Donor/Acceptor-Modified Electrodes for Photoelectrochemical and Photobioelectrochemical Applications

A 7-pyrrolidino-7-benzylamino-8,8-dicyanoquinodimethane, PBEDQ, (1), donor–acceptor–modified electrode yields, in the presence of hydroquinone, (2), an anodic photocurrent with quantum efficiency of 1.5%. The PBEDQ-functionalized electrode yields, in the presence of the electron acceptor diquat, (3), a cathodic photocurrent with a quantum efficiency corresponding to 2.1%. The electron transfer cascades leading to the anodic or cathodic photocurrents in the different systems are discussed. It is further demonstrated that the integration of 1,4-dihydronicotinamide adenine dinucleotide, NADH, as electron donor, with the PBEDQ-modified electrode leads to an anodic photocurrent. This allowed the assembly of a photobioelectrochemical integrated electrode composed of the photoactive PBEDQ donor–acceptor compound, NAD⁺ as cofactor, and the NAD⁺-dependent glucose dehydrogenase, GDH. Irradiation of the integrated electrode in the presence of glucose results in the GDH–biocatalyzed oxidation of glucose to gluconic acid with the concomitant generation of NADH that acts as electron donor for the photoactive donor–acceptor PBEDQ units, leading to the generation of steady-state anodic photocurrent. The photocurrent intensities are controlled by the concentrations of glucose. The integrated PBEDQ/NAD⁺/GDH electrodes introduces a functional photobioelectrochemical electrode for the detection of glucose, and demonstrates the assembly of a functional photo-biofuel cell that uses light and a biomass product (glucose) for the generation of electric power.