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Exciton migration in organic polymer dots (Pdots) is crucial for optimizing photocatalytic reactions at the particle surface, such as hydrogen evolution and carbon dioxide reduction. Despite the use of Pdots in photocatalysis, there is still a need for better understanding of exciton diffusion within these systems. This study investigates the exciton diffusion in PFBT Pdots stabilized with different weight percentages of the co-polymer surfactant PS-PEG-COOH and doped with perylene red as an internal quencher. Time-resolved fluorescence quenching data yields a quenching volume that the excitons explore during their lifetime (Vq), which is comparable to the volume of the hydrophobic core of PFBT Pdots. This indicates that excitons can migrate to the particle surface with high probability and suggests that the intrinsic exciton diffusion length (LD approximate to 19 nm) for PFBT is significantly larger than previously reported in Pdot studies from the literature (5.3 and 8.6 nm). Additionally, a larger quenching rate constant (kq) and smaller volume (Vq) is observed for the higher PS-PEG-COOH weight ratio, which are attributed to their smaller core. The study provides insights into the exciton migration within Pdots, with important implications for photocatalysis.

Charge-transfer reactions in proteins are important for life, such as in photolyases which repair DNA, but the role of structural dynamics remains unclear. Here, using femtosecond X-ray crystallography, we report the structural changes that take place while electrons transfer along a chain of four conserved tryptophans in the Drosophila melanogaster (6-4) photolyase. At femto- and picosecond delays, photoreduction of the flavin by the first tryptophan causes directed structural responses at a key asparagine, at a conserved salt bridge, and by rearrangements of nearby water molecules. We detect charge-induced structural changes close to the second tryptophan from 1 ps to 20 ps, identifying a nearby methionine as an active participant in the redox chain, and from 20 ps around the fourth tryptophan. The photolyase undergoes highly directed and carefully timed adaptations of its structure. This questions the validity of the linear solvent response approximation in Marcus theory and indicates that evolution has optimized fast protein fluctuations for optimal charge transfer.

Dye-sensitized photoelectrodes consisting of photosensitizers and molecular catalysts with tunable structures and adjustable energy levels are attractive for low-cost and eco-friendly solar-assisted synthesis of energy rich products. Despite these advantages, dye-sensitized NiO photocathodes suffer from severe electron-hole recombination and facile molecule detachment, limiting photocurrent and stability in photoelectrochemical water-splitting devices. In this work, we develop an efficient and robust biohybrid dye-sensitized NiO photocathode, in which the intermolecular charge transfer is enhanced by a redox polymer. Owing to efficient assisted electron transfer from the dye to the catalyst, the biohybrid NiO photocathode showed a satisfactory photocurrent of 141±17 μA·cm⁻² at neutral pH at 0 V versus reversible hydrogen electrode and a stable continuous output within 5 h. This photocathode is capable of driving overall water splitting in combination with a bismuth vanadate photoanode, showing distinguished solar-to-hydrogen efficiency among all reported water-splitting devices based on dye-sensitized photocathodes. These findings demonstrate the opportunity of building green biohybrid systems for artificial synthesis of solar fuels.

Molecular-based optoelectronic devices and photocatalytic systems often rely on the photogeneration of charge-separated states. Increasing the longevity of charge-separated states allows for access to higher-functioning devices and systems by extending the length of time before subsequent events are required to occur. In dye-sensitized solar cells (DSC), back electron transfer (BET) from a reduced metal oxide to an oxidized dye is an unproductive electron transfer pathway that determines the charge-separated state lifetime. This study seeks to limit BET by lowering the electronic coupling of the donor and acceptor in the charge-separated excited state through the use of sterics. A series of three dyes with a varying number of methyl groups (0-2) on the donor were studied using nanosecond transient absorption spectroscopy (nsTAS) to compare rates of BET. Novel dye CC10 (1 Me), designed with one methyl group in the donor region connected to the acceptor, was found to lower back electron transfer rates by 22x compared to the control dye, CC12 (0 Me), with no methyl groups.