Gibbs–Curie–Wulff-directed 2D cocrystal evolution for tunable in-plane anisotropic and isotropic photon transmission

Abstract

Two-dimensional (2D) molecular crystals, which could directionally manipulate the photons/electrons in a plane, hold great promise for on-chip optoelectronics. Molecular co-crystallization, a cost-effective approach without involving complicated chemical synthesis, has garnered growing interest for the construction of such 2D crystals. However, to date, 2D cocrystal evolution laws are highly unclear, lacking predictable patterns, so that rationally tailoring the 2D structures and properties from the same cocrystal remains a challenge. Here we report a Gibbs–Curie–Wulff-theory-based 2D cocrystal assembly and evolution law to modulate cocrystal microstructures and related light transmission properties. By tuning the temperature to adjust relative growth rates of different crystal facets, a 2D cocrystal was successfully evolved from the elongated hexagons to regular hexagons and then to rhombuses. This evolution follows the Gibbs–Curie–Wulff principle, demonstrating its applicability in complex multi-component co-crystallization. Furthermore, these 2D crystals exhibit distinct morphology-dependent anisotropic/isotropic photon transport behaviors, which display great potential in 2D on-chip optoelectronics.