Cobalt-dopedβ-peptide nanotubes: A class of spintronic materials

Abstract

We report a density functional theory based ab initio investigation of protein nanotubes formed by a stacking of $\ensuremath{\beta}$-peptide rings. We have optimized the structure of $\ensuremath{\beta}$-peptide rings arranged in a nanotube geometry. The calculated interatomic bond distances are found to agree with observations as is the equilibrium inter-ring separation. The electronic structure has been analyzed by calculating the density of states and band structures, which reveal wide band gap semiconducting properties of the tube. The possibility of doping $\ensuremath{\beta}$-PNT (peptide nanotube) with transition metal atoms is found to be energetically possible, and Co-doped $\ensuremath{\beta}$-PNT is found to be a strong ferromagnetic material, with relatively high ordering temperature and with impurity states just below the conduction band edge. This makes Co-doped $\ensuremath{\beta}$-PNT a very good potential candidate as an $n$-doped material in spintronics applications.