Highly porous polypyrrole (PPy)-coated TiO 2 /ZnO nanofibrous mat has been successfully synthesized. The core TiO 2 / ZnO nanofibers have an average diameter of ca. 100 nm and the shell of ultrathin PPy layer has a thickness of ca. 7 nm. The NH 3 gas sensor using the as-prepared material exhibited a fast response over a wide dynamic range and high sensitivity with a detection limit of 60 ppb (S/N ¼ 3). Compared to conventional pristine PPy film, the improved performance in NH 3 detection can be attributed to the free access of NH 3 to PPy and a minimized gas diffusion resistance through the ultrathin PPy layer.

Conductive core-sheath TiO2-PEDOT nanocables were prepared using electrospun TiO2 nanofibers as template, followed by vapor phase polymerization of EDOT. Various techniques were employed to characterize the sample. The results reveal that the TiO2 core has an average diameter of ∼78 nm while the PEDOT sheath has a uniform thickness of ∼6 nm. The as-prepared TiO2-PEDOT nanocables display a fast and reversible response to gaseous NO2 and NH3 with a limit of detection as low as 7 ppb and 675 ppb (S/N=3), respectively. This study provides a route for the synthesis of conductive nanostructures which show excellent performance for sensing applications.

Transparent conductive nanofibrous membranes have been successfully fabricated by sputter-coating a metal (Au, Pd, Pt, Ni, Ag, or Au/Pd alloy) onto a water-soluble-polymer nanofibrous template, followed by the dissolution of the template in a water bath. The size of the conductive nanofibers can be facilely controlled by adjusting the diameter of the polymer nanofibers as well as the sputter-coating time. The as-prepared samples were characterized by SEM, TEM, FTIR, and TGA, and the results reveal that the as-prepared conductive nanofibers consist of many metal nanoparticles held together after the dissolution of the polymer template, which is likely due to the coalescence of the metal nanoparticles as well as the bridging effect of the polymer chains between the adjoining metal nanoparticles. The transmittance of the film decreases but the conductivity of the film increases with the time of sputter-coating. The as-prepared transparent nanofibrous membrane also shows good mechanical and metallic properties, and its resistance displays humidity-dependent behavior most likely attributed to the swelling effect of the highly hydrophilic polymer chain that bridges the metal nanoparticles. This study provides a promising route to the facile synthesis of conductive nanofibers, which may have great potential in various applications.