Biomimetic Light-Harvesting Antenna Based on the Self-Assembly of Conjugated Polyelectrolytes Embedded within Lipid Membranes

Here we report a biomimetic light-harvesting antenna based on negatively charged poly(phenylene ethynylene) conjugated polyelectrolytes assembled within a positively charged lipid membrane scaffold constructed by the lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). Light harvested by the polymers was transferred via through-space mechanisms to a lipophilic energy acceptor (the cyanine dye DiI) whose effective molar absorption was enhanced by up to 18-fold due to the antenna effect. Absorption amplification of DiI was found to be due primarily to direct energy transfer from polymers. The efficiency of homoenergy transfer among polymers was next probed by the membrane embedding fullerene derivative phenyl-C-61-butryic acid methyl ester (PCBM) acting as an electron acceptor. PCBM was able to quench the emission of up to five polymers, consistent with a modest amount of homotransfer. The ability of the membrane to accommodate a high density of polymer donors without self-quenching was crucial to the success of electronic energy harvesting achieved. This work highlights the potential of lipid membranes as a platform to organize light-harvesting molecules on the nanoscale toward achieving efficient energy transfer to a target chromophore/trap.