Coaxial Electrospinning Technique Research Articles

Iron oxide/lignin-based hollow carbon nanofibers nanocomposite as an application electrode materials for supercapacitors

Iron oxide particle-decorated, hollow, carbon nanofibers (HCNFs), with poly(styrene-co-acrylonitrile) solution as the core and acetic acid lignin as the shell, were manufactured using a coaxial electrospinning technique, using iron(III) acetylacetonate as the iron oxide-precursor additive in the shell. The fabricated HCNFs exhibited a high specific capacitance of 121 F·g−1 at 0.5 A·g−1, which was 2.18-fold that of solid electrospun nanofibers under the same conditions. The samples also possessed a superior cycling life, with a 90% retention rate after 1000 cycles in 1 M sodium sulfite. In this system, HCNFs exhibited high surface areas, as the result of hollow structures and producing capacitance improvement, while iron oxide particles enhanced electrochemical properties via reversible redox reactions. The attractive performances exhibited by these supercapacitors yielded them potentially promising candidates for future energy storage systems.

Operating temperature and temperature gradient effects on the photovoltaic properties of dye sensitized solar cells assembled with thermoelectric–photoelectric coaxial nanofibers

In this work, the coaxial electrospinning technique was used to prepare coaxial nanofibers (CNFs) consisting of N-type thermoelectric Nb doped SrTiO3 (Nb/STO) coated with a thin layer of TiO2, which was referred to simply as TiO2–Nb/STO. Then a certain amount of TiO2–Nb/STO CNFs was added into the TiO2 nanocrystalline layer to obtain the composite photoanode of dye-sensitized solar cells (DSSCs). Owing to the high electrical conductivity and straightforward electron transport channels for TiO2-Nb/STO CNFs, the device assembled with 10 wt% TiO2-Nb/STO CNFs demonstrated the highest power conversion efficiency (PCE) of 7.25%, which was significantly higher than the reference one (6.45%). In order to investigate the temperature gradient (ΔT) on the photovoltaic performances of DSSCs assembled with TiO2-Nb/STO CNFs, a cold source (0 °C) and a heat source (75 °C) was placed on the Pt counter electrode to create a negative ΔT (−7 K) and a positive ΔT (+7 K), respectively. The mechanism model of thermoelectric effect on the charge transfer dynamic process of DSSCs under different ΔT is established and explained. Data showed that in response to temperature fluctuations, the performance of both reference device and 10% device could be affected. The cold source enable the reference device to obtain the highest PCE of 6.75% due to an increase in open-circuit voltage (Voc). This behavior is mainly ascribed to the reduced internal carrier recombination rates, caused by decreased carrier concentrations at low operating temperature. Herein, the operating temperature refers to an average value between the temperatures on both sides of each device. On the contrary, 10% device applying hot source results in an increase of short-circuit current density (Jsc) and fill factor (FF), yielding the highest PCE of 7.61% despite the negative effects of high operating temperature on Voc. It is found that the hot source benefits the fast electron transfer for 10% device under the synergistic effect of thermoelectromotive force and fast charge carrier diffusion. These results further confirm that the improved photovoltaic performance of 10% device under the condition of hot source was primarily attributed to the thermoelectric Seebeck effect of TiO2-Nb/STO CNFs.

Uniform Luminous Perovskite Nanofibers with Color-Tunability and Improved Stability Prepared by One-Step Core/Shell Electrospinning.

A one-step core/shell electrospinning technique is exploited to fabricate uniform luminous perovskite-based nanofibers, wherein the perovskite and the polymer are respectively employed in the core and the outer shell. Such a coaxial electrospinning technique enables the in situ formation of perovskite nanocrystals, exempting the needs of presynthesis of perovskite quantum dots or post-treatments. It is demonstrated that not only the luminous electrospun nanofibers can possess color-tunability by simply tuning the perovskite composition, but also the grain size of the formed perovskite nanocrystals is largely affected by the perovskite precursor stoichiometry and the polymer solution concentration. Consequently, the optimized perovskite electrospun nanofiber yields a high photoluminescence quantum yield of 30.9%, significantly surpassing the value of its thin-film counterpart. Moreover, owing to the hydrophobic characteristic of shell polymer, the prepared perovskite nanofiber is endowed with a high resistance to air and water. Its photoluminescence intensity remains constant while stored under ambient environment with a relative humidity of 85% over a month and retains intensity higher than 50% of its initial intensity while immersed in water for 48 h. More intriguingly, a white light-emitting perovskite-based nanofiber is successfully fabricated by pairing the orange light-emitting compositional perovskite with a blue light-emitting conjugated polymer.

Strategic design of cardiac mimetic core-shell nanofibrous scaffold impregnated with Salvianolic acid B and Magnesium l-ascorbic acid 2 phosphate for myoblast differentiation

The major loss of myocardial tissue extracellular matrix after infarction is a serious complication that leads to heart failure. Regeneration and integration of damaged cardiac tissue is challenging since the functional restoration of the injured myocardium is an incredible task. The injured micro environment of myocardium fails to regenerate spontaneously. The emergence of nano-biomaterials would be a promising approach to regenerate such a damaged cardiomyocytes tissue. Here, we have fabricated a dual bioactive embedded nanofibrous cardiac patch via coaxial electrospinning technique, to mimic the topographical and chemical cues of the natural cardiac tissue. The proportion and the concentration of the polymers were optimized for tailored delivery of bioactives from a spatio-temporally designed scaffold. The functionalization of polymeric core shell nanofibrous scaffold with dual bioactives enhanced the physico-chemical and bio-mechanical properties of the scaffolds that has resulted in a 3-dimensional topography mimicking the natural cardiac like extracellular matrix. The sustained delivery of bioactive signals, improved cell adhesion, proliferation, migration and differentiation could be attributed to its highly interconnected nanofibrous matrix with good extended morphology. Further, the expression of cardiac specific markers were found to increase on investigation of mRNA by real time PCR studies and proteins by immunofluorescence and western blotting techniques, confirming cell - biomaterial interactions. Flow cytometry analysis authenticated a potent mitochondrial membrane potential of cells treated with nanocomposite. In addition, in ovo studies in chicken chorioallantoic membrane assay confirm the efficacy of the developed scaffold in inducing angiogenesis required for maintaining its viability after transplantation onto the infarcted zone. These promising results demonstrate the potential of the composite nanofibrous scaffold as an effective biomaterial substrate for cardiac regeneration providing cues for development of novel cardiac therapeutics.

Core-Sheath Paraffin-Wax-Loaded Nanofibers by Electrospinning for Heat Storage.

Paraffin wax (PW) is widely used for smart thermoregulation materials due to its good thermal performance. However, the leakage and low thermal conductivity of PW hinder its application in the heat storage field. Accordingly, developing effective methods to address these issues is of great importance. In this study, we explored a facile approach to obtain PW-loaded core-sheath structured flexible nanofibers films via coaxial electrospinning technique. The PW as the core layer was successfully encapsulated by the sheath-layer poly(methyl methacrylate). The diameter of the fiber core increased from 395 to 848 nm as the core solution speed rate increased from 0.1 to 0.5 mL/h. In addition, it can be seen that higher core solution speed rate could lead to higher PW encapsulation efficiency according to the transmission electron microscopy results. The core-sheath nanofiber films, moreover, possessed the highest latent heat of 58.25 J/g and solidifying enthalpy of -56.49 J/g. In addition, we found that after 200 thermal cycles, there was little change in latent heat, which demonstrated that it is beneficial for the PW-loaded core-sheath structure to overcome the leakage issue and enhance thermal stability properties for the thermoregulation film.

Levan based fibrous scaffolds electrospun via co-axial and single-needle techniques for tissue engineering applications

This represents the first systematic study where levan polysaccharide was used to fabricate fibrous matrices by co-axial and single-needle electrospinning techniques. For this, hydrolyzed (hHL) and sulfated hydrolyzed (ShHL) Halomonas levan were chemically synthesized and used together with polycaprolactone (PCL) and polyethyleneoxide (PEO) for the spinning process. In co-axially spun matrices, ultimate tensile strength (UTS) were found to increase with increasing ShHL concentration and elongation at break of PCL + ShHL matrices increased up to ten-fold when compared to PCL matrices. Similarly, in single-needle spun matrices, higher elongation at break values were obtained by blending HL and ShHL with PEO pointing to the effective energy absorbing features. Dense and fine fibers were characterized by FTIR and SEM. Cell viability and fluorescence imaging of L929 fibroblasts and HUVECs as well as heparin mimetic activity of the matrices pointed to their high potential to be used in decreasing neointimal proliferation and thrombogenicity of grafts and prosthesis.

Fabrication and enhanced dielectric properties of polyimide matrix composites with core–shell structured CaCu3Ti4O12@TiO2 nanofibers

Core–shell structured CaCu3Ti4O12@TiO2 (CCTO@TiO2) nanofibers were prepared via a normal coaxial electrospinning technique with sol precursors. Polyimide (PI) nanocomposite films containing the core–shell structured CCTO@TiO2 nanofibers were fabricated by the solution casting method. The core–shell structure of the CCTO@TiO2 nanofibers was confirmed through transmission electron microscope. The percolation of the CCTO/TiO2 interfaces leads to much enhanced interfacial polarization of the CCTO@TiO2 nanofibers, which gives rise to substantially increased dielectric constant of the nanocomposites. Compared to the nanocomposites with CCTO nanofibers, the breakdown strength of the nanocomposites with CCTO@TiO2 nanofibers is also increased due to the charge shifting is limited to the interfacial zone of CCTO/TiO2 interfaces, instead of in the PI matrix to form a percolation path. For the nanocomposites with 5 vol% nanofibers, the dielectric constant of 5.55 was enhanced to 5.85 and the breakdown strength of 201 kV/mm was increased to 236 kV/mm by utilizing the TiO2 coated CCTO nanofibers, while the dielectric loss shows no obvious change. Meanwhile, the PI nanocomposite film filled with 1 vol% CCTO@TiO2 nanofibers exhibits a maximal energy density of 1.6 J/cm3. The core–shell structured nanofibers open up an effective way to optimize the dielectric properties of polymer nanocomposites with high energy density.

Preparation of hollow magnetic porous zirconia fibers as effective catalyst carriers for Fenton reaction

Hollow magnetic porous zirconia fibers as a high-dispersal Fenton catalyst carrier synthesized by a coaxial electrospinning technique.

Photoresponsive fiber scaffolds with a core-sheath nanostructure for regulating cell behaviors.

Herein, we report the fabrication of photoresponsive three-dimensional (3D) fiber scaffolds for the first time, where photoresponsive polymers are localized on their fiber surfaces of nano thickness, using a simple and practical co-axial (core-sheath) electrospinning technique. Cell adhesion to the 3D scaffolds was regulated by photostimulation.

Electrospun Thin-Walled CuCo2O4@C Nanotubes as Bifunctional Oxygen Electrocatalysts for Rechargeable Zn-Air Batteries.

Rational design of optimal bifunctional oxygen electrocatalyst with low cost and high activity is greatly desired for realization of rechargeable Zn-air batteries. Herein, we fabricate mesoporous thin-walled CuCo2O4@C with abundant nitrogen-doped nanotubes via coaxial electrospinning technique. Benefiting from high catalytic activity of ultrasmall CuCo2O4 particles, double active specific surface area of mesoporous nanotubes, and strong coupling with N-doped carbon matrix, the obtained CuCo2O4@C exhibits outstanding oxygen electrocatalytic activity and stability, in terms of a positive onset potential (0.951 V) for oxygen reduction reaction (ORR) and a low overpotential (327 mV at 10 mA cm-2) for oxygen evolution reaction (OER). Significantly, when used as cathode catalyst for Zn-air batteries, CuCo2O4@C also displays a low charge-discharge voltage gap (0.79 V at 10 mA cm-2) and a long cycling life (up to 160 cycles for 80 h). With desirable architecture and excellent electrocatalytic properties, the CuCo2O4@C is considered a promising electrocatalyst for Zn-air batteries.

Core-shell fibrous scaffold as a vehicle for sustained release of retinal pigmented epithelium-derived factor (PEDF) for photoreceptor differentiation of conjunctiva mesenchymal stem cells.

Coaxial electrospinning technique was introduced as a flexible and promising technique for the fabrication of core-shell fibrous scaffold from poly ethylene glycol/poly caprolactone (PEG/PCL), where retinal pigmented epithelium-derived factor (PEDF) was encapsulated in the core, for photoreceptor differentiation of conjunctiva mesenchymal stem cells (CJMSCs) seed on scaffolds. The morphology and structure of fibers were characterized using SEM and TEM and photoreceptor differentiation was examined by quantitative real time PCR (qPCR). Release study showed that, a sustained release of PEDF from PEG/PCL scaffold was observed over 14 days. qPCR analysis demonstrated that rhodopsin (as a main photoreceptor gene) was significantly expressed in CJMSCs cultured on scaffold loaded with PEDF. According to the result, the core-shell scaffold loaded with PEDF (PEG + PEDF)/PCL) has superior control over factor release profile and has a potential for guiding photoreceptor differentiation of mesenchymal stem cells and promoting retinal regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3514-3519, 2017.

Designer fibers from 2D to 3D – Simultaneous and controlled engineering of morphology, shape and size

Topography and surface morphology of micrometer and nanometer scaled fibrous biomaterials are crucial for bioactive component encapsulation, release, promoting cell proliferation and interaction within biological environment. Specifically, for drug delivery and tissue repair applications, surface engineering provides control on both aspects in tandem. In this study, the bioactive component (ganoderma lucidum spore polysaccharide (GLSP)) was loaded into zein prolamine (ZP) fiber matrices via coaxial electrospinning (CES) technique. During the CES process, various outer layer enveloping fluids were used to modulate fiber topography in-situ (from 2D to 3D). SEM and water contact angle tests indicate enveloping media impact electrospun fiber diameter (ranging from 400nm to 3.0μm) and morphologies (from flat ribbon-like to solid cylindrical structures), with the latter impacting GLSP release profile. Furthermore, CCK-8 assay assessment indicates fibroblast cell proliferation (L929 cell line), while cell extension was also observed for modified ZP fibers. The results demonstrate potential applications of modified fiber morphologies, which are tailored in-situ without impacting chemical stability and encapsulation.

Fabrication and SERS application of the thermoresponsive nanofibers with monodisperse Au@Ag bimetallic nanorods loaded shells

ABSTRACTMonodisperse Au@Ag bimetallic nanorods (Au@AgNRs) with gold nanorod core and silver shell were introduced into the shells of the thermoresponsive nanofibers with core‐shell structure by coaxial electrospinning technique using poly(N‐isopropylacrylamide‐co‐N‐hydroxymethylacrylamide) aqueous solution as core fluid and its Au@AgNRs mixture as shell fluid, followed by heat treatment. Their core‐shell structure and the oriented alignment of the Au@AgNRs embedded within their shells along their axes were confirmed by transmission electron microscopy observation. The produced composite nanofibrous membrane has high stability in aqueous medium and more remarkable and faster thermoresponsiveness than our previously reported composite nanofibrous membrane with homogeneous Au@AgNRs distribution inside its constituent nanofibers. The smart composite nanofibrous membrane as a free‐standing surface enhanced Raman spectroscopy substrate with temperature‐dependent surface enhanced Raman spectroscopy efficiency from 25 to 50 °C and good reproducibility is able to be used to detect 10−14 mol/L 4‐mercaptobenzoic acid in aqueous solution at 50 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45375.

Engineered core-shell nanofibers for electron transport study in dye-sensitized solar cells

In this study, a unique approach was developed to synthesize 1-D core-shell nanofibers of carbon nanotubes (CNTs) and TiO2 using combination of coaxial electrospinning and sol-gel technique. Diameters of the fabricated core-shell single wall carbon nanotube-TiO2 (SWCNT-TiO2) and multi wall carbon nanotube-TiO2 (MWCNT-TiO2) nano-composite fibers were between 50-100nm. Energy dispersive spectroscopy (EDS) and X-ray photon spectroscopy (XPS) were applied to confirm encapsulation of carbon nanotube (CNT) in the core-shell structure. Electron transport properties of both SWCNT-TiO2 and MWCNT-TiO2 in the Dye-sensitized solar cells (DSSCs) were studied for the first time. It was found that SWCNT-TiO2 based DSSC provided higher short circuit current relative to MWCNT-TiO2, which was explained by I-V and bode plots. These findings were further illustrated by semi-conductive properties of SWCNT.

Construction of CQDs-Bi20TiO32/PAN electrospun fiber membranes and their photocatalytic activity for isoproturon degradation under visible light

The CQDs-Bi20TiO32 photocatalysts exhibited high visible-light responsive photocatalytic activity. To achieve the cyclic utilization of CQDs-Bi20TiO32, the novel flexible CQDs-Bi20TiO32/PAN fiber membranes were prepared by a simple coaxial electrospinning technique. It was found that the CQDs-Bi20TiO32 photocatalyst could be firmly and uniformly fixed on the surfaces of electrospun fibers and the composite fiber membranes possessed the hierarchical macro- and mesoporous structure. The loaded CQDs-Bi20TiO32 endowed the composite fiber with an obvious photocatalytic activity for the degradation of the herbicide isoproturon under visible light irradiation. Among these samples, S3 at photocatalyst dosage 15w/v% had the highest degradation efficiency for isoproturon. Meanwhile, the core-shell structured inorganic-organic hybrid fiber membranes have a significant advantage in the recyclability for photocatalyts. The flexible CQDs-Bi20TiO32/PAN electrospun fiber membranes would have potential applications in efficient removal of organic contaminants.

Na3V2(PO4)3/C nanofiber bifunction as anode and cathode materials for sodium-ion batteries

Na3V2(PO4)3/C composite nanofibers are prepared successfully through a coaxial electrospinning technique and subsequent calcination. The diameter of the prepared nanofibers is uniformly distributed (about 100∼200 nm), and the composite nanofibers (NF-NVP/C) contain Na3V2(PO4)3 nanofibers and carbon nanofibers, and Na3V2(PO4)3 nanoparticles with diameters of 5–10 nm are embedded into the composite nanofibers. The NF-NVP/C anode exhibits a high reversible capacity 189.9 mAh/g at a current rate of 0.2 C (1 C=118 mA/g) in the voltage range of 0.01–3.00 V (vs. Na+/Na). Even at high rates of 5 and 10 C, this anode displays discharge capacities of 105.1 and 80.4 mAh/g at the second cycle and capacity retentions of 83 and 77% after 200 and 500 cycles, respectively. A sodium-ion full cell with NF-NVP/C as the electroactive material of both positive and negative electrodes presents two average operating voltages at ∼0.5 and ∼1.5 V and delivers a reversible capacity of 106.2 mAh/g at a current density of 100 mA/g in a voltage range of 0.01–4.00 V. The outstanding electrochemical performance is attributed to the unique nanofiber structure and uniform distribution of NVP nanoparticles in the highly conductive carbon matrix.

Luminescence properties and Judd–Ofelt analysis of SiO2:Ln3+ (Eu, Tb) hollow nanofibers fabricated by co-axial electrospinning method

Novel luminescent one-dimensional Ln3+ (Eu, Tb) doped SiO2 hollow nanofibers were successfully fabricated using a facile and economical co-axial electrospinning technique with subsequent calcination. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the as-obtained samples present obvious hollow morphology with an average diameter of 303 ± 11 nm and thin walls approximate 76 nm. For SiO2:xEu3+ hollow nanofibers, the highest luminescence intensity, the longest lifetime and the largest quantum efficiency were both in the composition of 6 mol% Eu3+. The large value of R21 indicated a highly disordered environment around Eu3+ ions in the host, which was better for intense visible red emission. Meanwhile, the spectral characteristics and radiative properties were also analyzed according to the Judd-Ofelt theory from the emission spectra. What's more, under ultraviolet excitation, the emission colors of samples could be tuned from red to green, including bisque by doping Eu3+, Tb3+ and co-doping Eu3+/Tb3+ ions, which indicated the obtained SiO2:Ln3+ hollow nanofibers are potential phosphors in nanostructured optical devices applications.

Essential Oil Bioactive Fibrous Membranes Prepared via Coaxial Electrospinning.

A novel antimicrobial composite material was prepared by encapsulating orange essential oil (OEO) in zein prolamine (ZP) via the coaxial electrospinning (ES) technique. By manipulating process parameters, the morphological features of ZP/OEO fibers were modulated. Fine fibers with diameters ranging from 0.7 to 2.3 μm were obtained by regulating ZP solution concentration and process parameters during the ES process. Optimal loading capacity (LC) and encapsulation efficiency (EE) of OEO in fibrous ZP mats were determined to be 22.28% and 53.68%, respectively, and were achieved using a 35 w/v% ZP ES solution. The encapsulation of OEO was found to be reliant on ZP solution concentration (the enveloping medium). SEM analysis indicates the surface morphology of ZP/OEO electrospun fibers is dependent on ZP solution loading volume, with lower ZP concentrations yielding defective fibrous structures (for example, beaded and spindled-string like morphologies). Furthermore, this loading volume also influences OEO LC, EE, mat water contact angle and oil retention. CCK-8 assay and cell morphology assessment (HEK293T cells) indicate no significant change with electrospun ZP and ZP/OEO fibrous membranes over an 8 h period. Antimicrobial activity assessment using Escherichia coli, suggests composite nonwovens possess sterilization properties; elucidating potential application in active food packaging, food preservation and therefore sustainability.

Starch/PCL composite nanofibers by co-axial electrospinning technique for biomedical applications

BackgroundIn this study, starch and polycaprolactone (PCL), composite nanofibers were fabricated by co-axial needle electrospinning technique. Processing parameters such as polymer concentration, flow rate and voltage had a marked influence on the composite fiber diameter. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), mechanical and physical properties (such as density, viscosity and electrical conductivity) of the composite fibres were evaluated. Moreover, a cell culture test was performed in order to determine their cytotoxicity for wound dressing application.ResultsThe effect of starch ratio in the solution on the properties and morphological structure of the fibers produced was presented. With lower starch concentration values, the fibers have greater ultimate tensile strength characteristic (mostly 4 and 5 wt%). According to SEM results, it can be figured out that the nanofibers fabricated have good spinnability and morphology. The mean diameter of the fibers is about 150 nm. According to results of cell culture study, the finding can be determined that the increase of starch in the fiber also increases the cell viability.ConclusionsComposite nanofibers of starch/PCL have been prepared using a co-axial needle electrospinning technique. PCL was successfully encapsulated within starch. Fiber formation was observed for different ratio of starch. With several test, analysis and measurement performed, some important parameters such as quality and effectuality of each fiber obtained for wound dressing applications were discussed in detail.

Facile electrospinning fabrication of nickel oxide nanotubes and their photocatalytic properties

Nickel oxide (NiO) nanotubes were fabricated by coaxial electrospinning technique combining a calcination process. The nanotubes obtained have diameters of 140–240 nm, and wall thickness of 50–70 nm. The crystallinity, morphology and structure features of the NiO nanotubes were investigated by powder X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. A possible formation mechanism for the evolution of nanotubes was proposed. The as-obtained NiO nanotubes showed high photocatalytic property to decompose rhodamine B pollutant, displaying great potential in environmental pollutant cleanup applications.