were not observed here under fluorescence microscopy due to the low concentration of 2 molecules, insufficient to afford the self-assembly of (S)-2PDI into nanofibers. In addition, a well-defined network of blue-green emitting fluorescent nanofibers, accompanied by several red spots was observed in the fluorescence images of the sample (R)-1NDI in the presence of 1. The distinct emission spectrum at different positions of the nanofibers (Figure ) indicates a large diversity of the major emitting species present in the sample. The inhomogeneity of the host-guest system likely arises from the random distribution of (S)-2PDI guests on the (R)-1NDI nanofibers during the solvent drying process, when the samples were drop-cast onto alkyl-coated glass slides, since such a broad emission band around 640 nm was negligible in the solution state. The dispersion of (S)-2PDI guests on the nanofibers resulted in energy transfer from (R)-1NDI nanofibers to individual (S)-2PDI units ((S)-2PDImono) due to the PDI molecules in their molecularly dispersed form similar to that in the MCH-rich solution. previous TEM studies in the solution phase. Additionally, the occurrence of bright red spots at the branching points of the thin nanofibers is quite apparent in these AFM images (Figure II-IV).