Enhanced thermal stability and monodomain growth in a 3D soft photonic crystal aided by graphene substrate

We report the growth of monodomain blue phase liquid crystal and its thermal stability on reduced graphene oxide-grown quartz substrates using optical reflection microscopy and spectroscopy. Optical textural images show that the graphene substrate enhances the thermal range of the blue phase by a factor of four compared to conventional ITO-coated glass substrate. The phase is stabilized down to sub-ambient temperatures (from 60 °C to 18 °C) with the blue phase domains remaining undistorted at ambient conditions for more than three months. Also, the graphene substrate aids the monodomain formation with the average BP platelet size being nearly two orders of magnitude larger compared to the ITO / bare quartz substrates. The enhanced thermal stability and single-crystal-like growth of the blue phase are due to the improved wettability and non-covalent π-π interaction between graphene layers and liquid crystal molecules, as confirmed from the contact angle and Raman spectroscopic measurements respectively. Thus, the room temperature stable, graphene layer-stabilized-blue phase is an ideal candidate for high-performance photonic applications. [Display omitted] •Large monodomain growth of BP on graphene substrates compared to ITO-glass / quartz substrates.•The monodomain growth of BP leads to superior selective reflection spectral purity.•Graphene substrate aids in enhancing the thermal stability of BP up to sub-ambient temperatures.•Better wettability between graphene layers and LC molecules is responsible for monodomain growth.