The photosynthetic electron transport chain allows for a fast charge transfer of excited electrons out of chloroplasts. Redox-active quinone groups take up electrons and forward them in the thylakoid membrane. We are mimicking this redox mediation with the quinone/catechol - redox pair of the bioinspired polymer polydopamine. Electropolymerization allows for the creation of ultrathin polydopamine membranes through which short ranged redox mediated electron transfer is possible. The membranes are functionalized on one side with photosensitizers, CdSe@CdS dot-in-rod nanorods (NRs), and on the other side with catalysts.

PDA is a redox-active, highly adhesive, functionalizable and versatile polymer. Its composition is based on the structure of mussel proteins. The NRs consist of a cadmium selenide (CdSe) core, that is encased with cadmium sulfide (CdS). Sunlight excites electrons that get separated along the NR’s length from electron holes that remain at the CdSe core. PDAs redox moieties, quinone and catechol groups, act as electron mediators. Thes support the transport of excited electrons, which counteracts recombination of electrons and electron holes, and fill electron holes in the photosensitizers, which reduces photodegradation. Furthermore the membrane allows for redox mediated electron transport of excited electron from the rods to the catalysts, enabling photocatalysis.

The versatility of this approach provides a general modular platform for the incorporation of (bio)catalysts for synthesis, degradation of pollutants and bio sensing and for biomimetic redox mediation in (bio-)electrical systems.