Polypyrrole nanoparticles with a high yield (93%) were synthesized by using unstirred polymerization in the absence of any template or surfactant.The structure，elctroconductivity and morphology of the polypyrrole nanoparticles were characterized by FT-IR

wide angle X-ray diffraction

four-probe techniques

scanning electron microscopy and transmission electron microscopy (TEM).The particle size and morphology of polypyrrole nanoparticles were systematically studied by changing synthetic conditions

such as oxidant type

molar ratio of ammonium persulfate (APS) to pyrrole

polymerization temperature and reaction medium species.It was found that the particle size and morphology of the polypyrrole nanoparticles varied significantly with the above-mentioned polymerization parameters.Using different synthetic conditions

we can control the diameters of polypyrrole nanoparticles ranging from 40 nm to 260 nm.The preparation conditions of ammonium persulfate as an oxidant

APS/pyrrole molar ratio of 0.25

at a polymerization temperature of 0℃ are optimal for the unstirred polymerization synthesis of polypyrrole nanoparticles.TEM images revealed that uniform polypyrrole nanoparticles in diameters of 43 nm were prepared in 1.0 mol/L HCl aqueous medium at 0℃ (using an ice bath) with APS/pyrrole molar ratio of 0.25.The room-temperature electroconductivity of the hydrochloride doped polypyrrole disk is up to 5.5 S/cm.