Hierarchical Growth of Fluorescent Dye Aggregates in Water by Fusion of Segmented Nanostructures

Dye aggregates are becoming increasingly attractive for diverse applications, in particular as organic electronic and sensor materials. However, the growth processes of such aggregates from molecular to small assemblies up to nanostructures is still not properly understood, limiting the design of materials’ functional properties. Here we elucidate the supramolecular growth process for an outstanding class of functional dyes, perylene bisimides (PBIs), by transmission electron microscopy (TEM), cryogenic scanning electron microscopy (cryo‐SEM), and atomic force microscopy (AFM). Our studies reveal a sequential growth of amphiphilic PBI dyes from nanorods into nanoribbons in water by fusion and fission processes. More intriguingly, the fluorescence observed for higher hierarchical order nanoribbons was enhanced relative to that of nanorods. Our results provide insight into the relationship between molecular, morphological, and functional properties of self‐assembled organic materials. Seeing is believing: Amphiphilic perylene bisimide aggregates were visualized by transmission electron microscopy and the self‐assembly of dye aggregates from small nanorods to large nanoribbons in water was observed on the molecular level. The fluorescence properties of these dye aggregates were enhanced for the higher order nanostructures.