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A supercapacitor is an electrical energy storage system with high power output. With worldwide awareness of sustainable development, developing cost-effective, environmentally friendly, and high-performance supercapacitors is an important research direction. The use of sustainable components like wood biochar in the electrode materials for supercapacitor uses holds great promise for sustainable supercapacitor development. In this study, we demonstrated a facile and powerful approach to prepare meso-microporous carbon electrode materials for sustainable and high-performance supercapacitor development by electrospinning polyacrylonitrile (PAN) with F-treated biochar and subsequent aerogel construction followed by stabilization, carbonization, and carbon activation. The resultant carbon nanofibrous aerogel electrode material (ENFA-FBa) exhibited exceptional specific capacitance, attributing to enormously increased micropore and mesopore volumes, much more activated sites to charge storage, and significantly greater electrochemical interaction with electrolyte. This electrode material achieved a specific capacitance of 407 F/g at current density of 0.5 A/g in 1 M H2SO4 electrolyte, which outperformed the state-of-the-art specific capacitance of biochar-containing electrospun carbon nanofibrous aerogel electrode materials (<300 F/g). A symmetric two-electrode cell with ENFA-FBa as electrode material showed an energy density of 11.2 Wh/kg at 125 W/kg power density. Even after 10,000 cycles of charging-discharging at current density of 10 A/g, the device maintained a consistent coulombic efficiency of 53.5% and an outstanding capacitance retention of 91%. Our research pointed out a promising direction to develop sustainable electrode materials for future high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

As a new and promising reinforcing filler, electrospun glass nanofibers (EGNFs) have attracted attention in the field of polymer composite materials. However, the reinforcing effectiveness of surface-modified EGNFs using different silane coupling agents in epoxy resin is still not quite clear. In this research, a series of silane coupling agents with increasing chain lengths in the order of methyl trimethoxysilane (MTMS), (3-aminopropyl) triethoxysilane (APTES), (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and dual silane coupling agent APTES–GPTMS were employed to carry out surface treatment on the EGNFs. The pristine and silane functionalized EGNFs were then incorporated into epoxy resin as reinforcing fillers at low loading levels, i.e., 0.25 wt.%, 0.5 wt.%, and 1 wt.%, and the mechanical properties of the resultant epoxy nanocomposites, including strength, stiffness, ductility, and toughness, were evaluated. A commercial product of glass nanoparticles (GNPs) was used as a control to compare the reinforcing effectiveness of the EGNFs and the GNPs. This study revealed that the EGNFs could provide significant reinforcing and toughening effects at ultra-low loading (0.25 wt.%) in epoxy nanocomposite materials. Furthermore, surface modification of the EGNFs with silane coupling agents with long chain lengths, e.g., by using dual silane coupling agents, APTES–GPTMS, could enhance the interfacial bonding between the EGNFs and the epoxy matrix and further increase the mechanical performance of the EGNF-reinforced epoxy nanocomposite materials. Through this research, we realized epoxy nanocomposite materials with much-improved mechanical properties, i.e., 37%, 24%, 18%, 57% improvement in strength, stiffness, ductility, and toughness, respectively, with respect to those of the cured neat epoxy material with an ultra-low loading (0.25 wt.%) of APTES–GPTMS–EGNFs. Our research paves the road for developing lighter and stronger epoxy nanocomposite materials with EGNFs. [ABSTRACT FROM AUTHOR]

As a short-chain PFAS (per- and polyfluoroalkyl substance), GenX was produced in recent years to replace traditional long-chain PFASs, such as perfluorooctanoic acid (PFOA). However, GenX turns out to be more toxic than people originally thought, posing health risks as a persistent environmental pollutant. In this research, for the first time, we incorporated chlorella, a single-celled green freshwater microalga that grows worldwide, with polyacrylonitrile (PAN) in equal amounts in electrospun nanofibers and studied the capability of the electrospun PAN/Algae bicomponent nanofibrous membrane (ES(PAN/Algae)) to bind and remove GenX from water. The incorporation of algae demonstrated a synergistic effect and significantly improved the GenX removal efficiency of the nanofibrous membrane. The maximum GenX removal capacity reached 0.9 mmol/g at pH 6, which is significantly higher than that of most of the reported GenX adsorbents as well as activated carbon. The GenX removal mechanism was investigated and discussed by using water contact angle, zeta potential, FTIR, and XPS techniques. This research demonstrated the potential to make highly efficient adsorbent/filter materials from common and economic materials to practically remediate short-chain PFASs from various water bodies. [ABSTRACT FROM AUTHOR]

The development of novel nanomaterials with well-controlledmorphologies/structuresto achieve excellent activities/sensitivities in surface-enhancedRaman scattering (SERS) is crucial in advancing the high-performanceSERS detections of chemical and biological species. In this study,amidoxime surface-functionalized polyacrylonitrile (ASFPAN) nanofibrousmembranes surface-decorated with silver nanoparticles (Ag NPs) wereprepared via the technique of electrospinning followed by the methodof seed-mediated electroless plating. High SERS activities/sensitivitieswere observed from the ASFPAN-Ag NPs nanofibrous membranes, whilethe density and size of Ag NPs had an important impact on the SERSactivity/sensitivity. The results confirmed that the enhancement ofRaman signals is due to the presence of hot spots between/among AgNPs on the nanofiber surfaces. Electrospun nanofibrous membranes surface-decoratedwith Ag NPs were mechanical flexible/resilient and could be used ashighly active/sensitive SERS substrates for a broad range of applications. [ABSTRACT FROM AUTHOR]

Abstract: In this study, hybrid multi-scale composites were developed from glass microfiber fabrics (GFs) and nano-epoxy resins containing electrospun glass nanofibers (EGNFs). The hypothesis was that, through dispersing a small amount of EGNFs into epoxy resin, mechanical properties (particularly out-of-plane mechanical properties) of the resulting hybrid multi-scale composites would be significantly improved. The composites were fabricated by the technique of vacuum assisted resin transfer molding (VARTM). The interlaminar shear strength, flexural properties, impact absorption energy, and tensile properties of the composites were evaluated, and the results were compared to those acquired from GFs/epoxy composite as well as GFs/epoxy composites containing chopped glass microfibers (GMFs); additionally, the reinforcement and/or toughening mechanisms were investigated. The study revealed that the nano-epoxy resin with 0.25wt.% of EGNFs resulted in substantial improvements on mechanical properties of the resulting hybrid multi-scale composites. [Copyright &y& Elsevier]

Abstract: Carbon nanofibrous mat (nano-felt) surface-attached with Pd nanoparticles was prepared from electrospun polyacrylonitrile nano-felt surface-functionalized with amidoxime groups, and its application for hydrogen sensing was explored. The material consisted of relatively uniform and randomly overlaid carbon nanofibers with diameters of ~300nm, while the attached Pd nanoparticles had sizes in the range from a few to tens of nanometers. The electrospun carbon nano-felt was mechanically flexible/resilient, and the resistance of the material varied upon exposure to H2 at room temperature. The study suggested that electrospun carbon nano-felts surface-attached with metal nanoparticles could be a material of choice for the fabrication of gas- and/or bio-sensors, and the amidoxime-functionalization of electrospun polyacrylonitrile nano-felt could be a general approach for the development of various carbon nano-felts surface-attached with different metal nanoparticles. [Copyright &y& Elsevier]

Abstract: Due to recent advances in the production of biotherapeutics, high capacity, high throughput adsorption media for efficient and economic separation of these medically important products are in great demand. One option that has been evaluated extensively is membrane/mat adsorption. While these media allow for rapid adsorption (due to the decreased internal diffusion) and high throughput processing (due to the open porous structure), they often suffer from low capacity and poor enrichment factors. Herein, we report the fabrication, characterization, and protein adsorption evaluation of an innovative type of membrane/mat adsorption media based on electrospun carbon nanofibers. By surface-functionalization of these nanofibers with a weak acid cation-exchange ligand, the capacity was doubled for binding a model protein (i.e., lysozyme) compared to commercial products; and the capacity value was over 200mg lysozyme per gram of adsorption media. Meanwhile, the thin nanofibers (having diameters of ∼300nm) along with open pores among nanofibers in the mats (having sizes of ∼10–15μm) allowed for higher operating flow rates and lower pressure drops. Furthermore, the incorporation of higher ligand density and the addition of a non-ionic surfactant (i.e., Triton X-305) into the adsorption buffer eliminated the non-specific binding of a competing protein (bovine serum albumin). In combination, this study suggested that electrospun carbon nanofiber adsorption media would provide a promising alternative to packed resin beds for bioseparations. [Copyright &y& Elsevier]

Abstract: Effects of electric poling, mechanical stretching, and dipolar interaction on the formation of ferroelectric (β and/or γ) phases in poly(vinylidene fluoride) (PVDF) have been studied in electrospun fibers of PVDF/polyacrylonitrile (PAN) and PVDF/polysulfone (PSF) blends with PVDF as the minor component, using wide-angle X-ray diffraction and Fourier transform infrared techniques. Experimental results of as-electrospun neat PVDF fibers (beaded vs. bead-free) showed that mechanical stretching during electrospinning, rather than electric poling, was effective to induce ferroelectric phases. For as-electrospun PVDF blend fibers with the non-polar PSF matrix, mechanical stretching during electrospinning again was capable of inducing some ferroelectric phases in addition to the major paraelectric (α) phase. However, after removing the mechanical stretching in a confined melt-recrystallization process, only the paraelectric phase was obtained. For as-electrospun PVDF blend fibers with the polar (or ferroelectric) PAN matrix, strong intermolecular interactions between polar PAN and PVDF played an important role in the ferroelectric phase formation in addition to the mechanical stretching effect during electrospinning. Even after the removal of mechanical stretching through the confined melt-recrystallization process, a significant amount of ferroelectric phases persisted. Comparing the ferroelectric phase formation between PVDF/PSF and PVDF/PAN blend fibers, we concluded that the local electric field–dipole interactions were the determining factor for the nucleation and growth of polar PVDF phases. [Copyright &y& Elsevier]

Abstract: In this study, polyacrylonitrile (PAN) nano-fibrous membranes with fiber diameters of ∼450nm were prepared by the technique of electrospinning; amidoxime nano-fibrous membranes were then prepared through treatment of PAN nano-fibrous membranes in hydroxylamine (NH2OH) aqueous solution. The –Con the surface of PAN nanofibers reacted with NH2OH molecules and led to the formation of –C(NH2)OH groups, which were used for coordination of Ag+ ions. Subsequently, the coordinated Ag+ ions were converted into silver nanoparticles (AgNP) with sizes being tens of nanometers. Morphologies, structures, and antimicrobial efficacies (against Staphylococcus aureus and Escherichia coli) of the membranes of electrospun PAN (ESPAN) nanofibers, ESPAN surface functionalized with amidoxime groups (ASFPAN), ASFPAN coordinated with silver ions (ASFPAN–Ag+), and ASFPAN attached with silver nanoparticles (ASFPAN–AgNP) were investigated. The study revealed that, with treatment of ESPAN membranes in 1M NH2OH aqueous solution for 5min, the resulting ASFPAN membranes became antimicrobial without distinguishable morphological variations; further treatment of ASFPAN membranes in 0.1M AgNO3 aqueous solution for 1h and the subsequent treatment in 0.01M KBr aqueous solution for 2h followed by photo-decomposition made the respective membranes of ASFPAN–Ag+ and ASFPAN–AgNP highly antimicrobial, which were capable of killing the tested microorganisms in 30min. The water permeability test indicated that these membranes possessed adequate transport properties for filtration applications. This study demonstrated a convenient and cost-effective approach to develop antimicrobial nano-fibrous membranes that are particularly useful for the filtration of water and/or air. [Copyright &y& Elsevier]

Abstract: We report a study of the fluorescence properties of the conjugated polymer poly [2-methoxy-5-(2′-ethyl hexyloxy)-p-phenylene vinylene] (MEH-PPV) and polyethylene oxide (PEO) nanofibers. MEH-PPV/PEO nanofibers with different compositions have been fabricated by the electrospinning technique. The fluorescence spectra of the nanofibers show that the emission shoulder at ∼630nm blue-shifts ∼45nm, whereas the main emission peak around 590nm blue-shifts ∼15nm with decreasing concentration of MEH-PPV in the nanofiber. In addition, confocal microscopic studies of a single MEH-PPV/PEO electrospun nanofiber indicate that the fluorescence spectra of the nanofiber do not show any polarization dependence. The results are discussed in terms of the aggregation of MEH-PPV in an inert matrix. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanofibers with new structural features, e.g. nanoporosity, hollow, U-shape cross-section, were generated by utilizing the phase separation behavior of polymer additive with polyacrylonitrile (PAN). The approach involved the formation of precursor fibers by electrospinning of binary mixtures of PAN with poly(ethylene oxide) (PEO), cellulose acetate (CA) or poly(methyl methacrylate) (PMMA), the removal of the polymer and the carbonization of the remaining PAN. The carbon nanofiber yield was ca 50% of PAN in all cases. Nanoporous carbon nanofibers with an average diameter of 100nm were generated from the water treated PAN/PEO precursors. Multi-channel hollow fibers (90–190nm diameters) were produced from the acetone treated PAN/CA precursors. Carbon fibers produced from the chloroform treated PAN/PMMA precursors were 250–400nm in diameters and consisted of varied hollow structures, i.e., hollow and U-shape cross-sections from those containing 30% and 50% PAN, respectively, and multi-channel hollow fibers from the 70/30 PAN/PMMA precursor. Carbonization of equal-mass PAN/PMMA as-spun fibers also produced similarly U-shape cross-sections as the chloroform treated ones, showing promise of direct carbonization. This simple and yet versatile approach to create new structural features in carbonized fibers has shown to depend on the distinct phase separation as well as the pyrolytic behaviors of the second polymer component. [Copyright &y& Elsevier]

The article discusses a study of the electrospun nano-scaled glass fiber reinforcement of 2,2'-bis[4-(methacryloxypropoxy)-phenyl]-propane/triethylene glycol dimethacrylate (bis-GMA/TEGDMA) dental composites. Aldrich Co. of Wisconsin has provided the materials used in the study. Acetone dispersion was part of the preparation of scanning electron microscopy (SEM) specimens. Results show that the surface-silanized electrospun nano-scaled glass fibers was able to improve the mechanical properties of the reinforced composites.

Abstract: The aim of this study was to investigate the preparation, characterization, and encapsulation/release performance of an electrospun composite nanofiber mat. The hypothesis was that the composite nanofiber mat with nano-scaled drug particles impregnated in biocompatible and biodegradable polymer nanofibers can serve as an innovative type of tissue engineering scaffold with desired and controllable drug encapsulation/release properties. To test the hypothesis, the composite nanofiber mat electrospun from an emulsion consisting of poly(lactic-co-glycolic acid) (PLGA) Rhodamine B (a model compound to simulate drugs), sorbitan monooleate (Span-80, a non-ionic emulsifier/surfactant that is presumably non-toxic/safe for cell-growth), chloroform, DMF, and distilled water was prepared and characterized; and the Rhodamine B encapsulation/release profile in phosphate buffered saline (pH=7.4) was recorded and analyzed. For comparison purposes, two additional nanofiber mats electrospun from (1) a solution containing PLGA and Rhodamine B, and (2) a solution containing PLGA, Rhodamine B, and Span-80 were also prepared and assessed as the control samples. The results indicated that the composite nanofiber mat electrospun from the emulsion had the most desired and controllable Rhodamine B encapsulation/release profile and the excellent morphological sustainability; thus, it could be utilized as both a drug encapsulation/release vehicle and a tissue engineering scaffold. [Copyright &y& Elsevier]

Abstract: Adsorptive membranes have shown great promise for bioseparations as an alternative to packed bed chromatography. Here we evaluate an adsorptive membrane (felt) made from electrospun cellulose acetate nanofibers as an ion-exchange medium for protein separations. The as-electrospun cellulose acetate nanofibers had diameters ranging from tens of nanometers to microns, and the pore sizes within the nanofiber felts were in the range from sub-microns to microns. The cellulose acetate nanofibers were hydrolyzed/deacetylated to yield regenerated cellulose nanofibers, which were then surface functionalized with diethylaminoethyl (DEAE) anion-exchange ligand. SEM imaging, along with FT-IR spectroscopy, and nitrogen content analysis were used to follow each stage of the process. For comparison, a regenerated cellulose microfiber adsorption medium, a commercially available regenerated cellulose adsorptive membrane, and bleached absorbent cotton balls, were all similarly treated and evaluated. The results indicated that the functionalized nanofiber felt had the highest static binding capacity of 40.0mg/g for bovine serum albumin (BSA), compared to 33.5mg/g, 14.5mg/g, and 15.5mg/g for the functionalized commercial membrane, cellulose microfiber medium, and cotton balls, respectively; and the DEAE nanofiber felt had over five times higher permeability of 10mM Tris buffer, pH 8.0 than the DEAE commercial membrane. It was also found that detrimental system dispersion, as determined by calculation of the Peclet number, could be limited by increasing the number of felt layers used for the adsorption bed, without compromising pressure limitations. Dynamic adsorption of BSA, at 10% breakthrough, was higher for the DEAE nanofiber felt (26.9mg/g) compared to the DEAE commercial membrane (20.9mg/g). [Copyright &y& Elsevier]

Abstract: Formation of cellulose acetate (CA) and poly(ethylene oxide) (PEO) bicomponent fibers by electrospinning of binary mixtures of these polymers was strongly influenced by their chain lengths, concentrations and mixed ratios as well as the solvents employed. Individually, the threshold molecular weights that supported fiber generation were 50kDa and 100kDa for CA and PEO, respectively. Adding dioxane, a lower dielectric constant co-solvent, enabled fiber formation from CA alone at a lower 30kDa as well as from binary systems with one low molecular weight polymer that was not fiber forming. While bicomponent fiber formation generally improved with longer polymers and higher concentrations, fiber sizes also increased with both these factors. PEO in the bicomponent fibers was clearly phase-separated and the phase separation of long chains was facilitated by DMF, whereas that of shorter chains by DMF/dioxane. A phase-separated CA core and PEO sheath structure of the bicomponent fibers was strongly supported by experimental evidence. [Copyright &y& Elsevier]

Abstract: Mechanically flexible mats consisting of electrospun carbon nanofibers (ECNFs) were prepared by first electrospinning aqueous mixtures containing a natural product of alkali lignin together with polyvinyl alcohol (PVA) into composite nanofiber mats followed by stabilization in air and carbonization in an inert environment. Morphological and structural properties, as well as specific surface area, total pore volume, average pore size, and pore size distribution, of the lignin-based ECNF mats were characterized; and their electrochemical performances (i.e., capacitive behaviors) were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The lignin-based ECNF mats exhibited outstanding performance as free-standing and/or binder-free electrodes of supercapacitors. For example, the ECNFs made from the composite nanofibers with mass ratio of lignin/PVA being 70/30 (i.e., ECNFs (70/30)) had the average diameter of ∼100 nm and the Brunauer–Emmett–Teller (BET) specific surface area of ∼583 m2 g−1. The gravimetric capacitance of ECNFs (70/30) electrode in 6 M KOH aqueous electrolyte exhibited 64 F g−1 at current density of 400 mA g−1 and 50 F g−1 at 2000 mA g−1. The ECNFs (70/30) electrode also exhibited excellent cycling durability/stability, and the gravimetric capacitance merely reduced by ∼10% after 6000 cycles of charge/discharge. [Copyright &y& Elsevier]

Abstract: In this study, electrospun immiscible blend fibers of poly(vinylidene fluoride) (PVDF)/polysulfone (PSF) were prepared. Due to the strong shearing during electrospinning, cocontinuous fibers of PVDF in the PSF matrix were obtained despite the minor composition of PVDF (5–30 wt.%) in the blend. After annealing these electrospun blend fibers above the melting temperature of PVDF (170 °C) and the glass transition temperature of PSF (185 °C), nanosized droplets (primarily 200–300 nm) of PVDF were developed inside the PSF matrix from the breaking up of PVDF nanofibers because of the Plateau–Rayleigh instability. Fractionated crystallization occurred in these PVDF nanodroplets with the heterogeneously nucleated crystallization in the range of 105–135 °C and the homogeneous nucleation at 55–60 °C. The mechanism of homogeneous nucleation was confirmed by the study of crystallization kinetics using differential scanning calorimetry. Only the nonpolar α-phase was observed by wide-angle X-ray diffraction despite of the homogeneously nucleated crystallization at a high supercooling in these PVDF nanodroplets. This study leads to a conclusion that nanoconfined crystallization at a moderate crystallization rate is less important than the local electric field to induce the ferroelectric phases of PVDF. [Copyright &y& Elsevier]

Abstract: Flexible electrospun titanium carbide (TiC) nano-felts were converted into carbide-derived carbon (CDC) by dry chlorination at temperatures between 200 and 1000°C and used as binder-free supercapacitor electrodes. In the carbide nano-felt, TiC nano-crystals (20–30nm) were embedded in a matrix of disordered carbon. After chlorination, the porous CDC nano-fibers/felts maintain their size, shape, and flexibility. With the increase of synthesis/chlorination temperature, the degree of carbon ordering increased. Electrochemical characterizations in 1M H2SO4 and 1.5M tetraethylammonium tetrafluoroborate in acetonitrile were carried out on binder-free electrodes with galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy. The highest gravimetric capacitance was identified for the CDC nano-felt synthesized at the highest temperature of 1000°C, reaching 135Fg−1 in aqueous and 120Fg−1 in organic electrolytes. In contrast to powder or monolithic supercapacitor electrodes made of conventional activated, templated, or carbide-derived carbons, this material demonstrated excellent high-power handling ability; and ∼50% of the low-rate capacitance was maintained at a very high scan rate of 5Vs−1. [Copyright &y& Elsevier]

Abstract: By utilizing electrospun blend fibers of polystyrene (PS) and poly(ethylene oxide) (PEO) with diameters in sub-microns, nanodroplets of the minor component (PEO) were obtained by annealing the blend fibers above the glass transition temperature (Tg ) of the matrix polymer (PS), as a result of the Rayleigh-Plateau instability in the melt. However, direct thermal annealing of the PS/PEO blend fibers led to poor Rayleigh breakup of the PEO fibers in the PS matrix, and fractionated crystallization with both homogeneous and heterogeneous nucleation was observed, probably due to a broad size distribution of PEO particles. On the contrary, after confining the PS/PEO blend fibers with a high Tg polymer, poly(4-tert-butyl styrene) (P4tBS, Tg  ∼ 143 °C), well-defined Rayleigh breakup of the PEO fiber was achieved by annealing the P4tBS-coated PS/PEO blend fibers at 150 °C. Consequently, exclusive homogeneously nucleated PEO crystallization was observed at −20 °C. This report could provide a universal method to achieve nano-sized droplets for the study of nanoconfinement effect by utilizing electrospun immiscible polymer blend fibers without addition of any compabitilizers. [Copyright &y& Elsevier]

Abstract: Herein we report that hierarchical electrospun SiO2 nanofibers incorporated with SiO2 nanoparticles with fiber diameters being ∼500nm and particle sizes being tens of nanometers were developed through the combination of sol–gel process and electrospinning technique followed by high-temperature pyrolysis; and their morphologies and BET surface areas were examined. The study revealed that the pre-gelation of tetraethyl orthosilicate (TEOS) in spin dopes was important to achieve the morphological consistence of the electrospun precursor nanofibers and the resulting final SiO2 nanofibers; additionally, SiO2 nanoparticles appeared to be enriched on the fiber surface, while the surface-roughness and/or porosity of the nanofibers could be controlled through adjusting the incorporation amount of SiO2 nanoparticles. The developed hierarchical electrospun SiO2 nanofibers are expected to have important applications in composites (particularly dental composites) as well as catalyst support and adsorption. [Copyright &y& Elsevier]

Abstract: Carbon nanofibers with diameters of 200–300nm were developed through stabilization and carbonization of aligned electrospun polyacrylonitrile (PAN) nanofiber bundles. Prior to the oxidative stabilization in air, the electrospun PAN nanofiber bundle was tightly wrapped onto a glass rod, so that tension existed during the stabilization. We also investigated several carbonization procedures by varying final carbonization temperatures in the range from 1000 to 2200°C. The study revealed that: (1) with increase of the final carbonization temperature, the carbon nanofibers became more graphitic and structurally ordered; (2) the carbon nanofiber bundles possessed anisotropic electrical conductivities, and the differences between the parallel and perpendicular directions to the bundle axes were over 20 times; and (3) the tensile strengths and Young''s moduli of the prepared carbon nanofiber bundles were in the ranges of 300–600MPa and 40–60GPa, respectively. [Copyright &y& Elsevier]

Abstract: Thermo-chemical reactions occurring during the oxidative stabilization of electrospun polyacrylonitrile (PAN) precursor nanofibers with diameters of approximately 300nm were investigated as well as the resulting structural conversions, and the results were compared to those of conventional SAF 3K (Courtaulds) precursor fibers. The study revealed that: (1) the nitrile groups in the electrospun nanofibers possessed a higher reactivity than those in the SAF 3K fibers; (2) the macromolecules in the electrospun nanofibers predominantly underwent inter-molecular cyclization/crosslinking while those in the SAF 3K fibers underwent intra-molecular cyclization during the early stages of stabilization; and (3) under the same stabilization conditions, the structural conversion from linear macromolecules to aromatic ring/ladder structures in the electrospun nanofibers occurred faster and more thoroughly than in the SAF 3K fibers. These characteristics combined with other properties, including small diameter and high degree of structural perfection, suggest that electrospun PAN precursor nanofibers may be used to develop continuous nano-scale carbon fibers with superior mechanical strength, especially if the electrospun nanofibers could be further aligned and stretched. [Copyright &y& Elsevier]

As a short-chain PFAS, GenX has gained increasing attention in recent years as a hazardous and emerging contaminant in water bodies. However, there is only limited research outcome up to date to address GenX remediation from water. In this research, we investigated amidoxime surface-functionalized PAN nanofibrous material from electrospinning as adsorbent to remove GenX from water. The nanofibrous adsorbent from 10 min treatment of electrospun PAN nanofibrous material in hydroxylamine (ASFPAN10) realized 35% GenX removal from a 100 mg/L aqueous solution at pH = 4 and 0.24 g/L loading after a simple one-time filtration with a GenX removal capacity of ~0.6 mmol/g. The mechanism study indicated that the GenX adsorption on PAN nanofibrous adsorbent could be mainly ascribed to hydrophobic interaction and dipole-dipole interaction between C N and C–F while the GenX adsorption on ASFPAN10 nanofibrous adsorbent could be mainly attributed to coulomb force between positive-charged C N+(OH)–H from ASFPAN10 and negative-charged COO− from GenX. Compared to that of PAN, the more hydrophilic surface of ASFPAN10 facilitated water access to the nanofibrous adsorbent surface and also contributed to the higher GenX removal efficiency. For the first time, this research pointed out a direction to use common economic materials for effective remediation of short-chain PFAS from water bodies especially at relatively high PFAS centration. • Amidoxime group was introduced to PAN nanofibrous adsorbent for GenX removal. • The maximum GenX removal capacity was observed as ~0.6 mmol/g ASFPAN10 at pH = 4. • The GenX removal capacity herein is comparable to other high-cost adsorbents. • GenX adsorption on PAN is via hydrophobic interaction & dipole-dipole interaction. • GenX adsorption on ASFPAN is mostly attributed to coulomb force. [ABSTRACT FROM AUTHOR]

• Growth behavior of S. cerevisiae and C. albicans upon contact with ESPAN was studied. • The yeast cells showed lower growth rate, morphology change, and reduced viability. • The inhibition effect of ESPAN on yeast cells may be determined by multiple factors. Electrospun nanofibers have been found in many applications such as air/water filtration, performance apparel, drug delivery, and scaffold for tissue engineering and started to be integrated in commercial products, which leads to their exposure to environment. Electrospun nanofibrous material is a relatively new material to microorganism in nature and little is known about the biological implication of interactions between electrospun nanofibrous mats and cellular fungal cells. Herein the interaction between electrospun polyacrylonitrile (ESPAN) nanofibrous mat and representative non-pathogenic/pathogenic cellular yeasts (Saccharomyces cerevisiae and Candida albicans) was investigated. It is demonstrated for the first time that when these cellular yeasts, species of the kingdom fungi, were exposed to ESPAN nanofibrous mat, they exhibited lower growth rate, radical change to morphology, and reduced viability without presence of any chemical antifungal agent. These responses were distinct from the cellular interactions with other forms of PAN materials (e.g. solid film or microfibrous mat). Exploration of mechanism indicated that the interaction between yeast cell and electrospun nanofibrous mat is a complex phenomenon in which both nanofibrous morphology and fiber surface composition/property play significant roles. The inherent anti-yeast and potential anti-fungal functionality of ESPAN nanofibrous mat may make an immediate impact on environmental microorganism and could also benefit the next-generation material design to control microbial growth through solely physical contact. [ABSTRACT FROM AUTHOR]

The rapidly developing technique of electrospinning has gained surging research interest since the 1990s due to its capability of yielding continuous fibers with diameters down to the nanometer scale. Despite enormous efforts devoted to explore applications of electrospun nanofibers, such as separation, catalysis, nanoelectronics, sensors, energy conversion/storage, and biomedical utilization, there are limited attempts to employ these nanofibers for reinforcement in polymer composites. Electrospun nanofibers, however, possess comprehensive advantages not typically shared by other nanoscale composite fillers/reinforcing agents, such as continuity, diverse material choice, controlled diameter/structure, possible alignment/assembly, mass production capability and so forth. Therefore electrospun nanofibers have great potential as promising reinforcement fillers for next-generation polymer composites. This is a comprehensive and state-of-the-art review of the latest advances made in development of electrospun nanofiber reinforced polymer composite materials with intention to stimulate interests in both academia and industry. [ABSTRACT FROM AUTHOR]

Low thermal conductivity carbon is a type of material for special uses such as thermal insulation/protection and particularly for ablative thermal protection material of reentry vehicles and rocket engine components. In this research, a low thermal conductivity carbon nanofibrous material was prepared by electrospinning polyacrylonitrile (PAN) with poly (methyl methacrylate) (PMMA) as well as silica nanoparticles (SNPs) followed by stabilization and carbonization. Morphology and structure of this carbon nanofibrous material were characterized by electron microscope, X-ray diffraction, Raman spectroscopy, and BET surface area analysis and correlated with its thermal conductivity. Introduction of PMMA and SNPs to PAN precursor nanofibers through multi-component electrospinning enabled a unique concurrent multi-scale (micro-, submicro- and nano-) porous structure in the resultant carbon nanofibrous mat and synergistically reduced the thermal conductivity by up to 98% with respect to the non-porous carbon film counterpart. This research demonstrated a novel and effective way to design and manufacture low thermal conductivity carbon materials. [ABSTRACT FROM AUTHOR]

Electrospun glass nanofibers (EGNFs) are emerging fillers to improve mechanical properties of polymer matrix composite materials. However, questions concerning their reinforcing effectiveness in comparison with other nanoscale fillers such as glass/silica nanoparticles (GNPs) are still to be answered because reinforcing mechanisms for conventional fiber reinforced polymer composites might not be applicable at distinctive nanometer scale. Herein a comparative study on reinforcing effect of EGNFs and their conventional counterpart GNPs was carried out for the first time. Four types of glass nanofillers, including pristine EGNFs and GNPs as well as amino surface-functionalized EGNFs and GNPs were investigated to make epoxy matrix nanocomposites at ultra-low loading level (≤0.5 wt%). Mechanical properties of these glass nanofiller reinforced epoxy composites were investigated and corresponding reinforcing and toughening mechanisms at nanometer scale were discussed. Due to shape factor (aspect ratio), EGNFs demonstrated much more pronounced reinforcing and toughening effectiveness and completely outperformed GNPs in all cases despite much lower specific surface area. This research provided meaningful data to fully understand the merit of EGNFs as reinforcing filler in polymer nanocomposites and paved the road for designing and modeling next-generation polymer matrix composite materials. [ABSTRACT FROM AUTHOR]

Abstract: Continuous bundles of aligned and stretched electrospun polyacrylonitrile (PAN) precursor nanofibers were prepared in an attempt to develop carbon nanofibers with superior strength. The bundles were prepared through collection of electrospun nanofibers with a flowing water bath followed by stretching in water at 97°C. Their morphologies, structures, and thermo-chemical properties were characterized by SEM, XRD, and DSC. The shrinkages in boiling water and the amounts of residual solvent were also measured. The results indicated that, the nanofibers in the bundles were uniform with smooth surfaces and small variations in diameters; after stretching the bundles by 4 times, the average fiber diameter was reduced to 56%, while the crystallinity of PAN was improved by 72%. The post-spinning stretching process facilitated the stabilization of PAN, as evidenced by the shift of the cyclization reaction to a lower temperature with smaller activation energy and larger enthalpy change. In comparison with the commonly adopted nanofiber collection method of a rotating drum, the flowing water bath method results in higher degree of uni-axial alignment and more desired structures of nanofibers. [Copyright &y& Elsevier]

Abstract: Herein we report that fibers of polybutadiene rubber (BR) with high morphological stability were made through combination of electrospinning and in-situ photo-crosslinking. This study revealed that (1) the formation of electrospun BR fibers was correlated with the overlap/entanglement of BR macromolecules in the spinning solutions; for the formation of uniform fibers without beads and/or beaded fibers, the concentration of spinning solution had to be higher than the “critical chain entanglement concentration (Ce)”; and (2) the in-situ photo-crosslinking was an effective method to considerably improve the morphological stability of electrospun BR fibers; upon prolonged storage under ambient condition or even upon immersion in tetrahydrofuran (a good solvent for BR), the crosslinked BR fibers well retained their morphology. It is envisioned that electrospun rubber fibers could be utilized for the development of innovative composites with substantially improved toughness and/or impact strength. [Copyright &y& Elsevier]

Abstract: Electrospun polyacrylonitrile (PAN) copolymer nanofibers with diameters of ∼0.3 μm were prepared as highly aligned bundles. The as-electrospun nanofiber bundles were then stretched in steam at ∼100 °C into 2, 3, and 4 times of the original lengths. Subsequently, characterizations and evaluations were carried out to understand morphological, structural, and mechanical properties using SEM, 2D WAXD, polarized FT−IR, DSC, and mechanical tester; and the results were compared to those of conventional PAN copolymer microfibers. The study revealed that: (1) the macromolecules in as-electrospun nanofibers were loosely oriented along fiber axes; although such an orientation was not high, a small extent of stretching could effectively improve the orientation and increase the crystallinity; (2) most of macromolecules in the crystalline phase of as-electrospun and stretched nanofibers possessed the zig-zag conformation instead of the helical conformation; and (3) the post-spinning stretching process could substantially improve mechanical properties of the nanofiber bundles. To the best of our knowledge, this study represented the first successful attempt to stretch electrospun nanofibers; and we envisioned that the highly aligned and stretched electrospun PAN copolymer nanofibers could be an innovative type of precursor for the development of continuous nano-scale carbon fibers with superior mechanical strength. [ABSTRACT FROM AUTHOR]

Abstract: Graphitic carbon nanofibers (GCNFs) with diameters of approximately 300 nm were developed using bundles of aligned electrospun polyacrylonitrile (PAN) nanofibers containing phosphoric acid (PA) as the innovative precursors through thermal treatments of stabilization, carbonization, and graphitization. The morphological, structural, and mechanical properties of GCNFs were systematically characterized and/or evaluated. The GCNFs made from the electrospun PAN precursor nanofibers containing 1.5 wt.% of PA exhibited mechanical strength that was 62.3% higher than that of the GCNFs made from the precursor nanofibers without PA. The molecules of PA in the electrospun PAN precursor nanofibers initiated the cyclization and induced the aromatization during stabilization, as indicated by the FT-IR and TGA results. The stabilized PAN nanofibers possessed regularly oriented ladder structures, which facilitated the further formation of ordered graphitic structures in GCNFs during carbonization and graphitization, as indicated by the TEM, XRD, and Raman results. [Copyright &y& Elsevier]

Electrospun nanofibrous scaffold is a promising implant for peripheral nerve regeneration. Herein, to investigate the effect of surface morphological features and electrical properties of scaffolds on nerve cell behavior, we modified electrospun cellulose (EC) fibrous mats with four kind of soluble conductive polymers derivates (poly (N-(methacryl ethyl) pyrrole) (PMAEPy), poly (N-(2-hydroxyethyl) pyrrole) (PHEPy), poly (3-(Ethoxycarbonyl) thiophene) (P3ECT) and poly (3-thiophenethanol) (P3TE)) by an in-situ polymerization method. The morphological characterization showed that conductive polymers formed aggregated nanoparticles and coatings on the EC nanofibers with the increased fiber diameter further affected the surface properties. Compared with pure EC scaffold, more PC12 cells were adhered and grown on modified mats, with more integral and clearer cell morphology. The results of protein adsorption study indicated that modified EC mats could provide more protein adsorption site due to their characteristic surface morphology, which is beneficial to cell adhesion and growth. The results in this study suggested that these conductive polymers modified scaffolds with special surface morphology have potential applications in neural tissue engineering. • Four soluble conductive polymer derivates modified electrospun cellulose nanofibrous mats by an efficient method. • Conductive polymers formed aggregated nanoparticles and coatings on the electrospun cellulose fibrous mats. • More PC12 cells were adhered and grown on modified mats, with more integral and clearer cell morphology. • Increased electrical activity and surface roughness of conductive polymers on the surface improved cell behavior. [ABSTRACT FROM AUTHOR]

Hybrid Li-ion capacitors (LICs) are a new kind of electrochemical energy storage device with high energy and power densities. In this work, phosphorus-doped TiO 2 /phosphorus-doped carbon nanofibers (PTO/PC NFs) are fabricated through a simple electrospinning method with disodium hydrogen phosphate as a phosphorus source. Differing from the PTO prepared by hydrothermal method, sol-gel method or calcining treatment at phosphorous atmosphere. The P-doping evenly distributed in PTO/PC NFs and PTO nanoparticles are embedded in PC, which improves the conductivity, structure stability and Li+ ions diffusion of TiO 2. As a result, the PTO/PC NFs anode shows high capacities of 329 and 150 mA h g−1 (0.1 and 2 A g−1), long cycle life (201 mA h g−1 after 1000 cycles at 1 A g−1, 69 mA h g−1 after 1000 cycles at 5 A g−1), and superior pseudocapacitance (87%, 2 mV s−1). Furthermore, the LICs assembled with PTO/PC NFs anode and AC cathode show outstanding capacity of 35 F g−1 at a current density of 0.1 A g−1, high energy density of 72 Wh kg−1 at the power density of 250 W kg−1, and cycle stability (54%, 10 000 cycles, 1 A g−1). This suggests that PTO/PC NFs is a potential anode material for high-performance LICs. Image 1 • P-doped TiO 2 /P-doped C nanofibers (PTO/PC NFs) are fabricated by electrospinning. • The PTO/PC NFs exhibited good conductivity, stability and Li+ ions diffusion. • The PTO/PC anode showed high capacity, long cycle life and high pseudocapacitance. • LIC assembled with PTO/PC NFs anode showed a high energy density and power density. [ABSTRACT FROM AUTHOR]

• Electrospun carbon nanofibrous (ECNF) membranes were investigated for oil absorption. • Results from ECNF membranes with porous and/or hollow individual fibers were compared. • Hollow ECNF structure did not play a favorable role in capacity of oil absorption. • The result is ascribed to nanostructures generated from co-axial electrospinning. • The findings provide insights to develop absorbent material for oil spills. Current commercial oil absorbents such as polypropylene based materials are lack of exciting absorption capability for oil spill cleanup. Designing economic, efficient and stable absorbent for oil spill is still a challenge. Herein three types of carbon nanofibrous membranes with porous and/or hollow individual carbon nanofibers from bicomponent and co-axial electrospinning were prepared and their morphology, porosity, surface property as well as oil absorption capacity and reusability were characterized and compared. The results indicated that the hollow structure from co-axial electrospinning does not play a favorable role in oil absorption. The reasons may be attributed to surface nature, pore volume and nanometer scale interconnected hollow channel/pore structure that are naturally associated with co-axial electrospinning. [ABSTRACT FROM AUTHOR]