Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue Engineering Applications

The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.

Influence of Sorbitan Monooleate on Morphology and Drug Release Behavior of Emulsion Electrospinning Polycaprolactone Nanofibers

Ultrafine polycaprolactone(PCL)fibers containing watersoluble drug tetracycline hydrochloride(Tet)were prepared by emulsion electrospinning.Sorbitan monooleate(Span80)was added as an essential additive to form stable water/oil emulsions and fabricate fibers with core-sheath structure.Different concentrations of Span80(0-40 g/L)were used to investigate the stability of emulsion and size of dispersed droplets.The scanning electron microscope(SEM)images indicated that the morphology of the fibers with Span80 were beaded-free with diameters of 200-400 nm,and Span80 enhanced the spinnability of electrospinning solution.The laser scanning confocal microscope(LSCM)images indicated that Tet was well encapsulated into the core region of the PCL fibers.The transmission electron microscope(TEM)image showed the formation of core-sheath structure.The loading efficiency(LE)and entrapment efficiency(EE)of Tet were calculated and release profiles in artificial saliva buffer solution(pH=6.8)were also analyzed.The results revealed that LE and EE of fibers with Span80decreased with the increase of its concentration.Fibers with coresheath structure had a longer effective release lifetime than without Span80.The increase of Span80 resulted in higher hydrophilicity of fibers and faster release rate of Tet.

Fabrication of High-Efficiency Polyvinyl Alcohol Nanofiber Membranes for Air Filtration Based on Principle of Stable Electrospinning

A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages and injection rates to figure out their influence on steadily fabricating polyvinyl alcohol(PVA)nanofibers prepared from PVA spinning solutions with two different mass fractions(10%and 16%).The results revealed that during the stable electrospinning,the influence resulted from the change of the injection rate approximately canceled out the impact brought by adjusting the applied voltage,leading to almost the same morphology as that of the PVA nanofibers.And the mass fraction of PVA in the spinning solution dominated the structure and the diameter distribution of the electrospun nanofibers.Under stable electrospinning conditions,the composite membrane was produced by depositing PVA nanofibers on the polyethylene terephthalate(PET)nonwoven substrate for an air filtration test.Furthermore,the prepared composite membrane exhibited a high air filtration efficiency(99.97%)and a low pressure drop(120 Pa)for 300-500 nm neutralized polystyrene latex(PSL)aerosol particles,demonstrating its potential as an alternative for a variety of commercial applications in air filtration.

Recent Progress on the Fabrication of Ultrafine Polyamide-6 Based Nanofibers Via Electrospinning: A Topical Review

Electrospinning is a highly versatile technique to prepare continuous fibers with diameters of the order of nanometers. The remarkable high aspect ratio and high porosity bring electrospun nanofibers highly attractive to various nanotechnological applications such as filtration membranes, protective clothing, drug delivery, tissue-engineering, biosensors, catalysis, fuel cells and so on. In this review, we collectively summarized the recent progress in developments of the electrospun ultrafine polyamide-6 based nanofibers preparation,characterization and their applications. Information of this polyamide-6 and composites together with their processing conditions for electrospinning of ultrafine nanofibers has been summarized in this review. The recent developments made during last few years on these materials are addressed in this review. We are anticipating that this review certainly drive the researchers for developing more intensive investigation for exploring in many technological areas.

Fabrication of TiO2 nanofiber assembly from nanosheets（TiO2-NFs-NSs） by electrospinning-hydrothermal method for improved photoreactivity

Hierarchically structured nanomaterials have attracted much attention owing to their unique properties.In this study,TiO2 nanofibers assembled from nanosheets(TiO2-NFs-NSs)were fabricated through electrospinning technique,which was followed by hydrothermal treatment in NaOH solution.The effect of hydrothermal reaction time(0-3 h)on the structure and properties of TiO2 nanofibers(TiO2-NFs)was systematically studied,and TiO2-NFs was evaluated in terms of the photocatalytic activity toward photocatalytic oxidation of acetone and the photoelectric conversion efficiency of dye-sensitized solar cells.It was found that(1)hydrothermal treatment of TiO2-NFs in NaOH solution followed by acid washing and calcination results in the formation of TiO2-NFs-NSs;(2)upon extending the hydrothermal reaction time from 0 h to 3 h,the BET surface area of TiO2-NFs-NSs(T3.0 sample)increases 3.8 times(from 28 to 106 m2 g^-1),while the pore volume increases 6.0 times(from 0.09 to 0.54 cm3 g^-1);(3)when compared with those of pristine TiO2-NFs(T0 sample),the photoreactivity of the optimized TiO2-NFs-NSs toward acetone oxidation increases 3.1 times and the photoelectric conversion efficiency increases 2.3 times.The enhanced photoreactivity of TiO2-NFs-NSs is attributed to the enlarged BET surface area and increased pore volume,which facilitate the adsorption of substrate and penetration of gas,and the unique hollow structure of TiO2-NFs-NSs,which facilitates light harvesting through multiple optical reflections between the TiO2 nanosheets.

Synthesis of Poly(N-vinylpyrrolidone) Nanofibers Containing Gold Nanoparticles via Electrospinning Technique

Poly（N-vinylpyrrolidone）（PVP）nanofibers containing gold nanoparticles were prepared by electrospinning method.This simple route was used to prepare composites on a large scale,and the syntheses are simple.The optical property of gold nanoparticles in PVP aqueous solution was investigated by UV-Visible absorption spectra.The morphology of the fibers and the distribution of particles were characterized by transmission electron microscopy.The structure of the composite was characterized by Fourier transform infrared spectroscopy.

Microstructural Changes of Graphene/PLA/PBC Nanofibers by Electrospinning during Tensile Tests

This study focuses on the nanostructure and nanostructural changes of novel graphene/poly（lactic acid） （PLA）/ poly（butylene carbonate） （PBC） nanofibers via electrospinning, which are characterized by differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile test and in situ small angle x-ray scattering. DSC indicates that the endothermic peak at 295℃ of pure PLA/PBC nanofibers shifted from 317℃ to lower 290℃ with the increasing graphene content. SEM observations reveal a fine dispersion of graphene in the nanofiber matrices. The graphene/PLA/PBC nanofiSers exhibit good improvements in mechanical property. The tensile strength of nanofibers increases with the addition of 0.01 g graphene but reduces with further addition of 0.04g graphene. The scattering intensities increase dramatically when the strain levels are higher than the yield point due to the nucleation and growth of nanovoids or crystals. However, the increasing content of graphene in the PLA/PBC matrix provokes a strong restriction to the deformation-induced crystals.

Preparation of α-Fe_2O_3 Nanofiber via Electrospinning Process

A thin PVA/FeCl_3 composite fiber was prepared by using sol-gel processing and electrospinning techniques. A nanofiber of α-Fe_2O_3 with the diameter of 50_150 nm was obtained via high temperature calcination of the PVA/FeCl_3 composite fiber. The material was characterized by infra-red(IR) spectroscopy, X-ray diffraction(XRD), and scanning electron microscopy(SEM). The results show that the fiber after the calcination at 700 ℃ was a pure α-Fe_2O_3 nanofiber.

Facile fabrication of TiO_2 nanoparticle–TiO_2 nanofiber composites by co-electrospinning–electrospraying for dye-sensitized solar cells

We report a facile method for the fabrication of TiO2 nanofiber-nanoparticle composite （FP） via. simulta- neous electrospraying and electrospinning for dye-sensitized solar cell （DSC） applications. The loading of nanoparticles on the fibers is controlled by varying their feed rates during electrospinning. The FP composites having three different particle loading are prepared by the methodology and the FP with the highest particle loading （denoted as FP-3 in the manuscript） showed the best overall efficiency of 9.15% in comparison to the other compositions of the FP （FP-2, 8.15% and FP-1, Z51%, respectively） and nanofibers （F） and nanoparticles （P） separately （7.21 and 7.81, respectively）. All the material systems are characterized by spec- troscopy, microscopy, surface area measurements and the devices are characterized by current-voltage （I-V）, incident photon-to-current conversion efficiency （IPCE）, electrochemical impedance measurements, etc. I-V, dye-loading and reflectance measurements throw light on the overall performance of the DSC devices.

Effect of Water-Soluble Drug Ionization on the Properties of Emulsion Electrospun Polycaprolactone Nanofibers

Core-shell drug-loaded nanofibers were investigated to reduce adverse effects of drugs and achieve stable storage and also to release drugs continuously. In this study,ultrafine polycaprolactone( PCL) fibers were obtained by emulsion electrospinning and the resulting fiber diameters were in the range of 219-475 nm. The fiber diameter,diameter distribution and its release behaviors varied depending on the type and concentration of the added drug solution.Study demonstrated that conductivity of the drug solution was a major parameter that affected the properties of the drug-loaded nanofibers.

Multiple Needle Electrospinning for Fabricating Composite Nanofibers with Hierarchical Structure

Electrospinning is a powerful method for fabricating micro/nano fibers that can be applied to various fields.Composite materials with nanoscale structure can show more excellent properties than their conventional partners.Here,we reported hierarchical structured nanofibers with beads and spheres by double needle electrospinning with an auxiliary airflow.Two different spinning solutions with different concentrations were placed into different syringes.The action of airflow was able to make the two differently morphological nanofibers mixed together evenly.The results showed that the obtained nanofiber membrane has a good hierarchical structure with different morphologies.

Direct fabrication of cerium oxide hollow nanofibers by electrospinning

Electrospinning technique was used to fabricate PVP/Ce（NO3）3 composite microfibers. Different morphological CeO2 nanofibers were obtained by calcination of the PVP/Ce（NO3）3 composite microfibers and were characterized by scanning electron microscopy （SEM）, Transmission electron microscopy （TEM）, X-ray diffraction （XRD）, thermal gravimetric and differential thermal analysis （TG-DTA）, and （FTIR）. SEM micrographs indicated that the surface of the composite fibers was smooth and became coarse with the increase of calcination temperatures. The diameters of CeO2 hollow nanofibers （300 nm at 600 ℃ and 600 nm at 800 ℃ ） were smaller than those of PVP/Ce（NO3）3 composite fibers （1-2 um ）. CeO2 hollow nanofibers were obtained at 600 ℃ and CeO2 hollow and porous nanofibers formed by nanoparti- cles were obtained at 800 ℃. The length of the CeO2 hollow nanofibers was greater than 50 um. XRD analysis revealed that the composite microfibers were amorphous in structure and CeO2 nanofibers were cubic in structure with space group O^5H - FM3m when calcination tem- peratures were 600-800 ℃. TG-DTA and FTIR revealed that the formation of CeO2 nanofibers was largely influenced by the calcination temperatures. Possible formation mechanism of CeO2 hollow nanofibers was proposed.

Microporous carbon nanofibers prepared by combining electrospinning and phase separation methods for supercapacitor

Microporous carbon nanofibers (MCNFs) derived from polyacrylonitrile nanofibers were fabricated via electrospinning technology and phase separation in the presence of polyvinylpyrrolidone (PVP). PVP together with a mixed solvent of N, N-Dimethylformamide and dimethyl sulfoxide was used as pore forming agent. The influences of PVP content in casting solution on the structure and electrochemical performance of the MCNFs were also investigated. The highest capacitance of 200 F/g was obtained on a three-electrode system at a scan rate of 0.5 A/g. The good performance was owing to the high specific surface area and the large amount of micro-pores, which enhanced the absorption and the transportation efficiency of electrolyte ion during charge/discharge process. This research indicated that the combination of electrospinning and phase separation technology could be used to fabricate microporous carbon nanofibers as electrode materials for supercapacitors with high specific surface area and outstanding electrochemical performance. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Polymer nanofibers prepared by low-voltage near-field electrospinning

Elcctrospiiming is a straightforward method to produce micro/nanoscale fibers from polymer solutions typically using an operating voltage of 10 kV 30 kV and spinning distance of 10 cm 20 cm. In this paper, polyvinyl pyrrolidone （PVP） non-woven nanofibers with diameters of 200 nm 900 nm were prepared by low-voltage near-field electrospinning with a working voltage of less than 2.8 kV and a spinning distance of less than 10 mm. Besides the uniform fibers, beaded-fibers were also fabricated and the formation mechanism was discussed. Particularly, a series of experiments were carried out to explore the influence of processing variables on the formation of near-field electrospun PVP nanofibers, including concentration, humidity, collecting position, and spinning distance.

Electrospinning Preparation and Mechanical Properties of Polymethyl Methacrylate (PMMA)/Halloysite Nanotubes (HNTs) Composite Nanofibers

The paper was aimed at the PMMA/HNTs composite nanofibers with well enhanced mechanical properties prepared by electrospinning technique for the first time. A series of characterizations were used to illustrate the structure and properties of the composite nanofibers by SEM, XRD, FTIR and DSC techniques. The effect of the PMMA/HNTs composite nanofibers in relationship to the mass percentage of HNTs was investigated. The results indicated that HNTs wrapped in polymer matrix were highly oriented and dispersed by the electrospinning technique, resulting in improved thermal stability of the polymer. Moreover, the mechanical properties of the PMMA/HNTs composite nanofibers which were dependent on HNTs mass content were measured, and good enhanced mechanical properties were obtained.

Synthesis and Electrical Properties of TiO_2 Nanoparticles Embedded in Polyamide-6 Nanofibers Via Electrospinning

We report on the synthesis and characterizations of TiO2 nanoparticles embedded in polyamide-6composite nanofibers by using electrospinning technique. The influence of substrate on the electrical characteristics of polyamide-6/TiO2 composite nanofibers was investigated. The resultant nanofibers exhibit good incorporation of TiO2 nanoparticles. The doping of TiO2 nanoparticles into the polyamide-6 nanofibers were confirmed by high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Photoluminescence（PL） and cathodoluminescence（CL） spectroscopy were also used to characterize the samples.The PL and CL spectra reveal that the as-spun polyamide-6/TiO2 composite nanofibers consisted of overlapping of two broad emission bands due to the contribution of polyamide-6（centered at about 475 nm）, which might originate from organic functional groups of polyamide-6 and TiO2 nanoparticles（centered around 550 nm）. The electrical conductivity of the polyamide-6/TiO2 composite nanofibers on different substrates was carried out.It was found that the electrical conductivity of the polyamide-6/TiO2 composite nanofibers on silicon substrate was in the range of 13 μA, and about 1 to 20 p A for the paper and glass substrates.

Controllable Fabrication of Spider-Web-Like Structured Anaphe Panda Regenerated Silk Nanofibers / Nets via Electrospinning / Netting

An Anaphe panda silk nanofibers / nets( NFN) membrane with attractive structures consisting of common electrospun nanofibers and two-dimensional( 2D) spider-web-like structured nano-nets were successfully fabricated via electrospinning / netting technology. The unique structures of NFN membranes such as extremely small diameter( < 20 nm),high porosity,large specific surface area. and biocompatibility make this Anaphe panda silk NFN membrane a promising candidate for biomedical applications. In the present study, field emission scanning electron microscopy( FESEM) was used to investigate the influence of polymer solution and humidity on nano-nets coverage and morphology. The FE-SEM images revealed that nano-net coverage area increased with increase in concentration of solution while lowering the humidity increased the nano-nets formation. Moreover,the mechanical properties of the membrane were also tested and the result showed that the silk NFN membrane displayed a breaking stress of 3. 7 MPa and breaking strain of 13. 8%. For further structural elucidation, Fourier transform infrared spectroscopy( FT-IR) was used to analyze the structural conformation changes from random coil to β-sheet in the NFN membrane which was an important factor effecting the usability of membrane. Thus,the results above confirmed the feasibility of Anaphe panda NFN structures applicability in cell tissue culture and other biomedical applications.

Electrospinning synthesis of porous boron-doped silica nanofibers for oxidative dehydrogenation of light alkanes

The discovery of the high activity and selectivity of boron-based catalysts for oxidative dehydrogenation(ODH)of alkanes to olefins has attracted significant attention in the exploration of a new method for the synthesis of highly active and selective catalysts.Herein,we describe the synthesis of porous boron-doped silica nanofibers(PBSNs)100-150 nm in diameter by electrospinning and the study of their catalytic performance.The electrospinning synthesis of the catalyst ensures the uniform dispersion and stability of the boron species on the open silica fiber framework.The one-dimensional nanofibers with open pore structures not only prevented diffusion limitation but also guaranteed high catalytic activity at high weight hourly space velocity(WHSV)in the ODH of alkanes.Compared to other supported boron oxide catalysts,PBSN catalysts showed higher olefin selectivity and stability.The presence of Si-OH groups in silica-supported boron catalysts may cause low propylene selectivity during the ODH of propane.When the ODH conversion of ethane reached 44.3%,the selectivity and productivity of ethylene were 84%and 44.2%g_(cat)^(-1)s^(-1),respectively.In the case of propane ODH,the conversion,selectivity of olefins,and productivity of propylene are 19.2%,90%,and 76.6 jimol g_(cat)^(-1)s^(-1),respectively.No significant variations in the conversion and product selectivity occurred during 20 h of operation at a high WHSV of 84.6 h^(-1).Transient analysis and kinetic experiments indicated that the activation of O2 was influenced by alkanes during the ODH reaction.

Electrospinning of Gelatin Functionalized with Silver Na-noparticles for Nanofiber Fabrication

The present paper deals with gelatin nanofibres functionalized with silver nanoparticles, prepared by electrospinning using solutions of gelatin mixed with silver nitrate (AgNO3). As a common solvent for gelatin and silver nitrate (AgNO3), a mixture of acetic acid and water (70:30 v/v) was selected. In this system, acetic acid was used as a solvent for gelatin, and at the same time reducing agent for silver ions in solution. Silver nanoparticles (nAg) were stabilized through a mechanism that involves an interaction of the oxygen atoms of the carbonyl groups of gelatin. The viscosity and the conductivity of the gelatinous solutions were found to increase with the solution concentration. There is an observed decrease in the viscosity of the nAg containing gelatin solutions with the aging time increasing, whereas the conductiity of the AgNO3—containing gelatin solutions was greater than that of the base gelatin solution. The gelatin nanofibres functionalized with silver nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and antimicrobial test. The results of investigations by TEM and XRD confirmed the presence of silver nanoparticles with diameters in the range of (2 - 10 nm), uniformly distributed over the surface of smooth nanofibres with an average diameter of 70 nm. The release of silver ions from both the 2- and 4-hrs crosslinked nAg containing gelatin fiber mats by a total immersion method in buffer and distilled water occurred rapidly during the first 60 minutes, and increased gradually afterwards. Lastly, the tests demonstrated that gelatin/Ag nanofibers have a good antimicrobial activity against some common bacteria found on burned wounds. The anti-bacterial activity of these materials was greatest against Staphylococcus aureus, followed by Escherichia coli, and Pseudomonas aeroginosa ≈ Candida albicans.

Transferring CdTe Nanoparticles from Liquid Phase to Polyvinylpyrrolidone Nanofibers by Electrospinning and Detecting Its Photoluminescence Property

The major aim of this work was to synthesize thio-stabilized CdTe nanoparticles（NPs） in an aqueous solution, which was then enwrapped with cetyltrimethylammonium bromide（CTAB）, and finally transferred to the polyvinylpyrrolidone（PVP） matrix by electrospinning. The PVP nanofibers containing CdTe NPs were characterized by scanning electron microscopy（SEM） and transmission electron microscopy（TEM）, to observe the morphology of the nanofibers and the distribution of CdTe NPs. The selective area electronic diffraction（SAED） pattern verified that CdTe NPs were cubic lattice. The photoluminescence（PL） spectrum indicated that CdTe NPs existed in an optical style in PVP nanofibers. Moreover, X-ray photoelectron spectra（XPS） revealed that thiol-stabilized CdTe NPs were enwrapped by CTAB, and PVP acted as a dispersant in the process of electrospinning.