Continual progress in technologies that rely on water splitting are often hampered by the slow kinetics associated with the oxygen evolution reaction (OER). Here, we show that the efficiency of top-performing catalysts can be improved, beyond typical thermodynamic considerations, through control over reaction intermediate spin alignment during electrolysis. Spin alignment is achieved using the chiral induced spin selectivity (CISS) effect and the improvement in OER manifests as an increase in Faradaic efficiency, decrease in reaction overpotential, and change in the rate determining step for chiral nanocatalysts over compositionally analogous achiral nanocatalysts. These studies illustrate that a defined spatial orientation of the nanocatalysts is not necessary to exhibit spin selectivity and therefore represent a viable platform for employing the transformative role of chirality in other reaction pathways and processes.

This work presents new results and summarizes literature results on the chiral induced spin selectivity (CISS) effect observed for amino acids, peptides, and DNA. To facilitate robust comparisons between measurements of different types and by different groups, we propose a convention for describing the spin-dependent properties of chiral materials and apply it in the discussion. Different phenomena known to affect the sign and magnitude of the spin polarization are described and critically analyzed, including: the molecule's orientation, the molecule's dipole moment direction with respect to the electron propagation direction, the molecular length, the molecule/substrate interface, and the role of the molecule's secondary structure. Lastly, we identify open key questions about spin-filtering by biomolecules at interfaces.

This work investigates how the conductance of a nucleic acid duplex with a “nick” in its backbone compares with that of a duplex with a fully covalent backbone. Statistical analyses of the single-molecule conductance properties reveal that molecular junctions with a nicked duplex have an average conductance close to that found for non-nicked structures but exhibit greater variability in the molecular conductance. This effect is shown for both DNA homoduplexes and DNA/PNA heteroduplexes, with the heteroduplexes showing a greater average molecular conductance and a smaller degree of variability. The average molecular conductance of the heteroduplexes is also shown to be affected by their PNA content; the conductance of duplexes increases as the ratio of PNA to DNA increases. These observations suggest that the charge-transfer properties of nucleic acid-based assemblies can support complex functions.

Protein voltammetry studies of cytochrome c, immobilized on chiral tripeptide monolayer films, reveal the importance of the electron spin and the film's homochirality on electron transfer kinetics. Magnetic film electrodes are used to examine how an asymmetry in the standard heterogeneous electron transfer rate constant arises from changes in the electron spin direction and the enantiomer composition of the tripeptide monolayer; rate constant asymmetries as large as 60% are observed. These findings are rationalized in terms of the chiral induced spin selectivity effect and spin-dependent changes in electronic coupling. Lastly, marked differences in the average rate constant are shown between homochiral ensembles, in which the peptide and protein possess the same enantiomeric form, compared to heterochiral ensembles, where the handedness of the peptide layer is opposite to that of the protein or itself comprises heterochiral building blocks. These data demonstrate a compelling rationale for why nature is homochiral; namely, spin alignment in homochiral systems enables more efficient energy transduction.

The flow of charge through molecules is central to the function of supramolecular machines, and charge transport in nucleic acids is implicated in molecular signaling and DNA repair. We examine the transport of electrons through nucleic acids to understand the interplay of resonant and nonresonant charge carrier transport mechanisms. This study reports STM break junction measurements of peptide nucleic acids (PNAs) with a G-block structure and contrasts the findings with previous results for DNA duplexes. The conductance of G-block PNA duplexes is much higher than that of the corresponding DNA duplexes of the same sequence; however, they do not display the strong even–odd dependence conductance oscillations found in G-block DNA. Theoretical analysis finds that the conductance oscillation magnitude in PNA is suppressed because of the increased level of electronic coupling interaction between G-blocks in PNA and the stronger PNA–electrode interaction compared to that in DNA duplexes. The strong interactions in the G-block PNA duplexes produce molecular conductances as high as 3% G 0, where G 0 is the quantum of conductance, for 5 nm duplexes.