The design and fabrication of supramolecular semiconductor nanowires formed by benzothienobenzothiophene (BTBT)-conjugated peptides

Abstract

π-Conjugated small molecules based on a [1]benzothieno[3,2-b]benzothiophene (BTBT) unit are of great research interest in the development of solution-processable semiconducting materials owing to their excellent charge-transport characteristics. However, the BTBT π-core has yet to be demonstrated in the form of electro-active one-dimensional (1D) nanowires that are self-assembled in aqueous media for potential use in bioelectronics and tissue engineering. Here we report the design, synthesis, and self-assembly of benzothienobenzothiophene (BTBT)–peptide conjugates, the BTBT–peptide (BTBT-C₃–COHN-Ahx-VVAGKK-Am) and the C₈-BTBT–peptide (C₈-BTBT-C₃–COHN-Ahx-VVAGKK-Am), as β-sheet forming amphiphilic molecules, which self-assemble into highly uniform nanofibers in water with diameters of 11–13(±1) nm and micron-size lengths. Spectroscopic characterization studies demonstrate the J-type π–π interactions among the BTBT molecules within the hydrophobic core of the self-assembled nanofibers yielding an electrical conductivity as high as 6.0 × 10⁻⁶ S cm⁻¹. The BTBT π-core is demonstrated, for the first time, in the formation of self-assembled peptide 1D nanostructures in aqueous media for potential use in tissue engineering, bioelectronics and (opto)electronics. The conductivity achieved here is one of the highest reported to date in a non-doped state.