Shanyuan Wang

Fabrication of multiwalled carbon nanotube-reinforced electrospun polymer nanofibers containing zero-valent iron nanoparticles for environmental applications

A new approach to immobilizing zero-valent iron nanoparticles (ZVI NPs) into electrospun polymer nanofibers with enhanced mechanical properties for environmental applications is presented. In this approach, multiwalled carbon nanotubes (MWCNTs) are mixed with polyacrylic acid (PAA)/polyvinyl alcohol (PVA) mixture polymer solution for subsequent electrospinning to form uniform nanofibers. The MWCNT-incorporated PAA/PVA nanofibers are crosslinked and then used as a nanoreactor to complex Fe(III) ions through binding with the PAA carboxyl groups for the reductive formation of ZVI NPs. The MWCNT-incorporated PAA/PVA nanofibers before and after immobilization with ZVI NPs are characterized using scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical property measurements. We show that the mechanical properties of uniform nanofibrous mats with and without ZVI NPs are significantly enhanced even with only 1.0 wt% MWCNTs incorporated. The MWCNT-reinforced PAA/PVA nanofibrous mats containing ZVI NPs (1.6 nm) display excellent capability to decolorize model dyes such as methyl blue, acridine orange, and acid fuchsine with a decoloration percentage of more than 90%. Likewise, the same nanofibrous mats are found to be able to effectively degrade trichloroethylene, a model chlorinated hydrocarbon contaminant, with a degradation efficiency approaching 93%. The MWCNT-reinforced PAA/PVA nanofibrous mats may be used for generating other functionalized nanofiber-based complex materials with enhanced mechanical properties for applications in environmental remediation, catalysis, sensing, and biomedical sciences.

Polyelectrolyte Multilayer-Assisted Immobilization of Zero-Valent Iron Nanoparticles onto Polymer Nanofibers for Potential Environmental Applications

We report a facile approach to synthesizing and immobilizing zero-valent iron nanoparticles (ZVI NPs) onto polyelectrolyte (PE) multilayer-assembled electrospun polymer nanofibers for potential environmental applications. In this approach, negatively charged cellulose acetate (CA) nanofibers fabricated by electrospinning were assembled with multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and polyacrylic acid (PAA) through electrostatic layer-by-layer assembly. The formed PAA/PDADMAC multilayers onto CA nanofibers were then used as a nanoreactor to complex Fe(II) ions through the binding with the free carboxyl groups of PAA for subsequent reductive formation of ZVI NPs. Combined scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetry analysis studies demonstrate that the ZVI NPs are successfully synthesized and uniformly distributed into the PE multilayers assembled onto the CA nanofibers. The produced hybrid nanofibrous mats containing ZVI NPs were found to exhibit superior capability to decolorize acid fuchsin, an organic dye in dyeing wastewater. We show that the loading capacity of ZVI NPs can be tuned by changing the number of PE layers and the cycles of binding/reduction process. Increasing the number of the binding/reduction cycles leads to a slight bigger size of the ZVI NPs, which is not beneficial for improving the reactivity of ZVI NPs. The present approach to synthesizing and immobilizing ZVI NPs onto polymer nanofibers opens a new avenue to fabricating various fiber-based composite materials with a high surface area to volume ratio for environmental, catalytic, and sensing applications.

Fabrication and characterization of water-stable electrospun polyethyleneimine/polyvinyl alcohol nanofibers with super dye sorption capability

We report the fabrication of water-stable electrospun polyethyleneimine (PEI)/polyvinyl alcohol (PVA) nanofibers that have super dye sorption capability. Electrospinning parameters including flow rate, applied voltage, and polymer concentration were optimized to obtain smooth and uniform PEI/PVA nanofibers. The nanofibers with a mean diameter of 490 ± 83 nm can be rendered water insoluble via crosslinking using glutaraldehyde vapor. The formed nanofibers with a smooth and uniform morphology before and after crosslinking were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical property testing. The sorption capability of the PEI/PVA nanofibers was confirmed by UV-vis spectrometry. We show that the water-stable nanofibrous mats can effectively absorb methyl blue, which is a typical dye used in the printing and dyeing industry. The dye sorption kinetics and isotherm follow the pseudo-second-order model and the Langmuir model, respectively. The developed polymer nanofiber system has a great potential in decolorizing dyeing wastewater for environmental remediation applications.

Effect of the Porous Microstructures of Poly(lactic-co-glycolic acid)/Carbon Nanotube Composites on the Growth of Fibroblast Cells

We report the effect of porous poly(lactic-co-glycolic acid) (PLGA) and PLGA/multiwalled carbon nanotubes (MWCNTs) scaffold materials prepared using both electrospinning and colloidal templating approaches on the cell growth. The viability of rat fibroblast cells cultured on these two types of scaffolds was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. The cell morphology was observed using scanning electron microscopy. We show that the incorporation of MWCNTs in PLGA scaffolds prepared using both methods tends to significantly promote fibroblast attachment, spreading, and proliferation when compared with PLGA fibrous mats and macroporous PLGA films without MWCNTs. The porous nature of the fibrous mats and macroporous polymer films with a similar composition does not appear to remarkably influence the cell attachment and proliferation. Electrospun porous fibrous mats show better cell proliferation and growth than macroporous films with similar composition at longer culture times. The fabricated porous PLGA/MWCNTs composite membranes could be further developed as tissue engineering scaffolds for applications in regenerative medicine.

Effects of twisting parameters on characteristics of rotor-spun composite yarns with spandex

Spandex fibers have superior stretch and elastic recovery ability. Composite yarns containing spandex are frequently used to manufacture elastic textile products and accessories. We have developed a composite yarn spinning system that produces different kinds of composite yarns containing spandex on a modified open-end rotor spinning frame. By changing the twisting parameter of composite yarns, we studied the structure and properties of rotor-spun composite yarns with spandex. The results indicate that the twisting parameter has great influence on the structure and properties of rotor-spun composite yarns with spandex. The linear density of spandex filament has influence on the properties of composite yarns too. In comparison with normal rotor-spun yarn, the appearance of composite yarns is clearer, the structure is much tighter, and the properties are improved.

Investigation on air texturing process for diacetate blending with polyester filaments

Influences of processing parameters on tensile property, stability and bulk of core-and-effect air textured yarns of diacetate and polyester filaments are mainly examined in this paper. When the air pressure is raised, the tenacity and breaking elongation of textured yarns are reduced, Instability I and II tend to decrease at first and then increase, the core bulk declines markedly at first and then changes slowly, whereas the overall bulk changes little at first and then goes up greatly. With increase in texturing speed, the yarn tenacity and breaking elongation both drop initially then begin to increase, the core bulk and overall bulk are almost linearly increased, while the yarn instability changes with an unclear trend. When the winding underfeed ratio is increased, the yarn tenacity, breaking elongation and core bulk are reduced, but the yarn stability is slightly improved. The wetting of the core component produces higher tenacity, breaking elongation, instability and bulk, compared with that of the effect component or that of both, but the difference is insignificant.

Properties of core-and-effect air textured yarns blended by diacetate and polyester filaments

In present work, PET FDY has been used to blend with diacetate filaments by air texturing process and core-and-effect air-textured yarns have been produced. The influences of both over-feeds of core and effect components on properties of textured yarns were mainly examined. It was observed that a spun-like effect of diacetate filaments occurred during air texturing and there were a little amount of free fiber ends besides loops on blended air textured yarns, while the number of free fiber ends changed little with variation in over-feeds. The tenacity of textured yarns decreased with increase in over-feeds of effect or core component. The breaking elongation increased with increase in over-feed of effect component, but decreased with increase in over-feed of core component. The yarn stability improves when both over-feeds are increased. The effect of over-feeds on boiling water shrinkage shows no clear trend. The core and average diameters are higher at high over-feed of effect component, but the over-feed of core component exhibits little effect on yarn diameters. The number and size of loops are increase with increased over-feed of effect component.

Polyelectrolyte multilayer film-assisted formation of zero-valent iron nanoparticles onto polymer nanofibrous mats

A facile approach that combines the electrospinning technique and layer-by-layer (LbL) assembly method has been developed to synthesize and immobilize zero-valent iron nanoparticles (ZVI NPs) onto the surface of nanofibers for potential environmental applications. In this approach, negatively charged cellulose acetate (CA) nanofibers fabricated by electrospinning CA solution were modified with bilayers composed of positively charged poly(diallyl-dimethyl-ammoniumchloride) (PDADMAC) and negatively charged poly(acrylic acid) (PAA) through electrostatic LbL assembly approach to form composite nanofibrous mats. The composite nanofibrous mats were immersed into the ferrous iron solution to allow Fe(II) ions to complex with the free carboxyl groups of PAA, and then ZVI NPs were immobilized onto the composite nanofibrous mats instantly by reducing the ferrous cations. Combined scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and thermogravimetry analysis demonstrated that the ZVI NPs are successfully synthesized and uniformly distributed into the polyelectrolyte (PE) multilayer films assembled onto the CA nanofibers. The present approach to synthesis ZVI NPs opens a new avenue to fabricating various materials with high surface area for environmental, catalytic, and sensing applications.

Effect of PH Values on Macromolecular Conformational Change

This paper investigates the conformational change of human serum albumin (HS A) macromolecules at polymer/liquid interface with different pH values using sum frequency generation (SFG) vibrational spectroscopy. SFG studies in situ demonstrate that adsorbed HSA macromolecules exhibit different conformational changes when exposed to different pH values. The results are useful for biomaterial design in the future.