Hydration-dependent band gap tunability of self-assembled phenylalanyl tryptophan nanotubes

Abstract Bioinspired peptide nanotubes have emerged as a brand new category of organic semiconductors employed in many nanotechnological applications. Trapped solvent, long-range ordering, and configurational versatility play important roles in the control and tuning of the electronic properties of these nanotubes. Here, the density-functional theory-based tight-binding approach is employed to study the impact of building block separation, caused by confined water molecules, on the geometry and electronic structure of phenylalanyl tryptophan nanotubes (PTNTs). The amount of water in the PTNT walls changes considerably the distance between the building blocks. This structural modification causes a modulation of the PTNT bandgap and changes its nature from indirect to direct. An effective control of the structure and electronic properties of these one-dimensional PTNTs can pave the way for potential applications in bioelectronic and medical devices.