The self-assembly of short amino acid chains appears to be one of the most promising strategies for the fabrication of nanostructures. Their solubility in water and the possibility of chemical modification by targeting the amino or carboxyl terminus give peptide-based nanostructures several advantages over carbon nanotube nanostructures. However, because these systems are synthesized in aqueous solution, a deeper understanding is needed on the effects of water especially with respect to the electronic, structural and transport properties. In this work, the electronic properties of L-diphenylalanine nanotubes (FF-NTs) have been studied using the Self-Consistent Charge Density-Functional-based Tight-Binding method augmented with dispersion interaction. The presence of water molecules in the central hydrophilic channel and their interaction with the nanostructures are addressed. We demonstrate that the presence of water leads to significant changes in the electronic properties of these systems decreasing the band gap which can lead to an increase in the hopping probability and the conductivity.

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A novel enzymatic platform for the sensing of H2O2 and glucose that uses L,L-diphenylalanine micro/nanostructures (FF-MNSs) as an enzyme support is shown. This platform is obtained by the self-assembly of poly(allylamine hydrochloride) (PAH), FF-MNSs, and microperoxidase-11 (MP11) anchored onto the peptide matrix, in two different crystal structures of FF-MNSs: hexagonal (P61) and orthorhombic (P22121). The electroactive area of the electrodes increases in the presence of FF-MNSs. We also demonstrate via theoretical calculations that the valence band energy of the orthorhombic structure allows it to be doped, similarly to p-type semiconductors, where PAH acts as a doping agent for the orthorhombic peptide structure, decreasing the band-gap by around 1 eV, which results in a smaller charge transfer resistance. These results are consistent with electrochemical impedance spectroscopy measurements, which further elucidate the role of the band structure of the orthorhombic FF-MNSs in the conductivity and electron transfer rates of the hybrid material. An effective communication between the electrode and the active site of a glucose oxidase enzyme through MP11-protein complexes occurs, paving the way for FF-MNSs in the orthorhombic phase for the future development of bioelectronics sensing devices.