Origin of the p-Type Character of AuCl₃ Functionalized Carbon Nanotubes

The microscopic origin of the p-type character of AuCl 3 functionalized carbon nanotubes (CNTs) is investigated using first-principles self-interaction corrected density functional theory (DFT). Recent DFT calculations suggest that the p-type character of AuCl 3 functionalized CNTs is due to the Cl atoms adsorbed on the CNTs. We test this hypothesis and show that adsorbed Cl atoms only lead to a p-type character for very specific concentrations and arrangements of the Cl atoms, which furthermore are not the lowest energy configurations. We therefore investigate alternative mechanisms and conclude that the p-type character is due to the adsorption of AuCl 4 molecules. The unraveling of the exact nature of the p-doping adsorbates is a key step for further development of AuCl 3 functionalized CNTs in water sensor applications.