We report on curled polyvinylpyrrolidone(PVP)microfibers fabricated by a modified electrospinning with a small nail as the tip collector.PVP(45 wt%)ethanol solution is electrospun under different working voltages rang...We report on curled polyvinylpyrrolidone(PVP)microfibers fabricated by a modified electrospinning with a small nail as the tip collector.PVP(45 wt%)ethanol solution is electrospun under different working voltages ranging from 10 to 15,20,30 and 40kV.It is found that with the increase of working voltage,the proportion of the curled fibers increases and the uniformity of the curled fibers improves,as well as the repeat distance of the curled structures reducing.Particularly,some curled fibers develop into helical structures under relatively high voltages.Further analyses indicate that the formation mechanism for the curled polymer fibers can be ascribed to electrical driven bending instability and/or mechanical jet buckling when hitting the collector surface.This modified electrospinning technique may be a cost-effective approach for the mass production of curled microfibers.展开更多
ZnO/TiO_(2) nanocomposite films on quartz substrates were prepared by the sol-gel method, and the corresponding optical absorption properties were investigated. In the ultraviolet region, it was found that the positio...ZnO/TiO_(2) nanocomposite films on quartz substrates were prepared by the sol-gel method, and the corresponding optical absorption properties were investigated. In the ultraviolet region, it was found that the position of fundamental absorption edge partially depends on the composition of the ZnO/TiO_(2 ) films, and shifts toward a shorter wavelength with the increasing content of ZnO in the films. Moreover, a blueshift of the absorption edge resulted from a quantum size effect and the quantum confinement effect was observed in the ZnO/TiO_(2) system.展开更多
基金Supported by the Program for New Century Excellent Talents in University of China under Grand No NCET-07-0472the National Natural Science Foundation of China under Grant No 11074138.
文摘We report on curled polyvinylpyrrolidone(PVP)microfibers fabricated by a modified electrospinning with a small nail as the tip collector.PVP(45 wt%)ethanol solution is electrospun under different working voltages ranging from 10 to 15,20,30 and 40kV.It is found that with the increase of working voltage,the proportion of the curled fibers increases and the uniformity of the curled fibers improves,as well as the repeat distance of the curled structures reducing.Particularly,some curled fibers develop into helical structures under relatively high voltages.Further analyses indicate that the formation mechanism for the curled polymer fibers can be ascribed to electrical driven bending instability and/or mechanical jet buckling when hitting the collector surface.This modified electrospinning technique may be a cost-effective approach for the mass production of curled microfibers.
基金Supported by the National Natural Science Foundation of China under Grant No.19834080the State Key Project of Fundamental Research of China.
文摘ZnO/TiO_(2) nanocomposite films on quartz substrates were prepared by the sol-gel method, and the corresponding optical absorption properties were investigated. In the ultraviolet region, it was found that the position of fundamental absorption edge partially depends on the composition of the ZnO/TiO_(2 ) films, and shifts toward a shorter wavelength with the increasing content of ZnO in the films. Moreover, a blueshift of the absorption edge resulted from a quantum size effect and the quantum confinement effect was observed in the ZnO/TiO_(2) system.
