The photocatalytic degradation of chloramphenicol with electrospun Bi2O2CO3-poly(ethylene oxide) nanofibers: the synthesis of crosslinked polymer,degradation kinetics,mechanism and cytotoxicity

Insoluble poly(ethylene oxide) (PEO) nanofibers were synthesized by adding pentaerythrotol triacrylate (PETA) into precursor solutions prior to electrospinning, and then the obtained fibers were exposed to an electron beam (EB) irradiation. Bi₂O₂CO₃ was incorporated into these fibers to extend their photocatalytic properties. Studies confirmed that EB irradiation induced characteristic changes in PEO and led to the formation of a crosslinked structure, from which we optimized the irradiation dose of fibers as 210 kGy. The optimum PEO/Bi₂O₂CO₃ membranes achieved 99.5% CPL degradation within 60 min, and we also proposed the possible degradation pathways of CPL in this study. Besides, all the water samples and extracts of nanomaterials showed no cytotoxicity on L-929 cells. The subtle variations in the cell viability of treated and untreated water samples could be due to the toxic intermediates arising from the photocatalytic process. Therefore, this photocatalyst-polymer membrane can be considered as a biocompatible composite system that can change the solubility of a polymer and also act as a highly efficient photocatalyst for organic wastewater treatments.

Insoluble poly(ethylene oxide) (PEO) nanofibers were synthesized by adding pentaerythrotol triacrylate (PETA) into precursor solutions prior to electrospinning, and then the obtained fibers were exposed to an electron beam (EB) irradiation.     

Acetone fractionation: a simple and efficient method to improve the performance of lignin for dye pollutant removal

In this work, it was found that the adsorption capacity of lignin to cationic dye (methylene blue, MB) from aqueous solution could be significantly improved by simple acetone fractionation. The removal efficiency of MB by acetone insoluble kraft lignin (AIKL) was 10 times that of unfractionated kraft lignin (KL). And the maximum capacity of AIKL could reach up to 623.4 mg g⁻¹. And the high removal rate could be achieved even at low concentrations. The effects of ionic strength, temperature, adsorbent dosage were systematically investigated. Adsorption kinetics showed the adsorption behavior obeyed the pseudo-second-order kinetic model. The equilibrium data was more consistent with the Langmuir isotherm model. Thermodynamic analyses proved that the adsorption was a spontaneous and endothermic physisorption process. In addition, the reasons for the enhanced adsorption effect by fractionation were clarified based on characterization by FT-IR. The enhancement of π–π interaction between AIKL and MB caused by fractionation plays an important role in the adsorption process.

In this work, it was found that the adsorption capacity of lignin to cationic dye (methylene blue, MB) from aqueous solution could be significantly improved by simple acetone fractionation.     

High ion adsorption densities of site-selective nitrogen doped carbon sheets prepared from natural lignin

Carbon fibers and sheets were prepared from jet-milled natural chitin and cellulose samples, and from natural lignin sample using ice-templating technique, respectively. Nitrogen doping treatments using melamine were also performed for the carbon fibers and sheets. Electric double layer capacitor (EDLC) electrode properties of the prepared carbon fibers and sheets including the nitrogen doped samples were investigated with aqueous (sulfuric acid) and organic (tetraethylammonium tetrafluoroborate in propylene carbonate) electrolytes. It was found that the nitrogen doped lignin carbon sheets having very small specific surface area of 66 m² g⁻¹ show very high EDLC capacitances of 227 F g⁻¹ and 80 F g⁻¹ determined by charge–discharge measurements at current density of 50 mA g⁻¹ for aqueous and organic electrolytes, respectively. X-ray photoelectron spectroscopy (XPS) measurements revealed that nitrogen atoms of the nitrogen doped lignin carbon sheets exist dominantly in pyridinic sites unlike other chitin and cellulose carbon fibers. We discussed that this site-selective nitrogen doping gives exceptionally high ion adsorption density per unit surface area of the nitrogen doped lignin carbon sheets.

Carbon fibers and sheets were prepared from jet-milled natural chitin and cellulose samples, and from natural lignin sample using ice-templating technique, respectively.     

Nanofibers with diameter below one nanometer from electrospinning

Sub-nanometer materials have received wide attention due to their unique properties in recent years. Most studies focus on the preparation and properties investigation of the inorganic sub-nanometer materials, while there are few reports on organic especially polymeric sub-nanometer materials such as sub-nanometer fiber due to the obstacles with respect to fabricating such small nanofibers. In this work we prepare PAA nanofibers with diameters ranging from hundreds of nanometers down to sub-nanometer via electrospinning from a polyamic acid (PAA) with ultrahigh molecular weight. The morphologies and size of the electrospun ultrathin nanofibers are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). AFM images combined with theoretic calculations show that sub-nanometer fiber of approximate 0.17–0.63 nm only containing one molecular chain was generated via electrospinning from ultra-dilute PAA solutions for the first time. These quite small sub-nanometer fibers would open a new area of electrospinning and provide further explorations on the production and application of electrospun sub-nanometer fibers with single molecular chains.

Super-fine nanofibers with diameter below 1 nanometer are prepared by electrospinning from ultra-dilute solutions.     

Bacteriophage nanofiber fabrication using near field electrospinning

M13 bacteriophage (phage) nano- and microfibers were fabricated using electrospinning. Using liquid crystalline suspension of the phage, we successfully fabricated nano- and microscale pure phage fibers. Through a near field electrospinning process, we fabricated the desired phage fiber pattern with tunable direction and spacing. In addition, we demonstrated that the resulting phage fibers could be utilized as an electrostatic-stimulus responsive actuator. The near field electrospinning would be a very useful tool to design phage-based chemical sensors, tissue regenerative materials, energy generators, metallic and semiconductor nanowires in the future.

Using liquid crystalline suspension of the phage, we successfully fabricated nano- and microscale pure phage fibers. Through a near field electrospinning process, we fabricated the desired phage fiber pattern with tunable direction and spacing.     

Flexible Fe3Si/SiC ultrathin hybrid fiber mats with designable microwave absorption performance

Flexible Fe₃Si/SiC ultrathin fiber mats have been fabricated by electrospinning and high temperature treatment (1400 °C) using polycarbosilane (PCS) and ferric acetylacetonate (Fe(acac)₃) as precursors. The crystallization degree, flexibility, electrical conductivity, dielectric loss and microwave absorption properties of the hybrid fibers have been dramatically enhanced by the introduction of Fe. Fe₃Si nanoparticles with a diameter around 500 nm are embedded in SiC fibers. As the Fe₃Si content increases from 0 to 6.5 wt%, the related saturation magnetization (M_s) values increase from 0 to 8.4 emu g⁻¹, and the electrical conductivity rises from 7.9 × 10⁻⁸ to 3.1 × 10⁻³ S cm⁻¹. Moreover, the flexibility of Fe₃Si/SiC hybrid fiber mats is greatly improved and remains intact after 500 times 180°-bending testing. Compared with pure SiC fibers, the Fe₃Si/SiC hybrid fibers process higher dielectric and magnetic loss, which would be further advanced as more Fe₃Si phase is introduced. At the optimal Fe₃Si content of 3.8 wt%, the Fe₃Si/SiC fibers/silicon resin composite (5 wt%) exhibits minimal reflection loss (RL) of −22.5 dB at 16.5 GHz and 2.5 mm thickness with a wide effective absorption bandwidth (EAB, RL < −10 dB) of 8.5 GHz. The microwave absorption performance can be further promoted by multi component stacking fiber mat composites which contain both low and high Fe₃Si content layers. Furthermore, the position of the microwave absorption bands can also be simply manipulated by designing the stacking components and structure.

Flexible Fe₃Si/SiC ultrathin fiber mats have been fabricated by electrospinning and high temperature treatment (1400 °C) using polycarbosilane (PCS) and ferric acetylacetonate (Fe(acac)₃) as precursors.     

A tough and sustainable fiber-forming material from lignin and waste poly(ethylene terephthalate)

In this report we describe repurposing of recycled polyesters as a matrix for lignin-a biorefinery coproduct that is used as a solid fuel and needs to find higher value-to make sustainable high-performance thermoplastic materials. Brittle lignin oligomers, isolated from plant biomass, require a low-melting host polymer matrix to form a rigid and tough renewable material. We demonstrate controlled lignin dispersion and interfacial interactions in softened recycled polyethylene terephthalate (PET) using a simple solvent-free, melt-blending technique. To avoid lignin degradation and devolatilization during melt processing, it was thermally treated. Tall oil fatty acid was used to enable PET processability at low enough temperature to accommodate lignin without charring. Chemical analysis reveals reduction of aliphatic hydroxyl content from 2 mmol g⁻¹ to 1.63 mmol g⁻¹ and an increase of total phenolic hydroxyl moieties from 5.86 to 6.64 mmol g⁻¹ and cleavage of β-O-4 ether linkages due to thermal treatment. Structural transformation of lignin macromolecules during heat treatment was further confirmed by an increase in molar mass and improved thermal stability. Interfacial interactions between lignin and PET were assessed from mechanical properties and thermal analyses. Thermal treatment not only helps to improve the stability of lignin but also slightly reduces the size of the dispersed lignin domains via favored interfacial interactions with the PET matrix. These methods improve mechanical properties of the material. Further, incorporation of lignin in the plasticized PET matrix increases the ductility in the blended products. The method we discuss here utilizes industrial wastes and co-products, and it does not require solvent or toxic chemicals during the reactive extrusion process that yields complete conversion to products.

This study reports a path for recycling polyester along with biorefinery coproduct, lignin, to make sustainable high-performance thermoplastic materials.     

Fabrication of polytetrafluoroethylene nanofibrous membranes for guided bone regeneration

In this study, we first prepared the precursor polytetrafluoroethylene (PTFE)/poly(ethylene oxide) (PEO) nanofibrous membranes by electrospinning with different PTFE/PEO weight ratios. These membranes exhibited three-dimensional interconnected pore structures. The average diameter of the precursor nanofibres decreased with increased PTFE contents from 633 ± 34 nm (PTFE/PEO weight ratio of 5 : 1) to 555 ± 63 nm (PTFE/PEO weight ratio of 7 : 1) because of the decrease in solution viscosity. Then, the precursor membranes were sintered with different temperatures to obtain the PTFE nanofibrous membranes, resulting in the average diameter of the nanofibres increasing from 633 ± 34 nm to 947 ± 78 nm with the increase in sintering temperature; consequently, the membrane became more compact. This compaction caused a decrease in porosity from 76.5 ± 2.9% to 69.1 ± 2.6% and an increase in water contact angle from 94.1 ± 4.2° to 143.3 ± 3.5°. In addition, the mechanical properties of the PTFE nanofibrous membranes increased with increasing sintering temperature. Cytocompatibility test results revealed that the PTFE350 membrane, which was sintered at 350 °C, promoted the proliferation and differentiation of MC3T3-E1 cells more rapidly than other membrane types. These results suggested that the PTFE nanofibrous membranes could be ideal biomaterials in tissue engineering for bone regeneration.

In this study, PTFE nanofibrous membranes were fabricated by sintering the previously electrospun polytetrafluoroethylene (PTFE)/poly(ethylene oxide) (PEO) nanofibrous membranes.     

Cotton-like micro- and nanoscale poly(lactic acid) nonwoven fibers fabricated by centrifugal melt-spinning for tissue engineering

Biodegradable materials in the form of nonwoven fibers have attracted increasing attention for tissue engineering applications because they offer large surface areas and interconnected networks. In this study, cotton-like nonwoven poly(lactic acid) (PLA) fibers were successfully fabricated by centrifugal melt-spinning. The effects of centrifugal speed and secondary melt-spinning processing on the morphology, mechanical properties, and cell compatibility of the fibers were investigated. Scanning electron microscopy, differential scanning calorimetry, and Fourier-transform infrared spectroscopy (FTIR), as well as cell culturing of MC3T3-E1 were used in this study. The results showed that centrifugal speeds from 350 to 1500 rpm satisfied the needs for fiber formation. The PLA fibers we prepared had three-dimensional structures with extensive diameter distribution from the nanoscale to several tens of micrometers, large pore sizes, and high porosities, significantly different from fibers produced by electrospinning. The fiber diameters and mechanical properties could be manipulated by controlling the centrifugal speed. The finest fibers were generated at 900 rpm with average diameters of 3.47 ± 3.48 μm. The fibers created by centrifugal melt-spinning exhibited lower cytotoxicity and higher cell proliferation than those obtained by electrospinning.

Schematic of the centrifugal melt spinning apparatus, consisting of (a) a rotary disk, (b) heating circuit, (c) electromotor, (d) filling inlet and (e) rotary collector on a drum.     

High-performance multi-functional graphene/hexagonal boron nitride/poly(ethylene oxide) nanocomposites through enhanced interfacial interaction by coordination

In this study, multi-functional nanocomposites with excellent mechanical, electrical and thermal properties were prepared through metal-ion coordination. Reduced graphene oxide (rGO) and hexagonal boron nitride (h-BN) interacted through calcium coordination bonding. Poly(ethylene oxide) (PEO) was added to bridge these two nanomaterials, providing more resistance to tensile deformation. The results of UV-Vis and FTIR spectra proved that coordination bonding was successfully formed among the three compounds. SEM images showed homogenous dispersions of the nanocomposite. After calcium-ion coordination, the mechanical, electrical and thermal properties of Ca²⁺-coordinated rGO/BN/PEO composite improved significantly, indicating that metal-ion coordination is a potential method for multi-functional nanocomposite fabrication.

A versatile method to bridge different nanomaterials by metal-ion coordination and enhance different properties simultaneously.     

Extraction of lignin and quantitative sugar release from biomass using efficient and cost-effective pyridinium protic ionic liquids

Lignocellulosic biomass is enormously abundant around the globe. It bears huge potential for renewable products as its components can be converted to many useful products via cheaper processes. Recently, the component of biomass that has attracted enormous attention is lignin owing to its several aromatic or phenolic constituents. The utilization of lignin, however, is hindered by its troublesome separation mainly due to the difficult nature of the lignocellulosic biomass. Protic ionic liquids have great potential for extraction of lignin from the lignocellulosic biomass to make it viable for various transformations. In this study, protic ionic liquids comprising a pyridinium cation and a dihydrogen phosphate anion (H₂PO₄⁻) were prepared and used for lignin extraction and subsequent saccharification of the cellulose pulp. The ILs exhibited appreciably high lignin yields (optimum 73%) under mild conditions (100 °C) and shorter time (2 h). Fairly good sugar (glucose) yields (77%) verify effective delignification. The analysis of ILs and biomass was accomplished by H-NMR, FT-IR, SEM, HSQC and GPC.

Lignocellulosic biomass is enormously abundant around the globe. It bears huge potential for renewable products as its components can be converted to many useful products via cheaper processes.     

Role of a “surface wettability switch” in inter-fiber bonding properties

The fiber surface wettability is one of the most important lignocellulosic fiber characteristics affecting the inter-fiber bonding properties of final bio-products. In this study, the surface wettability (evaluated by the surface free energy, surface lignin and surface charge) of mechanically refined fibers and the bonding properties of the fiber matrix (handsheets) were measured and correlated to each other. The results showed that the fiber surface charge increased from 48.38 mmol kg⁻¹ to 60.38 mmol kg⁻¹ and the surface lignin decreased from 87.1% to 77.5% during the fiber mechanical treatment, leading to the improvement of the fiber surface free energy from 46.63 mJ m⁻² to 54.45 mJ m⁻². As a result, the bonding strength index increased from 2.60 N m g⁻¹ to 9.73 N m g⁻¹ without significant loss of bulk properties. In a word, the fiber surface wettability could be adjusted to facilitate the inter-fiber bonding properties of the paper or paperboard products using lignin-rich fibers as raw materials.

The fiber surface wettability is one of the most important lignocellulosic fiber characteristics affecting the inter-fiber bonding properties of final bio-products.     

Investigating the draw ratio and velocity of an electrically charged liquid jet during electrospinning

The investigation of the draw ratio and velocity of an electrospinning polymer solution jet is of great interest for understanding the formation of nanofibers. During the electrospinning process, the charged polymer solution jets were stretched by electric force, resulting in the formation of ultrathin fibers. In this study, theoretical deduction and experimental calculation were applied to evaluate the velocities and draw ratios of the charged jets at different electrospinning stages. Depending on the diameter of the charged jets at different electrospinning stages, the velocities and draw ratios of the charged jets were calculated with values far lower than the data in a previous report. The theoretical calculation was compared with experimental data using polyamic acid as a model polymer for electrospinning. The results indicated that during electrospinning, as the collecting distance was increased from 0 to 30 cm, the diameter of the electrospinning jet decreased from 18 800 nm to a constant value of around 245 nm, the solvent in the jet decreased from 96.50 wt% to 25.45 wt%, and the density of the jet increased from 0.9504 to 1.0995 g cm⁻³. These parameters led to the draw ratio and velocity of the jet experiencing first an increase and then a decrease in the value, and the highest draw ratio and velocity were 869 and 867 m s⁻¹, respectively, which are quite different from the data in previous reports.

Theoretical calculations and experiments were performed to determine the draw ratio and velocity of an electrospinning jet.     

Novel pathway to produce high molecular weight kraft lignin–acrylic acid polymers in acidic suspension systems

Kraft lignin (KL) produced in kraft pulping process has a low molecular weight and solubility, which limits its application in industry. For the first time, KL was polymerized with acrylic acid (AA) in an acidic aqueous suspension system to produce a water soluble lignin–AA polymer with a high molecular weight in this work. The polymerization reaction was carried out using K₂S₂O₈ as an initiator, and the influence of reaction conditions on the carboxylate group content and molecular weight of resultant lignin polymers was systematically investigated. The mechanism of polymerization of KL and AA was discussed fundamentally. The resulting lignin–AA polymer was characterized by Fourier Transform Infrared spectrophotometry (FTIR), proton nuclear magnetic resonance (¹H-NMR) and elemental analyses. The results showed that the phenolic hydroxyl group (Ph-OH) content of KL promoted the polymerization under an acidic environment. Under the conditions of 1.5 wt% of initiator, 3.5 of pH, 10.0 of AA/lignin molar ratio, 0.15 mol L⁻¹ of lignin concentration, 3 h and 80 °C, the carboxylate group content and the molecular weight of the polymer were 7.37 mmol g⁻¹ and 7.4 × 10⁵ g mol⁻¹, respectively. The lignin–AA polymer was water soluble at a 10 g L⁻¹ concentration and a pH higher than 4.5. Furthermore, the flocculation performance of lignin–AA polymer in an aluminium oxide suspension was evaluated. Compared with polyAA, the lignin–AA polymer was a more efficient flocculant for aluminium oxide suspension, which shows its potential to be used as a green flocculant in industry.

Kraft lignin (KL) produced in kraft pulping process was polymerized with acrylic acid in an aqueous system.     

UV-protection from chitosan derivatized lignin multilayer thin film

Lignin is one of the most abundant renewable materials on the earth. Despite possessing useful antioxidant and UV absorbing properties, its effective utilization in technology has been hampered by its relative insolubility and difficulty to process. In this work, a simple chemical derivatization process is utilized which yields water-soluble lignin possessing anionic carboxylate groups. These carboxylate groups give lignin polyanionic behavior and enable its utilization in the growth of a functional film via layer-by-layer (LbL) assembly with biologically sourced chitosan. The growth mechanism of this film is hypothesized to be a result of both hydrogen bonding and ionic interactions. The film demonstrates excellent UV-absorptive capability. A 100 nm thick chitosan/lignin coating was applied to a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film and shown to reduce its degradation sixfold over the course of a 1 hour exposure to harsh UV light. This is the first demonstration of lignin being utilized in a fully biologically derived LbL film. Utilization of lignin in LbL assembly is an important step in the development of renewable nanotechnology.

An environmentally benign derivatization process enables the use of lignin in an entirely biosourced functional thin film.     

Flexible polypyrrolone-based microporous carbon nanofibers for high-performance supercapacitors

Flexible materials have drawn considerable attention due to the demand for wearable and flexible electronic products. Seeking new kinds of precursors for preparing carbon nanofibers with good flexibility for high-performance supercapacitors is a hot issue. In this work, a flexible polypyrrolone (BBB)/polyimide (PI) composite-based carbon nanofiber membrane (PBPICF) is prepared by a facile electrospinning and carbonization process. The PBPICF membranes exhibit a three-dimensional (3D) porous, fluffy and self-standing structure with good mechanical performance and flexibility, and can be arbitrarily bent and folded. PBPICF-65-35 (consisting of BBB (65 wt%) and PI (35 wt%)) exhibits a high specific capacitance of 172.44 F g⁻¹ in 6 M KOH aqueous solution, which is two-fold more than that of commercial polyacrylonitrile-based carbon nanofibers. In addition, PBPICF-65-35 also displays good power density (90 W kg⁻¹) and energy density (19.4 W h kg⁻¹), and the capacitance remains at 96% even after 10 000 cycles at 1.0 A g⁻¹. Therefore, the simple preparation and good capacitance performance of PBPICFs make them a promising binder-free electrode for wearable supercapacitors.

A flexible polypyrrolone (BBB)/polyimide (PI) composite-based carbon nanofiber membrane (PBPICF) has been prepared by a facile electrospinning and carbonization process.     

A new strategy for synthesizing silver doped mesoporous bioactive glass fibers and their bioactivity,antibacterial activity and drug loading performance

A new strategy for preparing mesoporous metal-doped bioactive glass fibers (MBGFs) was designed, which included electrospinning and sulfonating mesoporous PS fibers, precipitating metal ions and bioactive glass sol–gel precursor into the mesoporous polystyrene (PS) fibers and calcinations. Silver-doped mesoporous BGFs (Ag-MBGFs) with a uniform diameter of 1–2 μm and a specific surface area of 40.22 m² g⁻¹ were prepared as an example and characterized by SEM, XRD, TG, ICP and FTIR. These Ag-MBGFs showed excellent bioactivity, antibacterial properties and drug loading and release performance due to their special mesoporous and fibrous structure. The concentration of Staphylococcus aureus decreased from 1 × 10⁸ colony-forming units per mL (CFU mL⁻¹) to 2.5 × 10⁶ CFU mL⁻¹ in 2 h and then to 2 × 10² CFU mL⁻¹ in 12 h when the concentration of the Ag-MBGFs reached 16 mg mL⁻¹. BGFs of different compositions and functions could be prepared by the same strategy in a mesoporous PS fiber template, which could enrich materials for constructing orthopedic implants.

A new strategy for preparing mesoporous metal-doped bioactive glass fibers.     

The synthesis of nanofiber membranes from acrylonitrile butadiene styrene (ABS) waste using electrospinning for use as air filtration media

Acrylonitrile butadiene styrene (ABS) waste has been successfully recycled into nanofiber membranes by an electrospinning method for air filter applications. The ABS precursor solutions were made by dissolving the ABS waste in three different solvents, DMAc, DMF, and THF, with various concentrations of 10, 20, and 30 wt%. The solvent and solution concentrations affected the fiber properties (size and morphology) and membrane properties (wettability, crystallinity, and mechanical). Accordingly, we tested the fabricated membranes using SEM, FTIR, XRD, water contact angle, and tensile strength test measurements. The SEM images depicted three different morphologies, i.e. beads, beaded fibers, and pure fibers. The FTIR spectra showed that the solvents completely evaporated during the electrospinning process. The water contact angle test exhibited the hydrophobic properties of all the membrane samples. The XRD spectra showed the amorphous structures of all the membranes. The tensile strength test showed that the membranes fabricated using DMF and DMAc solvents had the best mechanical properties. Considering the fiber size, wettability, and mechanical properties, the membranes fabricated using DMAc and DMF solvents had the best criteria as air filter media. Filtration tests on the membranes fabricated using DMAc and DMF solvents with various solution concentrations depicted that the beads affected the membrane pressure drop and efficiency. The beads gave more space among the fibers, which facilitated the air flow through the membrane. The beads greatly reduced the pressure drop without an overly reduced membrane filtration efficiency. This led to a high-quality factor of the membranes that demonstrated their applicability as potential air filter media.

Acrylonitrile butadiene styrene (ABS) waste has been successfully recycled into nanofiber membranes by an electrospinning method for air filter applications.     

Multiwall-carbon-nanotube/cellulose composite fibers with enhanced mechanical and electrical properties by cellulose grafting

Multiwall-carbon-nanotube (MWCNT)-cellulose/cellulose composite fibers with promoted mechanical and electronic activities were synthesized. Remarkably, the dispersion of MWCNTs in the composite fibers was facilitated through cellulose grafting, resulting in the tensile strength of the obtained MWCNT-cellulose/cellulose composite fibers being increased to 304.6 MPa with 10 wt% MWCNTs involved, which was almost 106.8% higher than that of pristine MWCNT/cellulose fibers with the same amount of MWCNTs. In addition, the electrical conductivity of the MWCNT-cellulose/cellulose composite fibers was enhanced to 1.3 × 10⁻¹ S cm⁻¹ with the dispersion of 10 wt% MWCNTs, which was almost 108 times higher than that of pristine MWCNT/cellulose fibers with the same amount of MWCNTs.

MWCNT-cellulose/cellulose composite fibers with enhanced mechanical and conducting properties were prepared via facilitating the dispersion of MWCNTs in fibers.     

Anhydrous proton conductivity of electrospun phosphoric acid-doped PVP-PVDF nanofibers and composite membranes containing MOF fillers

A high-temperature proton exchange membrane was fabricated based on polyvinylidene fluoride (PVDF) and polyvinylpyrrolidone (PVP) blend polymer nanofibers. Using electrospinning method, abundant small ionic clusters can be formed and agglomerated on membrane surface, which would facilitate the proton conductivity. To further enhance the conductivity, phosphoric acid (PA) retention as well as mechanical strength, sulfamic acid (SA)-doped metal–organic framework MIL-101 was incorporated into PVP-PVDF blend nanofiber membranes. As a result, the anhydrous proton conductivity of the composite SA/MIL101@PVP-PVDF membrane reached 0.237 S cm⁻¹ at 160 °C at a moderate acid doping level (ADL) of 12.7. The construction of long-range conducting network by electrospinning method combined with hot-pressing and the synergistic effect between PVP-PVDF, SA/MIL-101 and PA all contribute to the proton conducting behaviors of this composite membrane.

A composite SA/MIL101@PVP-PVDF membrane was fabricated via electrospinning and reached a conductivity of 0.237 S cm⁻¹ at 160 °C with a moderate acid doping level (12.7).