Submitted Abstract
Properties of matter arise from the nature of the constituents and their organization. Similarly, the macroscopic properties of nanoparticles, especially if anisotropic, are strongly determined by their assembly. Graphene, a bidimensional nanomaterial, is known for its outstanding properties but only recently is emerging as a new member of the soft matter family with unique characteristics even at macroscopic scale due to the collective behaviour of the flakes in a liquid environment. The anisotropy of the flakes is remarkably high, being of monoatomic thickness and up to hundreds of micrometers of diameter, allowing the formation of ordered phase at extremely low concentrations. So far, due to its good dispersion in water thanks to the presence of functional groups, mainly graphene oxide (GO) has shown liquid crystal (LC) phases and an amazing optical response to very low electric fields inducing orientational order from optically isotropic states. The first aim of this project is to improve the current understanding of the properties of graphene oxide liquid crystal isolating fundamental aspects driving the assembly and the field response in the different phases often shaded by the high size polydispersity of the samples. Since graphene is generally regarded a more performing material, LC graphene dispersions are expected to be more responsive and with improved properties compared to GO LC and this was indeed recently confirmed. A second goal of this project is to realize new colloidal systems of graphene by extending an approach used for improving dispersions of carbon nanotubes based on the behaviour of surfactants below the Krafft temperature to increase the graphene concentration but at the same time minimizing the surfactant presence, thus the charges, while keeping the flakes separated. Besides aspects that belongs to colloidal science the final goal is to address various physical questions that are still not completely clear necessary to fully understand and properly exploit the system such as the mechanism inducing the reorientation of the flakes, the optical properties of the individual flakes and their contribution to the macroscopic optical properties.