Controlled Synthesis And Properties Of Metal Multilayer Nanowires

In recent years, with the rapid development of nanotechnology, the research of nanomaterials have developed from controlled synthesis and qualitative research to their unique properties and actual production applications. Multilayer nanowires have many potential applications in magneto-optical, magnetic, data storage, catalysis,sensors, biological technology and new energy devices. The controlled synthesis and characteristics of multilayer nanowires have become an important frontier subject of materials science research.In this thesis, the high-ordered metal multilayer nanowire arrays were fabricated by using self-prepared anodic alumina oxide(AAO) template and pulse electrochemical deposition technique, and their structure-related properties were investigated. The main research contents and results are shown as follows:1. Controlled synthesis of metal multilayer nanowires(1) By using AAO template and pulse electrochemical deposition technique, we successful prepared Au/Ni multilayer nanowire arrays with a wire-diameter of 70 nm.In our experiments, we set purposely the specific deposition time of Ni layers, so that the corresponding thickness of Ni layer would be 65 nm, 120 nm, 180 nm, and 300 nm,respectively, but the thickness of Au layers was kept at 70 nm all the time;(2) We fabricated Pt/Ni multilayer nanowire arrays with the wire-diameter of 70 nm by using the similar method. Through controlling the electrodeposition time of magnetic layer,we obtained a series of samples in which the thickness of Ni layer was 60 nm and 200 nm, respectively, but the thickness of the Pt layer was 35 nm. The morphologies and structures of these samples were investigated by scanning electron microscope(SEM),X-ray diffraction(XRD), and transmission electron microscopy(TEM).2. Magnetic properties of metal multilayer nanowires(1) We made a systematic study about the relation between the length of themagnetic layer Ni and the coercivity and remanence of Au/Ni multilayer nanowire arrays. The results show that, when the thickness of the Ni layers was 150 nm, the coercivity and remanence would have the corresponding maximum values;(2) We also studied the angular dependence of the coercivity and remanence of Au/Ni and Pt/Ni multilayer nanowire arrays. The results showed that the coercivity and remanence ratio significantly depended on the thinness of Ni layers; the easy magnetization direction was parallel to the axis of the nanowire and the magnetostatic interaction increased with the length of Ni layer increasing. At any angle, their coercivity and remanence ratio are greater than that of pure Ni nanowire arrays.3. Electrochemical properties of metal multilayer nanowires(1) we demonstrated that Au/Ni multilayer nanowires fabricated by an electrochemical method could be constructed a non-enzymatic glucose sensor. Due to the large surface to volume ration and special bimetallic structure, the sensor exhibited a very high sensitivity, a wide linear range and a low detection limit;(2) The catalytic activity and stability of Pt/Ni nanowires to the methanol oxidation were evaluated by cyclic voltammentry and chronoamperograms methods at room temperature. The results indicated that Pt/Ni nanowires had excellent catalytic activity and stability toward the electro-oxidation of methanol in alkaline medium, compared with the pure Pt and Ni nanowires.