions relies partially on the centrifugal cleaning process in the Hummers method. As the number of centrifugal cleaning cycle increases, the concentration of the residual salts of oxidizing reagents decreases, and the exfoliation of graphite oxide into GO sheets is enhanced. We found that the electrical sensitivity of a GO dispersion in its electro-optic dynamics increases sharply with an increasing number of cleaning cycles. We discovered that the removal of the residual salts decreases the solvent conductivity, and the exfoliation increases the aspect ratio of GO particles, which are closely related to the anisotropic polarizability of GO particles and the electrical sensitivity. (C) 2014 Elsevier Ltd. All rights reserved.