As-spun Mats Research Articles

Synthesis of surface modified hydrophobic PTFE-ZnO electrospun nanofibrous mats for removal of volatile organic compounds (VOCs) from air

The article reports a two-step synthesis of composite nanofibrous mats of polytetraflouroethylene/zinc oxide (PTFE-ZnO); first, emulsion electrospinning of precursor solution was performed to yield as-spun mats followed by heat treatment at 280 °C. The surface of pure PTFE nanofibrous mats was modified by varying the amount of ZnO loadings in the electrospinning solution from 10 to 20 wt.%. Physiochemical characterization of synthesized mats was performed by FESEM, EDX, AFM, FTIR, Raman, TGA and contact angle goniometry. It was observed that fiber mean diameter decreased from 0.243 ± 15.10 μm to 0.17 ± 30.50 μm, RMS roughness increased from 112 to 627 nm and CA improved from 102.56° to 121.55° with the rise in ZnO content up to 20 wt% compared to the pure PTFE mats. Higher surface area, roughness and hydrophobicity of PTFE-ZnO mats resulted into significantly enhanced adsorption ability of VOCs on their surfaces against three model VOCs, namely, toluene, acetone and formaldehyde. The results have demonstrated that surface adsorption capacity of tested VOCs has considerably increased to 10, 07 and 03 folds respectively for the nanofibrous mats containing 20 wt.% ZnO, compared to pure PTFE mats. Based on these findings, these nanofibrous mats can potentially be used as filters for VOCs and particulate removal from air in the processing industries.

Hydrogen production from sodium borohydride originated compounds: Fabrication of electrospun nano-crystalline Co3O4 catalyst and its activity

Electrospun nanofibers are prepared through electrospinning followed by post-treatment and preferred to use in catalytic applications. The electrospinning provides advantages for active catalysts design based on activity profiles and features of catalyst. In the present study, we fabricated nano-crystalline cobalt oxide (Co3O4) catalyst by electrospinning technique followed by thermal conditioning. Polyacrylonitrile (PAN) based Co as-spun mats (Co/NMs) with homogeneous diameter were prepared by electrospinnig process under several conditions as applied voltage (15–25 kV), working distance (5–7.5 cm) with the feed rate of 1 ml min−1. The calcination process as a post-treatment was applied at different temperatures (232 °C, 289 °C and 450 °C) to obtain electrospun nano-crystalline Co3O4 catalyst. Co/NMs catalysts were characterized by XRD, SEM, TEM, XPS, FT-IR, TG/DTG, and ICP-MS techniques. The parametrically study was performed for evaluating the hydrogen production activity of catalyst from sodium borohydride (NaBH4, SBH) and its originated compounds as ammonia borane (NH3BH3, AB) and methyl-amine borane (CH3NH2BH3, MeAB). The relation between the internal-external properties and catalytic activities of catalysts for hydrogen production was investigated. The beadless Co/NMs-1 catalyst with homogeneous diameter was obtained under electrospinnig process conditions at 15 kV applied voltage and 7.5 cm working distance. All catalysts showed activity for hydrogen production, also the significant effect of post treatment process was observed on the catalytic activity as given order: Co/NMs-1450 > Co/NMs-1289 > Co/NMs-1 > Co/NMs-1232. Furthermore, mesoporous Co3O4 cubic crystals (26 nm) in fibrous architecture was prepared by 450 °C-post-treatment. Hydrogen production rates were recorded at 60 °C as 2.08, 2.20, and 6.39 l H2.gcat−1min−1 for NaBH4, CH3NH2BH3, and NH3BH3, respectively.

Stabilization of chitosan based electrospun nanofibers through a simple and safe method

A simple and safe method was used to stabilize nanofibrous structure of chitosan (CS) based mats obtained from acidic solution. The electrospun CS based nanofibrous mats were fabricated using CS/poly ethylene oxide in acetic acid aqueous solution. Exposure to water vapor at 40–70 °C for 30–120 min was implemented in order to stabilizing the CS mats. Scanning electron microscopy of the treated mats revealed preservation of nanofibrous structure after immersion in phosphate buffered saline (pH = 7.4). This result along with infrared spectroscopy and thermogravimetric analysis confirmed removal of acetic acid residues and neutralization of CS mats after treatment with water vapor. Stabilization with water vapor also led to augmentation in tensile strength and elastic moduli of CS mats comparing to as-spun mats while the elongation was decreased. Furthermore, the crystallinity and thermal stability of mats were slightly increased after neutralization. In comparison with glutaraldehyde cross-linked mats, water vapor treated mats showed higher swelling ratio and enhanced cell compatibility.

Super Water-Repellent Cellulose Acetate Mats

A single-step synthesis of super-water-repellent oil sorbents based on cellulose acetate (CA) mats is reported in this paper. Key phenomenological mechanisms involving roughness and changes in chemistry are used to describe the change in hydrophobic behavior of the CA mats. Contact angle calculations followed by Cassie’s model apparent contact angle prediction have shown roughness alone is not capable of producing the super-hydrophobicity exhibited by as-spun mats. Fourier transform infrared spectroscopy of spin coated and electrospun mats shows a significant difference in the stretching of the hydroxyl bonds of the two materials. As it is this hydroxyl group which adds to the overall polarity of surface thus hydrophilicity of the material, we propose that the electrospinning process not only creates a rougher surface but also alters the chemistry of the electrospun cellulose acetate mats which ultimately gives rise to the reported hydrophobicity. Finally, due to their water repellent nature, and oleophilicity of the as-spun mats were tested as oil sorbent mats. The as-spun mats were capable of absorbing thirty times their weight in oil demonstrating their application for oil-water remediation.

Nanomechanics and Testing of Core-Shell Composite Ligaments for High Strength, Light Weight Foams

ABSTRACT Composite nanostructured foams consisting of a metallic shell deposited on a polymeric core were formed by plating copper via electroless deposition on electrospun polycaprolactone (PCL) fiber mats. The final structure consisted of 1000-nm scale PCL fibers coated with 100s of nm of copper, leading to final core-shell thicknesses on the order of 1000-3000 nm. The resulting open cell, core-shell foams had relative densities between 4 and 15 %. By controlling the composition of the adjuncts in the plating bath, particularly the composition of formaldehyde, the relative thickness of copper coating as the fiber diameter could be controlled. As-spun PCL mats had a nominal compressive modulus on the order of 0.1 MPa; adding a uniform metallic shell increased the modulus up to 2 MPa for sub-10 % relative density foams. A computational materials science analysis using density functional theory was used to explore the effects pre-treatment with Pd may have on the density of nuclei formed during electroless plating.

Improved genistein loading and release on electrospun chitosan nanofiber blends

Chitosan is a natural polysaccharide exhibiting excellent biocompatibility, biodegradability and nontoxicity, making Chitosan–based biomaterials ideal drug delivery systems and cell carriers for tissue engineering. The electrospinning technique, with optimized parameters, was used to fabricate chitosan/PVA as-spun mats. Field emission scanning electron microscopy (FESEM) was used to investigate the morphologies of the as-spun mats. We present a novel electrospun nanofiber-based drug delivery. In this system, genistein was loaded on nanofiber mats via three methods namely; passive loading, crosslinking after passive loading, and active loading. The way in which genistein was loaded significantly influenced its in-vitro drug release characteristics. The in-vitro release studies revealed that physical cross-linked nanofibers have a significantly delayed release demonstrating 21% progressive release after 30min and 69% after 24h, which is considered a superior drug delivery system compared to those reported before for genistein release.

Electrospun regenerated silk fibroin mats with enhanced mechanical properties

In this paper, a simple and effective method was applied to enhance regenerated silk fibroin (RSF) mats electrospun from aqueous solution. The mats were first mechanically drawn in 90vol.% ethanol aqueous solution and then immersed in the same solution for 30min. The morphology, structure, thermal and mechanical properties of the RSF mats with different draw rates and draw ratios were investigated by scanning electron microscope (SEM), Raman spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and tensile test. Results revealed that the content of β-sheet conformation, the crystallinity and the number of fibers aligned to the drawing direction increased evidently with the draw ratio. The breaking strength and breaking energy of the post-treated mats at 1.4× draw ratio and 0.1mm/s draw rate were 8.6MPa and 172.2J/kg, respectively. However, those of the as-spun mats were only 1.8MPa and 93.2J/kg, respectively. The enhanced RSF mats prepared from entirely aqueous solutions may have extensive applications for tissue engineering.

Hydroxypropyl chitosan/organic rectorite-based nanofibrous mats with intercalated structure for bacterial inhibition

This paper reported antibacterial hydroxypropyl chitosan (HPCS)/organic rectorite (OREC)-based nanofibrous mats with intercalated structure fabricated via solution intercalation method and electrospinning. Field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and inhibition zone surrounding circular mats disks measurement were performed to characterize the morphology, intercalation structure, elements analysis, and the antibacterial properties of the as-spun nanofibrous mats. The results showed that the nanofibrous mats were with better fiber shape with the addition of OREC, the polymer chains were successfully intercalated into the interlayer of OREC, and nanofibrous mats containing HPCS exhibited good antibacterial activities against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus. In addition, the bacterial inhibition ability of the nanofibrous mats was enhanced when OREC was added.

Nanofibrous mats layer-by-layer assembled via electrospun cellulose acetate and electrosprayed chitosan for cell culture

Negatively charged cellulose acetate (CA) and positively charged chitosan (CS) were layer-by-layer (LBL) assembled together by the electrospinning–electrospraying hybrid technique via physical deposition and electrostatic force for the first time. The morphology of the mats indicated that all of them were of a good fiber shape and a three-dimension structure. The X-ray photoelectron spectroscopy results verified the existence of CS on the surface of the as-spun mats. The thermogravimetric analysis and differential scanning calorimetry results illustrated that the thermal properties of the mats were affected by their compositions. In addition, the cell culture experiment demonstrated that the scaffolds with the LBL structured polysaccharide films were of good cell compatibility and no cytotoxicity for the mouse lung fibroblasts cells. Moreover, the ability of cell adhesion and spreading was affected by the number of deposition layers and the composition of outermost layer.

LBL fabricated biopolymer-layered silicate based nanofibrous mats and their cell compatibility studies

N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was synthesized from chitosan (CS). Organic rectorite (OREC) added into cellulose acetate (CA) was used to fabricate electrospun nanofibrous mats with improved thermal properties, as a result of depositing multilayers of the positively charged HTCC-OREC composites and the negatively charged sodium alginate (ALG) via layer-by-layer (LBL) technique. The morphology was affected by the number of deposition bilayers and the component of the outmost layer. Observed from the field emission scanning electron microscopy (FE-SEM) images, the LBL structured nanofibrous mats had much larger fiber sizes than CA-OREC nanofibrous mats. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results further confirmed that HTCC-OREC was assembled on nanofibrous mats. Additionally, cell experiments and MTT results demonstrated that OREC had little effect on the cytotoxicity of LBL template, but obviously affected both the cytotoxicity and the cell compatibility of LBL structured mats when OREC was in the deposition films.

Quaternized chitosan-layered silicate intercalated composites based nanofibrous mats and their antibacterial activity

Quaternized chitosan (HTCC)–organic rectorite (OREC) intercalated composites based electrospun nanofibrous mats were fabricated from HTCC–OREC/polyvinyl alcohol (PVA) solutions for the first time. The morphology, intercalated structure, and antibacterial activity of the as-spun mats were investigated. The transmission electron microscopy images taken from HTCC–OREC composites showed that HTCC chains were inside the OREC interlayer. Scanning electron microscopy results verified that more typical fibrous structure would be generated by adding OREC. Fourier transform infrared spectra and energy-dispersive X-ray spectroscopy results indicated that OREC existed in the HTCC–OREC/PVA nanofibrous mats. The intercalation structure in nanofibrous mats was confirmed by X-ray diffraction results, which confirmed that HTCC and PVA chains could intercalate into the interlayer of OREC. The antibacterial activity of the electrospun mats was enhanced when the amount of the OREC increased. Therefore, the novel ternary nanofibrous mats could be used in the field of food packaging and biomedical applications.

Cross-Linking Chitosan Nanofibers

In the present study, we have electrospun various grades of chitosan and cross-linked them using a novel method involving glutaraldehyde (GA) vapor, utilizing a Schiff base imine functionality. Chemical, structural, and mechanical analyses have been conducted by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Kawabata microtensile testing, respectively. Additionally, the solubilities of the as-spun and cross-linked chitosan mats have been evaluated;solubility was greatly improved after cross-linking. SEM images displayed evidence that unfiltered low, medium, and high molecular weight chitosans, as well as practical-grade chitosan, can be electrospun into nanofibrous mats. The as-spun medium molecular weight chitosan nanofibers have a Young's modulus of 154.9 +/- 40.0 MPa and display a pseudo-yield point that arose due to the transition from the pulling of a fibrous mat with high cohesive strength to the sliding and elongation of fibers. As-spun mats were highly soluble in acidic and aqueous solutions. After cross-linking, the medium molecular weight fibers increased in diameter by an average of 161 nm, have a decreased Young's modulus of 150.8 +/- 43.6 MPa, and were insoluble in basic, acidic, and aqueous solutions. Though the extent to which GA penetrates into the chitosan fibers is currently unknown, it is evident that the cross-linking resulted in increased brittleness, a color change, and the restriction of fiber sliding that resulted in the loss of a pseudo-yield point.

Preparation and Characterization of Novel Bone Scaffolds Based on Electrospun Polycaprolactone Fibers Filled with Nanoparticles

Novel bone-scaffolding materials were successfully fabricated by electrospinning from polycaprolactone (PCL) solutions containing nanoparticles of calcium carbonate (CaCO(3)) or hydroxyapatite (HA). The diameters of the as-spun fibers were found to increase with the addition and increasing amounts of the nanoparticles. The observed increase in the diameters of the as-spun fibers with the addition and increasing amounts of the nanoparticulate fillers was responsible for the observed increase in the tensile strength of the obtained fiber mats. An increase in the concentration of the base PCL solution caused the average diameter of the as-spun PCL/HA composite fibers to increase. Increasing applied electrical potential also resulted in an increase in the diameters of the obtained PCL/HA composite fibers. Lastly, indirect cytotoxicity evaluation of the electrospun mats of PCL, PCL/CaCO(3), and PCL/HA fibers based on human osteoblasts (SaOS2) and mouse fibroblasts (L929) revealed that these as-spun mats posed no threat to the cells, a result that implied their potential for utilization as bone-scaffolding materials.

Molybdenum and Tungsten Oxide Nanowires Prepared by Electrospinning

ABSTRACTTungsten oxide (WO3) and molybdenum oxide (MoO3) nanowires were synthesized through utilizing sol gel and electrospinning methods. Mixtures of metal oxide sol gel and polyvinylpyrrolidone (PVP) in ethanol solution were electrospun and resulted in metal oxide composite nanofiber mats. Precise annealing process removed all organic material, and pure metal oxide single crystal nanowires remained. Both the as-spun nanocomposite mats and the heat-treated nanofiborous materials were characterized using Scanning and Transmission Electron Microscopes. The average diameter of the nanofibers was concluded to be proportional to the flow rate used and inversely proportional to the metal oxide concentration in the solution.