Dye-sensitized solar cells based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) nanofibers

Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers were prepared by the electrospinning method and used as polymer electrolytes in dye-sensitized solar cells (DSSCs). The electrolyte uptake and ionic conductivity of electrospun PVDF-HFP nanofibers with different diameters changed significantly, regardless of the nanofiber thickness. The PVDF-HFP nanofibers prepared from a 15 wt% spinning solution showed high ionic conductivity (1.295 S/cm) and electrolyte uptake (947 %). DSSCs based on the 15 wt% PVDF-HFP nanofiber electrolyte showed an electron transit time of 6.34 × 10^?3 s, electronic recombination time of 5.88 × 10^?2 s, and conversion efficiency of 3.13 %. Thus, we concluded that the electrospun PVDF-HFP nanofibers can be used as polymer electrolytes in flexible DSSCs as well.     

Preparation and characterization of poly(vinylidene fluoride)/sulfonated poly(phthalazinone ether sulfone ketone) blends for proton exchange membrane

Poly(vinylidene fluoride)/sulfonated poly(phthalazinone ether sulfone ketone) (PVdF/SPPESK) blend membranes are successfully prepared by solution blending method for novel proton exchange membrane (PEM). PVdF crystallinity, FTIR‐ATR spectroscopy, thermal stability, morphology, water uptake, dimension stability, and proton conductivity are investigated on PVdF/SPPESK blends with different PVdF contents. XRD and DSC analysis reveal that the PVdF crystallinity in the blends depends on PVdF content. The FTIR‐ATR spectra indicate that SPPESK remains proton‐conducting function in the blends due to the intactness of ? SO₃H group. Thermal analysis results show a very high thermal stability (T_d1 = 246–261°C) of the blends. PVdF crystallinity and morphology study demonstrate that with lower PVdF content, PVdF are very compatible with SPPESK. Also, with lower PVdF content, PVdF/SPPESK blends possess high water uptake, e.g., P/S 10/90 and P/S 15/85 have water uptake of 135 and 99% at 95°C, respectively. The blend membranes also have good dimension stability because the swelling ratios are at a fairly low level (e.g., 8–22%, 80°C). PVdF/SPPESK blends with low PVdF content exhibit very high proton conductivity, e.g., at 80°C, P/S 15/85 and P/S 10/90 reach 2.6 × 10^?2 and 3.6 × 10^?2 S cm^?1, respectively, which are close to or even higher than that (3.4 × 10^?2 S cm^?1) of Nafion115 under the same test condition. All above properties indicate that the PVdF/SPPESK blend membranes (particularly, with 10–20% of PVdF content) are very promising for use in PEM field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication and characterization of hollow nanofibrous PA6 yarn reinforced with CNTs

Core-sheath nanofibrous yarns were obtained through electrospinning of polyamide 6 (PA6) solution containing different concentrations of multi-wall carbon nanotubes (MWNTs) as sheath and PVA multifilament as the yarn core. By dissolving PVA, for obtaining conductive hollow nanofibrous PA6/MWNTs yarn, two types of porosity could be obtained including hollow central tube due to the structure of hollow yarn and nano-porous areas embedded in electrospun nanofibers. SEM results showed that the diameters of nanofibers were varying in the range of 103–145 nm obeying MWNTs concentrations and TEM results revealed that the MWNTs were embedded in nanofiber matrix as straight and aligned form. DSC analysis showed that electrospinning process caused the formation of less-ordered γ phase in nanofibers. The electrical conductivity of yarns increased from 10^?13 S m^?1 to 2.4?×?10^?6 S m^?1 with increasing the concentration of nanotubes from 0 wt.% to 7 wt.%.     

A morpholinium-functionalized poly(ether sulfone) as a novel anion exchange membrane for alkaline fuel cell

A methyl morpholinium-functionalized poly(ether sulfone) (MM-PES) copolymer was prepared as a novel anion exchange membrane. The MM-PES polymer was synthesized by polycondensation between the morpholine-containing hydroquinone and bisphenol A with bis(4-fluorophenyl)sulfone, followed by methylation of the morpholine group. The membrane obtained from MM-PES showed an IEC of 0.90 meq/g with high hydroxide conductivity of 1.6 × 10^?2 S/cm at r.t. and 7.9 × 10^?2 S/cm at 80 °C. The methyl morpholinium-functionalized PES membrane also displayed good hydrolytic, thermal, mechanical and chemical stabilities.     

Highly selective sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene)/poly(ether sulfone) blend proton exchange membranes for direct methanol fuel cells

Proton exchange membranes (PEMs) based on blends of poly(ether sulfone) (PES) and sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene) (sPVdF‐co‐HFP) were prepared successfully. Fabricated blend membranes showed favorable PEM characteristics such as reduced methanol permeability, high selectivity, and improved mechanical integrity. Additionally, these membranes afford comparable proton conductivity, good oxidative stability, moderate ion exchange capacity, and reasonable water uptake. To appraise PEM performance, blend membranes were characterized using techniques such as Fourier transform infrared spectroscopy, AC impedance spectroscopy; atomic force microscopy, and thermogravimetry. Addition of hydrophobic PES confines the swelling of the PEM and increases the ultimate tensile strength of the membrane. Proton conductivities of the blend membranes are about 10^?3 S cm^?1. Methanol permeability of 1.22 × 10^?7cm² s^?1 exhibited by the sPVdF‐co‐HFP/PES10 blend membrane is much lower than that of Nafion‐117. AFM studies divulged that the sPVdF‐co‐HFP/PES blend membranes have nodule like structure, which confirms the presence of hydrophilic domain. The observed results demonstrated that the sPVdF‐co‐HFP/PES blend membranes have promise for possible usage as a PEM in direct methanol fuel cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43907.     

Novel polyimide-based electrospun carbon nanofibers prepared using ion-beam irradiation

This paper describes a novel study focused on preparing carbon nanofibers, with a narrow fiber diameter distribution, from a fluorinated polyimide using both electrospinning and ion-beam irradiation. We specifically focused on the effects of ion species and ion fluences on the electrical conductivity of the nanofiber. The nanofibers were successfully prepared in the diameter range from 340 nm to 1500 nm by varying the concentration of polyimide solution using electrospinning. The Raman spectrum of the ion-irradiated nanofiber included the two well-known D (1360 cm^?1) and G (1580 cm^?1) peaks, indicating that the nanofiber surface changed to a carbon-enriched material. The carbon nanofibers underwent a more ordered graphitic carbon structure with an increase in the ion fluence and the electrical conductivity of the nanofiber irradiated at 1 × 10¹⁶ ions/cm² of Ar⁺ was 0.18 S/cm. In addition, the electrical conductivities of the ion-irradiated nanofibers increased in the order, He⁺ < Ne⁺ < Ar⁺, which indicated that the amount of nuclear energy in the ion species had the most influence on the electrical conductivity. However, the higher electrical conductivity of the carbon nanofibers is required to realize their industrial applications. This paper is the first to address the properties of the electrical conductivity of the carbon nanfibers prepared by electrospinning and ion irradiation as a new approach.     

Synthesis of (Z)‐3‐hexen‐1‐yl acetate by lipase immobilized in polyvinyl alcohol nanofibers

Polyvinyl alcohol (PVA)‐nanofibers‐immobilized lipase were formed by electrospinning. The specific surface area of the nanofiber (5.96 m²/g) was about 250 times larger than that of PVA‐film‐immobilized lipase (0.024 m²/g). The PVA‐nanofibers‐immobilized lipase were used as the catalyst for the esterification of (Z)‐3‐hexen‐1‐ol (leaf alcohol) with acetic acid in hexane. The activity of the nanofiber is equivalent to that of commercially available immobilized lipase (Novozym‐435). The ester conversions of the nanofibers, Novozym‐435, the film and lipase powder reached 99.5% at 5 h, 100% at 5 h, 11.5% at 6 h, and 81.1% at 5.75 h, respectively. The nanofibers‐immobilized lipase showed higher activity for the esterification than the film‐immobilized lipase and lipase powder, probably because it has high specific surface area and high dispersion state of lipase molecules in PVA matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Silanization of ZnO nanofibers by tetraethoxysilane

Zinc oxide (ZnO) nanofibers are synthesized by electrospinning technique and then silanized to tailor its structural, optical, and electrical properties. The modification of ZnO nanofibers by chemical treatment of tetraethoxysilane (TEOS) is clearly evident from the appearance of relevant Fourier transform infrared peak at about 1000 cm^?1 corresponding to Zn? O? Si bond. The height of this peak increases linearly with increase in concentration of silane up to 400 μL, and afterward become plateau up to 500 μL. Diffuse reflectance spectroscopy measurement shows that band gap decreases from 3.35 eV for pure zinc oxide nanofibers to 3.11 eV with successive increase in concentration of TEOS from 100 to 500 μL. The electrical characteristics of modified ZnO nanofibers are analyzed by impedance spectroscopy. It is observed that impedance of ZnO nanofibers increases (resistance from 1.69 × 10⁸ to 2.618 × 10⁹ ohm and capacitance from 2.043 × 10^?12 to 7.618 × 10^?13 F) with increase of TEOS concentration. This study provides guidelines for tailoring the electrical properties of ZnO nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45378.     

Electrospinning synthesis and negative thermal expansion of one-dimensional Sc2Mo3O12 nanofibers

Orthorhombic Sc₂(MoO₄)₃ nanofibers have been prepared by ethylene glycol assisted electrospinning method. The effects of annealing temperature, precursor concentration, spinning distance and solvent on the preparation of Sc₂(MoO₄)₃ nanofibers were characterized by XRD, SEM, HRTEM, EDX and high-temperature XRD. XRD analysis shows as-prepared nanofibers are amorphous. Orthorhombic Sc₂(MoO₄)₃ nanofibers can be fabricated after annealing at different temperatures in 500–800 °C for 2 h. The crystallinity of Sc₂(MoO₄)₃ nanofibers improves and the nanofiber diameter decreases gradually as the annealing temperature increases. However, the nanofiber structure was destroyed at the annealing temperature above 700 °C. Higher precursor concentration results in a slight increase of diameter and decrease in destroying temperature of Sc₂(MoO₄)₃ nanofibers. Spinning distance also affects the diameter of nanofibers, and the nanofiber diameter decreases as the distance increases. One-dimensional orthorhombic Sc₂(MoO₄)₃ nanofibers exhibit anisotropic negative thermal expansion. In 25–700 °C, the coefficients of thermal expansion (CTE) of α_a, α_b and α_c are ?5.81 × 10^?6 °C^?1, 4.80 × 10^?6 °C^?1 and -4.33 × 10^?6 °C^?1, and the α_l of Sc₂(MoO₄)₃ nanofibers is ?1.83 × 10^?6 °C^?1.     

ZnO nanocrystallites/cellulose hybrid nanofibers fabricated by electrospinning and solvothermal techniques and their photocatalytic activity

ZnO nanocrystallites have been in situ embedded in cellulose nanofibers by a novel method that combines electrospinning and solvothermal techniques. Zn(OAc)₂/cellulose acetate (CA) precursor hybrid nanofibers with diameter in the range of 160–330 nm were first fabricated via the electrospinning technique using zinc acetate as precursor, CA as the carrier, and dimethylformamide (DMF)/acetone(2 : 1) mixture as cosolvent. The precursor nanofibers were transformed into ZnO/cellulose hybrid fibers by hydrolysis in 0.1 mol/L NaOH aqueous solution. Subsequently, these hybrid fibers were further solvothermally treated in 180°C glycerol oil bath to improve the crystallite structure of the ZnO nanoparticles containing in the nanofibers. The structure and morphology of nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. It was found that hexagonal structured ZnO nanocrystallites with the size of ～ 30 nm were dispersed on the nanofiber surfaces and within the nanofibers with diameter of about 80 nm. The photocatalytic property of the ZnO/cellulose hybrid nanofibers toward Rhodamine (RhB) was tested under the irradiation of visible light. As a catalyst, it inherits not only the photocatalytic ability of nano‐ZnO, but also the thermal stability, good mechanical property, and solvent‐resistibility of cellulose nanofibers. The key advantages of this hybrid nanofiber over neat ZnO nanoparticles are its elasticity, dimensional stability, durability, and easy recyclability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

P123对聚醚砜纳米纤维膜结构和性能的影响

通过静电纺丝法制备了聚醚砜(PES)/聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123,PEO₂₀PPO₇₀PEO₂₀,M_a=5800)纳米纤维膜,考察了P123含量对纺丝液的黏度和表面张力的影响,以及对所制备的纳米纤维膜的结构和性能的影响。实验结果表明:P123含量从3%(质量)增至9%时,其纺丝液的黏度由300 mPa·s增至1000 mPa·s,表面张力在36.5～37.8 mN·m^-1范围内;P123改性的PES纳米纤维直径约为360 nm,分布均匀,其表面也比较光滑,取向趋于一致;此外,该纳米纤维膜具有良好的机械性能和耐溶胀性能,较大的比表面积(>39 m²·g^-1),孔隙率,可用作催化剂载体。     

Palladium nanoparticles embedded chitosan/poly(vinyl alcohol) composite nanofibers as an efficient and stable heterogeneous catalyst for Heck reaction

In this study, palladium nanoparticles were successfully embedded into modified chitosan/poly(vinyl alcohol) composite nanofibers (Pd-CS/PVA nanofibers) by electrospinning. Then, the Pd-CS/PVA nanofibers were treated at evaluated temperature to improve its solvent resistance and in situ reduce Pd²⁺ cations into Pd⁰ active species. The incorporated palladium nanoparticles with ultra small mean diameter of 3.73 ± 1.04 nm are evenly distributed inside the Pd-CS/PVA nanofiber. The resulting Pd-CS/PVA nanofiber mat exhibits high catalytic activity for Heck reaction of aromatic iodides with alkenes and can be recycled for 18 times without loss of initial activity. The high catalytic activity and stability of Pd-CS/PVA nanofiber mat can be attributed to the ultra small diameter nanofibers, strong chelating ability of chitosan, and fine embedment of palladium species inside the nanofiber. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48026.     

Preparation and molten salt-assisted KOH activation of porous carbon nanofibers for use as supercapacitor electrodes

Carbon nanofiber paper was prepared by electrospinning from thermosetting phenolic resin, followed by activation via KOH-containing molten salt at high temperature. By adding a small dosage of KOH in the molten salt the porous volume and specific surface area could be greatly improved. The obtained porous carbon nanofibers had a specific surface area of 1007 m² g^?1, total pore volume of 0.363 cm³ g^?1, micropore volume of 0.247 cm³ g^?1. The electrochemical measurements in 6 M KOH aqueous solution showed that the porous carbon nanofibers possessed high specific capacitance and considerable rate performance. The maximal specific capacitance of 288 F g^?1 was achieved at 0.2 A g^?1 and the specific capacitance could still remain 204 F g^??1 at 20 A g^?1 with the retention of 71%. In the molten salt system, the reaction between activating agent and carbon could be more efficient, hence, such molten salt-assisted activation method was considered as a general activation method for the high-specific-surface-areaed carbons.     

Characterization of triple electrospun layers of PVDF for direct contact membrane distillation process

Recently, electrospinning technique was applied successfully to fabricate porous hydrophobic membranes for MD applications. In this work, a novel triple layer configuration with diameter gradient for PVDF nanofiber membranes is proposed, with the objective of to minimize mass transfer resistance and heat loss. In outer layers of these membranes, the minimum concentration of PVDF (20 wt%) was used to produce bead-free nanofibers with thinner diameters and middle layers were composed of thicker nanofibers formed at higher polymer concentrations (21.5-26 wt%). Characterization of prepared membranes was conducted by the measurement of porosity, thickness, liquid entry pressure (LEP), scanning electron microscopy (SEM), contact angle, thermal and mechanical properties. Direct contact membrane distillation performance of fabricated membranes was tested using 42 g/L NaCl as feed solution. Water permeate flux of triple layer membranes (27.8-31.5 kg/m² h) was found to be considerably higher than that obtained from single layer membrane (15.4 kg/m² h), indicating the proposed configuration can effectively improve evaporation efficiency.     

Synthesis of pH‐responsive crosslinked poly[styrene‐co‐(maleic sodium anhydride)] and cellulose composite hydrogel nanofibers by electrospinning

BACKGROUND: Stimuli‐sensitive materials show enormous potential in the development of drug delivery systems. But the low response rate of most stimuli‐sensitive materials limits their wider application. We propose that electrospinning, a technique for the preparation of ultrafine fibrous materials with ultrafine diameters, may be used to prepare materials with a fast response to stimuli. RESULTS: Poly[styrene‐co‐(maleic sodium anhydride)] and cellulose (SMA‐Na/cellulose) hydrogel nanofibers were prepared through hydrolysis of precursor electrospun poly[styrene‐co‐(maleic anhydride)]/cellulose acetate (SMA/CA) nanofibers. In the presence of diethylene glycol, the SMA/CA composite nanofibers were crosslinked by esterification at 145 °C, and then hydrolyzed to yield crosslinked SMA‐Na/cellulose hydrogel nanofibers. These nanofibers showed better mechanical strengths and were pH responsive. Their water swelling ratio showed a characteristic two‐step increase at pH = 5.0 and 8.2, with the water swelling ratio reaching a maximum of 27.6 g g^?1 at pH = 9.1. CONCLUSION: The crosslinked SMA‐Na hydrogel nanofibers supported on cellulose showed improved dimensional stability upon immersion in aqueous solutions. They were pH responsive. This new type of hydrogel nanofiber is a potential material for biomedical applications. Copyright © 2009 Society of Chemical Industry     

Preparation of poly(ether sulfone) nanofibers by gas‐jet/electrospinning

Poly(ether sulfone) (PES) nanofibers were prepared by the gas‐jet/electrospinning of its solutions in N,N‐dimethylformamide (DMF). The gas used in this gas‐jet/electrospinning process was nitrogen. The morphology of the PES nanofibers was investigated with scanning electron microscopy. The process parameters studied in this work included the concentration of the polymer solution, the applied voltage, the tip–collector distance (TCD), the inner diameter of the needle, and the gas flow rate. It was found from experimental results that the average diameter of the electrospun PES fibers depended strongly on these process parameters. A decrease in the polymer concentration in the spinning solutions resulted in the formation of nanofibers with a smaller diameter. The use of an 18 wt % polymer solution yielded PES nanofibers with an average diameter of about 80 nm. However, a morphology of mixed bead fibers was formed when the concentration of PES in DMF was below 20 wt % during gas‐jet/electrospinning. Uniform PES nanofibers with an average diameter of about 200 nm were prepared by this electrospinning with the following optimal process parameters: the concentration of PES in DMF was 25 wt %, the applied voltage was 28.8 kV, the gas flow was 10.0 L/min, the inner diameter of the needle was 0.24 mm, the TCD was 20 cm, and the flow rate was 6.0 mL/h. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Fabrication of continuous nanofiber yarn using novel multi‐nozzle bubble electrospinning

A novel multi‐nozzle bubble electrospinning apparatus, including spinning unit, metering pump, constant flow pump, metal funnel and yarn winder, was designed for the preparation of continuous twisted polyacrylonitrile nanofiber yarns, and the principle of nanofiber yarn spinning was studied. An innovative spinning unit consisting of nozzle and air chamber was used to improve the production of nanofibers. Double conjugate electrospinning was developed using two pairs of oppositely charged spinning units to neutralize the charges. The effects of applied voltage, air flow rate, overall solution flow rate and funnel rotary speed on the fiber diameter, production rate and mechanical properties of the nanofiber yarns were analyzed. Nanofibers could be aggregated stably and bundled continuously, then twisted into nanofiber yarns uniformly at an applied voltage of 34 kV, air flow rate of 1200 mL min^?1 and overall solution flow rate of 32 mL h^?1. With an increase in the funnel rotary speed, the twist angle of the nanofiber yarns gradually increased when the take‐up speed was constant. The yarn tensile strength and elongation at break showed an increasing trend with increasing twist angle. Nanofiber yarns obtained using this novel method could be produced at a rate from 2.189 to 3.227 g h^?1 with yarn diameters ranging from 200 to 386 µm. Nanofiber yarns with a twist angle of 49.7° showed a tensile strength of 0.592 cN dtex^?1 and an elongation at break of 65.7%. © 2013 Society of Chemical Industry     

An applicable electrospinning process for fabricating a mechanically improved nanofiber mat

Engineered polymer scaffolds play an important role in tissue engineering. An ideal scaffold should have good mechanical properties and provide a biologically functional implant site. Considering their large surface area and high porosity, nanofibers have good potential as biomimetic scaffolds. However, the main shortcomings of scaffolds consisting of nanofibers are their mechanical inability to sustain a stress environment for neotissues and shape‐ability to form a variety of shapes and sizes. In this study, we produced design‐based poly (ε‐carprolactone) (PCL) nanofiber mats using an electrospinning method with various auxiliary electrodes and an x‐y moving system. To achieve stable initial solution at a nozzle tip of the electrospinning, various types of auxiliary electrodes were introduced. To characterize the effect of the electrodes in the electric‐field distribution near the nozzle tip, we calculated the electric field concentration factor and compared it with the experimental results. The nanofiber mat produced using the moving x‐y target system demonstrated orthotropic mechanical properties due to the fiber orientation, and human dermal fibroblasts seeded on the structure tended to grow according to nanofiber orientation. POLYM. ENG. SCI., 47:707–712, 2007. © 2007 Society of Plastics Engineers.     

电纺制备聚乳酸/聚醚砜复合纳米纤维膜及性能研究

采用同轴静电纺丝制备聚乳酸/聚醚砜(PLA/PES)复合纳米纤维膜,通过改变皮层溶液的挤出速率以及在芯层溶液中分别添加石墨烯（GO）、碳纳米管(MWCNTs)、埃洛石（HNTs）纳米粒子,制备了系列皮芯结构的复合纳米纤维膜。通过扫描电子显微镜、纤维强伸度仪、接触角测定仪等仪器测试表征了复合纳米纤维膜的纤维结构、拉伸强度、疏水性以及吸油倍率等性能。结果表明,制备的复合纳米纤维膜的接触角均大于130 °,表现出较好的亲油疏水性;当往芯液中添加石墨烯(GO)时,纳米纤维膜的吸油性能、拉伸性能最好,在甘油中的吸油倍率可达到67.61倍,食用油中可达到48.02倍,纵向断裂强度为62.68 MPa,横向断裂强度为43.98 MPa,横向断裂伸长率可达到697.76 %。     

Montmorillonite‐reinforced sulfonated poly(phthalazinone ether sulfone ketone) nanocomposite proton exchange membranes for direct methanol fuel cells

To produce a composite membrane with high conductivity and low permeability, SPPESK with a degree of sulfonation of 101% was carefully selected for the preparation of montmorillonite (MMT)‐reinforced SPPESK using solution intercalation. The fundamental characteristics such as water uptake, swelling ratio, proton conductivity, methanol permeability, and mechanical properties of the composite membranes were studied. Water uptake is improved when organic MMT (OMMT) loading increase. The composite membranes with CTAB‐MMT loading of 4–0.5% show 0.143–0.150 S cm^?1 proton conductivity at 80°C, which approaches the value of Nafion112. In addition, methanol permeability was decreased to 6.29 × 10^?8 cm² s^?1 by the addition of 6 wt % OMMT. As a result, the SPPESK‐MMT composite membrane is a good candidate for use in direct methanol fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39852.