Unstirred preparation of soluble electroconductive polypyrrole nanoparticles

Soluble electro-conductive polypyrrole nanoparticles (PPY-NPs) doped with organic sulfonic acid can be easily prepared via a new method for unstirred polymerization. The yield, size, morphology, electrical conductivity and solubility of the PPY-NPs were optimized by changing the feeding oxidant method, the sulfonic acid, the oxidant, and steric stabilizers. The PPY-NPs were characterized by FTIR, wide angle X-ray diffraction and four-point probe techniques. The morphology of the nanoparticles was investigated using scanning electron microscopy (SEM) and transmission electron microscopy. The PPY-NPs doped with p-toluenesulfonic acid exhibit a small diameter, an electrical bulk conductivity of 52.7 S·cm−1, and can be obtained in high yield. PPY-NPs doped with naphthalene-2-sulfonic acid have a minimum mean diameter of around 71 nm (as found by SEM). All doped PPY-NPs are well solube in dimethylformamide, dimethyl sulfoxide, formic acid and sulfuric acid.