Hexagonal single crystals of perylene with patterned heterogeneous domains

Abstract

Hexagonal single crystals of perylene were grown on a substrate by solution evaporation. Fluorescence microscopy images showed patterned heterogeneous domains with different fluorescence colors. Polarized ultra-low-frequency Raman microscopy revealed that the crystal structure is homogeneous throughout the entire crystal despite the domains observed in the fluorescence images. We concluded that hexagonal crystals were formed by the further growth of the rhombic β-crystal, which is one of the two polymorphs of the perylene crystal. This mechanism explains the formation of domains with different crystal qualities, resulting in different fluorescence colors.