With a average diameter of 700-900 nm and a length of 20-35 mu m, sub-micrometer fibers of polyaniline/nano-ZnO composites (PANI/nm-ZnO) were synthesized in a toluene/water emulsion stabilized by ZnO nanoparticles. It was found that the morphology of the resulting PANI/nrn-ZnO composites depended on the volume ratio of toluene to water (R) in the reaction mixture. When R was in the range of 0.03-0.07, stable Pickering emulsion was formed and the oxidative polymerization of aniline was confined at the toluene/water interface, generating sub-micrometer PANI/nm-ZnO fibers. When R = 0.11 and 0.01, the composites with dendritic and polyhedral morphology, respectively, were formed. TEM, XRD, FrIR and TGA etc. were used to characterize the sub-micrometer fibers. It was found that the structure of PANI in the composite fibers was identical to that of the amorphous emeraldine form. The sub-micrometer fibers showed hydrophilic features and their conductivity was higher than that of the PANI/nm-ZnO composites with dendritic or polyhedral morphology. (c) 2004 Elsevier B.V. All rights reserved.