Ultrabright Fluorescent Organic Nanoparticles Based on Small‐Molecule Ionic Isolation Lattices**

Ultrabright fluorescent nanoparticles (NPs) hold great promise for demanding bioimaging applications. Recently, extremely bright molecular crystals of cationic fluorophores were obtained by hierarchical coassembly with cyanostar anion-receptor complexes. These small-molecule ionic isolation lattices (SMILES) ensure spatial and electronic to prohibit aggregation quenching dyes. We report a simple, one-step supramolecular approach formulate SMILES materials into NPs. Rhodamine-based NPs stabilized glycol amphiphiles show high fluorescence quantum yield (30 %) brightness per volume (5000 M−1 cm−1/nm3) 400 dye molecules packed 16-nm particles, corresponding particle absorption coefficient 4×107 cm−1. UV excitation the component leads higher (>6000 cm−1/ nm3) energy transfer rhodamine emitters. Coated stain cells are thus promising bioimaging.