| This work was focused on the morphology control of electrospun nanofibers for nano materials.Several helical nanofibers,ropes,and 3D balls were made by the alternated method with the assisted of oppositely charged collector and opposite spinneret.In addition,the electrospinning condition were also discussed in this thesis.(1)Double helical microropes of polyvinylpyrrolidone(PVP)with diameters less than 10 ?m and lengths up to 5 cm were fabricated by a new electrospinning technique.Different from the typical electrospinning setup,a negatively charged rotating collector tip was used in this work,so that the two jets from two positively charged spinnerets were induced to two bundles that met at the rotating collector tip,leading to the formation of microropes.The pitch of microropes could be monitored by simply adjusting the distance of two spinnerets.(2)To create precisely controlled helical nano assemblies,we developed a novel approach via the off-axis near-filed co-electrospinning with high speed rotating(ONCE).This method,based on ONCE,could be readily applied to the preparation of nano helix of a broad range of materials:polymers,semiconductors,oxides,and metals.We expect that this class of manufacturing will allow the design of a variety of other two-and three-dimensional architectures and can serve as building blocks for new metamaterials.(3)Surface hybridization with carbon nanolayers of Ti02 nanofibers with length in centimeters were fabricated.Comparing with Ti02 nanofibers,the carbon layer covered Ti02 nanofibers photocatalyst presented a higher photocatalytic activity under ultraviolet(UV)irradiation for the degradation of organics(methylene blue).TiO2 modification with carbon nanolayers to increase substrate adsorption in the vicinity of the photocatalytic sites and the high migration efficiency of photoinduced electrons at the carbon/TiO2 interface lead to a photocatalyst with enhanced efficiency.Photostability kept after five times recycled under UV irradiation. |
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