Porous electrospun nanofibers, as new materials for solid‐phase extraction, were synthesized by electrospinning and coupled with ultra high performance liquid chromatography and mass spectrometry to determine sulfonamide residues in environmental water. Aligned porous polystyrene electrospun nanofibers were fabricated under the mechanism of phase separation. The high‐specific surface of these nanofibers (70 m2/g) could improve recoveries of the target sulfonamides 4–10 times compared with that of polystyrene nonporous material (3.8 m2/g). Under the optimized conditions, 13 sulfonamide residues showed an excellent linear relationship in the range of 0.125–12.5 ng/mL with a linear correlation coefficient (r2) greater than 0.99, and the detection limits of sulfonamides were as low as 0.80–5.0 ng/L. Compared to the commercial C18 and HLB columns, the homemade porous nanofibers columns had some merits including simple fabrication and extraction process, short process time and environmental friendliness. The optimized method was applied to eight water samples collected from different livestock farms (Xuzhou, China). The results showed that polystyrene porous nanofibers were promising to preconcentrate sulfonamides of different polarities in the waste water. 相似文献
Flexible and lead-free piezoelectric nanocomposites were synthesized with BaTiO3 nanowires (filler) and poly(vinylidene fluoride) (PVDF) (matrix), and the piezoelectric performances of the composites were systematically studied by varying the aspect ratio (AR) and volume fraction of the nanowire and poling time. BaTiO3 nanowires with AR of 18 were synthesized and incorporated into PVDF to improve the piezoelectric performance of the composites. It was found that high AR significantly increased the dielectric constant up to 64, which is over 800% improvement compared to those from the composites containing spheroid shape BaTiO3 nanoparticles. In addition, the dielectric constant and piezoelectric coefficient were also enhanced by increasing the concentration of BaTiO3 nanowires. The piezoelectric coefficient with 50-vol% BaTiO3 nanowires embedded in PVDF displayed 61 pC/N, which is much higher than nanocomposites with spheroid shape BaTiO3 nanoparticles as well as comparable to, if not better, other nanoparticle-filled polymer composites. Our results suggest that it is possible to fabricate nanocomposites with proper mechanical and piezoelectric properties by utilizing proper AR fillers. 相似文献
Polyvinylidene fluoride (PVDF) is a significant polymer in the formation of nanofiber webs via the electrospinning technique. In this paper, three PVDF-wrinkled fiber webs with different molecular weights (MWs) (180000, 275000, and 530000) were generated via the electrospinning method by using tetrahydrofuran/N,N-dimethylformamide at the solvent ratio of 1:1 as a mixed solvent. The formation mechanism of the wrinkled electrospun PVDF fibers is demonstrated. Furthermore, the relationships between the MW and the surface structure, mechanical properties, crystalline phases, and piezoelectric properties of electrospun PVDF fibers are comprehensively investigated. The results reported that the surface structure, mechanical properties, crystalline phases, and piezoelectric properties of wrinkled electrospun PVDF fibers can be affected intensely by maneuvering the MW. We believe this study can be served as a good reference for the effect of MW on the morphology and properties of electrospun fibers. 相似文献
Electrospinning is a versatile and straight forward process for synthesizing one-dimensional (1D) nanostructures of diverse
materials. Recently, a large variety of oxide ceramics have been synthesized in combination with conventional sol-gel processing.
Here, the synthesis of BaTiO3 nanofibers via electrospinning is reported. The structural evolution from amorphous to crystalline is presented under various
heat treatment conditions. Nanofibers with well-defined perovskite tetragonal phase were achieved with an average crystallite
size of about 20 nm. Furthermore, single crystalline BaTiO3 nanofibers with 50 nm in diameter and lengths up to 1 μm were found, which is a novelty in electrospinning of ferroelectrics.
XRD peak splitting confirmed the tetragonal perovskite structure, and this was fully supported by further evidence from selected
area electron diffraction and Raman spectroscopy. 相似文献
In the paper cesium tungstate nanofibers for the first time have been fabricated successfully by a simple electrospinning technique followed by heat treatment. The cesium tungstate nanofibers have been characterized by XRD, SEM, and FTIR techniques. The results indicated the morphology and quality of the annealed electrospun samples are strongly dependent on the citric acid content within electrospinning solution. It is found with increasing the citric acid content from 7 to 22% the samples morphology changed from a particle structure to a fibrous structure. The average diameter of nanofibers was ~350 nm. XRD analysis reveals that all of the samples have good crystallinity with the same diffraction peaks that can be indexed to the tetragonal phase of Cs2W3O10. Furthermore, the photocatalyst properties of cesium tungstate has not been reported to date. In the work the synthesized Cs2W3O10 nanofibers were found to exhibit photocatalytic performance in the photodegradation of RhB aqueous solution used as a pollutant model. 相似文献
We have examined the poling time dependence of the field-induced phase transition (from phase II to polar phase II) of biaxially oriented poly(vinylidene fluoride) films by x-ray methods. These results were compared with the poling-time dependence of the piezoelectric response (d31 and e31) determined using a piezotron Model U (Toyo Seiki, Tokyo). The piezoelectric response shows an initial rapid increase with poling time followed by a slow increase as the poling time increases. The x-ray results show that the field-induced phase transition is time dependent, and occurs first for those crystallites with their a axes perpendicular to the film surface. Crystallites with a in the plane of the film transform at a much slower rate. The data indicate that the poling time dependence of d31 and e31 (and, presumably, film polarization) are dependent on the transition rates. 相似文献
Nanofibers of naturally modified polymer such as carboxymethyl cellulose (CMC) blended with poly(vinyl alcohol) (PVA) at different ratios was obtained by electrospinning technique. The blended solutions of CMC and PVA loaded with and without diclofenac sodium (DS) were electrospun using environmentally benign electrospinning technique in the absence of organic solvents. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) were used to investigate the surface morphology functional groups, as well as the thermal stability of DS loaded CMC/PVA nanofibers mat. The mechanical properties of the as prepared electrospun nanofibers was also evaluated. The entrapment efficiency and the in vitro release of DS loaded CMC/PVA nanofibers were characterized using UV-Vis spectroscopy. The obtained results displayed that the blended nanofibers have shown a smooth morphology, no beads formation when the concentration of CMC was equal or below 5% and beads formation above 5%. FTIR data demonstrated that there were good interactions between CMC and PVA possibly via the formation of hydrogen bonds. The electrospun blended CMC/PVA nanofibers exhibit good mechanical properties. From the in vitro release data, it was found that with the presence of CMC, the release of DS from the nanofibers mats became sustained controlled. Due to the biocompatibility and low cost of the two blended polymers (CMC and PVA), the blended nanofibers system can be considered as one of the promising materials for the preparation of excellent drug carrier. 相似文献
Continuous NiTiO3 nanofibers have been successfully synthesized by a sol–gel assisted electrospinning method followed by calcination at 600 °C in air. These nanofibers were characterized for the morphological, structural and optical properties by scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and UV–visible (UV–vis) diffuse reflectance spectroscopy (DRS). SEM results reveal that the obtained NiTiO3 nanofibers are 175 nm in diameter and several micrometers in length after annealing at 600 °C. The XRD analysis shows that the nanofibers possess highly crystalline structure with no impurity phase. In contrast, the NiTiO3 nanoparticles synthesized at the identical conditions by a sol–gel route have impurities including TiO2 and NiO. Moreover, the electrospun NiTiO3 nanofibers are endowed with an obvious optical absorbance in the visible range, demonstrating they have visible light photoresponse. 相似文献
Summary: Poly(N‐vinylpyrrolidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles. N,N‐Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag+ ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. The Ag nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.
TEM image of a PVA nanofiber electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. 相似文献
Ag nanoparticle-embedded one-dimensional β-CD (β-cyclodextrin)/PVP composite nanofibers were prepared using a one-step electrospinning
technique. Ag nanoparticles were obtained in the AgNO3/β-CD/DMF solution, in which silver nitrate been introduced as the precursor, DMF as solvent, β-CD as reducing and capping
agent. After electrospinning of the composite solution at room temperature, the β-CD/PVP nanofibers containing Ag nanoparticles
were obtained. The electrospun composite solution containning Ag nsnopsrticles were confirmed by UV-visible absorption spectra;
the resulting composite nanofibers were characterized by scanning electron microscopy , transmission electron microscopy,
and X-ray diffraction. Ag-β-CD/PVP nanofiber exhibits good antibacterial property for Escherichia coli and Staphylococcus aureus. Consequently, we propose that these Ag nanoparticle-embedded 1D-nanostructures prepared via electrospinning may be used
as antibacterial material. 相似文献
Summary: Electrically conducting polypyrrole‐poly(ethylene oxide) (PPy‐PEO) composite nanofibers are fabricated via a two‐step process. First, FeCl3‐containing PEO nanofibers are produced by electrospinning. Second, the PEO‐FeCl3 electrospun fibers are exposed to pyrrole vapor for the synthesis of polypyrrole. The vapor phase polymerization occurs through the diffusion of pyrrole monomer into the nanofibers. The collected non‐woven fiber mat is composed of 96 ± 30 nm diameter PPy‐PEO nanofibers. FT‐IR, XPS, and conductivity measurements confirm polypyrrole synthesis in the nanofiber.
An SEM image of the PPy‐PEO composite nanofibers. The scale bar in the image is 500 nm. 相似文献
The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid(90%) was measured in the concentration range of 5 wt%-25 wt% using a programmable viscometer. Electrospinning of nylon-6,6 solutions was carried out under controlled parameters. The chemical structure, morphology and thermal properties of the obtained nanofibers were investigated using Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and differential scanning calorimetry(DSC), respectively. Entanglement concentration(ce) was found to be 15 wt% and a power law relationship between specific viscosity and solution concentration was observed with exponents of 2.0 and 3.3 for semi-dilute unentangled(c ce) and semi-dilute entangled(c ce) regimes, respectively. The diameter and uniformity of the nanofibers were found to be dependent on the viscosity. Moreover, the average diameter of electrospun nanofibers was found to be dependent on zero shear rate viscosity and normalized concentration(c/ce) in a power law relationship with exponents of 0.298 and 0.816, respectively. For nylon-6,6 solutions, the entanglement concentration(ce = 15 wt%) provides the threshold viscosity required for the formation of a stable polymeric jet during electrospinning and producing uniform beadless fibers. For concentrations less than ce, beaded fibers with some irregularities are formed. DSC analysis showed an increase in crystallinity of all electrospun samples compared to original polymer. Furthermore, Based on FTIR spectroscopy, α phase is dominant in electrospun nanofibers and minor amount of β and γ phases is also available. 相似文献
Poly (N-isopropylacrylamide)/poly (2-acrylamido-2-methylpropanesulfonic acid) (PNIPAAm/PAMPS) nanofibers was prepared using the electrospinning technique. The electrospinning process parameters such as solution concentration, voltage, receiver distance and flow rate were determined by the orthogonal experiments. The appropriate electrospinning parameters were 7.0% of solution concentration, 10.0 kV of voltage, 20 cm of distance and 3.1 μL·min?1 of flow rate, respectively. The major factor affecting the nanofibers diameter was the solution concentration and the diameter increased with the solution concentration. The Fourier-transform infrared spectroscopy (FTIR) was conducted to characterize the structure of the components for electrospinning. Scanning electron microscopy (SEM) was taken to observe the morphology, and the contact angle (CA) measuring was carried out to determine the wettability of the nanofibers with temperatures. The results of SEM observation showed that the surfaces of nanofibers were smooth with uniform fibrous diameters and without the formation of beads. The CA detections showed that the electrospun PNIPAAm/PAMPS nanofibers exhibited thermo-sensitivity of hydrophilicity at 20°C and hydrophobicity at 40°C. 相似文献
This paper describes the effect of embedding MgO and Al2O3 nanoparticles on the diameter of electrospun composite polyacrylonitrile (PAN) nanofibers. Diameter of nanofibers determines the important properties of the nanofibrous mats used in a variety of developed applications such as tissue engineering scaffolds, drug delivery, catalysis, ultra filtration, sensors, and nanoelectronics. The results showed that the type and amount of nanoparticles dispersed in PAN solutions affect the conductivity as well as the viscosity of the electrospinning solutions. Increasing the amount of MgO and Al2O3 leads to higher conductivity and higher viscosity of the electrospinning solution and ultimately to a smaller nanofiber diameter. Moreover, the results showed that higher conductivity of the electrospinning solution overcomes the effect of higher viscosity. Finally, no interaction was detected between metal oxide nanoparticles and PAN macromolecules. 相似文献
In this study, it was aimed to increase the piezoelectric and pyroelectric properties of electrospun polyvinylidene fluoride (PVDF) nanofibers simultaneously by using specific nanofillers. Graphene oxide (GO), graphene, and halloysite nanotubes with different concentrations (0, 0.05, 0.4, and 1.6% wt/wt) were combined with PVDF solution and were fabricated in the form of nanofibers through electrospinning. Pyroelectric properties of samples were measured by submerging sealed samples in hot water (360°K) and ice (270°K). The piezoelectric properties of the samples were evaluated through bending tests. The microstructural, mechanical, and thermal properties of the electrospun PVDF nanocomposite were investigated using scanning electron microscope, Instron instrument, and thermogravimetric analysis, respectively. To further support the experimental observations for generating electric voltage in the bended nanogenerator, the PVDF nanogenerator (PNG) was also modeled by a finite element analysis based on the theory of linear piezoelectricity using COMSOL Multiphysics simulation software. Experimental results showed that adding nanofillers could improve the piezoelectric and pyroelectric properties of all samples, associated with the increment of β‐phase in the nanofibers. It was concluded that adding nanofillers could increase pyroelectricity about 50% more than piezoelectricity in pristine PVDF nanofiber web. The PNG containing 1.6 wt% GO showed the highest efficiency in terms of piezoelectricity and pyroelectricity. In addition, the results showed that the ratio of piezoelectric to pyroelectric coefficients was constant (~1.5) and it was independent of the nanofiller type and content. The effect of external force and vibration frequency on the output voltage was also investigated. Increasing the compressive force and vibration frequency caused a greater output voltage. Finally, the fabricated nanogenerator was integrated on insole and elbow to investigate its energy harvesting capabilities from body movement. 相似文献