Electrospinning of beta silicon carbide nanofibers

Silicon carbide exhibits many unique properties such as its mechanical robustness, chemical inertness, and thermal stability, which make the material appealing for many applications. Some of these applications include its use as a support for nanocomposites or as a high temperature filter material. The ability to fabricate nanofibers of SiC could enhance its utility in these applications. In the current study, nanofibers of β-SiC have been fabricated through the technique of concentric electrospinning. This method demonstrates the ability to fabricate uniform SiC nanofibers with a diameter ranging from 1 to 2 nm, the smallest to date.     

Electrospinning carbon nanotube polymer composite nanofibers

The unique and exceptional physical properties of carbon nanotubes have inspired their use as a filler within a polymeric matrix to produce carbon nanotube polymer composites with enhanced mechanical, thermal and electrical properties. A powerful method of synthesising nanofibers comprising these polymer composites is electrospinning, which utilises an applied electric stress to draw out a thin nanometer-dimension fiber from the tip of a sharp conical meniscus. The focussing of the flow due to converging streamlines at the cone vertex then ensures alignment of the carbon nanotubes along the fiber axis, thus enabling the anisotropic properties of the nanotubes to be exploited. We consider the work that has been carried out to date on various aspects encompassing preprocessing, synthesis and characterisation of these electrospun polymer composite nanofibers as well as the governing mechanisms and associated properties of such fibers. Particular attention is also dedicated to the theoretical modelling of these fiber systems, in particular to the electrohydrodynamic modelling of electrospinning polymer jets.     

Electrospinning of polystyrene/dicyanopyrazine-linked porphyrin nanofibers

We have fabricated fluorescing polystyrene/dicyanopyrazine-linked porphyrin (PS/4-TDCPP) nanofibers using the electrospinning technique. UV-vis spectroscopy shows a strong Soret band and two relatively weak Q bands from the PS/4-TDCPP films and fibers, and reveals that the 4-TDCPP molecules are homogeneously dispersed in the films and fibers. Scanning electron microscopy (SEM) reveals the effect of solvent and collecting distance on the morphology of the electro-spun PS/4-TDCPP fibers. Fibers spun from a 50% dimethlyformamide (DMF), 50% methylethylketone (MEK) solution have ultra-fine structures with an average diameter of 300 nm. In the case of fibers from pure DMF and DMF:MEK (1:3) solutions, beads are formed along the length of the fibers. Variation of the collecting distance from 20 to 30 cm does not induce significant differences in the morphology of the electro-spun PS/4-TDCPP fibers. However, at a collecting distance of 15 cm, many beads are formed along the fibers. Acid-sensing capability of the PS/4-TDCPP fibers is demonstrated by fluorescence microscopy.     

静电纺丝法制备PVP/PVDF复合微/纳米纤维

研究了不同条件下聚乙烯吡咯烷酮/聚偏氟乙烯(PVP/PVDF)的N,N-二甲基乙酰胺(DMAc)溶液的静电纺丝.采用扫描电镜(sEM)观察不同条件下制备的PVP/PVDF复合微/纳米纤维的微观形貌,并利用傅立叶变换红外光谱分析(FT-IR)纤维结构特征.结果表明,当PVP:PVDF为6:4时,制得的PVP/PVDF复合微/纳米纤维较好.     

电纺丝技术--一种高效低耗的纳米纤维制备方法

电纺丝技术是一种高效低耗的纳米纤维制备方法。电纺丝技术的基本装置由高压直流电源、带有细小喷丝头的样品管和收集板三部分组成。描述了使用该技术将高分子制备成纳米纤维的基本原理。对11种处于发展和完善中的电纺丝装置进行了简要介绍。     

Electrospun chitosan/PEDOT nanofibers

Plasma-modified chitosan and poly(3,4-ethylenedioxythiophene) were blended to obtain conducting nanofibers with polyvinyl alcohol as a supporting polymer at various volumetric ratios by electrospinning method. Chemical compositions and molecular interactions among nanofiber blend components were determined using Fourier transform infrared spectroscopy (FTIR). The conducting blends containing plasma-modified chitosan resulted in a superior antibacterial activity and thinner fiber formation than those containing chitosan without plasma-modification. The obtained nanofiber diameters of plasma-modified chitosan were in the range of 170 to 200 nm and those obtained from unmodified chitosan were in the range of 190 to 246 nm. The electrical and electrochemical properties of nanofibers were also investigated by four-point probe conductivity and cyclic voltammetry measurements.     

Electrospinning of chitosan nanofibrous structures: feasibility study

In this paper a range of acid aqueous solutions are studied towards their suitability for developing chitosan nanofibres by electrospinning. It was found that parameters such as type of solvent, pH, concentration of chitosan, viscosity, charge density, applied voltage, solution flow rate, distance from nozzle tip to collector surface and time play a role in the characteristics of the obtained nanofibrous structures. After a preliminary study to select the most suitable composition of the chitosan containing solution (90% acetic acid), a detailed study was done to find the optimal conditions for chitosan nanofibrous structure development. Finally long-term experiments were performed, which showed that the formation of the nanofibrous structure distorts the electrical field.     

Electrospun chitosan/hydroxyapatite nanofibers for bone tissue engineering

Chitosan (CS) nanofibers were prepared by an electrospinning technique and then treated with simulated body fluid (SBF) to encourage hydroxyapatite (HA) formation on their surface. The CS/HA nanofibers were subjected to scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy, and X-ray diffraction (XRD) to confirm HA formation as well as determine the morphology of the nanofibrous scaffolds. The SEM image indicated that the distribution of HA on the CS nanofibers was homogeneous. The results from EDS and XRD indicated that HA was formed on the nanofibrous surfaces after 6-day incubation in the SBF. The calcium/phosphorus ratio of deposited HA was close to that of natural bone. To determine biocompatibility, the CS/HA scaffolds were applied to the culture of rat osteosarcoma cell lines (UMR-106). The cell densities on the CS/HA nanofibers were higher than those on the CS nanofibers, the CS/HA film, and the CS film, indicating that cell proliferation on CS/HA nanofibers was enhanced. Moreover, the early osteogenic differentiation on CS/HA was also more significant, due to the differences in chemical composition and the surface area of CS/HA nanofibers. The biocompatibility and the cell affinity were enhanced using the CS/HA nanofibers. This indicates that electrospun CS/HA scaffolds would be a potential material in bone tissue engineering.     

Electrospinning of polycarbonate nanofibers with solvent mixtures THF and DMF

The current work demonstrates the electrospinning of polycarbonate dissolved in solvent mixtures of tetrahydrofuran (THF) and dimethylformamide (DMF) to obtain fibers on a nanoscale. The solvent mixtures played a significant role on the morphology of the fibers. The spun fibers showed the characteristics of strong networking with each other as the THF ratio was increased in the solvent mixtures (like 60:40, 70:30 of THF:DMF). The electrostatic voltage, viscosity and surface tension also showed major effects on the fiber morphology and formation of beads. At lower THF and DMF ratios and lower spinning voltages, the bead revealed a globular mushroom shape, while at higher ratios and higher voltages, the beads formed the shape of spindle. The microstructures of the electrospun polycarbonate fibers were quantitively investigated by Scanning Electron Microscope (SEM) and Transmission Electron Microscope as a function of processing variables.     

Electrospinning fabrication of color-tunable flexible composite nanofibers containing lanthanide ions

A novel color-tunable PVP/[Tb(BA)₃phen+Eu(BA)₃phen] luminescent composite nanofibers had been fabricated by single axial electrospinning. The morphology and elements components of the as-prepared nanofibers were characterized by field emission scanning electron microscopy and energy dispersive spectroscopy. The luminescent properties were systematically investigated by photoluminescence spectroscopy. The obtained nanofibers had excellent fibrous morphology and smooth surface, and the average diameter was about 200 nm. The novel luminescent composite nanofibers exhibited the green, orange and red fluorescence emission peaks at 490, 545, 592 and 616 nm, which were ascribed to the ⁵D₄ → ⁷F₆ (490 nm) and ⁵D₄ → ⁷F₅ (545 nm) energy transitions of Tb³⁺ ions, and the ⁵D₀ → ⁷F₁ (592 nm), ⁵D₀ → ⁷F₂ (616 nm) transitions of Eu³⁺ ions, respectively. The emitting color of the luminescent composite nanofibers could be tuned by adjusting the mass ratio of terbium complexes and europium complexes in a wide color range of red-yellow-green under the excitation of 274-nm single-wavelength ultraviolet light. The color-tunable luminescent composite nanofibers have potential applications in the fields of display panels, lasers and bioimaging.     

Electrospinning of nanofibers: Characterization of jet dynamics and humidity effects

Electrospinning is a method to produce submicron polymer fibers for a wide range of applications. In many applications, the average electrospun fiber size and uniformity are important for the product's performance and process economics. Thus, it is desirable for electrospinning to achieve consistent and controllable fiber diameters. However, the current state-of-the-art electrospinning process can result in variable fiber diameters, both run-to-run and during a run. This paper investigates how the operating regime as well as several important process factors affect fiber diameter using a vision-based system. For aqueous polyethylene oxide (PEO) solutions, it is found that the relative humidity has a strong effect on fiber diameter. Correlations between measurable parameters and fiber diameter are also developed to provide the ability to achieve the desired fiber diameters. The jet dynamics are experimentally identified through step response for development of appropriate control strategies.     

Electrospinning fabrication and electrochemical properties of LiFePO4/C composite nanofibers

LiFePO₄/C composite nanofibers were synthesized by calcination of the [LiOH + Fe(NO₃)₃ + H₃PO₄]/PVP electrospun nanofibers. Polyvinyl pyrrolidone (PVP) was used as the electrospinning template and carbon source. During the calcination [LiOH + Fe(NO₃)₃ + H₃PO₄] were transformed to LiFePO₄ and PVP was decomposed into carbon. The morphology and properties of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area analysis, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. The results indicate that the mean diameter of as-prepared LiFePO₄/C composite nanofibers is 179.08 ± 29.66 nm and the BET specific surface area is 66.59 m² g^?1. The addition of carbon does not affect the structure of LiFePO₄, but improves its electrochemical performances. At the current density of 0.2 C, the initial discharge capacity of LiFePO₄/C electrode is 133.6 mAh g^?1 and there is no obvious capacity fading after 100 cycles. The formation mechanism of the LiFePO₄/C composite nanofibers was also proposed.     

Electrospinning of zein/propolis nanofibers; antimicrobial properties and morphology investigation

In this work, for the first time, zein nanofiber mats loaded with ethanol extracts propolis (EEP) were successfully produced. Raw propolis was extracted by ethanol 70% and total flavonoid content was estimated by aluminum chloride colorimetric method. The anti-microbial activity of the EEP was investigated and compared with amoxicillin via zone of inhibition test against various microorganisms included gram-positive: Staphylococcus aureus, Staphylococcus epidermidis, gram-negative: Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and fungus: Candida albicans. The EEP showed activity only against gram-positive types and fungus, whereas no activity was observed against gram-negative types. Electrospun zein nanofiber was obtained from 70% ethanolic solutions included different content of zein, 15–40?wt.%. The SEM images revealed a smooth ribbon-like morphology for zein nanofibers without any beads in zein content more than 25?wt.%. As well, the SEM images of electrospun zein nanofibers containing different content of propolis (0–40?wt.% based on the zein content) disclosed the increase in the average size of fibers with propolis content from 264 to 419?nm. This increasing was more probably due to the reduction in ionic conductivity of zein solutions with propolis content. The proteinic nature of zein along with the antimicrobial activity and the herbal nature of the propolis make the obtained mats promising candidate for more evaluation in wound healing study.

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Electrospinning of CeO2-ZnO composite nanofibers and their photocatalytic property

CeO₂-ZnO composite nanofibers were fabricated via the electrospinning technique using zinc acetate and cerium nitrate as the precursors, poly(vinylpyrrolidone) as the fiber template, and 2:1(v/v) ethanol/water mixtures as the co-solvent, followed by thermal treatment at 600 °C for 3 h. Various characterization methods were employed to investigate the morphologies and structures of the nanofibers. The calcined composite nanofibers showed a continuous line feature with an average diameter of 46 nm composed of 15 ± 3 nm CeO₂ and ZnO nanoparticles. Photocatalytic activity experiments showed that the Rhodamine B was almost completely decomposed when it was catalyzed by CeO₂-ZnO nanofibers within 3 h, while only 17.4% and 82.3% were decomposed under catalysis by CeO₂ and ZnO nanofibers respectively. Such CeO₂-ZnO composite nanofibers could have potential applications in the treatment of organic-polluted water.     

Wet chemical process to enhance osteoconductivity of electrospun chitosan nanofibers

In this study, chitosan/hydroxyapatite (CS/HA) nanofibers were prepared using a wet chemical method. First, CS nanofibers with uniform diameters were fabricated using electrospinning. Then, a wet chemical process was used to mineralize nanofiber surfaces to form a homogeneous HA deposit. Reactions with three cycles were found to optimize biomimetic properties of the HA. The mineralization process required only approximately 3 h, which corresponded to a saving of 98 % in preparation time compared with that needed by the process using a simulated body fluid (SBF). According to the attachment and spreading of UMR (rat osteosarcoma) cells on the CS/HA composite fibers, the deposited mineralization layer significantly enhanced cell affinity of the CS nanofibers and the HA created by the wet chemical method was as effective as that created by the SBF. The composite nanofibrous scaffolds produced by the wet chemical process also promoted osteogenic differentiation by inducing ossification. Thus, expressions of collagen type I, alkaline phosphatase, osteocalcin, bone sialoprotein, and osterix were all enhanced. These results demonstrated that composite electrospun fibers can be efficiently prepared using wet chemical method and the resulting nanofibrous scaffolds have considerable potential in future bone tissue engineering applications.     

Physico-chemical/biological properties of tripolyphosphate cross-linked chitosan based nanofibers

In this study, chitosan-PEO blend, prepared in a 15 M acetic acid, was electrospun into nanofibers (~ 78 nm diameter) with bead free morphology. While investigating physico-chemical parameters of blend solutions, effect of yield stress on chitosan based nanofiber fabrication was clearly evidenced. Architectural stability of nanofiber mat in aqueous medium was achieved by ionotropic cross-linking of chitosan by tripolyphosphate (TPP) ions. The TPP cross-linked nanofiber mat showed swelling up to ~ 300% in 1 h and ~ 40% degradation during 30 day study period. 3T3 fibroblast cells showed good attachment, proliferation and viability on TPP treated chitosan based nanofiber mats. The results indicate non-toxic nature of TPP cross-linked chitosan based nanofibers and their potential to be explored as a tissue engineering matrix.     

Electrospinning of polymer nanofibers: Effects on oriented morphology,structures and tensile properties

The interest in fabrication of nanofibers using electrospinning method has attracted considerable attention due to its versatile maneuverability of producing controlled fiber structures, porosity, orientations and dimensions. Although the process appears to be simple and straightforward, an understanding of the technique and its influence on the morphology, structural and mechanical properties is still not completely clear. Recently, the size effect on the mechanical properties was reported for fibers across different length scales. Both modulus and strength of poly(ε-capro-lactone) (PCL) fibers were found to increase significantly when the diameter of the fibers was reduced to below ∼500 nm. In this article, for the first time, we critically review and evaluate the role of the microstructures on the fiber deformation behavior and present possible explanations for the enhanced properties of the nanofibers. Our discussions are focused on the techniques to obtain controlled structures and the mechanisms behind the size effect in electronspun fibers are given. In-depth understanding of these mechanisms can provide fruitful outcomes in the development of advanced nanomaterials for devices and miniaturized load-bearing applications.     

Electrospinning preparation and luminescence properties of one-dimensional SrWO4: Sm3+ nanofibers

One-dimensional Sm³⁺ doped SrWO₄ with or without different charge compensation approaches (co-doping Li⁺, Na⁺ and K⁺) nanofibers were prepared by electrospinning. The structure, morphology and luminescence properties of the obtained nanofiber phosphors were investigated. The X-ray diffraction, Fourier transformation infrared and thermogravimetric results show that the Sr_(1?x)WO₄: Sm _x ³⁺ samples crystallize at 700 °C. Scanning electron microscope results indicate that as prepared nanofibers before/after calcination present uniform fiberlike morphology. The luminescence results show that Sr_(1?x)WO₄: Sm _x ³⁺ phosphors can be excited efficiently by ultraviolet (UV) and near-UV light. The emission spectrum consists of three emission peaks at 561, 596 and 643 nm, corresponding to ⁴G_5/2 → ⁶H_5/2, ⁴G_5/2 → ⁶H_7/2 and ⁴G_5/2 → ⁶H_9/2 transitions of Sm³⁺, respectively. The optimal doping concentration of Sm³⁺ in SrWO₄ is experimentally ascertained to be 4 mol%. The introduction of charge compensator R⁺ (R = Li, Na and K) can enhance the emission intensity of phosphors significantly. The co-doping of Li⁺ has the best compensation effect. The present investigation indicates that Sm³⁺ doped SrWO₄ is a promising orange phosphor for light-emitting diode based on UV chip technology.     

Preparation of chitosan/PLA blend micro/nanofibers by electrospinning

The chitosan/PLA blend micro/nanofibers have been prepared for the first time by electrospinning. Trifluoroacetic acid (TFA) was found to be the co-solvent for electrospinning. The chitosan/PLA blend solutions in various ratios were studied for electrospinning into micro/nanofibers. The morphology of the fibers was shown by scanning electron microscope (SEM). It was found that the average diameter of the chitosan/PLA blend fibers became larger, and the morphology of the fibers became finer with the content of PLA increasing. To show the molecular interactions, chitosan/PLA fibers were characterized by Fourier transform infrared spectroscopy (FTIR). The spun micro/nanofibers are expected to be used in the native extracellular matrix for tissue engineering.