Zinc porphyrin/fullerene/block copolymer micelle for enhanced electron transfer ability and stability

Abstract

Inspired by the structures of antenna-reaction centers in photosynthesis, a complex micelle was prepared from zinc tetrakis(4-sulfonatophenyl) porphyrin (ZnTPPS), modified fullerene (mC₆₀) and poly(ethylene glycol)-block-poly(L-lysine) (PEG-b-PLys) by electrostatic interactions. The core–shell structure made the donor–acceptor system work in an aqueous environment. In the micellar core, ZnTPPS and mC₆₀ molecules were surrounded by each other which ensured effective energy migration from the donor to the acceptor. The emission of the porphyrin was quenched efficiently which was confirmed by a series of fluorescence spectra. In comparison with the ZnTPPS micelle, the interaction of the mC₆₀ with the porphyrin inhibited the generation of singlet oxygen, which was measured by electron paramagnetic resonance (EPR) and iodide method. In addition, enhanced generation of the superoxide radical was detected by reduction of nitro blue tetrazolium (NBT) in the presence of an electron donor. What is more, the complex micelle exhibited high electron transfer performance in the photocatalytic reduction of methyl viologen. The complex micellar structure endowed the donor–acceptor system with improved stability in an acidic environment. This strategy would be helpful for designing a new electron transfer platform and artificial photosynthetic system.