Polypyrrole/ZnS Core/Shell Coaxial Nanowires Prepared by Anodic Aluminum Oxide Template Methods

The polypyrrole/ZnS core/shell coaxial nanowires are fabricated through a two-step process with the assistance of anodic aluminum oxide (AAO) templates. First, ZnS nanotube arrays are synthesized within AAO templates by using the metal organic chemical vapor deposition (MOCVD) method. Then, polypyrrole (PPy) is electrochemically deposited into as-prepared ZnS nanotubes, creating PPy/ZnS core/shell coaxial nanowires. The morphology and structure of PPy/ZnS coaxial nanowires are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Fourier-transform infrared (FTIR) spectroscopy verifies that the in-plane deformation vibration of the pyrrole (Py) ring shows a blue shift from 1144 cm(-1) in PPy nanowires to 1173 cm(-1) in the PPy/ZnS coaxial nanowires. In X-ray photoelectron spectroscopy analysis (XPS), the changes of the N 1s peak and S 2p peak reveal an electron transfer from the ZnS shell to the PPy core in PPy/ZnS coaxial nanowires, which lowers the reduction potential of PPy at the interface to -0.2 V as compared with -0.88 V observed for pure PPy; nanowires. The current-voltage (I-V) characteristics of the ZnS nanotube show the semiconducting behavior, while ohmic behavior is observed for the PPy nanowire. Remarkably, the I-V characteristics of a single core-shell coaxial nanowire exhibit a rectification behavior, probably due to electron transfer between PPy and ZnS. Therefore, this kind of core/shell coaxial nanowires, which combine properties of core and shell materials of different components, might be applicable for nanosccale optoelectronics.