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La-doped ZnO nanofibers were fabricated via electrospinning and calcination at 800°C. The surface morphology and crystal structure of the La-doped ZnO nanofibers were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photoelectric properties of La-doped ZnO nanofibers were also investigated. It was found that the photoelectric current increased obviously under light illumination (308 nm and 365 nm). However, the photocurrent reduced with increasing La-doping level, which may be ascribed to the increased defects inducing by La-doping.

A metal-semiconductor-metal photoconductive detector was fabricated using Ce-doped ZnO nanofibers synthesized by electrospinning and calcinations. UV photocurrents were carried out to study optoelectronic properties of Ce-doped ZnO nanofibers. The current-voltage (I–V) characteristics of photodetector device were analyzed under different wavelength UV illumination. The photocurrent increased by about 300 times under UV illumination. Results showed that the photocurrent of the device increased with the decrease of the wavelengths. A maximum photocurrent and photo-responsivity was observed at 365 nm, 308 nm, 254nm, respectively, under 30 V bias. The response and recovery time of the nanofibers was 16 s and 16 s at 365 nm, 10 s and 12 s at 308nm, 4 s and3 s at 254nm under 30 V bias, respectively.

Aligned poly (vinylidene fluoride) (PVDF) nanofibers and the nanoropes have been fabricated via a novel electrospinning technique. And then conducting polyaniline (PANI) was coated on the surfaces of the nanoropes using an in situ chemical oxidative polymerization method. It is found that the conductivity increased drastically at first and then tended to be saturation in the polymerization process. In addition, the flexibility and stretchability of the composites have been measured: With an increase of bending curvature and tensile strain, the conductivity rose at the beginning because the fibers among the nanoropes get tight; and then the conductivity dropped, which may due to the PANI layer broke and becomes discontinuous with the adding stress.

Ultrathin indium oxide (In2O3) microtubes were successfully fabricated by electrospinning, magnetron sputtering and followed calcination. The hollow In2O3tubes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy. Outer diameter of the microtubes was in the range of 700-900 nm, and inner diameter was about 400-600 nm. Optoelectronic properties of the In2O3tubes were investigated by irradiation of UV light with different wavelengths (254, 308 and 365 nm). It was found that the In2O3microtubes had a fast and strong response to UV irradiation.

Besides the conductive patterning substrate, spatially well-defined microfibrous architectures can also be electrospun by using an insulating topographically structured collector (e.g.a nylon fabric). In both cases, it is proposed that the formation of the electrospun microfibrous patterns can be ascribed to the re-distribution of static electric field whenever collectors with different topography are introduced. Moreover, a series of simulation of the static electric field for various collectors (e.g.flat Al foil, conductive and insulating patterned substrates) have been systematically made to illustrate the formation mechanism, respectively. Our results are considered to warrant further scientific understanding on the formation of electrospun microfibrous patterning constructs, and helpful for easy generation of spatially defined architectures which have applications in a variety of areas such as tissue engineering, cell adhesion, proliferation and migration,etc.

Soft conductive elastomer materials have wide potential applications in material science and electronic engineering. Through electrospinning and in-situ polymerization, a kind of well-organized coaxial polyaniline/polyvinylidence fluoride (PANI/PVDF) microfibers with conductivity about 0.6 S/cm were fabricated, which combined the advantages of conducting polymer and elastic material. It is found that the resistance of the fibers was changed with the curvature variation. The results indicate that the PANI/PVDF microfibers could be used as strain sensor with high flexibility, high sensitivity, and stable repeatability.

In this paper, a novel fluorescent material with high conductivity as 0.45 S·cm-1 and strong fluorescence has been successfully synthesized basing on polyaniline (PANI) nanostructures doped with a new prepared fluorescein TPABTDBN. The PANI nanostructures were prepared via a simplified template-free method (STFM) with FeCl3 as oxidant and dopant. The resulting sample was characterized by SEM, IR and fluorescence spectroscopy. The fluorescence intensity of synthesized composite improves with the increasing content of TPABTDBN. The electrical properties of pressed composite pellets were measured from room temperature about 291K down to 132K, the conductance follow the exponential temperature dependence of three-dimensional variable-range hopping (VRH) model.

Fluorescent crossbar arrays and microropes of fluorescein/PMMA and rhodamine B/PS composite nanofibers have been fabricated via centrifugal electrospinning, respectively. The morphology and structures were measured by SEM and fluorescence microscope. The two as-spun fluorescent structures have potential applications in fluorescent security, fluorescent detection, and so on. By regulating the number of the nanofibers consisted in the microropes, the fluorescence intensity of the microropes can be manipulated, as well as the mechanical property of individual nanofibers, which can be calculated easily by testing that of the whole microrope.

A modified electrospinning setup with two-grounded-frame collector is proposed to fabricate aligned fiber arrays and fiber ropes. In this setup, two frames are placed under the spinneret, with the outer frame rotated with an electromotor and the inner frame hold still in a horizontal direction. Aligned nanofiber arrays can be collected rapidly on the inner frame. Influence of included angle and motor rotating speed on the arrays is discussed. In addition, through rotating one side of the inner frame, twisted fiber ropes with diameter 30~40 μm and length of 12 cm are obtained. Mechanical properties of the individual nanofiber ropes are also measured and discussed.

Nanocrystalline and porous barium titanate (BaTiO3) nanofibers with diameter 200-400 nm were synthesized via electrospinning and followed calcinations. The morphology and microstructure of the nanofibers were characterized using field emission scanning electron microscope, X-ray diffractometer and transmission electron microscope, respectively. And the electrical and humidity sensing properties of the nanofibers were also measured. The results reveal that the BaTiO3 nanofibers have a conductivity of about 0.3 S/cm, and show an ultrafast response time (~0.7 s) and a recovery time (~0.4 s) to humidity at room temperature. In addition, the sensing mechanism was also discussed briefly based on its nanocrystalline and porous microstructure of the electrospun material.

Gold-poly (3,4-ethylenedioxythiophene) (Au-PEDOT) nanowires with Au nanoparticles embedded in the polymer matrix and polyvinylpyrrolidone (PVP) modified Au-PEDOT coaxial nanocables with a core-shell structure have been synthesized by a new and facile self-assembly method. The morphology and structure features of the composites were characterized by transmission electron microscopy, selected-area electron diffraction, and energy-dispersive x-ray spectrometry. The room-temperature electrical conductivity of the casted composite films was about 0.21 S/cm. Photoresponse of the films were also investigated with respect to wide potential applications of the multifunctional composites. Clear photocurrent switching characteristic during switching on/off of a xenon lamp was observed.

Electrospinning is a simple and practical method for fabricating uniform fibers with diameters range from several micrometers down to a few nanometers. In order to achieve highly ordered arrays of nanofibers, a novel and feasible approach, named contact-transfer printing of electrospun fibers, is reported in this paper. Via this method, large-scale aligned nanofibers on various rigid or flexible substrates can be assembled. This technique is demonstrated to be efficient on transferring of electrospun nanofibers with a high degree of alignment (~88.2%) on a SiO2 substrate. In addition, it is found that the printing outcome highly depends on the pressure between collecting and receiving substrate.

Polyaniline (PANI) is a promising functional polymer in the field of toxic gas detection. In this paper, nano-branched coaxial PANI fibers were grown on electrospun poly(methyl methacrylate) (PMMA) nanofibers by an in situ chemical oxidative polymerization method. The resultant PANI/PMMA fibers were characterized by scanning electronic microscopy and Raman spectrum analysis. The conductivity of an individual coaxial PANI/PMMA fiber is about 2.123 S/cm and that of the conducting PANI coating layer is about 21.8 S/cm. The ammonia sensing properties of the samples were tested by means of impedance analysis. The nano-branched PANI fibers can response significantly to low concentration of ammonia due to large specific surface area, and the sensitivity shows good linear relationship to the ammonia concentration of ppm level. These results indicate that nano-branched coaxial PANI fibers are promising candidate for detection of toxic ammonia gas.

LiMn2O4 nanofibers were prepared via electrospinning and followed by calcination. The surface morphology of as-spun and pure LiMn2O4 nanofibers was characterized by a scanning electron microscope (SEM) with an average diameter of 180 nm. After calcination at 800 °C in air for 5 h, charge/discharge capacity of pure LiMn2O4 nanofibers was measured in the potential range of 3.0 to 4.3 V. Battery testing showed that LiMn2O4 have a high discharge capacity of 80 mAh/g and 85% of the initial charge capacity was maintained for 5 cycles.

In this paper, non-woven micro-/nanofibers and wavelike micro-ribbons were produced by a low-voltage near-field electrospinning with working voltage less than 2.8 kV and spinning distance less than 8 mm. A series of experiments were carried out to explore the influence of processing variables on the formation of near-field electrospun nanofibers (polyvinyl pyrrolidone (PVP) as an example), including concentration, humidity and spinning distance. The formation mechanism of helical fibers and wavelike micro-ribbons was also discussed, which can be ascribed to electrical driven bending instability and/or mechanical jet buckling when hitting the collector surface. The results indicate that the morphology of the electrospun fibers can be controlled by experimental variables. And the low-voltage near-field electrospinning is a promising technique which may be used in precision deposition of nanofibers for nanodevices, direct-write nanofabrication, etc.

In this paper, we report on fabrication and physical properties of carbon microcoils, which are prepared by a chemical vapor deposition (CVD) process with Ni-catalyzed pyrolysis of acetylene, and characterized by a scanning electron microscope, a transmission electron microscope and an infrared spectrometer. The dark electrical conductivity of an isolated carbon microcoil is about 81 S/cm at room temperature, and its temperature dependence follows three-dimensional Mott variable-range hopping (VRH) model. Particularly, evident photocurrent is observed in the carbon microcoil upon cameral flash illumination. In addition, it is found that the surface of microcoil film is hydrophobic, showing a large water contact angle of about 135°. These results indicate that carbon microcoils have excellent physical properties, and can be used as optoelectronic and reinforced materials.

Barium titanate (BTO, BaTiO3) nanofiber was prepared via electrospinning and followed annealing process. The as-spun and calcined BTO nanofibers were characterized by a scanning electron microscope (SEM). After annealing at 800 °C in air for 3 h, polycrystalline BTO nanofibers with 120-200 nm in diameter were successfully obtained. I-V characteristic curves of single BTO nanofiber were measured. The p-type semiconducting fiber shows a room-temperature conductivity of about 0.3 S/cm. In addition, the small humidity hysteresis demonstrates the application prospects of electrospun BTO nanofibers in the fabrication of a high-sensitive humidity sensor.

Curled polyvinylpyrrolidone (PVP) microfibers were prepared successfully with a modified electrospinning setup in which the commonly used collector, a piece of aluminum foil was replaced by a steel nail (a tip collector). PVP (45 wt %) ethanol solution was used.with the increase of voltage, the proportion of the curled fibers increased and the uniformity of the curled fibers improved, also the repeat distance (wavelength) of the curled structures became smaller. In addition, some curled fibers developed into helical structures under relatively high voltages. Further analyses suggest that the mechanism for the curled PVP fibers could be ascribed to electric driven bending instability and/or mechanical jet buckling when hitting the hard collector surface.

In this paper, extraordinary self-assembled three-dimensional (3D) fibrous stackings have been fabricated by electrospinning from poly(vinylpyrrolidone)/nitrate solution and polystyrene solution. The stackings show cone-like shape, self-standing fiber arrays shape, or rockwork-like shape, which are quite different from the conventional electrospun 2D nonwoven mats. Especially, the stackings are able to reach to as high as 17 cm with the bottom diameter of 20 cm. In addition, it is found that the formation of the unique stackings is dependent on humidity, solution concentration/viscosity and volatility, which may strongly influence the solidification and stacking processes of the electrsopun fibers.

Ribbon-like microfibers of a new composite of europium complex Eu(aspirin)3(Phen) (aspirin is acetylsalicylic acid; Phen represents 1,10-phenanthroline) and polystyrene (PS) were prepared successfully by electrospinning with different mass ratios of Eu(aspirin)3(Phen) complex to PS = 1:10, 1:40 and 1:160. The microfibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and fluorescence spectrophotometry. It was found that the fibers displayed excellent photoluminescence properties compared with rare-earth complex. The photoluminescence intensity and the emission intensity of the peak at 616 nm (5D0→7F2) of Eu-ions increased with the Eu(aspirin)3(Phen) loading. No obvious fluorescence quenching was observed. Further discussion on the structural and optical properties of the microribbons was presented. This kind of materials might be expected to be applied for optical or optoelectronic devices.

In this work, we report on conducting polyaniline (PANI) nanostructures synthesized by a simplified template-free self-assembly method, which are doped with different oxidants such as ammonium persulfate (APS), FeCl3, Fe(NO3)3, and Fe2(SO4)3. It is found that the morphologies of the as-prepared PANI nanowires are dependent on the oxidant and the molar ratio of aniline to oxidant. The PANI nanostructures are semiconducting with room-temperature conductivity ranging from 10-2to 100S/cm, and the temperature dependence of conductivity follows three-dimensional Mott variable range hopping (3D Mott-VRH) model. In addition, the PANI pellets exhibit hydrophilic behavior.