As-prepared Nanofibers Research Articles

Preparation and Characterization of Multi-layer Poly(arylene sulfide sulfone) Nanofibers Membranes for Liquid Filtration

Owing to the excellent filtration performance and low energy cost, polymeric nanofibers microfiltration (MF) membranes have attracted increasing attentions. Poly(arylene sulfide sulfone) (PASS), as one of the structurally modified polymers based on poly-(phenylene sulfide) (PPS), has been selected as the raw material to fabricate nanofibers MF membranes via electrospun techniques. The effects of PASS solution and the electrospinning processing parameters on the structural morphology of nanofibers were investigated in detail. The average diameter of PASS nanofibers was (296 ± 46) nm under the optimal condition: polymer concentration of 0.27 g·mL−1 PASS/DMI, applied voltage of 20 kV, and speed of collector drum of 300 r·min−1. And then the multi-layer PASS nanofibers MF membranes were fabricated from cold-pressing the optimized PASS nanofibers (as-prepared PASS nanofibers) membrane. The morphology, porosity, pore size, mechanical properties, and surface wettability of the multi-layer PASS nanofibers MF membranes could be tuned by the layers of as-prepared nanofibers membrane. The results demonstrated that the membrane with 6 layers (marked as PASS-6) exhibited the smallest porosity, smallest pore size, highest mechanical property, and best surface wettability. Meanwhile, the multi-layer PASS nanofibers MF membranes showed that the rejection ratio gradually increased, while the pure water flux decreased with increasing membranes thickness. The PASS-6 membrane exhibited large water flux of 747.76 L·m−2·h−1 and high separation efficiency of 99.9% to 0.2 µm particles, making it a promising candidate for microfilter.

Direct Z-scheme heterostructure of p-CuAl2O4/n-Bi2WO6 composite nanofibers for efficient overall water splitting and photodegradation

Constructing heterostructures can facilitate photoinduced charge separation, leading to enhanced photocatalytic performance. However, spatial separation of charge carriers in traditional type II heterojunctions is at the expense of their redox ability. In this paper, well-designed direct Z-scheme systems (ZSS) of p-CuAl2O4/n-Bi2WO6 composite nanofibers with uniform non-woven web nanostructure was built by electrospinning technique and solvothermal reactions. The formation mechanism of the ZSS and the charge migration pathway is investigated in detail. Results show that as-prepared composite nanofibers exhibit desirable photocatalytic performance for overall water splitting due to its stronger redox power and efficient charge separation. Meantime, it shows great activity for photodegradation of various organic pollutant models (RhB, MO, 4-NP), which is 1 order of magnitude higher than the single-component CuAl2O4 and Bi2WO6. Furthermore, the composite nanofibers exhibit well separable properties by natural sedimentation because of its ultra-long and non-woven web nanostructure. The paper explores CuAl2O4 and its Z-scheme heterostructures in water splitting for the first time, which may highlight its new applications.

Controllable preparation of methyltriethoxysilane xerogel nanofibers

In recent years, the controllable preparation of silicone xerogel nanofiber without the addition of a carrier polymer is becoming more and more attractive. The methyltriethoxysilane (MTES) sol prepared using MTES/H2O/ethanol in a molar ratio of 1:5:6 under acidic catalysis conditions has excellent spinnability in a long span of spinning time. Further, pure silicone nanofibers with different gelation times were prepared by electrospinning. The influence of gelation time on the colloidal particle morphology and size, cross-linking degree, and viscosity of as-synthesized silicone sols was studied in depth with SEM, DLS, and ATR-FTIR, and the effects on the morphology, hydrophobicity, and thermal stability of as-prepared xerogel nanofibers were also determined. As the gel time increased, there was a higher increase in the colloidal particle size, cross-linking degree, and viscosity of sol. The xerogel nanofibers with long gelation time exhibited higher hydrophobicity and thermal stability due to sufficient hydrolysis and condensation. The optimum gelation time was approximately 200 h, and the optimum viscosity range was in between 300 and 1000 cp, which were obtained for stable fiber jet and for preparing uniform and continuous xerogel nanofibers with excellent physical and chemical properties.

Controllable generation of nanofibers through a magnetic-field-assisted electrospinning design

Electrospinning technology is taken as the most versatile process to generate continuous nanofibers. However, effects should be taken to achieve better understanding and precisely control the actual mechanics in the formation of nanofibers through better system design. In this article, the diameter and the deposition area of the as-prepared nanofibers can be controlled by added helix tube which can provide external electric-magnetic field. The spinning process can be controlled employing a magnetic flux (B) analytical model which is based on the magnetic field calculation modelof the solution and the electrostatic charge repulsion in the jet. This method includes the thermo-mechanical properties based on as-prepared electrospun nanofiber films and the capability of tribology-mechanical and mathematical physics. A novel investigation of the whole output increase at per unit spinning area is presented in this article to describe the whipping instability which is an important feature of the Taylor Cone phenomenon. The present design and process for electrospinning are based on a solution differential calculus, which a single stainless steel spinning nozzle can generate multi-squirt flow. With the purpose of providing useful jet initial behaviour design for the further technology applications, we attempt to set up a differential calculus method with evenly distributed circumferential electric field, yet giving more design guidance to produce controllable nanofibers through magnetic-field-assisted electrospinning technology.

Development of nanofibrous collagen-grafted poly (vinyl alcohol)/gelatin/alginate scaffolds as potential skin substitute.

The main objective of this work is to fabricate a nanofibrous scaffold to regenerate skin tissue. A scaffold composed of poly (vinyl alcohol)/gelatin/alginate was prepared using electrospinning method. To improve scaffold biocompatibility and wound healing properties, collagen, extracted from rat tail, was grafted on as-prepared nanofibers. The prepared scaffolds were characterized by SEM, FTIR, swelling ratio test, and water vapor transmission rate (WVTR) measurement. Cytotoxicity of the scaffolds against human fibroblasts and L929 (NCBI C161) cells were tested using direct and indirect methods, respectively. Fibroblast cell adhesion and proliferation on the scaffold were also investigated. Results of morphological studies showed that beadless nanofibers with 229 nm diameter were prepared. ATR-FTIR spectra of collagen grafted nanofiber mats confirmed presence of the collagen on their surface. Collagen grafted nanofibers showed higher swelling ratio than nanofibers without collagen graft. Collagen grafting decreased VWTR. Collagen grafting decreased both tensile strength and Young's modulus of the nanofibrous scaffolds while increased their elongation at break. MTT results showed that both scaffolds are biocompatible with higher cell viability for nanofibers with collagen grafting. Fibroblast cell culture on the scaffolds demonstrated that both of scaffolds have good cell viability and proliferation while collagen grafted scaffold showed better results.

Investigation of dopant effect on the electrochemical performance of 1-D polypyrrole nanofibers based glucose biosensor

Glucose plays an imperative role in human metabolism and any imbalance in glucose concentration can cause chronic disease like diabetes mellitus. With the drastic increase in the number of diabetic patients around the world, demand for point of care testing device for continuous monitoring of blood glucose level has been accelerated. In this respect, electrochemical glucose biosensors play a vital role for measurement of glucose concentration in human blood. In this work, for the first time, we demonstrate a systematic study of the effect of two different types of dopants viz. lithium perchlorate (LiClO4) and para-toluenesulfonic acid (p-TSA) on the performance of polypyrrole (PPy) based enzymatic glucose biosensor. Both the dopants (LiClO4 and p-TSA) were utilized with the aim of improving the charge transfer capability of PPy films. The PPy nanofibers were synthesized over a Platinum coated glass substrate by electrochemical method. The morphological and electrochemical properties of electrosynthesized PPy nanofibers utilizing template-free method have been tailored by dopant variation (LiClO4 and pTSA) during electropolymerization. The as-prepared PPy nanofibers were used as a support matrix for enzyme immobilization. The as-fabricated enzymatic biosensors were later examined for the detection of glucose. Both the morphological and electrochemical properties of PPy electrode have been observed to improve with p-TSA (PPy–pTSA), as compared to LiClO4 (PPy–LiClO4). The as-fabricated PPy–pTSA/GOx based glucose biosensor has exhibited the highest sensitivity of 6.12 mA cm−2 M−1 with a linear range of 0.1–7.5 mM, which is better as compared to PPy-LiClO4/GOx biosensor. Additionally, the as-prepared PPy–pTSA/GOx biosensor has presented noteworthy stability, selectivity, and reproducibility that validates the importance of the dopant effect in electrosynthesized PPy based biosensing applications.

Copper(ii)-based coordination polymer nanofibers as a highly effective antibacterial material with a synergistic mechanism.

Nanofibers of a copper(ii)-based coordination polymer [Cu(HBTC)(H2O)3] were synthesized via a microwave-assisted hydrothermal process, while macroparticles and bulk crystals were prepared via a hydrothermal method. X-ray analysis revealed that this compound possesses one-dimensional zig-zag chains, in which the coordination polyhedron of the copper(ii) center is a five-coordinate distorted square-pyramid. The width of the as-prepared nanofibers was about 150 nm, while the size of the macroparticles was about 200 μm. The antibacterial activities of the nanofibers and macroparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated by determining the minimal inhibitory concentration (MIC), the growth curve of the bacteria and the bacterial reduction assay. The nanofibers showed higher antibacterial performance as compared with macroparticles, commercial copper nanoparticles, and pure ligands alone. The bacteriostatic rates of nanofibers and macroparticles were up to 99.9% and 96.7% against E. coli, while 99.1% and 96.2% against S. aureus, respectively, when the concentration was 250 μg mL-1. The synergistic antibacterial mechanism was also proposed based on the generation of reactive oxygen species (ROS) and the release of Cu2+ ions.

Ultrafine polycrystalline titania nanofibers for superior sodium storage

Abstract Sodium ion batteries have a huge potential for large-scale energy storage for the low cost and abundance of sodium resources. In this work, a novel structure of ultrafine polycrystalline TiO2 nanofibers is prepared on nickel foam/carbon cloth by a simple vapor deposition method. The as-prepared TiO2 nanofibers show excellent performance when used as anodes for sodium-ion batteries. Specifically, the TiO2 nanofibers@nickel foam electrode delivers a high reversible capacity of 263.2 mAh g−1 at 0.2 C and maintains a considerable capacity of 144.2 mAh g−1 at 10 C. The TiO2 nanofibers@carbon cloth electrode also shows excellent high-rate capability, sustaining a capacity of 148 mAh g−1 after 2000 cycles at 10 C. It is believed that the novel nanofibrous structure increases the contact area with the electrolyte and greatly shortens the sodium ion diffusion distance, and meanwhile, the polycrystalline nature of nanofibers exposes more intercalation sites for sodium storage. Furthermore, the density functional theory calculations exhibit strong ionic interactions between the exposed TiO2 (101) facets and sodium ions, leading to a preferable sodiation/desodiation process. The unique structural features endow the TiO2 nanofibers electrodes great advantages in rapid sodium storage with an outstanding high-rate capability.

Electrospun Enzymatic Hydrolysis Lignin-Based Carbon Nanofibers as Binder-Free Supercapacitor Electrodes with High Performance.

Carbon nanofibers consisting of Poly(acrylonitrile) (PAN) and enzymatic hydrolysis lignin (EHL) were prepared in the present study by electrospinning followed by stabilization in air and carbonization in N2 environment. The morphology and structure of the electrospun carbon nanofibers were characterized by Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET), Roman, and the electrochemical performances were then evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS)methods. When the amount of EHL was 60 wt. %, the as-prepared nanofibers have the smallest average diameter of 172 nm and the largest BET specific surface area of 675 m2/g without activating treatment. The carbon nanofiber electrode showed excellent specific capacitance of 216.8 F/g at the current density of 1 A/g, maintaining 88.8% capacitance retention after 2000 cycles. Moreover, the carbon nanofiber electrode containing 60 wt. % exhibited a smaller time constant (0.5 s) in comparison to that of carbon nanofibers in literatures. These findings suggest the potential use of EHL could be a practical as a sustainable alternative for PAN in carbon electrode manufacturing.

Electrospinning of Ag/ZnWO4/WO3 composite nanofibers with high visible light photocatalytic activity

Distinctive Ag/ZnWO4/WO3 composite nanofibers have been successfully synthesized by a simple electrospinning method followed by subsequent annealing treatment. The as-prepared composite nanofibers are systematically characterized by SEM, XRD, XPS, UV–vis DRS and PL spectra. The photocatalytic activity of Ag/ZnWO4/WO3 composite nanofibers to the degradation of Methyl Blue (MB) is evaluated under UV–vis light irradiation. The result shows that the photocatalytic degradation rate of Ag/ZnWO4/WO3 composite nanofibers reaches to 94% within 80 min, which is higher than that of single WO3 nanofibers and Ag/WO3 binary composite nanofibers. The enhanced photocatalytic efficiency of Ag/ZnWO4/WO3 composite nanofibers is attributed to the synergistic effect of three different activated materials.

Facile preparation of WO3 nano-fibers with super large aspect ratio for high performance supercapacitor

WO3 nano-fibers with super large aspect ratio are synthesized on a Cu conductive current collector by using a simple hydrothermal method. The as-prepared WO3 nano-fibers can accommodate a large number of electrolyte ions and provide a rapid route for the migration of electrons and electrolyte ions due to its direct growth, high specific surface area, and one dimensional (1D) pipeline structure. The WO3 nano-fibers exhibit excellent cyclic reversibility (98% at 1.0 A g−1), good cycling stability (93% after 5000 cycles), high specific capacitance (436 F g−1 at 1.0 A g−1) and low charge transfer resistance (29 Ω). After the WO3 nano-fibers are assembled into a symmetric supercapacitor, the symmetric supercapacitor device has a wide effective operating range of 0–1.8 V and high energy density of 99.0 W h kg−1 at the power density of 450 W kg−1. The good electrochemical performances of as-prepared WO3 nano-fibers make it an attractive candidate for high energy storage systems and promising supercapacitor electrode material.

Preparation and electrochemical performance of electrospun biomass-based activated carbon nanofibers

Biomass-based nanofibers were prepared by electrospinning a mixture of polyacrylonitrile and acid-treated biomass from industrial hemp straw. The as-prepared biomass-based nanofibers were then carbonized and activated by high-temperature carbonization and KOH to obtain the activated biomass-based carbon nanofibers. The scanning electron microscopy images show that the precursors and carbon nanofibers are composed of fibers 179 nm in diameter, and the nitrogen adsorption/desorption measurements indicate that the carbon nanofibers possess a high-specific surface area of 2348.73 m2·g−1. The carbon nanofibers exhibit excellent electrical performance. The specific capacitance is as high as 244.8 F·g−1 at a current density of 1 A·g−1. The specific capacitance remains at 96% after 3000 cycles of charge and discharge at a current density of 2 A·g−1, showing excellent cycle stability. This work provides new ideas for the future development of supercapacitors electrode materials and enhances the development of biomass energy.

High-performance polyimide nanofiber membranes prepared by electrospinning

Polyimide (PI) nanofiber membranes were successfully prepared from a PI/N-methyl-2-pyrrolidone (NMP) solution via electrospinning. This technique simply and facilely produced efficient high-performance PI fibers. The morphology, surface wettability, thermal stability, mechanical properties, and filtration performance of the as-prepared PI nanofiber membranes were characterized in detail. The membranes exhibited smooth and hydrophobic surfaces. The nanofibers were well distributed in the membranes with fiber diameters in the range of 140–400 nm. All the PI nanofiber membranes showed excellent thermostability, and their initial decomposition temperature ( Td) and heat resistance temperature ( THRI) exceeded 544.4°C and 198.8°C, respectively. The PI nanofiber membranes also possessed reasonable mechanical properties with a tensile strength and a Young’s modulus reaching 10.5 and 927.6 MPa, respectively. Regarding the filtration performance, the developed nanofiber membranes achieved the best filtration efficiency of 90.4%. Such electrospun PI nanofiber membranes can be a promising candidate for hot gas filtration.

Hybridizing CNT/PMMA/PVDF towards high-performance piezoelectric nanofibers

Piezoelectric nanofibers are of great importance in their potential applications as smart fibers and textiles to bring changes to daily lives. By employing the technique of electrospinning, polyvinylidene fluoride (PVDF) nanofibers modified with polymethyl methacrylate (PMMA) and single-wall carbon nanotubes (CNTs) (referred to as CNT/PMMA/PVDF) are prepared. The electric field induced displacement of the as-prepared nanofibers is characterized by piezoresponse force microscopy. Compared with the pure PVDF nanofibers, the CNT/PMMA/PVDF nanofibers exhibit a great enhancement of about 196% for the electric field induced displacement, while increments of about 104% and 78% are obtained for the PMMA/PVDF and CNT/PVDF nanofibers, respectively. A structural analysis indicates that the hydrogen bonding between the O atom in the carbonyl group of PMMA and the hydrogen atom in the CH2 groups of PVDF, the promotion of the nucleation of crystallites by CNTs, work synergistically to produce the high electroactive response of the CNT/PMMA/PVDF nanofibers. Based on the high-performance nanofibers, a prototype of a flexible nanofiber generator is fabricated, which exhibits a typical electrical output of 3.11 V upon a repeated impact-release loading at a frequency of 50 Hz.

Phosphorus-Doped Hard Carbon Nanofibers Prepared by Electrospinning as an Anode in Sodium-Ion Batteries.

Phosphorus-doped hard carbon nanofibers with macroporous structure were successfully synthesized by electrospinning followed by a thermal treatment process using polyacrylonitrile and H3PO4 as carbon and phosphorus precursors, respectively. X-ray photoelectron spectroscopy analysis reveals that the doped phosphorus atoms can incorporate into the carbon framework and most of them are connecting with carbon atoms to form P-C bond. The (002) plane interlayer spacing was taken from the X-ray diffraction pattern, which shows a large spacing of 3.83 Å for the obtained P-doped hard carbon nanofibers. When used as an anode in sodium-ion batteries, the as-prepared P-doped hard carbon nanofibers can deliver a reversible capacity of 288 and 103 mAh g-1 at a current density of 50 mA g-1 and 2 A g-1, respectively. After 200 cycles at 50 mA g-1, the capacity retention of P-doped hard carbon nanofibers still reaches 87.8%, demonstrating good cycling durability. These excellent electrochemical performances of P-doped hard carbon nanofibers can be attributed to the macroporous structure, large interlayer spacing, and the formation of P-C bond.

Removal and reuse of Ag nanoparticles by magnetic polyaniline/Fe3O4 nanofibers

For the treatment of wastewater containing Ag nanoparticles (NPs), PANI/Fe3O4 nanofibers were firstly prepared by a novel self-assemble. And then, the efficiency for the removal of Ag NPs from wastewater was investigated. The magnetic performance of PANI/Fe3O4 nanofibers could be optimized by adjusting the pH of the self-assemblied system. Under pH of 3, the as-prepared nanofibers exhibited the highest magnetism and also displayed good efficiency (> 12 mg g−1) for the removal of Ag NPs. Importantly, the resulted product (PANI/Fe3O4/Ag composite) could act as a catalysis for cleaning durable pollutant, 4-nitrophenol. After 10 cycles, only slight decrease in rate constant was found, indicating excellent reusability. Those approaches provide a new way to merge the recovery of Ag NPs as pollutants and reuse of recovered Ag NPs as recyclable material for environmental remediation.

The continuous flexible three dimensional curly carbon-based hybrid nanofibers with good resilience and electrochemical performance

Continuous flexible three dimensional curly carbon-based hybrid nanofibers are prepared via airspinning followed by heat treatment under different atmosphere. The as-prepared hybrid nanofibers are disordered and show fluffy structure, which endows the hybrid nanofibers with good elasticity after heat treatment. The effect of low temperature carbonization on the formation of different carbon-based hybrid nanofibers is investigated based on different heat treatment methods. Moreover, through the carbothermic reaction between TiO2 and amorphous carbon (or N2), inorganic nanoparticles which are homogeneously distributed in the nanofibers (or on the surface of the nanofibers) can be obtained. Meanwhile, a little graphene is formed around these inorganic compounds. In addition, the TiC, C0.7N0.3Ti and TiN hybrid nanofibers all present high discharge capacity and good cyclic stability. Compared with other TiN hybrid nanofibers reported before, our TiN hybrid nanofibers show higher discharge capacities of 251mAhg−1 at a current density of 0.1Ag−1 in the first cycle. Furthermore, the as-prepared TiN hybrid nanofibers possess good cyclic stability with the capacity retention about 91.8% after 100cycles. The good electrochemical performance and excellent flexibility promote TiN hybrid nanofibers to be a promising and alternative in many applications such as electronic devices.

Template-free synthesis of MgO mesoporous nanofibers with superior adsorption for fluoride and Congo red

MgO mesoporous nanofibers were obtained by a template-free electrospinning method. The unique bumpy-structure was obtained on the surface of nanofibers that could enhance the surface area and provide more active sites for adsorption. The formation mechanism of the bumpy-structure has been investigated. The as-prepared MgO nanofibers with a high surface area of 194.17 m2 g−1 exhibited excellent adsorption capacities for fluoride of 237.49 mg g−1. Furthermore, the MgO nanofibers showed selective adsorption for different organic dyes and have superior adsorption capacity for Congo red (4802.27 mg g−1). The adsorption processes for both fluoride and Congo red were systematically investigated, which were found to follow the pseudo-second-order kinetic model. By comparison with the reported fabrication routes and adsorption capacities of mesoporous MgO, the synthesis process is simple, controllable and template-free, and the superior adsorption performance provided a potential adsorbent for the removal of fluoride and Congo red in wastewater treatment. The high surface area of the MgO mesoporous nanofibers might also promote its application in basic catalysis and other fields.

A Facile synthesis of superparamagnetic Fe3O4 nanofibers with superior peroxidase-like catalytic activity for sensitive colorimetric detection of l-cysteine

Superaramagnetic Fe3O4 nanomaterials are good candidates as enzyme mimics due to their excellent catalytic activity, high stability and facile synthesis. However, the morphology of Fe3O4 nanomaterials has much influence on their enzyme-like catalytic activity. In this work, we have developed a simple polymer-assisted thermochemical reduction approach to prepare Fe3O4 nanofibers for peroxidase-like catalytic applications. The as-prepared Fe3O4 nanofibers show a higher catalytic activity than commercial Fe3O4 nanoparticles. The steady-state kinetic assay result shows that the Michaelis–Menten constant value of the as-obtained Fe3O4 nanofibers is similar to that of horseradish peroxidase (HRP), indicating their superior affinity to the 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 substrate. Based on the outstanding catalytic activity, a sensing platform for the detection of l-cysteine has been performed and the limit of detection is as low as 0.028 μM. In addition, an excellent selectivity toward l-cysteine over other types of amino acids, glucose and metal ions has been achieved as well. This work offers an original means for the fabrication of superparamagnetic Fe3O4 nanofibers and demonstrates their delightful potential applications in the fields of biosensing, environmental monitoring, and medical diagnostics.

Morphologically well-defined Gd0.1Ce0.9O1.95 embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ nanofiber with an enhanced triple phase boundary as cathode for low-temperature solid oxide fuel cells

Controlling triple phase boundary (TPB), an intersection of the ionic conductor, electronic conductor and gas phase as a major reaction site, is a key to improve cell performances for low-temperature solid oxide fuel cells. We report a synthesis of morphologically well-defined Gd0.1Ce0.9O1.95 (GDC) embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) nanofibers and their electrochemical performances as a cathode. Electrospun fibers prepared with a polymeric solution that contains crystalline Ba0.5Sr0.5Co0.8Fe0.2O3-δ particles in ∼200 nm size and Gd(NO3)3/Ce(NO3)3 precursors in an optimized weight ratio of 3 to 2 result in one dimensional structure without severe agglomeration and morphological collapse even after a high calcination at 1000 °C. As-prepared nanofibers have fast electron pathways along the axial direction of fibers, a higher surface area of 7.5 m2 g−1, and more oxygen reaction sites at TPBs than those of GDC/BSCF composite particles and core-shell nanofibers. As a result, the Gd0.1Ce0.9O1.95 embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ nanofiber cell shows excellent performances of the maximum power density of 0.65 W cm−2 at 550 °C and 1.02 W cm−2 at 600 °C, respectively.