Fabrication and characterization of electrospun titania nanofibers

Titania (TiO₂) nanofibers were fabricated by electrospinning three representative spin dopes made of titanium (IV) n-butoxide (TNBT) and polyvinylpyrrolidone (PVP) with the TNBT/PVP mass ratio being 1/2 in three solvent systems including N,N-dimethylformamide (DMF), isopropanol, and DMF/isopropanol (1/1 mass ratio) mixture, followed by pyrolysis at 500 °C. The detailed morphological and structural properties of both the as-electrospun precursor nanofibers and the resulting final TiO₂ nanofibers were characterized by SEM, TEM, and XRD. The results indicated that the precursor nanofibers and the final TiO₂ nanofibers made from the spin dopes containing DMF alone or DMF/isopropanol mixture as the solvent had the common cylindrical morphology with diameters ranging from tens to hundreds of nanometers, while those made from the spin dope containing isopropanol alone as the solvent had an abnormal concave morphology with sizes/widths ranging from sub-microns to microns. Despite the morphological discrepancies, all precursor nanofibers were structurally amorphous without distinguishable phase separation, while all final TiO₂ nanofibers consisted of anatase-phased TiO₂ single-crystalline grains with sizes of approximately 10 nm. The electrospun TiO₂ nanofiber mat is expected to significantly outperform other forms (such as powder and film) of TiO₂ for the solar cell (particularly dye-sensitized solar cell) and photo-catalysis applications.     

Fabrication and characterization of electrospun mullite nanofibers

Continuous mullite (3Al₂O₃·2SiO₂) nanofibers were fabricated by a sol-gel electrospinning technique. The detailed crystallization development and micromorphological evolution of both the as-electrospun nanofibers and the sintered mullite nanofibers were investigated. Results indicated that the spinnability and micromorphological evolution of mullite nanofibers are largely dependent on the viscosity η of the mullite sol, which can be adjusted by polyvinylprrolidone (PVP) content. Mullite nanofibers with common cylindrical morphology and diameters ranging from 400 nm to 800 nm could be obtained easily and rapidly when PVP content is ranged from 5 wt.% to 8 wt.%. High purity polycrystalline mullite nanofibers with diameters of about 200 nm were obtained after sintering at 1200 °C for 2 h. All sintered nanofibers consisted of single crystalline grains with size of approximately 100 nm.     

Fabrication and characterization of electrospun CdS-OH/polyacrylonitrile hybrid nanofibers

CdS-OH/polyacrylonitrile (PAN) hybrid nanofibers with strong photoluminescence and photocatalytic hydrogen production efficiency were synthesized by one-step co-electrospinning for the first time. The suspension of CdS-OH nanoparticles (size: 5 nm) in N,N-dimethylformamide (DMF) was mixed with PAN/DMF solutions to make spinning solutions, followed by electrospinning to make CdS-OH/PAN hybrid nanofibers. Their morphology and structure were characterized by SEM, TEM, XRD and fluorescence spectrophotometer. TEM and XRD measurements proved that the crystallographic structure of CdS-OH nanoparticles is identical to that of CdS. The CdS-OH nanoparticles were evenly distributed in PAN nanofibers of 320 nm in diameter. Thermogravimetrical analysis demonstrated that hybrid nanofibers were more thermally stable than neat PAN nanofibers. The hybrid nanofibers displayed excellent photoluminescent property. Additionally, they showed good photocatalytic hydrogen production efficiency with a rate of 13.5 μmol/h g fiber containing 60 mg of CdS-OH nanoparticles.     

Fabrication and characterization of electrospun Ag doped TiO2 nanofibers for photocatalytic reaction

Titanium dioxide is one of the best semiconductor photocatalysts available for photocatalytic reaction of dye pollutants. To prevent the recombination caused by the relatively low photocatalytic efficiency, Ag doped TiO₂ nanofiber was prepared by electrospinning method. The photocatalysts (pure TiO₂ nanofiber and Ag doped TiO₂ nanofiber) were characterized by FE-SEM, XRD, XPS, and PL analysis. These photocatalysts were evaluated by the photodecomposition of methylene blue under UV light. Ag doped TiO₂ nanofiber was found to be more efficient than pure TiO₂ fiber for photocatalytic degradation of methylene blue. The photocatalytic degradation rate was applied to pseudo-first-order equation. The degradation of Ag doped TiO₂ nanofiber was significantly higher than the degradation rate of pure TiO₂ nanofiber. Activation energy was calculated by applying Arrhenius equation from the rate constant of photocatalytic reaction. The activation energies for the pure TiO₂ nanofibers calcined at 400 and 500 °C were 16.981 and 12.187 kJ/mol and those of Ag doped TiO₂ nanofibers were 18.317 and 7.977 kJ/mol, respectively.     

Fabrication and evaluation of polyamide 6 composites with electrospun polyimide nanofibers as skeletal framework

In this study, two types of polyimide (PI) nanofiber mats, including (1) the mats consisting of (almost) randomly overlaid PI nanofibers and (2) the mats consisting of highly aligned PI nanofibers, were prepared by the materials-processing technique of electrospinning. The nanofiber mats were subsequently used to develop composites with polyamide 6 (PA6) via the composites – fabrication method of polymer melt infiltration lamination (PMIL). Owing to superior mechanical properties (i.e., the tensile strength and modulus were 1.7 GPa and 37.0 GPa, respectively) and large specific surface area of electrospun PI nanofibers, the PI/PA6 composites with PI nanofiber mats as skeletal framework demonstrated excellent mechanical properties. In particular, the PI/PA6 composite containing 50 wt.% of aligned PI nanofibers had the tensile strength and modulus of 447 MPa and 3.0 GPa along the longitudinal direction, representing ～700% and ～500% improvements as compared to neat PA6.     

Electrical properties of electrospun carbon nanofibers

Electrospun carbon nanofibers (ECNs) were prepared through stabilization and carbonization of electrospun polyacrylonitrile nanofibers as the precursor, and their morphological, structural, and electrical properties were evaluated. Temperature dependencies of resistivity of ECNs carbonized at several temperatures were investigated. The character of the temperature dependencies of resistivity was typical for semiconducting materials. The values of corresponding activation energies were obtained for ECN samples carbonized at different temperatures, and the results showed that the activation energy of ECNs decreased with the increase of carbonization temperature.     

静电纺淀粉纳米纤维的交联改性研究

通过静电纺丝技术制备纯淀粉纳米纤维膜,并在密闭容器中和戊二醛蒸汽进行交联。利用环境扫描电子显微镜(ESEM)、傅里叶变换红外光谱(FT-IR)对纤维交联前后的表面形貌和结构进行观察和分析,通过电子万能材料拉伸试验机、接触角测试仪等考察了交联反应对纤维膜性能的影响。结果表明,戊二醛与淀粉分子之间发生了缩醛化交联反应,淀粉纳米纤维膜经戊二醛蒸汽交联后仍能较好的保留原纤维的形态,并且拉伸性能和耐水性能均得到一定程度的提高。     

PVC/Fe electrospun nanofibers for high frequency applications

In this article, we present a study on the microwave frequency properties of poly(vinyl chloride)/Fe composite nanofibers, with different concentrations of iron particles incorporated in poly(vinyl chloride) matrix. Using electrospinning, composite nanofibers were obtained with size ranging between 100 and 500 nm. The absorption properties of synthesized nanofibers were measured between two open-end rectangular waveguides in the 8–12 GHz frequency domain. The transmission loss measurements for poly(vinyl chloride)/Fe composite nanofibers demonstrated that this material can be used as protection material in X-band frequency domain. The applied magnetic field significantly modifies the measured scattering parameters in our samples case in a rather large domain of values for the field.     

Fabrication of mineralized electrospun PLGA and PLGA/gelatin nanofibers and their potential in bone tissue engineering

Surface mineralization is an effective method to produce calcium phosphate apatite coating on the surface of bone tissue scaffold which could create an osteophilic environment similar to the natural extracellular matrix for bone cells. In this study, we prepared mineralized poly(d,l-lactide-co-glycolide) (PLGA) and PLGA/gelatin electrospun nanofibers via depositing calcium phosphate apatite coating on the surface of these nanofibers to fabricate bone tissue engineering scaffolds by concentrated simulated body fluid method, supersaturated calcification solution method and alternate soaking method. The apatite products were characterized by the scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffractometry (XRD) methods. A large amount of calcium phosphate apatite composed of dicalcium phosphate dihydrate (DCPD), hydroxyapatite (HA) and octacalcium phosphate (OCP) was deposited on the surface of resulting nanofibers in short times via three mineralizing methods. A larger amount of calcium phosphate was deposited on the surface of PLGA/gelatin nanofibers rather than PLGA nanofibers because gelatin acted as nucleation center for the formation of calcium phosphate. The cell culture experiments revealed that the difference of morphology and components of calcium phosphate apatite did not show much influence on the cell adhesion, proliferation and activity.     

Critical variables in the alignment of electrospun PLLA nanofibers

Electrospun polymer nanofibers show promise as components of scaffolds for tissue engineering because of their ability to orient regenerating cells. Our research focuses on aligned electrospun fiber scaffolds for nerve regeneration. Critical to this are highly aligned fibers, which are frequently difficult to manufacture reproducibly. Here we show that three variables: the distance between the spinneret tip and collector, the addition of DMF to the solvent, and placement of an aluminum sheet on the spinneret together greatly improve the alignment of electrospun poly-L-lactide (PLLA) nanofibers. We identified the most important variable as tip-to-collector distance. Nanofiber alignment was maximal at 30 cm compared to shorter distances. DMF:chloroform (1:9) improved nanofiber uniformity and was integral to maintaining a uniform stream over the 30 cm tip-to-collector distance. Other ratios caused splattering of the solution or flattening or beading of the fibers and non-uniform fiber diameter. The aluminum sheet helped to stabilize the electric field and improve fiber alignment provided that it was placed at 1 cm behind the tip, while other distances destabilized the stream and worsened alignment. This study demonstrates that control of these variables produces dramatic improvement in reproducibly obtaining high alignment and uniform morphology of electrospun PLLA nanofibers.     

Evaluation of proanthocyanidin-crosslinked electrospun gelatin nanofibers for drug delivering system

Electrospun nanofibers are excellent candidates for various biomedical applications. We successfully fabricated proanthocyanidin‐crosslinked gelatin electrospun nanofibers. Proanthocyanidin, a low cytotoxic collagen crosslinking reagent, increased the gelatin crosslinking percentage in the nanofibers from 53% to 64%. The addition of proanthocyanidin kept the nanofibers from swelling, and, thus, made the fibers more stable in the aqueous state. The compatibility and the release behavior of the drug in the nanofibers were examined using magnesium ascorbyl phosphate as the model drug. Proanthocyanidin also promoted drug loading and kept the drug release rate constant. These properties make the proanthocyanidin‐crosslinked gelatin nanofibers an excellent material for drug delivery. In the cell culture study, L929 fibroblast cells had a significantly higher proliferation rate when cultured with the gelatin/proanthocyanidin blended nanofibers. This characteristic showed that proanthocyanidin‐crosslinked gelatin electrospun nanofibers could potentially be employed as a wound healing material by increasing cell spreading and proliferation.     

Blinking CsPbBr3 perovskite nanocrystals for the nanoscopic imaging of electrospun nanofibers

Blinking fluorophore perovskite nanocrystals (NCs) were employed to image the fine structure of the polystyrene (PS) electrospun fibers. The conditions of CsPbBr3 NCs embedded and dispersed into PS were investigated and optimized. The stochastic optical reconstruction microscopy is employed to visualize the fine structure of the resulted CsPbBr3@PS electrospun fibers at sub-diffraction limit. The determined resolution in the reconstructed nanoscopic image is around 25.5 nm, which is much narrower than that of conventional fluorescence image. The complex reticulation and multicompartment in bead sub-diffraction-limited structures of CsPbBr3@PS electrospun fibers were successfully mapped with the help of the stochastic blinking properties of CsPbBr3 NCs. This work demonstrated the potential applications of CsPbBr3 perovskite NCs in super-resolution fluorescence imaging to reconstruct the sub-diffraction-limited features of polymeric material.     

Fabrication of poly(3-methylthiophene)/poly(ethylene oxide)/ruthenium oxide composite electrospun nanofibers for supercapacitor application

Journal of Materials Science: Materials in Electronics - In the present work, composites of poly(3-methylthiophene)/poly(ethylene oxide)/ruthenium oxide nanofibers (PMT/PEO/RuO2) were fabricated by...     

Gas flow-assisted alignment of super long electrospun nanofibers

Electrospinning provides a simple and versatile method for generating ultra thin fibers with diameters ranging from nanometer to micron out of various materials. However, there are still challenges in the alignment of electrospun nanofibers, which is an important step toward the exploitation of these fibers in applications. In this letter, we report a method using the gas flow to assist the alignment of electrospun nanofibers, which can form well-aligned super long polymeric nanofibers over large areas with the length of more than 20 cm. The improved collector is built by coupling a "T"-shaped electrode and a rectangle electrode, and it can make the electrospun nanofiber form a fixed site at the "T"-shaped electrode under the electric field and make it possible to use an assisting gas flow (AGF) to draw the other part of the nanofiber to fly toward the upside of the rectangle electrode and obtain well-aligned long nanofibers. These well-aligned long nanofibers can be further applied easily without disturbing the aligned structure, which is convenient for the measurement and device fabrications.     

Preparation and characterization of electrospun SiO2 nanofibers

The objective of this study was to prepare and characterize electrospun SiO2 nanofibers for composite (particularly dental composite) applications. We investigated (1) tetraethyl orthosilicate (TEOS) as the alkoxide precursor, (2) polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP) as the carrying polymers, (3) several solvents for making the spin dopes, and (4) the morphological and structural properties of the electrospun SiO2 nanofibers and their relationship with the pyrolysis temperatures. We also investigated the morphology durability of the prepared SiO2 nanofibers by subjecting them to vigorous ultrasonic vibrations. The results indicated that the uniform (beads-free) amorphous SiO2 nanofibers with an average diameter of approximately 500 nm were successfully prepared. These SiO2 nanofibers also retained their overall fiber morphology when subjected to vigorous ultrasonic vibrations. The electrospun SiO2 nanofibers were, therefore, nano-scaled glass (amorphous SiO2) fibers, and could be used for reinforcement of dental composites.     

Atomic force microscopy of electrospun organic-inorganic lipid nanofibers

An organic-inorganic hybridization strategy has been proposed to synthesize polymerizable lipid-based materials for the creation of highly stable lipid-mimetic nanostructures. We employ atomic force microscopy (AFM) to analyze the surface morphology and mechanical property of electrospun cholesteryl-succinyl silane (CSS) nanofibers. The AFM nanoindentation of the CSS nanofibers reveals elastic moduli of 55.3?±?27.6 to 70.8?±?35 MPa, which is significantly higher than the moduli of natural phospholipids and cholesterols. The study shows that organic-inorganic hybridization is useful in the design of highly stable lipid-based materials.     

SiC nanofibers by pyrolysis of electrospun preceramic polymers

Silicon carbide (SiC) nanofibers of diameters as low as 20 nm are reported. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fiber flowing during pyrolysis. Electrospun SiC fibers were characterized by Fourier transform infrared spectroscopy, thermo gravimetric analysis-differential thermal analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electron diffraction. Fibers were shown to be polycrystalline and nanograined with β-SiC 4H polytype being dominant, where commercial methods produce α-SiC 3C. Pyrolysis of the bulk polymer blend to SiC produced α-SiC 15R as the dominant polytype with larger grains showing that electrospinning nanofibers affects resultant crystallinity. Fibers produced were shown to have a core–shell structure of an oxide scale that was variable by pyrolysis conditions.     

Fabrication of DNA-magnetite hybrid nanofibers for water detoxification

DNA-magnetite hybrid nanofibers were fabricated by electrospinning a spin dope consisting of oleic acid coated magnetite nanoparticles and DNA-CTMA in ethanol/chloroform mixed solvent. The fabricated nanofibers exhibit superparamagnetic behaviour owing to embedded magnetite nanoparticles. It is demonstrated that these nanofibers can be used as effective detoxification materials in aqueous media as a combined result of DNA's affinity to both organic and inorganic toxicants, high surface area of the nanofibers and the fast and easy separation due to magnetite nanoparticles under external magnetic field. In addition to detoxification, these novel hybrid nanofibers have potential applications in many technological areas such as catalysis and drug delivery.