Two-photon absorbing block copolymer as a nanocarrier for porphyrin: Energy transfer and singlet oxygen generation in micellar aqueous solution

A novel amphiphilic water-soluble 2PA-chromophore-containing block copolymer was designed and synthesized. Micelles (nanostructures) were generated in the aqueous solution using the block copolymer and characterized using dynamic light scattering (DLS) and atomic force microscopy (AFM). We demonstrated that hydrophobic porphyrin could be incorporated into aqueous solution with the assistance of micelles. The results from DLS showed that the average diameters are in the range of 59-77 nm. Efficient energy transfer (as high as 96%) from the 2PA chromophore to porphyrin was observed in micellar aqueous solution even though the donor and acceptor were not covalently bonded. Furthermore, the energy transfer contributes to the efficient generation of the singlet oxygen (by a factor of 2.6 at 800 nm) from the porphyrin guest molecules.