Construction Of Special Polypyrrole Micro/nanostructures Based On One Dimensional Nanostructures Of Polypyrrole

One-dimensional (1D) nanostructures, such as nanowires and nanotubes, are considered to be building blocks as well as interconnect for fabricating nanoscale devices. Therefore, the assembly of 1D nanostructures in the fabrication of nanoelectronic and nanophotonic devices is currently attracting significant attention. In this regard, controlled fabrication of self-assembled 1D nanostructure, such as hierarchical structures with junctions and branches, nanowires with well order or with ultra high length, is important from the fundamental as well as technological point of view. In this research, several hierarchical structures with novel morphologies as well as the ordered nanowire arrays and ultra long nanowires of polypyrrole (PPy) were sythesized easily by using biomolecules as morphology directing agents. These synthesis methods offered some appealing characteristics such as simple, cheap, rapid, mild and environmentally benign. The morphology, structure, and electrochemical performance of the samples were systematically studied by scanning electron microscopy (SEM), fourier-transform infrared spectroscopy (FTIR), energy dispersive spectrometry (EDS), and cyclic voltammetry (CV). The influences of the experimental conditions on the morphologies of the products and the surface performance have been investigated, and the formation mechanism of the hierarchical structures was also discussed. The main contents are shown as follows:The controlled synthesis of hierarchical structures made of short nanowires/ micron-sized "hills and valleys" or nanowire networks/ micron-sized "cauliflower" has been successfully realized via a simple two step electrochemical method by using ITO as work electrode. In the first step, microstructured PPy films were prepared by electropolymerization in an electrochemical system. Then PPy nanowires were electro-deposited on the surface of the as-synthesized microstructured PPy films in another electrochemical system by employing starch as morphology directing agent. As a result, two typical dual-scale hierarchical structures of PPy were obtained. The surface wettabilities of the resulting nanowire-based PPy hierarchical structures were examined. It was found that although having almost the same chemical composition, the two PPy hierarchical structures exhibited entirely different surface wettability. The surface of the short nanowire-based hierarchical structure was hydrophobic, with water contact angle 95～129°; while the surface of the nanowire network-based hierarchical structure exhibited a superhydrophilic property, the contact angle of which was close to 0°.The controlled synthesis of hierarchical structures made of nanowires/ microspheres or nanowires/ nanorods has been successfully realized via another simple two step electrochemical method by using Ni as work electrode. The whole process was conducting in only one electrochemical system involving gelatin as morphology directing agent. In the first step, a high potential was applied to prepare PPy microspheres or nanorods. Then a low potential was used to synthesize nanowires on the as-prepared PPy microspheres or nanorods. As a result, another two novel hierarchical structures of PPy were gained.Ordered nanowire arrays and nanowires with ultra high length (up to 10μm) have been successfully synthesized on Ni electrodes by one step electrochemical method under potentiostatic or galvanostatic technique with the assistance of gelatin. It is demonstrated that the morphology of the final products is significantly affected by the applied potential, current and the reaction time. The morphology evolvement and the growth mechanism have been studied carefully, and the gelatin-induced oriented growth mechanism was proposed for the formation mechanism of the nanowires.