Hollow microstructured polyaniline prepared using cuprous oxide crystals as templates

Hollow octahedrons or microspheres of polyaniline (PANI) were successfully prepared using cuprous oxide (Cu2O) crystals as new templates in the presence of H3PO4 and ammonium peroxydisulfate as a dopant and an oxidant, respectively. Interestingly, the hollow octahedrons (in the reduced form with a conductivity of <10(-8) S.cm(-1)) could transform into conductive microspheres (in the emeraldine salt form with a conductivity of 10(-2) S.cm(-1)) when the [APS]/[An] ratio was changed from 1:1 to 2:1. Compared with the common template reported, Cu2O crystal is not only a new type of template in terms of both shape and quality, but also omits post-treatment due to soluble Cu2+ formed by the reaction of Cu2O with APS during the polymerization process. The universality of Cu2O as a template to prepare microstructured PANI was proved by changing the morphology of the Cu2O crystal. It was found that the morphology, oxidation and protonation state of PANI microstructures prepared with octahedral Cu2O as the template were affected by the [Cu2O]/[An] and [APS]/[An] ratio due to the competitive reaction of aniline and Cu2O with APS.