Frequency-dependent electro-optic properties of graphene oxide liquid crystal

Aqueous graphene oxide (GO) has recently been recognized as a promising liquid crystal (LC) material with significant application potential in electro-optic devices. Previous studies have predominantly focused on a single electric frequency of 10 kHz for achieving highly sensitive responses, while the electro-optic properties of GO-LC across a broad frequency range remain unexplored. Investigating the frequency dependence of electro-optic performance is crucial for optimizing the electric-field-driven alignment of GO-LC. In this paper, we investigate the electro-optic properties of GO-LC at various concentrations in the frequency range of 1 Hz–50 MHz. GO-LC in the bi-phase or isotropic liquid crystalline phase exhibits the highest electro-optic birefringence within the frequency range of 100 Hz to 2 × 10⁵ Hz, and the nanosheet reorientation phenomenon at the nematic phase is observed. The frequency-dependent characteristics of field-induced birefringence are successfully explained using electrokinetic effects and Maxwell-Wagner-O'Konski's (MWO) theory at different frequency ranges. This study demonstrates that the electro-optic properties and the orientation of GO nanosheets can be effectively controlled by modulating the electric frequency, which is critical for nanosheet alignment manipulation and the development of optical modulators and other electro-optic devices.