Electric-Field-Mediated Electron Tunneling of Supramolecular Naphthalimide Nanostructures for Biomimetic H2 Production

The design and synthesis of two semiconducting bis (4-ethynyl-bridging 1, 8-naphthalimide) bolaamphiphiles (BENI-COO- and BENI-NH3+) to fabricate supramolecular metal-insulator-semiconductor (MIS) nanostructures for biomimetic hydrogen evolution under visible light irradiation is presented. A H-2 evolution rate of ca. 3.12 mmol g(-1).h(-1) and an apparent quantum efficiency (AQE) of ca. 1.63 % at 400 nm were achieved over the BENI-COO--NH3+-Ni MIS photosystem prepared by electrostatic self-assembly of BENI-COO- with the opposite-charged DuBois-Ni catalysts. The hot electrons of photoexcited BENI-COO- nanofibers were tunneled to the molecular Ni collectors across a salt bridge and an alkyl region of 2.2-2.5 nm length at a rate of 6.10x10(8) s(-1), which is five times larger than the BENI-NH3+ nanoribbons (1.17x10(8) s(-1)). The electric field benefited significantly the electron tunneling dynamics and compensated the charge-separated states insufficient in the BENI-COO- nanofibers.