Biocidal nanofibers via electrospinning

To achieve biocidal properties, a cyclic N‐halamine precursor, 7,7,9,9‐tetramethyl‐1,3,8‐triazaspiro[4.5]‐decane‐2,4‐dione (TTDD), was synthesized and introduced into nanosized polyacrylonitrile fibrous mat by an electrospinning technique. It was rendered antimicrobial by exposure to dilute hypochlorite solution. Synthesis routes and characterization data are presented. Scanning electron microscopy (SEM) demonstrated that the ultrafine fiber possessed average diameter 414 nm (from 240 to 650 nm). The chlorinated nanofibrous composites provided about 4.9 log reductions of both Gram‐positive bacteria Staphylococcus aureus (ATCC 6538) and Gram‐negative bacteria Escherichia coli O157:H7 (ATCC 43895) within 5 min of contact time. This is indicative of promising possible applications in the filtration of water and air. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

静电纺丝制备聚丙烯腈纳米碳纤维

利用静电纺丝制备连续的聚丙烯腈纳米碳纤维;介绍了静电纺丝的原理、影响静电纺丝的主要因素以及制备纳米碳纤维、纳米活性炭纤维、纳米碳纤维复合材料的方法和原理;分析了静电纺丝产率低,难以得到单向平铺的纤维等问题,影响静电纺丝的参数主要有溶液特性、纺丝工艺参数、纺丝环境参数。由静电纺丝得到纳米聚丙烯腈纤维,然后再经预氧化和碳化制备纳米碳纤维,或把纳米纤维预氧化,经活化、碳化制备纳米活性炭纤维。并指出纳米碳纤维具有巨大的潜在应用空间。     

Polymeric nanofibers containing solid nanoparticles prepared by electrospinning and their applications

Generally, polymer solution or sol–gel is used to produce electrospun nanofibers via the electrospinning technique. In the utilized sol–gel, the metallic precursor should be soluble in a proper solvent since it has to hydrolyze and polycondensate in the final solution; this strategy straitens the applications of the electrospinning process and limits the category of the electrospinnable materials. In this study, we are discussing electrospinning of a colloidal solution process as an alternative strategy. We have utilized many solid nanopowders and different polymers as well. All the examined colloids have been successfully electrospun. According to the SEM and FE SEM analyses for the obtained nanofiber mats, the polymeric nanofibers could imprison the small nanoparticles; however, the big size ones were observed attaching the nanofiber mats. Successfully, the proposed strategy could be exploited to prepare polymeric nanofibers incorporating metal nanoparticles which might have interesting properties compared with the pristine. For instance, PCL/Ti nanofiber mats exhibited good bioactivity compared with pristine PCL. The proposed strategy can be considered as an innovated methodology to prepare a new class of the electrospun nanofiber mats which cannot be obtained by the conventional electrospinning technique.     

Fabrication of cadmium titanate nanofibers via electrospinning technique

Here we present an electrospinning technique for the fabrication of cadmium titanate/polyvinyl-pyrrolidone composite nanofibers. The composite nanofibers are then annealed at 600 °C to obtain ilmenite rhombohedral phase cadmium titanate nanofibers. The structure, composition, thermal stability and optical properties of as synthesized and annealed cadmium titanate nanofibers are characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy. The average diameter and length of the nanofibers are found to be ～150–200 nm and ～100 μm, respectively.     

Bipolymer nanofibers: Engineering nanoscale interface via bubble electrospinning

Modern applications in biomedicine, drug delivery, and tissue engineering demand versatile materials capable of meeting multifaceted requirements. Conventional mono-functional materials fall short of addressing these complex demands. To tackle this challenge, this study introduces an innovative approach utilizing bubble electrospinning for the fabrication of bipolymeric side-by-side nanofibers. These nanofibers incorporate distinct hydrophilic and hydrophobic domains aligned parallel to their axis, achieved through the electrospinning of polyvinyl alcohol (PVA) as the hydrophilic component, alongside either poly(ε-caprolactone) (PCL) or Nylon6 as the hydrophobic component. The optimal diameter of the bubble electrospinning reservoir was theoretically determined via simulation of electric field using Maxwell 3D software and experimentally validated. Successful electrospinning resulted in nanofibers with hydrophilic and hydrophobic domains derived from PVA/Nylon6 and PVA/PCL polymer combinations. This innovative process yielded nanofibers with diameters as fine as 101 nm in the PVA/Nylon6 bipolymeric nanofibers. Transmission electron microscopy images provide compelling insights into the distinct interfaces formed during polymer-polymer interactions within the nanofibers, manifesting the Janus structure. Furthermore, Fourier-transform infrared spectroscopy confirms the presence of both polymers within the nanofiber matrix. This research represents a significant advancement in the efficient production of bipolymer nanofibers, holding promise for a wide range of applications.     

A method for scale‐up of co‐electrospun nanofibers via flat core‐shell structure spinneret

An approach to the scale‐up of co‐electrospinning via a flat core‐shell structure spinneret has been developed in this study. The spinneret with a flat surface involves shell‐holes and core‐needles. Electric field simulation reveals that the flat core‐shell spinneret configuration creates a more uniform electric field gradient. Experimental study shows that in comparison with the conventional needle co‐electrospinning, core‐shell nanofibers produced by this new designed setup are finer and of better morphology. Composite nanofibers with special morphologies can be fabricated by modifying the structure of this spinneret. The production rate of the core‐shell nanofibers can be enhanced by increasing the hole and needle number of the spinneret. This novel design is expected to provide a promising method towards the massive production of core‐shell nanofibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41027.     

Conductive polypyrrole nanofibers via electrospinning: Electrical and morphological properties

Conductive polypyrrole nanofibers with diameters in the range of about 70-300 nm were obtained using electrospinning processes. The conductive nanofibers had well-defined morphology and physical stability. Two methods were employed. Electrospun nanofibers were prepared from a solution mixture of polypyrrole (PPy), and poly(ethylene oxide) (PEO) acted as a carrier in order to improve PPy processability. Both the electrical conductivity and the average diameter of PPy nanofibers can be controlled with the ratio of PPy/PEO content. In addition, pure (without carrier) polypyrrole nanofibers were also able to be formed by electrospinning organic solvent soluble polypyrrole, [(PPy3)⁺ (DEHS)⁻]_x, prepared using the functional doping agent di(2-ethylhexyl) sulfosuccinate sodium salt (NaDEHS) [Jang KS, Lee H, Moon B. Synth Met 2004;143:289-94. [24]]. Electrospun blends of sulfonic acid (SO₃H)-bearing water soluble polypyrrole, [PPy(SO₃H)-DEHS], with PEO acting as a carrier, are also reported. The factors that facilitate the formation of electrical conduction paths through the electrospun nanofiber segments are discussed.     

Influence of additive on structure of PVDF nanofibers electrospun via new spinneret design

Surface morphology and internal structure of polyvinylidene fluoride (PVDF) nanofibers were investigated in this study. PVDF nanofibers were electrospun by two types of spinnerets, nozzle and channel spinneret, with different contents of tetrabutylammonium chloride (TBAC) and at various take‐up velocities. The new spinneret design, channel spinneret, resulted in thicker fibers while high β‐phase content and small d‐spacing were obtained, especially in the case of low TBAC content. And high TBAC content led to finer PVDF nanofibers with high β‐phase content and small d‐spacing compared to low TBAC content regardless of spinneret types, while an increase in take‐up velocity did not have significant effect on both morphology and internal structure of PVDF nanofibers regardless of TBAC content. It suggests that electrostatic drawing acted dominantly rather than mechanically drawing in the system cooperating TBAC. However, the decreasing difference between two types of spinnerets was observed in terms of β‐phase content with an increase in TBAC content. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1752–1758, 2013     

Preparation of chitosan bicomponent nanofibers filled with hydroxyapatite nanoparticles via electrospinning

Chitosan (CS) bicomponent nanofibers with an average diameter controlled from 100 to 50 nm were successfully prepared by electrospinning of CS and poly(vinyl alcohol) (PVA) blend solution. Finer fibers and more efficient fiber formations were observed with increased PVA contents. On this contribution, a uniform and ultrafine nanofibrous CS bicomponent mats filled with hydroxyapatite (HA) nanoparticles were successfully electrospun in a well devised condition. An increase in the contents of HA nanoparticles caused the conductivity of the blend solution to increase from 1.06 mS/cm (0 wt % HA) to 2.27 mS/cm (0.5 wt % HA), 2.35 mS/cm (1.0 wt % HA), respectively, and the average diameter of the composite fibers to decrease from 59 ± 10 nm(0 wt % HA) to 49 ± 10 nm (0.5 wt % HA), 46 ± 10 nm (1.0 wt % HA), respectively. SEM images showed that some particles had filled in the nanofibers whereas the others had dispersed on the surface of fibers, and EDXA results indicated that both the nanoparticles filled in the nanofibers and those adhered to the fibers were HA particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication of magnetic nanofibers via surface-initiated RAFT polymerization and coaxial electrospinning

A simple and continuous approach for fabricating magnetic polyacrylonitrile nanofibers (MNFs) with the diameter of about 200 nm has been developed by combining surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization and coaxial electrospinning. The RAFT polymerization of acrylonitrile was carried out on the surface of RAFT agent immobilized Fe₃O₄ nanoparticles. The room-temperature saturation magnetizations of the prepared MNFs can be easily adjusted. In addition, the aligned fibers can be conveniently obtained via magnetic electrospinning using a specially designed fiber collector.     

Filtration properties of electrospinning nanofibers

Electrospinning is a relatively simple method to produce submicron fibers from solutions of different polymers and polymer blends. The extensive application in future of electrospinning nanofibers is filtration. In this article, the filtration properties of electrospinning nanofibers were investigated. During the experiments, nanofibers layers with different area weight were electrospun on the spunbonded or meltblown sublayers. Fiber diameter, pore diameter, filtration efficiency as well as filtration resistance of nanofibers web and sublayers were measured, respectively, through a series of experiments. The results show that the fiber diameter of nanofibers is much smaller than that of sublayers. It is also found that the pore diameter of nanofibers web is much smaller than sublayers and coefficient variation of the pore diameter of nanofibers web is much smaller than sublayers. Moreover, the filtration efficiency and filtration resistance of sublayers are lower than nanofibers webs. The balance between efficiency and press drop is also investigated in the article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1285–1290, 2006     

Splashing needleless electrospinning of nanofibers

This article proposes a new needleless electrospinning apparatus applying the method of splashing polymer solution onto the surface of a metal roller spinneret. When a high voltage is applied, many spinning jets form on the free surface of polymer solutions. Multiple electrified jets undergo strong stretching and bending instability, solvent evaporates, and solidified nanofibers deposit on the collector, as in an ordinary single‐needle electrospinning process. The production of nanofibers is enhanced by 24–45 times comparing with a single‐needle system. And the productivity is easy to scale up. The effects of processing parameters, including solution concentration, applied voltage, distance between spinneret to collector, and rotational speed of the roller spinneret on the morphology of nanofibers are investigated in this article. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Polymer melt differential electrospinning from a linear slot spinneret

Preparation of melt electrospun fibers with high efficiency and high productivity remains a big challenge. A polymer melt differential electrospinning system with linear slot spinneret (LSSP) was proposed in this work. Under a high electric field, multiple jets distributed at the tip of LSSP were self-organized from the polymer melt film with controlled thickness. The spinning parameters were investigated, and the electric filed between spinneret and collector was analyzed. The results showed that the interjet distance decreased significantly with the decrease of the thickness of polymer melt film and the Tayler cone size. The smallest average interjet distance of 1.9 mm with deviation of 0.5 mm was obtained under the condition of applied voltage of 45 kV, collecting distance of 9 cm, temperature of 250 °C, and slot thickness of 0.2 mm. The high output of 75.6 g/h was achieved and could be increased just by increasing the slot width. It was demonstrated that the proposed technology was a promising way to fabricate melt electrospun fibers with high efficiency. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48922.     

Physical and electrochemical studies of polyphenylsilane-derived porous carbon nanofibers produced via electrospinning

Polyacrylonitrile (PAN)/polyphenylsilane (PPS)-based composite carbon nanofibers (CCNFs) are prepared by one-step electrospinning and subsequent thermal treatment to produce organic-inorganic hybrid CCNFs. We investigate the electrochemical behavior and structural properties of these CCNF materials as a function the PAN/PPS ratio. The CCNFs show large specific surface area, high electrical conductivity and high thermal stability. In addition, the electrochemical performance of the organic–inorganic hybrid CCNF electrode is improved by the special porous structure and the silicon oxycarbide (Si–O–C)-related structure.     

Antibacterial ciprofloxacin HCl incorporated polyurethane composite nanofibers via electrospinning for biomedical applications

We report on the preparation and characterization of polyurethane (PU) composite nanofibers by electrospinning. Two different approaches were adopted to obtain the PU composite nanofibers. In the first approach, a homogeneous solution of 10 wt% PU containing ciprofloxacin HCl (CipHCl) drug was electrospun to obtain PU/Drug composite nanofibers. And in the second approach, the PU with ciprofloxacin HCl drug and ceramic hydroxyapatite (HA) particles were electrospun to obtain the PU/Drug and PU/Drug/HA composite nanofibers. The surface morphology, structure, bonding configuration, optical and thermal properties of the resultant products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and UV–vis spectroscopy. The antibacterial activity was tested against common food borne pathogenic bacteria, namely, Staphylococcus aureus, Escherichia coli by the minimum inhibitory concentration (MIC) method. Our result results demonstrate that these composite nanofibers possess superior characteristics which can utilized for variety of applications.     

Field-responsive superparamagnetic composite nanofibers by electrospinning

Superparamagnetic polymeric nanofibers were produced via an electrospinning technique from colloidally-stable suspensions of magnetite nanoparticles in polyethylene oxide and polyvinyl alcohol solutions. The magnetite nanoparticles were aligned in columns parallel to the fiber axis direction within the fiber by the electrospinning process. The polymer/magnetite nanofibers exhibited superparamagnetic behavior at room temperature, and deflected in the presence of an applied magnetic field. The mechanical properties of the nanofibers were maintained or improved after incorporating the magnetite nanoparticles.     

Upward needleless electrospinning of multiple nanofibers

A new approach to electrospinning of polymer nanofibers is proposed. A two-layer system, with the lower layer being a ferromagnetic suspension and the upper layer a polymer solution, is subject to a normal magnetic field provided by a permanent magnet or a coil. As a result, steady vertical spikes of magnetic suspension perturbed the interlayer interface, as well as the free surface of the uppermost polymer layer. When a normal electric field is applied in addition to the system, the perturbations of the free surface become sites of jetting directed upward. Multiple electrified jets undergo strong stretching by the electric field and bending instability, solvent evaporates and solidified nanofibers deposit on the upper counter-electrode, as in an ordinary electrospinning process. However, the production rate is shown to be higher.     

Needle and needleless electrospinning for nanofibers

A metallic needle is most often used in conventional electrospinning, where a point‐plate electric field with nonuniform distribution is formed in single‐needle electrospinning (SNE). Low flow rate in SNE has restricted the application of electrospinning on an industrial scale. Multiple needles have been introduced to enhance the flow rate. However, multiple needles make the electric field distribution much more complex. To resolve this problem, alternative electrospinning setups with more uniform electric field have to be developed. Flat spinnerets have been demonstrated to replace the needle in SNE setups. The operating diagrams for flat spinneret electrospinning (FSE) were determined and differed significantly from those for SNE. Nanofibers produced by FSE were more uniform than those from SNE. These differences were explained by the differences in electric fields simulated using finite element analysis (FEA). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrospun nanofibers from a multihole spinneret with uniform electric field

This study presents a multihole spinneret with a metal flat electrode to obtain uniform electric field and meet a high production requirement. We demonstrate that the multihole spinneret produces finer fiber diameters and more concentrated fiber mat compared to the conventional multineedle electrospinnig system. This study focuses on the effect of the electric field distribution on the spinning process and the resultant nanofibers. The three‐dimensional electric field simulation results show that the multihole spinneret creates not only a more uniform electric field, but also a stronger electric field except for the area very close to the spinneret. The measurement of the electric field verifies the simulation results. This study shows that fine fibers, as well as concentrated and thick fiber mat can be obtained by this multihole electrospinning system at a high production rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3221–3228, 2013     

Fabrication and characterization of carbon nanofibers with a multiple tubular porous structure via electrospinning

Carbon nanofibers with a multiple tubular porous structure were prepared via electrospinning from a polymer blend solution of polyacrylonitrile (PAN) and polylactide (PLA) followed by carbonization. The electrospun composite nanofibers underwent pre-oxidization and carbonization, which selectively eliminated PLA phases and transformed the continuous PAN phase into carbon, thereby porous structure formed in the carbon nanofibers. The morphologies of as-spun, pre-oxidized and carbonized nanofibers were studied by scanning electron microscope (SEM) and transmission electron microscopy (TEM). It was found that carbon nanofibers with an average diameter about 250 nm and a multiple tubular porous structure were obtained. The chemical changes during thermal treatment were studied by Fourier transform infrared spectrometer (FTIR), Raman spectra, differential thermal analysis (DTA) and thermogravimetric analysis (TG). The results showed that PLA phases were effectively removed and the continuous PAN phase was completely carbonized. The obtained carbon nanofibers had more disordered non-graphitized structures than non-porous nanofibers.