Nanofiber Webs Research Articles

In situ synthesis of chemically active ZIF coordinated with electrospun fibrous film for heavy metal removal with a high flux

In this work, Zeoliticimidazolate framework-8 (ZIF-8)-based hybrid nanofibrous films were successfully fabricated by a simple strategy of in situ loading on a polymer substrate. In addition, the hybrid film was confirmed by scanning electron microscopy and X-ray diffraction. This hybrid-structure nanofibrous web was applied in heavy metal treatment by combining the unique properties of microporous material as active sizes for heavy metal adsorption with a high surface area of electrospun polyacrylonitrile (PAN) film as the porous substrate. This structure performed with a high permeation flux of 180 L/(m2·h·psi), and the capacity of heavy metal removal from water increased more than three times compared with pure electrospun PAN film. Moreover, the capacity of heavy metal removal was maintained after several recycling processes, which is a significant characteristic of the hybrid electrospun film as a filtering membrane. The hybrid electrospun film is suitable for heavy metal removal from water.

Electrospinning, preparation and photoluminescence properties of CoNb2O6:Dy3+ incorporated polyamide 6 composite fibers

3mol% Dy3+ doped cobalt niobate (CoNb2O6) compound has been synthesized by molten salt method using Li2SO4/Na2SO4 salt mixture as a flux at a relatively low temperature as compared to solid state reaction. X-ray diffraction patterns of 3mol% Dy3+ doped CoNb2O6 compound indicated orthorhombic columbite single phase. SEM analysis revealed that Dy3+ doped CoNb2O6 has a submicron particle size. The photoluminescence of CoNb2O6:Dy3+ phosphor has exhibited in a dominant yellow emission at 579nm with an excitation wavelength of 366nm. The synthesized submicron phosphor particles were successfully incorporated into Polyamide 6 fibers by utilizing electrospinning technique. The average fiber diameter obtained through the process ranged between 192±62nm and 387±341nm. Mechanical characteristics of the produced nanofibrous webs were strongly influenced by the fiber morphologies and size (diameter) distribution rather than the phosphor particles incorporated into the fibers and/or located on the web. The photoluminescence of composite fiber material increased with the increasing phosphor content.

Effects of electric field on the maximum electro-spinning rate of silk fibroin solutions

Owing to the excellent cyto-compatibility of silk fibroin (SF) and the simple fabrication of nano-fibrous webs, electro-spun SF webs have attracted much research attention in numerous biomedical fields. Because the production rate of electro-spun webs is strongly dependent on the electro-spinning rate used, the electro-spinning rate becomes more important. In the present study, to improve the electro-spinning rate of SF solutions, various electric fields were applied during electro-spinning of SF, and its effects on the maximum electro-spinning rate of SF solution as well as diameters and molecular conformations of the electro-spun SF fibers were examined. As the electric field was increased, the maximum electro-spinning rate of the SF solution also increased. The maximum electro-spinning rate of a 13% SF solution could be increased 12×by increasing the electric field from 0.5kV/cm (0.25mL/h) to 2.5kV/cm (3.0mL/h). The dependence of the fiber diameter on the present electric field was not significant when using less-concentrated SF solutions (7–9% SF). On the other hand, at higher SF concentrations the electric field had a greater effect on the resulting fiber diameter. The electric field had a minimal effect of the molecular conformation and crystallinity index of the electro-spun SF webs.

Two‐Dimensional Piezoelectric MoS2‐Modulated Nanogenerator and Nanosensor Made of Poly(vinlydine Fluoride) Nanofiber Webs for Self‐Powered Electronics and Robotics

AbstractWith the widespread use of wearable electronics, portable and flexible energy harvesting devices with a high sensitivity have attracted considerable interest. Herein, an ultrasensitive piezoelectric nanogenerator (PNG) made of a few layers of 2 D‐MoS2‐incorporated electrospun poly(vinlydine fluoride) (PVDF) nanofiber webs (NFW) is described for the first time. As a result of the semiconducting properties and piezoelectric functionalities of 2 D‐MoS2, the resultant piezoelectric performance of PNG can be modulated, which leads to a material suitable for wearable electronics to power devices and to fabricate self‐powered biomedical nanosensors for diagnosis, such as heartbeat monitoring, pressure mapping from footsteps, and speech signal abnormality. We have demonstrated that our PNG has a 70 times improvement in acoustic sensitivity than nanosensors made of neat PVDF NFW and are able to charge a capacitor quickly (e.g., 9 V is charged within 44 s). As a result of the ultrafast charging performance and external low‐impact detection capability of 2 D‐MoS2‐modulated PNG, this paves the way to design cost‐effective self‐powered wearable electronics and robotics.

Synthesis and studies on effect of indium doping on physical properties of electrodeposited CdSe thin films

Semiconducting CdSe and indium doped CdSe (In: CdSe) thin films have been synthesized on stainless steel and fluorine doped tin oxide coated glass substrates in an aqueous medium using a potentiostatic mode of electrodeposition. The doping concentration of indium has been optimized to 0.15 vol% using the reliable photoelectrochemical technique. To study the effect of indium doping these films are characterized using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, Raman spectroscopy, contact angle measurement and UV–visible spectrophotometry techniques. CdSe and In: CdSe thin films are low crystalline with a cubic crystal structure. The valence states of CdSe and In: CdSe thin films are analyzed by means of XPS. Undoped CdSe thin film shows fiberlike morphology, which transforms into a beautiful web of nanofibers upon doping. The Elemental composition of both films analyzed by means of energy dispersive X-ray spectroscopy. Raman studies show transverse optical and longitudinal optical modes of phonon. Indium doping improves the hydrophilic nature of CdSe photoanode. The optical band gap (direct) found to be decreased from 2.02 to 1.67 eV upon indium doping. Both films are photoactive in nature.

Electrospun N-doped porous carbon nanofiber webs as anodes for lithium-ion batteries

Nitrogen-doped porous carbon nanofiber webs (NPCNFs) were prepared from mixtures of polyacrylonitrile and melamine byelectrospinning, followed by oxidative stabilization, carbonization and steam activation. The NPCNFs are free-standing,exhibit an interconnected non-woven nanofibrous morphology and a well-developed microporous structure, and can be used directly as anodes for lithium ion batteries without adding binder or conductive filler. The NPCNF from the mixture with a melamine/polyacrylonitrile mass ratio of 1:3 has a high specific capacity of 856 mAh·g-1 and a satisfactory rate capability. These intriguing characteristics make the NPCNFs promising anode candidates for high-performance lithium ion batteries.

Transport properties of aerogel-based nanofibrous nonwoven fabrics

In this study, nanofiber web was laminated onto nonwoven fabric and silica aerogels were applied between these two layers during laminating process. The transport properties of the obtained fabrics were examined in terms of air permeability, water vapor permeability as well as thermal performance. Especially, the effect of aerogel areal density and thermal adhesive on thermal insulation properties of layered fabrics were investigated and analyzed. It was observed that air permeability and water vapor permeability of these layered fabrics were determined by nanofiber web and nonwoven substrate respectively, aerogels present in this layered structure showed limited influence on air permeability and insignificant effect on water vapor permeability. Results also indicated that thermal resistance of layered fabrics was directly proportional to areal density of aerogel with a correlation coefficient 0.91. The use of adhesive in textile structure would significantly reduce the thermal insulation performance. A series model was considered for thermal resistance of layered fabrics, and the results showed a good agreement between theoretical model and experimental values.

Fast-Dissolving, Prolonged Release, and Antibacterial Cyclodextrin/Limonene-Inclusion Complex Nanofibrous Webs via Polymer-Free Electrospinning.

We have proposed a new strategy for preparing free-standing nanofibrous webs from an inclusion complex (IC) of a well-known flavor/fragrance compound (limonene) with three modified cyclodextrins (HPβCD, MβCD, and HPγCD) via electrospinning (CD/limonene-IC-NFs) without using a polymeric matrix. The experimental and computational modeling studies proved that the stoichiometry of the complexes was 1:1 for CD/limonene systems. MβCD/limonene-IC-NF released much more limonene at 37, 50, and 75 °C than HPβCD/limonene-IC-NF and HPγCD/limonene-IC-NF because of the greater amount of preserved limonene. Moreover, MβCD/limonene-IC-NF has released only 25% (w/w) of its limonene, whereas HPβCD/limonene-IC-NF and HPγCD/limonene-IC-NF released 51 and 88% (w/w) of their limonene in 100 days, respectively. CD/limonene-IC-NFs exhibited high antibacterial activity against E. coli and S. aureus. The water solubility of limonene increased significantly and CD/limonene-IC-NFs were dissolved in water in a few seconds. In brief, CD/limonene-IC-NFs with fast-dissolving character enhanced the thermal stability and prolonged the shelf life along with antibacterial properties could be quite applicable in food and oral care applications.

A New Concept of Flexible Electrodes for Lithium/Sulfur Batteries

According to the progress of electronics industry, electronic devices have been diversified to various forms such as roll-up displays, smart cards, and wearable devices. Flexible electronic devices are demanding has various properties such as lightweight, ultrathin, and flexibility. Therefore, batteries as their power sources are required to have same properties. In addition, high energy density and operational safety are needed. Until now commercial lithium-ion batteries (LIBs) are the only viable candidates for flexible devices. Recently, the flexible lithium/sulfur (Li/S) battery has been proposed with a high theoretical energy density of 2600 Wh kg-1. As most active materials considered in these studies are rigid and brittle, flexible cathodes were achieved by the physical combination of rigid active materials with flexible current collectors such as carbon-based materials or polymers. This integrated design has two inevitable disadvantages; (1) during deformation the active material can detach from the current collector; (2) the capacity per electrode is reduced by the presence of electrochemically inactive materials such as current collector, binder and conducting agents. Therefore, there is a strong need for a new approach to the flexible cathode which consists of only active material without a separate current collector. Sulfurized polyacrylonitrile (SPAN) composite could be a good candidate due to its good electric conductivity, high sulfur utilization, and stable cycle life. In addition, it can be fabricated as either particle or nanofiber. However, the SPAN electrodes reported so far were prepared by mixing SPAN, conductive agent, and binder which were pasted on metallic current collector. In carbon nanotube paper and graphene paper, it is well-known that the strain during deformation decreases with the diameter of the fiber. Therefore, in this work, the SPAN nanofiber web cathode which does not include conductive agent, binder, as well as current collector was fabricated from PAN nanofiber web and sulfur by heat treatment process. Also, pre-lithiated carbon felt was used as anode in order to make all flexible full cell and investigated its electrochemical properties.

Preliminary Investigation into the Antimicrobial Activity of an Electrospun Polyamide Nanofibrous Web with Micro Particles of Baltic Amber

Preliminary Investigation into the Antimicrobial Activity of an Electrospun Polyamide Nanofibrous Web with Micro Particles of Baltic Amber

Effect of Iodination Temperature on the Polyvinyl Alcohol Based Carbon Nanofiber for Lithium Ion Battery Anodes

Nanofibers has broad application areas including energy, filtration, biomedical and many other engineering fields due to their high porosity, high surface area to volume ratio. Researchers studied several materials and production methods in order to obtain different superior properties from nanofibers. Recently, lithium ion batteries has achieved huge importance due to growing demand for portable electronics, electric vehicles and grid energy storage,etc. Batteries have different components among them anodes have crucial importance on the battery capacity, cycle life and rate capability. One of the promising 1D anode material as carbon nanofibers can provide fast electron transport, reduced lithium ion diffusion lenghts and enhanced surface area comparing to commercial electrodes. There are several carbon nanofiber precursors, such as polyacrylonitril(PAN), lignin, pitch, polyimide(PI).. etc. among them polyvynil alcohol has important advantage because of their environmentally friendly, water soluble and low cost properties. Polyvinyl alcohol (PVA) is a water-soluble polyhydroxy polymer with a broad range of industrial and technical applications. It has been used as a carbon precursor or directly used as anode, cathode or separator in Li-ion batteries. PVA based carbon nanofibers can be easily obtained by electrospinning and subsequent carbonization PVA might be an environmentally friendly alternative material for PAN based carbon fibers. However rather than oxidative stabilization in PAN based precursors, linear PVA chains must be stabilized via other suitable processes. There are various routes that have been proposed to suppress the thermal degradation of PVA before carbonization step, such as using HCl, H2SO4, NH4 vapour or chemical impregnation into different salts. Stabilization of PVA under iodine vapour is a promising approach with high carbon yield for obtaining carbon nanofibers. In this study, we investigated the effect of iodination temperature on the morphology, chemical structure, and electrical properties of carbon nanofiber webs fabricated from electrospun PVA nanofibers. Obtained nanofibers were subjected to different iodination temperature and then converted into carbon nanofibers. It was found that increasing the iodination temperature provides higher carbon yield. Carbon nanofibers were used as binder free, self- standing anode for lithium ion battery. Battery performances showed that PVA based carbon nanofibers are promising anode materials for lithium ion batteries.

Electrospun polyvinylidene fluoride-polyoctafluoropentyl acrylate blend based piezocapacitive pressure sensors

In this study, neat polyvinylidene fluoride (PVDF) and its blend with polyoctafluoropentyl acrylate (POFPA) were electrospun under controlled conditions, and studied for their physico-mechanical and piezo-responsive behaviours. Initial FTIR studies confirmed the effect of thermal annealing on the crystalline phase transformations and chaindipole orientation in PVDF as a function of POFPA content. SEM data exhibited “root-shaped” morphology in the blend sample. Higher tensile strength (65.2±0.4 kPa) for the blend compared to that of neat PVDF (1.5±0.03 kPa) confirmed the elastic nature of the blend nanoweb. Peak-to-peak piezoelectric output signal (Vp-p 0.976 V) and capacitance hysteresis showed reduced tendency, whereas the capacitance maxima is higher for the blend sample (Cmax 0.182 nF) compared to that of neat PVDF (Vp-p 1.195, Cmax 0.147 nF). Overall, even 10 wt% addition of POFPA in PVDF greatly enhanced the tensile strength of nanofiber web along with improved piezocapacitive characteristics, a combination of great potential for many commercial sensor applications.

Effect of solvent and blended polymer on electrical conductivity of PEDOT:PSS/polymer blended nanofibers

Poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS) and polyethylene oxide (PEO) (or polyvinyl alcohol (PVA)) blended electrospun nanofibers were prepared in the presence of dimethyl sulfoxide (DMSO) and ethylene glycol (EG). The effects of added solvents (DMSO and EG) and blended polymers (PEO and PVA) on electrical conductivity and current-voltage (I-V) response were investigated. Electrical conductivity was dependent on both the additional solvent and blended polymers. PEDOT:PSS/PEO blended nanofibers showed a much higher electrical conductivity than PEDOT:PSS/PVA. EG blended PEDOT:PSS/PEO blended nanofibers showed much higher electrical conductivity than DMSO. The PEDOT:PSS/PEO/EG blended nanofibers web showed the highest value in I-V response.

Polyacrylonitrile/polyaniline composite nanofiber webs with electrostatic discharge properties

In this study, composite nanofibers of polyacrylonitrile (PAN) and polyaniline (PANI) were successfully produced by electrospinning technique and the effects of different dopants such as camphorsulfonic acid (CSA), dodecylbenzene sulfonic acid (DBSA) and dodecylbenzene sulfonic acid sodium salt (DBSANa+), and different solvents such as dimethylsulfoxide (DMSO) and N, N′-dimethylformamide (DMF) on the properties of PAN/PANI composite nanofiber webs have been investigated. It has been observed that nanofibers produced from DMSO generally had larger fiber diameters and higher breaking strength than nanofibers produced from DMF. CSA could dope better than DBSA(iso) and DBSANa+. CSA resulted in the highest conductivity when DMSO was used while it resulted in lower conductivity in DMF. The insulator PAN became a semiconductive material with the incorporation of CSA-doped PANI. The highest electrical conductivity obtained was 10−6 S/cm which is in the range suitable for electrostatic discharge applications.

Cellulose acetate nanofiber electrospun on nylon substrate as novel composite matrix for efficient, heat-resistant, air filters

Cellulose acetate (CA) nanofibers were prepared via electrospinning to obtain a high quality factor (QF) fibrous mat for aerosol particle filtration. To this purpose, special attention was paid to the substrate material used to collect the nanofibers. Different materials (glassine paper, Lyocell, nylon grids) were investigated for use as substrates in the membrane spinning process. Membrane and membrane fiber morphologies were characterized by optical microscope and scanning electron microscope (SEM) analyses. Results show that the arrangement of the membrane fibers is directly correlated to the morphology of the collecting substrate material. Experiments shows that the electrospun nanofiber web tends to recreate the specific character of the supporting textile texture. A support with a pronounced bi-dimensional structure should be preferred. A regular grid, made of nylon, is selected for the composition with CA nanofibres.By maintaining the same support, various electrospinning parameters such as the spinning solution CA concentration (14wt%, 18wt%) and spinning volume (15–120μL) of the membranes are tested in terms of air filtration performance. Filtration tests are performed by measuring the filter penetration against neutralized aerosol particles. Basis weight, solid volume fraction and thickness parameter were investigated to find the best arrangement.The filtration efficiency of stacked layers is analyzed at variable thickness of the building block element. An electrospun membrane of above 60μm thickness, combined with the selected substrate, increases the QF and improve its reproducibility. The QF can be further increased with an optimized porosity of the nylon substrate. The best QF of 0.080±0.050Pa−1 at 300nm was obtained by spinning a 14wt% CA solution in an acetone- DMSO-acetic acid solvent mixture on a nylon grid with 100μm mesh size producing fleeces with a very low pressure drop (7Pa). Thermogravimetric analyses (TGA) and SEM imaging demonstrated the stability of the composite filter morphology up to 200°C.

Surface Morphology Analysis and Mechanical Characterization of Electrospun Nanofibrous Structure

The extraordinary properties of nanofibrous structure have gained ever-increasing appeal as an attractive candidate in a myriad of applications, especially for the water filtration. This type of structure has permeability due to its porous structure. Electrospinning is one of the most viable approaches in fabricating nanofibrous web that exhibits novel and outstanding performance in membrane separation as compared to those produced through conventional methods. Thus, the optimization of electrospinning processes is actively pursued by many researchers in order to obtain the best structure suitable for real-life applications. In this study, the surface morphology analysis and mechanical characterization of nanofibrous structure are addressed. For this purpose, polyvinylidene fluoride (PVDF) is considered. The polymeric nanofibrous structures are fabricated through electrospinning technique. Parameters such as polymer concentration and applied voltage for electrospinning process were varied and the resulting morphology of the structure were observed using SEM. In addition, the macroscopic mechanical responses of the structure were probed by means of tensile tests with special attention given to membrane anisotropy and behavior under cyclic loading.

Adhesion and protective properties of electrospun PVA/ES composites obtained by using spiral disk spinnerets

The parameters of electrospinning polyvinylalcohol (PVA) of different molecular weights using spiral disk spinnerets were explored. Ethylene-propylene side-by-side (ES) nonwoven was used as the substrate. Electrospun PVA/ES composite membranes were fabricated by laminating a nanofiber web onto the nonwoven substrate via the hot-press method. The adhesion properties between the PVA nanofiber mat and the ES nonwoven were studied. The results showed that the adhesion properties were significantly affected by temperature, pressure, and processing time. The resultant composite membranes, when treated at 145℃ with a pressure of 100 Pa for 10 minutes, exhibited a preferable adhesion energy of 7.95 J/m2 and a maximum peeling strength of 20.17 cN, as well as a maximum air permeability of 73.92 dm3/(m2s). Simultaneously, the effect of electrospinning time on the characteristics of PVA/ES composites was also explored. The filtration efficiency increased with the prolongation of the electrospinning time, whereas the air permeability decreased. All of the samples were grade A in terms of the electrostatic half-life period (which was less than two seconds), and the softness slowly declined with the addition of nanofibrous layers. The breaking stress, the initial modulus, and the elongation were enhanced with the prolongation of electrospinning time.

Optimal spinneret layout in Von Koch curves of fractal theory based needleless electrospinning process

Needleless electrospinning technology is considered as a better avenue to produce nanofibrous materials at large scale, and electric field intensity and its distribution play an important role in controlling nanofiber diameter and quality of the nanofibrous web during electrospinning. In the current study, a novel needleless electrospinning method was proposed based on Von Koch curves of Fractal configuration, simulation and analysis on electric field intensity and distribution in the new electrospinning process were performed with Finite element analysis software, Comsol Multiphysics 4.4, based on linear and nonlinear Von Koch fractal curves (hereafter called fractal models). The result of simulation and analysis indicated that Second level fractal structure is the optimal linear electrospinning spinneret in terms of field intensity and uniformity. Further simulation and analysis showed that the circular type of Fractal spinneret has better field intensity and distribution compared to spiral type of Fractal spinneret in the nonlinear Fractal electrospinning technology. The electrospinning apparatus with the optimal Von Koch fractal spinneret was set up to verify the theoretical analysis results from Comsol simulation, achieving more uniform electric field distribution and lower energy cost, compared to the current needle and needleless electrospinning technologies.

Eco-Friendly Fabricated Porous Carbon Nanofibers Decorated with Nanosized SnOx as High-Performance Lithium-Ion Battery Anodes

In this work, one-dimensional polyvinylpyrrolidone-derived porous carbon nanofibers decorated with SnOx nanoparticles (denoted as SnOx@PCNFs) were prepared by an electrospinning technique, followed by a simple one-step heat treatment and a postetching process. The structural evolution of SnOx and the morphological change of the carbon nanofiber webs during the heat treatment are investigated by varying the content of the SnOx precursor in the electrospinning solutions. The highly interconnected pores, created by etching off the in situ generated SiO2 template in the carbon nanofibers, are beneficial for the easy penetration of Li+-carrying electrolyte into the nanocomposites and thus enable the direct contact between embedded SnOx nanoparticles and electrolyte. When tested as anode materials for lithium-ion batteries, SnOx@PCNFs with optimal SnOx component show outstanding initial reversible capacity of 1057 mA h g–1 at 0.2 A g–1, long cycling capability (511 mA h g–1 at 1 A g–1 after 900 cycles), and goo...

이중전기방사법을 이용한 키토산/PVA 나노섬유 웹과 필름의 제조 및 특성

Polyvinyl alcohol (PVA) is a non-toxic, water-soluble, biocompatible, and biodegradable synthetic polymer, which is widely used in the biomedical field. As one of the most abundant natural polysaccharides, chitosan is well known for its biocompatible and biodegradable properties. Blended chitosan/PVA nanofiber webs and films were investigated for applications in the biomedical field. Pure chitosan nanofiber web, blended nanofiber web, and skin-core nanofiber webs were prepared by electrospinning. Chitosan/PVA blended films were prepared by the solution casting method. Scanning Electron Microscope photographs showed that the skin-core nanofiber web (chitosan skin, PVA core) had the best uniformity and was suitable for electrospinning. The PVA, chitosan, and blend films had better hydrophilicity and moisture regain than PVA, blend, and skin/core nanofibers. The FT-IR and DSC analyses demonstrated compatibility between PVA and chitosan. Also, nanofiber web and films with chitosan had better mechanical properties than pure PVA nanofiber web and film; the presence of chitosan reduced the tensile strength of nanofiber webs and films, but increased their Young`s modulus. All nanofiber webs showed remarkably similar elongation, and chitosan was shown to reduce the elongation of films. This study concluded that blended chitosan/PVA nanofiber web and films are well suited for applications in medical materials, such as wound dressing.