Polystyrene/polythiophene (PSt/FTh) core/shell nanoparticles were successfully synthesized via a one-pot Fe(3+)-catalyzed oxidative and soap-free emulsion polymerization process. A small amount of sodium styrene sulfonate (NaSS) was used to maintain the colloidal stability of the PSt/PTh nanoparticles. Hydrogen peroxide (H(2)O(2)) and a trace of iron chloride (FeCl(3)) were used to carry out the free-radical polymerization of styrene and the oxidative polymerization of thiophene. The dual initiation characteristics of H(2)O(2)/FeCl(3) in the PSt/PTh core/shell nanoparticle formation were investigated by observing the time-evolution of the particle morphology. In addition, photoluminescent property, particle size distribution, core/shell morphology and the formation mechanism of the PSt/PTh nanoparticles were studied by spectrofluorophotometery, dynamic light scattering (DLS), in-situ IR, zeta-potential, and timeevolution field-emission scanning electron microscope (FE-SEM) analyses. (C) 2011 Elsevier Ltd. All rights reserved.