Search

Surface wettability of a film plays a critical role in its practical applications. To control the surface wettability, modification on the physical surface structures has been a useful method. In this paper, we reported the controlling physical surface structure of polyvinyl butyral (PVB) films by different film-forming methods, spin-coating, bar-coating, and electrospinning. The wettability of these PVB films was examined, and the surface morphologies and roughness were investigated. The results indicated that coating PVB films were hydrophilic, while electrospun films were hydrophobic. The physical surface structure was the key role on the interesting transition of their surface wettability. Theoretical analyses on these results found that the coating PVB films showed different mechanism with electrospun ones. These results may help to find the way to control the PVB film surface wettability and then guide for applications.

Due to a variety of outstanding physical and chemical properties such as wide band gap, low resistance, good catalysis, high surface-to-volume ratio, high sensitivity and strong interaction with gas molecules, one-dimensional (1D) micro- and nanoscale indium oxide (In2O3) structures are capable for high-performance optical, electrical and chemical devices, which have attracted much attention in the last decade. In this paper, we first summarize various fabrication methods of 1D micro- and nanoscale In2O3 structures such as chemical vapor deposition, hydrothermal method, thermal evaporation method and electrospinning, then the interesting electrical and optical properties and their potential applications including gas sensors, field-emission transitions, photocatalysts and ultraviolet detectors are reviewed. At last, in order to fulfill the potential applications of 1D micro- and nanoscale In2O3 structures, some challenges have also been discussed.

Pure n-type ZnO nanofibers and p-type Ce-doped ZnO nanofibers were prepared by electrospinning followed by calcination. Their surface morphology, elemental composition, crystal structure, and optical and electronic properties were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and photoluminescence and UV-visible spectroscopy techniques and by their current–voltage (I–V) curves. The energy-dispersive X-ray spectroscopy and X-ray diffraction spectra showed that Ce was successfully incorporated into the ZnO crystal lattice and that the atomic percentage of Ce to Zn was 1.46%. The photoluminescence integrated intensity ratio of the UV emission to the deep-level green emission for Ce-doped ZnO nanofibers was over twice than that of pure ZnO. The UV-visible absorption edge of the Ce-doped ZnO nanofibers red-shifted by 2.6 nm compared with the pure ZnO nanofibers. The ZnO nanofibers had a good response to ultraviolet radiation. The sensitivity (Imax/I0) of the Ce-doped ZnO nanofibers was 102, which was one order higher in magnitude than that of pure ZnO nanofibers. The field-effect curve suggested that the synthesized Ce-doped ZnO nanofibers were p-type semiconductors. A p–n homojunction device was prepared using the ZnO nanofibers and showed good rectifying behavior. The turn-on voltage reduced by about 10 V under UV irradiation. Both the ZnO nanofibers and the ZnO p–n homojunction had excellent UV sensibilities. These results suggest that Ce-doped ZnO nanofibers may have widespread applications in optical and electronic devices.

Traditional indicator paper is disposable after use, requires a large number of target solutions and can only detect one item. In this study, recyclable upconversion-fluorescence indicator papers consist of upconversion nanorods and plasmonic nanostructures are fabricated by electrospinning. Human-body fluids containing different riboflavin concentration and pH are used as target solution, because these two items are usually detected in clinic to distinguish ambiguous diseases but often performed by two different testing processes that inevitably need more target solutions. Significantly different from conventional detecting system, this recyclable indicator paper can simultaneously achieve riboflavin and pH detections by using only a single droplet of target solution. As low as 0.01 ppm riboflavin can be sensitively detected, which is superior to most reported detection limit of fluorescence sensor. Moreover, this indicator paper can detect a single droplet (~10 μl) rather than a large amount of target solution (>1 ml) needed by traditional detecting system, and the pH can also be simultaneously in-situ detected using the same indicator paper. After the detection, the target solution is easily removed so that it brings about excellent recyclability, which is another advantage over traditional detecting system.

A conventional electrospinning setup cannot work without a plug (electricity supply). In this article, we report a self-powered electrospinning setup based on a hand-operated Wimshurst generator. The new device has better applicability and portability than a typical conventional electrospinning setup because it is lightweight and can work without an external power supply. Experimental parameters of the apparatus such as the minimum number of handle turns to generate enough energy to spin, rotation speed of the handle and electrospinning distance were investigated. Different polymers such as polystyrene (PS), poly(vinylidene fluoride) (PVDF), polycaprolactone (PCL) and polylactic acid (PLA) were electrospun into ultrathin fibers successfully by this apparatus. The stability, reliability, and repeatability of the new apparatus demonstrate that it can be used as not only a demonstrator for an electrospinning process, but also a beneficial complement to conventional electrospinning especially where or when without a power supply, and may be used in wound healing and rapid hemostasis, etc.

Aligned poly(methyl methacrylate) (PMMA) fibers were fabricated by electrospinning and then nanostructured polyaniline (PANI) was grown on the surface of the parallel PMMA fibers via in situ solution polymerization. The structure and morphology of the aligned PANI/PMMA composite fibers were characterized by scanning electron microscopy (SEM) and Raman spectrometry. The gas sensing properties of the composite fibers were investigated under ultra-low ammonia concentrations at room temperature. It is found that the arranged fibers exhibited high sensitivity and fast response upon exposure to ammonia vapor of 1–30 ppm. The normalized resistance R/R0 increased linearly with the ammonia concentration increasing. The sensing mechanism was also discussed. The results indicate that aligned PANI/PMMA composite fibers are promising candidate for fast detection of toxic ammonia gas.

Titanium dioxide (TiO2) nanorods with anatase phase were successfully fabricated by electrospinning and followed calcination. The TiO2 nanorods were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and UV-visible spectroscopy. The diameter of the TiO2 nanorods was about 60–150 nm and the length was 200 nm–2 μm. Electrical properties under bending were investigated by fixing the device to a curved surface with different curvatures, and the device showed a fast and stable resistance response to curvature changing. Photoelectric properties were studied by irradiation with different light intensities. The device exhibited a short response time (∼10 s) and a high sensitivity (∼103) which increased with the light intensity increasing. These results indicate that electrospun anatase TiO2 nanorods have potential applications in flexible photodetectors and solar cells.

For large scale electrospun (e-spun) nanofibre production, a variety of electrospinning (e-spinning) techniques such as multi-needle e-spinning and needleless e-spinning have been developed recently. In this paper, we propose a new design of efficient needleless e-spinning for fabrication of polymer nanofibres. A circular rotary bead wire driven by a DC motor is used as needleless electrode. When e-spinning, numerous solution jets are generated from the bead wire electrode through wrapping the electrode with solution from the solution brush. The design, construction and testing of the novel needleless e-spinning from rotary bead wire electrode are described in detail. The average diameter of the resultant polyvinyl pyrrolidone (PVP) fibres produced under 15–30 kV is around 200 nm. This needleless e-spinning technique may be promising for mass production of nanofibres.

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.

Due to a variety of outstanding properties, such as large surface area, high length-to-diameter ratio, flexible surface functionality, tunable surface morphologies and superior mechanical performance, electrospun ultrathin fibers are suitable for flexible and stretchable devices, which have aroused much attention nowadays. In this review, we aim to summarize recent developments in the fabrication of flexible/stretchable electronic devices via electrospinning, including strain and pressure sensors, supercapacitors, organic field-effect transistors, and transparent electrodes, which are the key components of flexible/stretchable devices. Moreover, in order to further improve the performance of these devices, some challenges facing electrospun fibers (e.g. production on large scale, precise deposition and flexibility improvement of electrospun inorganic fibers) and subsequent integration for flexible/stretchable electronic devices have also been discussed.

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.

Uniaxially aligned and cross-aligned arrays of ultrafine polymer fibers have been fabricated by a novel and effective centrifugal electrospinning setup with rotating polymer solution jets. Comparing with conventional electrospinning (10–30 kV) and centrifugal spinning (4,000–12,000 rpm), this technique only requires a lower working voltage (2.8–6.0 kV), a slower rotational speed (360–540 rpm), and a shorter spinning distance (2.0–4.0 cm). In addition, the influences of experimental parameters such as working voltage, rotational speed, collecting distance, and solution concentration on the alignment of the as-spun fibers are investigated using image analysis techniques. It is found that the working voltage and rotational speed mainly influence the perpendicular and linear velocities of the fibers, respectively. The polymer fibers tend to show higher alignment degree when these two velocities are very close. Optimum conditions (working voltage 3.0 kV, rotational speed 420 rpm, collecting distance 2.5 cm, and solution concentration 18 wt%) to maximize alignment degree (~97%) of polystyrene fibers are also obtained.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polyvinylpyrrolidone (PEDOT:PSS/PVP) composite nanofibers were successfully fabricated via electrospinning and used as a quartz crystal microbalance (QCM) sensor for detecting CO gas. The electrical property of individual PEDOT:PSS/PVP nanofibers was characterized and the room temperature resistivity was at the magnitude of 105 Ω·m. The QCM sensor based on PEDOT:PSS/PVP nanofibers was sensitive to low concentration (5–50 ppm) CO. In the range of 5–50 ppm CO, the relationship between the response of PEDOT:PSS nanofibers and the CO concentration was linear. Nevertheless, when the concentration exceeded 50 ppm, the adsorption of the nanofiber membrane for CO gas reached saturation and the resonant frequency range had no change. Therefore, the results open an approach to create electrospun PEDOT:PSS/PVP for gas sensing applications.

The flexible ZnO/SiO2 hybrid nanofiber membrane was prepared via electrospinning followed by high-temperature annealing at 600 °C in the air. The hybrid membrane was researched to prepare a flexible pressure sensor, and the experimental results suggest that the flexible pressure sensor has excellent flexibility under different bending conditions. The sensitivity (I max/I 0) of ZnO/SiO2 hybrid nanofibers is about 12.75 when the blending curvature radius is 1.25 cm−1. Among them, I max means current value when the sample is bending with curvature of 1.25 cm−1 at a voltage of 30 V, and I 0 means current value when the sample is relaxing at a voltage of 30 V. Besides, the prepared nanofibers have excellent pressure sensibilities under various pressures, and the sensitivity (I max/I 0) is up to 20.12 under 32.60 kPa pressure. In addition, the sensor exhibits high sensitivity, reversibility/reproducibility and good performance. The energy-dispersive x-ray spectroscopy shows that atomic percentage of Si to Zn was 43.9%. Additionally, it can be observed from the PL (photoluminescence spectrum) pattern that the sample has fine surface performance. The mechanisms of flexibility and pressure sensitivity are investigated. These results indicate that flexible ZnO/SiO2 hybrid nanofiber films have a bright future in the field of flexible electronic devices.

Barium titanate (BTO) nanofibers were synthesized by electrospinning and followed calcination. The morphologies and microstructures of the nanofibers were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Calcinating temperature and process greatly influenced the surface morphology of the nanofibers. In addition, parallel BTO nanofibers were also successfully produced by a centrifugal electrospinning technique. And the humidity sensing properties of the nanofibers were measured. The results showed an ultrafast response time (~0.5 s) and a recovery time (~0.4 s) to humidity at room temperature, which revealed excellent humidity sensitivity performance.

Ultrathin indium oxide (In2O3) hollow fibers were successfully fabricated by electrospinning poly(vinylidene fluoride) (PVDF) nanofibers, magnetron sputtering of In2O3 on PVDF fibers followed by calcination of In2O3/PVDF composite fibers. The hollow In2O3 fibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and UV-Visible spectroscopy. The outer diameter of the hollow fibers was in the range of 700–900 nm, and the inner diameter was about 400–600 nm. The optoelectronic properties of the In2O3 fibers were investigated by the irradiation of UV light with different wavelengths (254, 308 and 365 nm). It was found that the In2O3 hollow nanofibers had a fast and strong response to UV irradiation. The response time was less than 10 s, and the sensitivity (~102) decreased with the UV light wavelength increasing or the light intensity decreasing.

Ce-doped p-type ZnO nanofibers were synthesized by electrospinning and followed calcinations. The surface morphology, elementary composition, and crystal structure of the nanofibers were investigated. The field effect curve confirms that the resultant Ce-doped ZnO nanofibers are p-type semiconductor. A p-n heterojunction device consisting of Ce-doped p-type ZnO nanofibers and n-type indium tin oxide (ITO) thin film was fabricated on a piece of quartz substrate. The current-voltage (I-V) characteristic of the p-n heterojunction device shows typical rectifying diode behavior. The turn-on voltage appears at about 7 V under the forward bias and the reverse current is impassable.

Colorful nanofibrous membranes have attracted much attention for their visual varieties and various functionalities. In this article, a colored solution electrospinning process was used to fabricate colorful hydrophobic poly(vinyl butyral) (PVB)/cationic dye nanofibrous membranes (NFMs) successfully. The color and morphology of these as-spun nanofibrous membranes have been analyzed by colorimetry, spectroscopy, and scanning electron microscopy (SEM). It is shown that the as-spun colorful PVB-based membranes exhibit excellent level-dyeing property and color stability. Furthermore, the doping of cationic dye and the increase of dye concentration can decrease the diameter of the as-spun colored fibers, which results in better level-dyeing property and higher water contact angle more than 140°. The stained PVB fibrous membranes with excellent level-dyeing property and hydrophobicity are promising in some applications such as textiles, wallpapers, and anticorrosive coating/painting. Electronic supplementary material The online version of this article (doi:10.1186/s11671-016-1763-4) contains supplementary material, which is available to authorized users.