Light harvesting and amplification of emission of donor perylene–acceptor perylene aggregates in aqueous medium.

With the aid of rational design, we have synthesized a pair of water-soluble donor- and acceptor-type twisted perylene bisimide units, which together form aggregates upon lowering the pH of the medium, providing bright yellow fluorescence. The light-harvesting efficiency of the co-assembled system can be tuned by controlling the ratio of donor to acceptor and 98.1 % efficiency has been achieved.