Structure Design And Applications Of Several Inorganic Nanowire Assembly

In material science and technology,large scale assembly of one-dimensional nanowires into well-defined superstructures is a significant pre-requisite for realizing ultimate control over the properties and to recognize multi-functional systems and sub-systems established on one-dimensional nanostructures.The physicochemical properties of one-dimensional nanomaterials are not only dependent on their shape and size,but also on the synergy of the assembly.Therefore macroscopic-scale nanofabrication using nanowires is one of the key scientific issues to solve the future application of nanomaterials.Moreover,a specific structural alignment produced by self-assembly exhibits superior properties including mechanical,thermal,electrical,and optical properties etc.as compared to randomly organized structures.In addition,a precise control in orientation,position and spacing of various lengths is crucial to attain the fundamental application of highly ordered nanowires structures in nanotechnology fields.Although great progress has been achieved in nanoassembly but for the successful integration of NWs,various developments in appropriate assembly methods are required and many rational assembly strategies are desirable to build complex structures with novel collective properties for device fabrication.In this concern,looking for an inexpensive and efficient way to assemble nanomaterials into functional structures is the intention and direction of our research.In this dissertation,we intend to demonstrate the different strategies for self-assembly of NWs such as self-assembly of W18O49NWs on 2-D graphene sheet,magnetic induced assembly of SiO2-coated Fe3O4-Ag NWs and their implication to investigate diverse properties like gas sensing properties,supercapacitance properties,magnetic field perception and magnetocaloric effect.The main findings are summarized as the following:1.An efficient solvothermal process was established for assembly of W18O49NWs on 2D graphene sheet.During the in situ assembly process,the ultrathin W18O49NWs having a diameter around 5nm were successfully grown on the surface of GO sheet by using WCl6 salt as precursor and different weight ratio of GO(0.2%,0.5%,1%and 1.5%).2.For the preparation of well-defined arrangement,a simple method was developed for orienting SiO2-coated Fe3O4-AgNWs with tunable magnetic properties through employing magnetic field which shows good orientational ordering.The controlled fabrication of SiO2-coated Fe3O4-AgNWs was achieved by coating nonmagnetic AgNWs with Fe3O4 nanoparticles through the modified solvothennal process and then further coating with SiO2.For magnetic assembly of NWs an experimental setup was established by placing a transparent PET film in a container and then a magnet was inserted below the substrate outside the container.The applied magnetic field translocated high aspect ratio SiO2-coated Fe3O4-AgNWs along the strong component of magnetic field vector,resulting in films with high alignment degree.Moreover,the assembly control was achieved by optimizing dispersion medium and SiO2 shell thickness around Fe3O4-AgNWs.3.The self-assembled W18O49NW/rGO composites were subjected to the gas sensing application and a systematic study was established for the gas sensing properties of W18O49NWs and W18O49NW/rGO composites on toluene vapors.Furthermore,the effects of rGO on the gas sensing performance of W18O49 NW/rGO-composites were discussed briefly.At last,a sensing mechanism for the assembled structure was also elaborated for toluene gas detections.Secondly,by using magnetic self-assembled film,we demonstrated the magnetic anisotropy in ordered structures.The obtained assembled paramagnetic SiO2-coated Fe3O4-AgNWs films exhibited the higher magnetization properties as compared to disordered NWs and revealed highly anisotropic magnetization under different angle magnetic field,hence based upon the properties of our films we investigated the magnetocaloric effect and bioinspired magnetic-field-perception system.In third application,by using W18O49NW/rGO composites,the electrochromic supercapacitors were designed.With the help of LB assembly method,the assembled film of ultra-long ultrafine AgNWs and W18O49NWs was fabricated in order to prepare a conductive nanowire network.After that the W18O49NW/rGO composites were deposited on the film by using LB apparatus in different layers and electrochromic supercapacitance properties were measured.