With an average diameter of 150−340 nm and a conductivity of 10-1−100 S/cm, nanostructures (e.g., nanotubes or nanorods) of polyaniline (PANI) were synthesized by a self-assembly method in the presence of inorganic acids (e.g., HCl, H2SO4, HBF4, and H3PO4) as dopants. It was found that the morphology, size, and electrical properties of the resulting nanostructures depended on the dopant structures and the reaction conditions. In particular, all these PANI nanostuctures showed hydrophilic features, and the contact angles with water were measured to be about 27−40° depending on the dopant. The FTIR spectrum, UV−vis absorption spectrum, XPS, and X-ray diffraction were used to characterize the molecular structures of the nanostructures. It was found that their main chain structure and electric structure were identical to those of the emeraldine salt form of PANI. The micelles formed by anilinium cations act as the template like in the formation of PANI nanostructures.