Electrospun Polystyrene Fibers Research Articles

Polyaniline hollow tubes loading tiny platinum nanoparticles for boosting methanol oxidation

We report a facile approach to prepare high density of tiny Pt nanoparticles less than 3 nm loaded on the polyaniline hollow tubes in uniform way. Polyaniline hollow tubes in diameter of micro size are synthesized via the polymerization of aniline onto the template of sulfonated electrospun polystyrene fibers, followed by the removal of core polystyrene fibers. The as-prepared highly crystalline Pt nanoparticles on the surface of polyaniline microtubes show the much higher electrochemical active surface area of 90.49 m2/g, high mass catalytic current density, good durability toward the methanol oxidation reaction as well as the excellent carbon monoxide tolerance. The hollow-structure-conductive-polymer- based synthesis strategy for high performance catalyst in this study could be applied to produce other catalysts with the enhanced activities.

Wall thickness-tunable AgNPs-NCNTs for hydrogen peroxide sensing and oxygen reduction reaction

The nitrogen-rich carbon nanotubes doped with well-dispersed fine silver nanoparticles (AgNPs-NCNTs) were fabricated by carbonization of the silver-polydopamine (AgNPs-PDA) multilayers. The wall thickness of the nanotube is tunable by varying the numbers of the layer-by-layer alternate deposition of Ag and PDA on electrospun polystyrene (PS) fibers. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrate the tunable tubular structure by various AgNPs-PDA layers and the uniform distribution of fine silver nanoparticles with the size of about 6 nm in the nanotube. The composition of the nanocomposites was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrate that the electrochemical properties of AgNPs-NCNTs depend on the numbers of AgNPs-PDA layers. The composite material shows excellent electrocatalytic activity to H2O2 reduction, with a low limit of detection (LOD) of 0.03 μM (S/N ≥ 3) and a sensitivity of 1004.9 μA mM−1 cm−2. Meanwhile, the AgNPs-NCNTs present a high catalytic activity to O2 reduction reaction with near 4-electron transfer process. The related catalysis mechanisms were proposed and validated by rotating disk electrode and dissolved oxygen analysis. This catalyst shows high stability for oxygen reduction over 500 cycles.

Surface morphologies of electrospun polystyrene fibers induced by an electric field

The electric field plays a key role in the formation of fibers during the electrospinning process. The electric field strength and shape caused by the applied voltage between the spinneret and collector govern the electrospinning process. In this study, a comprehensively designed and correctly implemented analysis was carried out to investigate the effects of the electric field on jet behavior and fiber morphology. Both working distance and applied voltage, respectively, were adjusted to manipulate the electric field shape and strength. The three-dimensional electric fields were simulated to understand the electric field distribution; in addition, a high-speed camera was adopted to capture the images of jet motion. Four parameters, namely straight jet length, envelope cone, height of the bending area, and velocity of the bending jet, were measured to describe the jet behavior. It can be revealed that the shape and strength of the electric field are responsible for the jet behavior and the fiber morphology, which include resultant ripples, grooves, and pores.

Three-Dimensional Nitrogen-Doped Hollow Carbon Fiber with a Micro-Scale Diameter as a Binder-Free Oxygen Electrode for Li-O2 Batteries

A nitrogen-doped hollow carbon fiber was prepared using polydopamine and electrospun polystyrene fibers as a sacrificial template for the oxygen electrode of Li-O2 batteries. Owing to the fiber structure, a binder is not needed to fabricate the electrode, which eliminates the possibility of side reactions associated with a binder. It was demonstrated that the hollow tubular structure with a large inner diameter is highly effective for accommodating a substantial amount of discharge products without hindering the mass transfer of reactants, even under the fully discharged condition. The reversibility and rate capability were improved by optimizing the length of the fiber. The nitrogen-doped carbon reduced the overall overpotential between the oxygen reduction and oxygen evolution reactions. Therefore, the nitrogen-doped hollow carbon fiber can be used to obtain a highly effective oxygen electrode for Li-O2 batteries.

Aligned continuous cylindrical pores derived from electrospun polymer fibers in titanium diboride

AbstractThe use of electrospun polystyrene (PS) fibers to create continuous long range ordered multi‐scale porous structures in titanium diboride (TiB2) is investigated in this work. The introduction of electrospun PS fibers as a sacrificial filler into a colloidal suspension of TiB2 allows for easy control over the pore size, porosity, and long range ordering of the porous structures of the sintered ceramics. Green bodies were formed by vacuum infiltrating an electrospun‐fiber‐filled mold with the colloidal TiB2 suspension. The size, volume, distribution, and dispersion of the pores were optimized by carefully selecting the sacrificial polymer, the fiber diameter, the solvent, and the solid content of TiB2. The green bodies were partially sintered at 2000°C to form a multi‐scale porous structure via the removal of the PS fibers. Aligned continuous cylindrical pores homogeneously distributed across the samples were derived from the PS fibers in a range of ~5‐20 μm and partial sintering produced inter‐particle porosity with sizes of ~0.3‐1 μm. TiB2 near‐net‐shaped parts with the multi‐scale porosities (~50‐70%) were successfully cast and sintered. This low‐cost processing technique can be used in the production of thermally and mechanically anisotropic structures into near‐net shape parts, for extreme environment applications, such as high temperature insulation.

Effects of Jet Path on Electrospun Polystyrene Fibers.

In this study we investigated the effects of jet path on the morphology and mat size of synthetic polystyrene (PS) fibers during the electrospinning process. In addition, the mechanism of the fiber mats, which were prepared by varying the solution concentration, was evaluated. The straight jet length, envelope cone and whipping frequency of each electrospun jet were studied using images captured by a high-speed photography camera. The results showed that higher solution concentrations led to longer straight jet lengths, smaller envelope cones and lower whipping frequencies. The diameter and surface morphology of the PS fibers were also characterized by scanning electron microscopy (SEM). It was found that fibers spun with higher solution concentrations exhibited larger diameters and diameter distributions because of their jet path features. Furthermore, the electrospun jets with higher concentrations increased elongation and produced smaller fiber mats and higher breaking forces as a result of their different jet paths, which was a consequence of varying the solution concentration.

Electrospun polystyrene fibers knitted around imprinted acrylate microspheres as sorbent for paraben derivatives

Parabens are used as antimicrobial preservatives in food, cosmetic products and pharmaceuticals regardless of their endocrine disrupting effect. In this study, highly selective molecular imprinted polymers (MIPs) were synthesized in submicron-sizes and converted to an SPME fiber coating through electrospinning process in order to determine parabens in water samples. Conversion of MIP to a fiber is achieved via creation of spacial knitting around MIP by polystyrene. The selectivity and extraction ability of the fibers were compared with the commercial fibers and the corresponding non-imprinted polymer (NIP) coated fiber. The coated fiber showed better extraction ability among them. Also, the results revealed that the fiber has better selectivity for benzyl paraben and the other structurally-related compounds, such as methyl and propyl paraben. Extraction efficiency of prepared fibers for three parabens has been tested by spiking bottled, tap and sea water samples. The recoveries changed between 92.2 ± 0.8 and 99.8 ± 0.1 for three different water types. This method could be used for selective and sensitive determination of parabens in aqueous samples.

Fabrication and assessment of an electrospun polymeric microfiber-based platform under bulk flow conditions with rapid and efficient antigen capture.

This study investigated the fabrication and proof of concept design demonstrating rapid and highly sensitive antigen capture utilizing electrospun polystyrene (PS) microfiber mat substrates paired with vacuum pump pressurization to induce bulk flow. In comparison with conventional flat PS surfaces used for immunoassay purposes, this system optimizes the increased surface area of the electrospun polystyrene (ESPS) fiber mat substrates and the accelerated propagation of the antigen through the detection platform by using a vacuum pump to enable efficient and rapid antigen capture. The novelty of this work was demonstrated through a parametric study detailing how a fiber substrate can capture antigen sensitively and at high speeds. In terms of sensitivity, the current system is comparable to the conventionally used flat PS substrates. Additionally, the amount of antigen captured on a flat PS substrate in 60 minutes was surpassed in under 5 seconds when utilizing the ESPS-vacuum system. Three-dimensional ESPS fiber mats were then noted as a comparison between Damkohler numbers and between flat PS and ESPS-vacuum systems. The bulk flow of the ESPS-vacuum system allows for a Damkohler number of 0.37 indicating a balance between the flow rate and the reaction rate as opposed to a PS flat platform of 5.80 × 104 which illustrates a diffusion rate limited system. Finally, the overall ESPS-vacuum system was tested for its immunoassay capability. A sandwich fluorescence-based immunoassay was performed on both PS flat-diffusion and ESPS-vacuum systems. The ESPS-vacuum system indicated a wider detection range capability from 5 to 1000 ng mL-1 in comparison with the PS flat-diffusion system at 5 to 100 ng mL-1.

Morphology transformations of electrospun polymer fibers annealed on polymer films with thickness-controlled growth rates of undulation

Electrospun polymer fibers have attracted great attention in recent years because of their unique properties and applications in various areas such as tissue engineering and drug delivery. It remains a great challenge, however, to understand the morphology and property changes of electrospun polymer fibers induced by post-treatment, especially thermal annealing. In this work, we investigate the morphology evolution of electrospun polystyrene (PS) fibers thermally annealed on poly(vinyl alcohol) (PVA) films. Driven by the surface and interfacial tensions, the PS fibers transform to a series of regularly aligned anisotropic particles embedded in the PVA films via a Rayleigh instability-type transformation. From the in-situ observed optical microscopy (OM) images, higher growth rates of undulated amplitude can be obtained for thinner PVA films, revealing the effect of the underlying glass substrates.

Tuning the Morphology and Activity of Electrospun Polystyrene/UiO-66-NH2 Metal-Organic Framework Composites to Enhance Chemical Warfare Agent Removal.

This work investigates the processing-structure-activity relationships that ultimately facilitate the enhanced performance of UiO-66-NH2 metal-organic frameworks (MOFs) in electrospun polystyrene (PS) fibers for chemical warfare agent detoxification. Key electrospinning processing parameters including solvent type (dimethylformamide [DMF]) vs DMF/tetrahydrofuran [THF]), PS weight fraction in solution, and MOF weight fraction relative to PS were varied to optimize MOF incorporation into the fibers and ultimately improve composite performance. It was found that composites spun from pure DMF generally resulted in MOF crystal deposition on the surface of the fibers, while composites spun from DMF/THF typically led to MOF crystal deposition within the fibers. For cases in which the MOF was incorporated on the periphery of the fibers, the composites generally demonstrated better gas uptake (e.g., nitrogen, chlorine) because of enhanced access to the MOF pores. Additionally, increasing both the polymer and MOF weight percentages in the electrospun solutions resulted in larger diameter fibers, with polymer concentration having a more pronounced effect on fiber size; however, these larger fibers were generally less efficient at gas separations. Overall, exploring the electrospinning parameter space resulted in composites that outperformed previously reported materials for the detoxification of the chemical warfare agent, soman. The data and strategies herein thus provide guiding principles applicable to the design of future systems for protection and separations as well as a wide range of environmental remediation applications.

Extreme Toughness Exhibited in Electrospun Polystyrene Fibers

Polystyrene (PS) commonly exhibits brittle behavior and poor mechanical properties due to the presence of structural heterogeneities promoting localized failure. The removal of this localized failure is shown here by processing PS into fibers with a range of diameters using electrospinning. Mechanical properties of individual electrospun fibers were quantified with atomic force microscopy based nanomechanical tensile testing. The resultant stress–strain behavior of PS fibers highlights considerable enhancement of mechanical properties when fiber diameter decreases below 600 nm such that polystyrene toughness increases significantly by over two orders of magnitude compared to the bulk. Consideration of the network properties of polystyrene is used to demonstrate the increase of draw ratio toward a theoretical limit and is potentially applicable to a range of glassy polymeric materials. image

Superfine powdered activated carbon incorporated into electrospun polystyrene fibers preserve adsorption capacity

A composite material consisted of superfine powdered activated carbon (SPAC) and fibrous polystyrene (PS) was fabricated for the first time by electrospinning. SPAC is produced by pulverizing powdered activated carbon. The diameter of SPAC (100–400nm) is more than one hundred times smaller than conventional powdered activated carbon, but it maintains the internal pore structure based on organic micropollutant adsorption isotherms and specific surface area measurements. Co-spinning SPAC into PS fibers increased specific surface area from 6m2/g to 43m2/g. Unlike metal oxide nanoparticles, which are non-accessible for sorption from solution, electrospinning with SPAC created porous fibers. Composite SPAC-PS electrospun fibers, containing only 10% SPAC, had 30% greater phenanthrene sorption compared against PS fibers alone. SPAC particles embedded within the polymer were either partially or fully incorporated, and the accessibility of terminal adsorption sites were conserved. Conserving the adsorptive functionality of SPAC particles in electrospun non-woven polymeric fiber scaffolding can enable their application in environmental applications such as drinking water treatment.

Effects of symmetry and the number of positive charges on the photocatalytic activity of indium phthalocyanines when embedded in electrospun fibers

Photooxidations of bisphenol A and 4-chlorophenol were carried out in this study using two asymmetric indium(III) phthalocyanines photosensitizers: the first consisting of one quaternized 4-pyridyloxyl and no other substituents (complex 1) and the second containing three quaternized 4-pyridylsulfanyl units and one aminophenoxy (complex 3). The asymmetry of complex 3 is additionally caused by the presence of two linking atoms (O and S). The symmetrically substituted indium(III) phthalocyanine containing four quaternized 4-pyridyloxyl units (complex 2) was also studied. The complexes were embedded in electrospun polystyrene fiber for heterogeneous photocatalytic transformation of 4-chlorophenol and bisphenol A. When immobilized on electrospun fibers, complexes 1, 2 and 3 gave singlet oxygen values of 0.31, 0.39 and 0.50 in water, respectively. Complex 3 showed the best photocatalytic behavior with observed rate constants of 2.8×10−3min−1 for bisphenol A and 3.8×10−3min−1 for 4-chlorophenol.

MoSe2 Nanosheets Grown on Polydopamine‐Derived Porous Fibers: A High‐Performance Catalyst for Hydrogen Evolution Reaction

The development of platinum‐free electrocatalyst for hydrogen evolution reaction (HER) is highly essential to the large‐scale production and application of water splitting devices. Herein, a novel type of molybdenum diselenide decorated porous carbon fiber (MoSe2‐PCF) composite has been reported for HER. Notably, the unique mesoporous structure of electrospun polystyrene (PS) fibers is perfectly duplicated via the in situ self‐polymerization of dopamine by using PS fibers as the hard template, while porous carbon fibers are formed after the subsequent thermal annealing of polydopamine‐coated PS fibers. Thus obtained porous carbon fibers exhibit largely improved surface area which could provide highly conductive framework for electron transport, being an ideal substrate for the decoration of MoSe2. With maximally exposed active edge sites from the perpendicularly orientated MoSe2 nanosheets, the MoSe2‐PCF composite exhibits high catalytic activity toward HER, holding great potentials as highly efficient metal‐free electrodes for energy related applications.

A study on the potential of doped electrospun polystyrene fibers in arsenic filtration

Arsenic exposure is a global health hazard, particularly in areas with industrial wastewater runoff and high levels of naturally occurring arsenic-bearing soil. Current water filtration devices lack portability, severely limiting their use for wide-scale public health. In the present study, bone char, hydroxyapatite, and goethite were incorporated into electrospun polystyrene scaffolds to evaluate their arsenic binding or adsorption properties in a cost-effective, stable device with the potential for portability. Feasibility of incorporation for all dopants in the study was demonstrated using electron microscopy. Arsenic testing on contaminated water with either dopant alone or dopant-incorporated electrospun scaffolds demonstrated that the dopant-incorporated electrospun scaffolds increased arsenic binding over control, with a trend of increased arsenic binding over the dopant only counterparts. The results indicate that the low-cost, easily fabricated electrospun polystyrene is a prime choice for creating filter materials impregnated with metal binding or adsorbing materials for use in water filtration devices.

Preparation of Au nanoparticles decorated polyaniline nanotube and its catalytic oxidation to ascorbic acid

With sulfonated electrospun polystyrene fiber as a template, uniform polyaniline(PANI) nanotubes were fabricated via polymerization of aniline followed by template removal. Au nanoparticles(Aunano) were decorated on the PANI nanotube successfully via auto-reduction of HAuCl4 on the PANI nanotube. The morphology of the nanotubes was characterized by means of scanning electron microscopy(SEM) and transmittance electron microscopy(TEM). By varying precursor concentration and incubation time, Aunano-PANI with different size of Aunano was obtained conveniently. Glassy carbon electrode modified with the Aunano decorated PANI nanotubes (Aunano-PANI/GCE) was prepared and used seccessfully for the catalytic oxidation of ascorbic acid(AA). The results of differential pulse voltammetry indicate that there is a good linear relationship between the peak currents and the concentrations of AA in the range of 5―3000 μmol/L, with the limit of detection of 1 μmol/L(S/N>3). There is no mutual interference between AA and dopamine. The electrode has been successfully applied in the detection of AA in vitamin C tablet sample.

Fabrication of Electrospun Polymer Fibers with Nonspherical Cross-Sections Using a Nanopressing Technique.

The fabrication of electrospun polymer fibers is demonstrated with anisotropic cross-sections by applying a simple pressing method. Electrospun polystyrene or poly(methyl methacrylate) fibers are pressed by flat or patterned substrates while the samples are annealed at elevated temperatures. The shapes and morphologies of the pressed polymer fibers are controlled by the experimental conditions such as the pressing force, the pressing temperature, the pressing time, and the surface pattern of the substrate. At the same pressing force, the shape changes of the polymer fibers can be controlled by the pressing time. For shorter pressing times, the deformation process is dominated by the effect of pressing and fibers with barrel-shaped cross-sections can be generated. For longer pressing times, the effect of wetting becomes more important and fibers with dumbbell-shaped cross-sections can be obtained. Hierarchical polymer fibers with nanorods are fabricated by pressing the fibers with porous anodic aluminum oxide templates.

Effect of Experimental Parameters on Morphological, Mechanical and Hydrophobic Properties of Electrospun Polystyrene Fibers

Polystyrene (PS) dissolved in a mixture of N, N-dimethylformamide (DMF) and/or tetrahydrofuran (THF) was electrospun to prepare fibers with sub-micron diameters. The effects of electrospinning parameters, including solvent combinations, polymer concentrations, applied voltage on fiber morphology, as well as tensile and hydrophobic properties of the fiber mats were investigated. Scanning electron microscope (SEM) images of electrospun fibers (23% w/v PS solution with applied voltage of 15 kV) showed that a new type of fiber with double-strand morphology was formed when the mass ratio of DMF and THF was 50/50 and 25/75. The tensile strength of the PS fiber film was 1.5 MPa, indicating strong reinforcement from double-strand fibers. Bead-free fibers were obtained by electrospinning 40% (w/v) PS/DMF solution at an applied voltage of 15 kV. Notably, when the ratio of DMF and THF was 100/0, the maximum contact angle (CA) value of the electrospun PS films produced at 15 kV was 148°.

Electrospun polystyrene fiber diameter influencing bacterial attachment, proliferation, and growth.

Electrospun materials have been widely investigated in the past few decades as candidates for tissue engineering applications. However, there is little available data on the mechanisms of interaction of bacteria with electrospun wound dressings of different morphology and surface chemistry. This knowledge could allow the development of effective devices against bacterial infections in chronic wounds. In this paper, the interactions of three bacterial species (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) with electrospun polystyrene meshes were investigated. Bacterial response to meshes with different fiber diameters was assessed through a combination of scanning electron microscopy (SEM) and confocal microscopy. Experiments included attachment studies in liquid medium but also directly onto agar plates; the latter was aimed at mimicking a chronic wound environment. Fiber diameter was shown to affect the ability of bacteria to proliferate within the fibrous networks, depending on cell size and shape. The highest proliferation rates occurred when fiber diameter was close to the bacterial size. Nanofibers were found to induce conformational changes of rod shaped bacteria, limiting the colonization process and inducing cell death. The data suggest that simply tuning the morphological properties of electrospun fibers may be one strategy used to control biofilm formation within wound dressings.

Visible light transformation of Rhodamine 6G using tetracarbazole zinc phthalocyanine when embedded in electrospun fibers and in the presence of ZnO and Ag particles

Herein, we report the photocatalytic transformation of Rhodamine 6G (Rh 6G) using tetracarbazole zinc phthalocyanine (TCbZnPc) when alone or when conjugated with ZnO macroparticles (ZnOMPs) and silver nanoparticles (AgNPs), represented as TCbZnPc–ZnOMPs and TCbZnPc–AgNPs, respectively. The photocatalysts were supported onto electrospun polystyrene fibers. The efficiency of TCbZnPc was improved by the presence of both ZnOMPs and AgNPs. HPLC equipped with UV–vis was used to study phototransformation products. The mechanism of transformation was via the N-de-ethylation of Rh 6G.