Photocurrent generation in peptide-based self-assembled monolayers on gold electrodes

Mimicking Nature: A Novel Peptide‐based Bio‐inspired Approach for Solar Energy Conversion

“…We showed that this system was able to form a tightly packed SAM on a (111) Au surface and to generate photocurrent under illumination, with a 0.04 % photon to current conversion efficiency at the pyrene absorption maximum (340 nm). We also demonstrated the helical macrodipole effect on the electron transfer process, the anodic photocurrent value being sevenfold higher than the cathodic one 7c. Herein we demonstrate that the SSU6Pyr peptide may be immobilized on gold covered TiO 2 surfaces and used in the DSSC technology.…”

“…We recently reported on photocurrent generation experiments carried out on thermally stable and conformationally constrained peptide materials, able to self‐assemble on (111) gold surface and to promote light‐induced electron‐hole separation in appropriately placed chromophores 7. In a contribution in this field, we synthesized a 3 10 ‐helical hexapeptide, based on the strongly folding inducer C α ‐tetrasubstituted α‐aminoisobutyric acid (Aib, U) residue,9 containing a pyrene (Pyr) unit and functionalized at the N‐terminus by an ( S , R ) lipoyl (Lipo) anchoring group (SSU6Pyr, Figure 1), to bind the gold surface via an Au‐S linkage 7c. The Lipo group was placed at the N‐terminus to optimize the ET process toward the surface, thus limiting the surface/dye recombination processes 8.…”

Self-assembled monolayers formed by helical peptide building blocks: a new tool for bioinspired nanotechnology

“…CV experiments confirmed that also SSA6Pyr, despite the shortness of the peptide chain, can form a densely packed SAM on the gold electrode, inhibiting almost completely the discharge of K 3 [Fe(CN) 6 ]. 68 The photocurrent generated upon photoirradiation of the SSA6Pyr SAM in the presence of TEOA is shown in Figure 12, where repeated on/off cycles of photoexcitation, each one 30 s long, are reported for different excitation wavelengths. 69 The action spectrum, that is, the photocurrent response vs the excitation wavelength, of the SSA6Pyr SAM shows a very good agreement with the absorption spectrum of pyrene in ethanol solution (inset of Figure 12).…”

Electron Transfer across Helical Peptides

“…Unlike the previously described spectroscopic photoinduced ET measurements, in which the role of the dipole was still under debate, and especially in comparison with the standard electrochemical ET rate, in which the dipole did not seem to have a major role in determining the ET rate, in the electrochemical photocurrent measurements it was established that the dipole had a major role in achieving efficient photocurrent generation 65. 66, 70–74 In this context, it was shown that the ET direction via a certain α‐helical peptide–chromophore could be switched from anodic to cathodic photocurrents as a function of the quencher in solution73 or pH 71. However, in both cases, the photocurrent generated when the ET was in the direction of the dipole was more efficient than that in the opposite direction.…”

“…In all of the studies, the photocurrent was generated through a dense monolayer of α‐helical peptides (sometimes in the form of a mixed monolayer with an additional alkyl chain) that were connected to a gold electrode. Currently used chromophore–quencher pairs for cathodic photocurrent generation are as follows: ethylcarbazolyl (ECz)–methyl viologen (MV),65, 71 anthracene–nicotinamide adenine dinucleotide phosphate (NADP),66 tris(bpy)Ru II –MV70 and pyrene–MV;73 for anodic photocurrent generation, they are as follows: ECz–triethanolamine (TEOA),65, 70, 71 Nap–TEOA,67, 69 pyrene–TEOA,72, 73 and tryptophan–TEOA 74. It is important to stress that this classification of cathodic and anodic photocurrent is at zero potential.…”