Optimization of particle size for high birefringence and fast switching time in electro-optical switching of graphene oxide dispersions

In order to use graphene oxide (GO) dispersions for electro-optical applications, both a high GO concentration and a high electrical sensitivity are essential; however, these have not been achieved to date. Here, we report that by optimizing the mean size of GO particles to approximately 0.5 μm, one can obtain a high GO concentration of up to 2 wt% and high electrical sensitivity simultaneously. By reducing the mean GO-particle size, the interparticle interaction and the rotational viscosity can be significantly reduced, and a high-concentration isotropic phase can be obtained. As a result, the maximum birefringence increases and the dynamic response becomes faster. However, further decrease of the mean size below 0.1 μm causes a decrease in the anisotropy of electrical polarizability, resulting in the reduction of the electrical sensitivity of GO dispersions.