Analysis of the electro-optical response of graphene oxide dispersions under alternating fields

Abstract Recently, graphene oxide (GO) has attracted much attention because of its many potential applications, such as the fabrication of transparent electrodes or drug delivery, in addition to its use as a precursor for large-scale production of graphene flakes. However, the interaction of this material with electric fields is yet poorly understood, and only recently the orientation of GO particles with an electric field was achieved. In this work, we analyse the electro-orientation of GO flakes in aqueous suspension in the absence of interparticle interactions, under different experimental conditions. From the measurement of linear dichroism, the electrical polarizability of the GO flakes as a function of the field frequency was calculated. The results show a pronounced relaxation process in the kHz range that leads to a large high-frequency polarizability. This phenomenology is explained as follows: For high-frequency fields, the polarizability is that of conducting particles immersed in a dielectric; for frequencies below the kHz range, in contrast, ions in solution redistribute and screen the induced dipole. Hence, the use of high-frequency electric fields strongly enhances GO electro-orientation. Furthermore, from the linear dichroism measurements, the particle absorption coefficient and the sample size distribution could be obtained.