Strong emission of excimers realized by dense packing of pyrenes in tailored bola-amphiphile nano assemblies

Pyrene is known for the quenched emission of excimers, especially in aqueous solution. Here, we report strong emission of pyrene excimers realized in amphiphile assemblies by controlling the face-to-face distance between the pyrene planes. We find that both the self-assembly behavior and emission properties of a cationic pyrene-containing amphiphile (denoted by PRB) are altered by exchanging the counterions. Upon the addition of sodium mesitylenesulfonate (Na MtS), the excimer emission of pyrene in self-assembled aggregates of PRB is greatly enhanced in aqueous solution. Concomitantly, the disk-like assemblies of PRB are converted to spherical particles, in which the repulsive interactions of the head groups are screened by replacing the counterions of the PRB molecules. The quantum yield of PRB increases from 0.5% to 16.6%, which is attributed to the dense packing of pyrene moieties in the aggregates. This study demonstrates that controlling supramolecular interactions is a feasible avenue to enhance the emission of pyrene excimers in amphiphile assemblies.