Polyvinyl Alcohol Nanofibers Research Articles

Facile immobilization of gold nanoparticles into electrospun polyethyleneimine/polyvinyl alcohol nanofibers for catalytic applications

We report a facile approach to immobilizing gold nanoparticles (AuNPs) into electrospun polyethyleneimine (PEI)/polyvinyl alcohol (PVA) nanofibers for catalytic applications. In this study, electrospun PEI/PVA nanofibers with a mean diameter of 490 nm were first crosslinked with glutaraldehyde vapor to render them water stable. Then, the water-insoluble nanofibrous mats were used as nanoreactors to complex AuCl4− anions via binding with the free amine groups of PEI for subsequent formation and immobilization of AuNPs. The formed AuNPs with a diameter of 11.8 nm within the nanofibers do not significantly change the morphology of the nanofibers; while importantly the mechanical property of the fibers was greatly improved compared to the crosslinked fibers without AuNPs. Scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, energy dispersive spectroscopy, and thermogravimetric analysis were used to characterize these hybrid nanofibers. Furthermore, we show that the AuNP-containing nanofibers display an excellent catalytic activity and reusability for the transformation of 4-nitrophenol to 4-aminophenol. The present approach to fabricating AuNP-containing nanofibers may be extended for producing other nanoparticle-containing composite nanofibrous materials for various applications in catalysis, sensing, and biomedical sciences.

Fabrication and characterization of water-stable electrospun polyethyleneimine/polyvinyl alcohol nanofibers with super dyesorption 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.

10.2478/s11814-009-0309-1

Precise control of fiber diameter during electrospinning is very crucial for many applications. A systematic and quantitative study on the effects of processing variables enables us to control the properties of electrospun nanofibers. In this contribution, response surface methodology (RSM) was employed to quantitatively investigate the simultaneous effects of four of the most important parameters, namely solution concentration (C), spinning distance (d), applied voltage (V) and volume flow rate (Q), on mean fiber diameter (MFD) as well as standard deviation of fiber diameter (StdFD) in electrospinning of polyvinyl alcohol (PVA) nanofibers.

Research on Water Resistance of Polyvinyl Alcohol Nanofiber Mats

In electrospinning, non-woven fabrics are commonly used as substrates to receive polymer nanofibers. Nanofiber mats formed in this process have many advantages, such as extensive application prospects in the thermal insulation, filtration, protection and so on. Polyvinyl alcohol (PVA) is the main electrospun material with excellent physical properties, biodegradable properties, chemical resistance, and good mechanical properties in the dry state. However, PVA has a poor water resistance which limits its application. In this study, The PVA nanofibrous mats prepared by electrospinning were chemically crosslinked with glutaraldehyde (GA) in acetone. Scanning Electron Micrograph (SEM) and Fourier Transform Infrared (FTIR) spectrometry were employed to characterize the morphology and structure of crosslinked PVA nanofiber mat and PVA nanofiber mat. The differences of morphology and structure between the modified and nonmodified nanofiber mat were revealed. Such nanofibrous mat has good water resistance and excellent warmth retention property. Thus, the practical applications of PVA nanofiber mats were broadened.

Preparation and Antibacterial Activity of Poly (vinyl Alcohol)/Silk Fibroin Composite Nanofibers Containing Silver Nanoparticles

Silk fibroin (SF) and polyvinyl alcohol (PVA) solutions were prepared respectively by formic acid and deionized water as solvent, the solutions were then blended, and after that AgNO3 was added. The PVA/SF/AgNO3 solution was electrospun to form nanofibers. A number of particles were generated on the surface of nanofibers during electrospinning, which was confirmed by transmission electron microscopy (TEM). The diameter distribution of the nanofibers was narrow and the particles were nano-sized and well-dispersed. X-ray diffraction (XRD) patterns of the composite nanofibers indicated that the component of the nanoparticles was silver. By annealing the composite nanofibers at 155°C for 5 minutes, the silver nanoparticles possibly clustered into the larger size. The size of Ag nanoparticles was 2.25nm without post treatment, and this value increased to 3.76nm after the heat treatment. The antibacterial activity of the heat-treated PVA/SF composite nanofibers containing Ag nanoparticles was evaluated and the resultant nanofibers showed strong antimicrobial activity on Staphylococcus aureus and Escherichia coli. Moreover, the antibacterial PVA/SF composite nanofibers containing Ag nanoparticles have the possibility to be used in wound dressing due to the electrospun PVA nanofibers could preserve the web structure in water after the heat treatment.

Surface modified electrospun poly(vinyl alcohol) membranes for extracting nanoparticles from water

Contamination of water from nanomaterials will be an emerging problem in the future due to incorporation of nanomaterials in many commercial products and improper disposal of waste materials. In this report, electrospun polyvinyl alcohol nanofibers (PVA NFs) with diameters ranging between 300 and 500 nm were used for the extraction of nanosized contaminants from the aqueous environment. To obtain the best extraction efficiency, surface hydroxyl groups of PVA NFs were chemically modified with functional groups, such as thiols and amines. Two model nanoparticles (silver and gold) dissolved in water were used for adsorption studies. Depending on the nature of the surface functionalities, the fibers showed unique ability to adsorb nanoparticles. The extraction studies revealed that the amine and thiol modified PVA NFs showed 90% extraction efficiency for both silver and gold nanoparticles. The thiol and amine functionalized PVA NFs showed maximum adsorption capacities (Q(t)) towards Au NPs, which were around 79-84 mg g(-1). Similarly for Ag NP extraction, amine functionalized PVA NFs showed a value for Q(t) at 56 mg g(-1). Our results highlight that functionalized nanofibers have high extraction efficiency for dissolved nanoparticles in water and can be used for removal of the nanocontaminants from the aqueous environment.

Nano Ag loaded PVA nano‐fibrous mats for skin applications

Silver nano-particles (Ag NPs) loaded polyvinyl alcohol (PVA) electro-spun fibers were fabricated using a combination of microwave-heated and electro-spinning methods for wound healing. A thermic process was then applied to resurface and increase the number of the Ag NPs on the surface of the PVA fiber. The diameter of the Ag NPs loaded electrospun PVA (PVA-Ag) mats were between 100 and 500 nm after heat treatments at different temperatures. When samples were subjected to 60 s of microwave irradiation and 150°C heat treatment, the maximum number of 50-100 nm Ag NPs resurfaced on the PVA nano-fiber. The nano mats significantly inhibited E. coli (gram-positive) and S. aureus (gram-negative) bacteria and displayed high mechanical stability (>45 MPa).

Performance of composite Nafion/PVA membranes for direct methanol fuel cells

This work has been focused on the characterization of the methanol permeability and fuel cell performance of composite Nafion/PVA membranes in function of their thickness, which ranged from 19 to 97μm. The composite membranes were made up of Nafion® polymer deposited between polyvinyl alcohol (PVA) nanofibers. The resistance to methanol permeation of the Nafion/PVA membranes shows a linear variation with the thickness. The separation between apparent and true permeability permits to give an estimated value of 4.0×10−7cm2s−1 for the intrinsic or true permeability of the bulk phase at the composite membranes. The incorporation of PVA nanofibers causes a remarkable reduction of one order of magnitude in the methanol permeability as compared with pristine Nafion® membranes. The DMFC performances of membrane–electrode assemblies prepared from Nafion/PVA and pristine Nafion® membranes were tested at 45, 70 and 95°C under various methanol concentrations, i.e., 1, 2 and 3M. The nanocomposite membranes with thicknesses of 19μm and 47μm reached power densities of 211mWcm−2 and 184mWcm−2 at 95°C and 2M methanol concentration. These results are comparable to those found for Nafion® membranes with similar thickness at the same conditions, which were 210mWcm−2 and 204mWcm−2 respectively. Due to the lower amount of Nafion® polymer present within the composite membranes, it is suggested a high degree of utilization of Nafion® as proton conductive material within the Nafion/PVA membranes, and therefore, significant savings in the consumed amount of Nafion® are potentially able to be achieved. In addition, the reinforcement effect caused by the PVA nanofibers offers the possibility of preparing membranes with very low thickness and good mechanical properties, while on the other hand, pristine Nafion® membranes are unpractical below a thickness of 50μm.

Effect of solution concentration on diameter and morphology of PVA nanofibres in bubble electrospinning process

Bubble elecrospinning is an excellent and novelty method to fabricate nanofibres with high throughout. This paper investigates experimentally the effects of solution concentration and its viscosity on diameter and morphology of bubble electrospun polyvinyl alcohol (PVA) nanofibres, where pure water is used as a solvent for environmental consideration. The experiment shows that the as spun fibres change their morphology from few beads, smooth surfaces and finally to larger diameter fibres when PVA solution concentration increases gradually. An allometric relation between the fibre diameter and the solution concentration is obtained. The minimal diameter is as small as 38·3 nm.

Using Orthogonal Design in Optimizing Parameters for Bubble Electrospinning of Polyvinyl Alcohol (PVA) Nanofibers

The present work was aimed at studying the effects of process parameters on morphologies of Polyvinyl alcohol (PVA) nanofibers in a novel electrospinning technique, bubble electrospinning. The process was optimized by constructing L 9(34) orthogonal experimental array design. Three factors were investigated and nine tests were run under lower, medium and higher levels of these factors. The results showed that PVA solution concentration plays an important role in affecting the morphologies of PVA nanofibers in bubble electrospinning process. With the increase of the concentration of PVA solution, the morphologies of fibers were changed from beaded fibers to uniform cylinder fibers and the average nanofiber diameter also increased. The optimization process was 12w% for PVA solution, 30kV for applied voltage and 10cm for spinning distance.

Novel flexible chemical gas sensor based on poly(3,4-ethylenedioxythiophene) nanotube membrane

Poly(3,4-ethylenedioxythiophene) nanotubes (PEDOT NTs) flexible membrane was successfully fabricated by vapor deposition polymerization (VDP) mediated electrospinning for ammonia gas detection. PVA nanofibers (NFs) were electrospun as a core part and polyvinyl alcohol (PVA)/PEDOT coaxial nanocables (NCs) were prepared by VDP method via EDOT monomer adsorption onto the electrospun PVA NFs as templates. To obtain the PEDOT NTs membrane, the PVA NFs were removed from PVA/PEDOT coaxial NCs with distilled water. PVA/PEDOT coaxial NCs and PEDOT NTs had the conductivities of 71 and 61 S cm −1 and were applied as a transducer for ammonia gas detection in the range of 1–100 parts per million (ppm) of NH 3 gas. They exhibited the minimum detectable level of ca. 5 parts per million (ppm) and fast response time (less than 1 s) towards ammonia gas. In a recovery time, the PEDOT NTs membrane sensor was ca. 30 s and shorter compared to that of the membrane sensor based on the PVA/PEDOT NCs ( ca. 50 s). In addition, sensor performance of PEDOT NTs membrane was also undertaken as a function of membrane thickness. Thick membrane sensor (30 μm) had the enhanced sensitivity and the sensitivity on the membrane thickness was in the order of 30 μm > 20 μm > 10 μm at 60 ppm of NH 3 gas.

Transversal electrostatic strength of patterned collector affecting alignment of electrospun nanofibers

Conventional electrospinning produces randomly ordered nanofibers, however many potential applications require precisely defined morphology and anisotropic properties of nanofibrous materials. In this work, a collector consisting of two segments has been used to prepare uniaxially ordered nanofibers. Optimized collector design comes from both analytical calculations of electrostatic strength in the vicinity of the electrodes and from experimental verification by polyvinyl alcohol nanofibers fabrication. The transversal electric strength is a key factor in achieving very well aligned nanofibers. The results presented here help provide a better understanding of the electrically induced alignment mechanism.

Influence of Glyoxal in the Physical Characterization of PVA Nanofibers

The influence of solution composition is directly related to the properties of polyvinyl alcohol (PVA) nanofibers. Electrospinning is a viable technique to develop PVA nanofibers. The presence of a crosslinking agent such as glyoxal can produce variations not only in anti-water solubility effect, but also in the morphology of the electrodeposited fibers. The objective of this study was to characterize the influence of glyoxal on PVA nanofibers. Thus, we studied fiber dimensions, the weight of deposited fibers, and fiber crystallinity. The relation between those properties and the properties of the nanofiber web (color, opacity, and roughness) were studied. In this study we changed glyoxal concentration. Scanning electron microscopy, differential scanning calorimetry, and atomic force microscopy showed changes in the fiber properties. We could observe how the diameter fiber increased, the collector surface was widely covered, and the fiber crystallinity decreased. Regarding the properties of the web, the roughness decreased and the color turned whiter.

Surface Modification of Polypropylene Non-woven Substrates by Padding with Antistatic Agents for Deposition of Polyvinyl Alcohol Nanofiber Webs by Electrospinning

In recent years, the electrospinning process has become one of the most interesting processes to obtain nanofiber webs with interesting properties for uses in a wide variety of industrial sectors such as filtration, chemical barriers, medical devices, etc., as a consequence of the relatively high surface-to-volume ratio. Among the wide variety of polymers, polyvinyl alcohol (PVA) offers good advantages since it is water-soluble and this fact enables easy processing by electrospinning. There are many variables and parameters to be considered in order to optimize PVA nanofiber webs: some of them are related to the polymer solution, some others are related to the process, and some of them are related to the collector substrate. In this work a study on the effects of two different surface pre-treatments on a non-woven polypropylene substrate as a collector of PVA nanofiber webs has been carried out. In particular, a chemical treatment with anionic antistatics and a physical treatment with low-pressure plasma have been investigated. The effects of these pre-treatments on morphology of PVA nanofiber webs have been evaluated by scanning electron microscopy. Results show that surface resistivity is one of the main parameters influencing the web formation as well as the nature of the electric charge achieved by the pre-treatment. The plasma treatment promotes changes in surface resistivity but it is not enough for good web deposition. Chemical pre-treatment (padding) with anionic antistatic leads to a decrease in surface resistivity up to values in the 1 × 10 9— 1 × 1011 Ω which is enough for good nanofiber deposition.

Synthesis and characterization of electrospun polymer nanofibers incorporated with CdTe nanoparticles

CdTe nanoparticles were incorporated in polyvinyl alcohol (PVA) nanofibers by electrospinning. The hybrid nanofibers were characterized morphologically and optically by scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL) measurements. The average diameter of the hybrid nanofibers was about 150 nm and the CdTe nanoparticles were present both inside them and on their surfaces. Compared with the PL of the CdTe nanoparticles dispersed in solution, the PL peak of the CdTe nanoparticles in the CdTe/PVA hybrid nanofibers was shifted from 525 to 426 nm. This blue shift of the PL peak results from the different quantum confinement effects, due to the different environment surrounding the CdTe nanoparticles, in the case of those dispersed in solution and those embedded in the PVA nanofibers.

In vivo wound healing and antibacterial performances of electrospun nanofibre membranes

In this work, nanofibre membranes have been produced from polyvinyl alcohol (PVA), polycaprolactone (PCL), polyacrylonitrile (PAN), poly (vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP), and polymer blend of PAN and polyurethane (PEU) using an electrospinning technique, and wound healing performance of the as-spun nanofibre membranes was examined in vivo using female Sprague-Dawley rats. To understand the nutrition effect, a wool protein was coated on PVA and PCL nanofibres and incorporated into PVA nanofibres via coelectrospinning of a PVA solution containing the wool protein. Silver nanoparticles were also applied to PVA nanofibres to improve antibacterial activity. It was found that the wound healing performance is mainly influenced by the porosity, air permeability, and surface wettability of the nanofibre membranes. A nanofibre membrane with good hydrophilicity and high porosity considerably facilitates the healing of wound especially at the early healing stage. However, the fiber diameter and antibacterial activity have little effect on the wound healing efficiency. As pores in nanofibre membranes are typically smaller than that of conventional cotton gauze, the nanofibre membrane should be able to decontaminate and prevent exogenous infections via sieve effect. This work provides basic understanding of material structure-property relationship for further design of efficient nanofibre-based wound dressing materials.

Polyvinyl alcohol–collagen–hydroxyapatite biocomposite nanofibrous scaffold: Mimicking the key features of natural bone at the nanoscale level

Polyvinyl alcohol (PVA) nanofibers, PVA/Type I Collagen (Col) and their composites with hydroxyapatite nanoparticles (nano-HAp) were prepared by electrospinning techniques. The composite nanofibrous membranes were subjected to detailed analysis. Morphological investigations show that the generated nanofibers (NFs) have uniform morphology with an average diameter of ∼160 nm for pure PVA, ∼176 nm for PVA/n-HAp, ∼245 nm for PVA/Col and ∼320 nm for PVA/Col/n-HAp. It is of interest to observe that large numbers of HAp nanorods are preferentially oriented parallel to the longitudinal direction of the electrospun PVA and/or PVA/Col NFs. FTIR and thermal analysis demonstrated that there was strong intermolecular hydrogen bonding between the molecules of PVA/Col/n-HAp. Furthermore, the obtained PVA/Col/nHAp NFs scaffold (7 cm × 11 cm) has a porous structure with adjustable pore size and shape. The pore size is in the range of 650 μm with a porosity of 49.5%. On the other hand, mechanical characterizations revealed that the incorporating of 5 wt% n-HAp into the matrix of PVA/Col nanofibers could significantly improve the rigidity of the resultant biocomposite nanofibrous scaffold. These results strongly suggest a huge potential of the prepared scaffold for bone tissue engineering.

A new approach for optimization of electrospun nanofiber formation process

Precise control of fiber diameter during electrospinning is very crucial for many applications. A systematic and quantitative study on the effects of processing variables enables us to control the properties of electrospun nanofibers. In this contribution, response surface methodology (RSM) was employed to quantitatively investigate the simultaneous effects of four of the most important parameters, namely solution concentration (C), spinning distance (d), applied voltage (V) and volume flow rate (Q), on mean fiber diameter (MFD) as well as standard deviation of fiber diameter (StdFD) in electrospinning of polyvinyl alcohol (PVA) nanofibers.

Synthesis of CuAlO 2 nanofibrous mats by electrospinning

Electrospinning as a versatile method for preparation of nanofibers has been used to fabricate the polyvinylalcohol nanofibers containing equal molar of aluminum nitrate and copper acetate. After pretreated at 400 °C, the composite fibrous mats were annealed at 1100 °C in air for 5 h and then the delafossite-structured p-type CuAlO 2 ceramics fibrous mats were obtained. The obtained CuAlO 2 ceramics fibrous mats were characterized by scanning electrical microscope, X-ray diffraction and diffuse reflectance spectroscopy. The direct energy gap of the prepared CuAlO 2 ceramics fibrous mats was measured to be about 3.38 eV. The CuAlO 2 behaved like semiconductors and the thermally activated energy was about 0.25 eV.

Stress-strain behavior of individual electrospun polymer fibers using combination AFM and SEM

AbstractTensile deformation of individual electrospun polyvinyl alcohol (PVA) nanofibres was performed using a novel combination atomic force microscope (AFM)- scanning electron microscope (SEM) technique. The AFM was used to provide manipulation and mechanical testing of individual PVA nanofibers while the SEM was used to observe the deformation process. Resultant stress-strain curves show how the elastic modulus shows comparable, or even slightly increased, values to isotropic films. In addition, the electrospun fibers were tested to failure to measure their tensile strength.