Coaxial nanocables of codoped double-walled carbon nanotubes

The electronic and optical properties of codoped double-walled carbon nanotubes (DWNTs), in which nucleophilic atoms (potassium) are adsorbed outside the outer tube and electrophilic molecules (NO(2)) are adsorbed inside the inner tube, are investigated by density functional theory. It is found that the inner core tube is p-type doped and the outer shell tube is n-type doped, forming a radial p-n junction of DWNTs. A type-II band energy alignment is formed at the interface of two constituting walls of codoped DWNTs. Moreover, optical calculations show that the band edge absorption is zero for pristine DWNTs, while it is pronounced for the codoped DWNTs. This absorption of codoped DWNTs leads to charge separation in the interface of two walls of DWNTs with holes located on core tube while electrons located on shell one. The properties of DWNT coaxial nanocables demonstrated here can find future applications in electronic and optoelectronic devices.