Composite Nanofiber Mats Research Articles

Synergistic enhancement of coaxial nanofiber-based triboelectric nanogenerator through dielectric and dispersity modulation

Abstract The increased use of triboelectric nanogenerators (TENGs) has shown that enhancement of the output performance is a primary requirement for their development. Here, a synergistic enhancement via dielectric and dispersity modulation in nanoscale is reported for a novel barium titanate-doped coaxial nanofiber-based triboelectric nanogenerator (BTCN-TENG). Polydimethylsiloxane (PDMS) and barium titanate nanoparticles (BT NPs) are combined as the core of the coaxial nanofiber instead of conventional composite film by in situ curing during electrospinning process, and BT NPs incorporated in the PDMS core layer are shown to effectively increase the dielectric constant of the composite nanofiber mat as well as the output performance of the BTCN-TENG. Furthermore, an improved dispersity of BT NPs in the PDMS core layer compared to that achieved in the poly(vinylidene fluoride) (PVDF) shell layer was found to contribute significantly to the output performance of the BTCN-TNEG. The optimized BTCN-TENG exhibits a high output voltage of 1020 V, a current of 29 μA, and a maximum power density of 2.2 W/m2 under a 30 MΩ load resistance. In power supply application, the BTCN-TENG could successfully drive various electronic devices via mechanical energy conversion.

Electrospun poly(vinyl alcohol)/silver nanoparticle/carbon nanotube multi-composite nanofiber mat: Fabrication, characterization and evaluation of thermal, mechanical and antibacterial properties

Multi-composite nanofiber mats composed of poly(vinyl alcohol), silver nanoparticle and carbon nanotube were fabricated by electrospinning method. Transmission electron microscopy and X-ray diffraction investigations supported the coexistence of silver nanoparticle, carbon nanotube and poly(vinyl alcohol) matrix in which silver nanoparticle and carbon nanotube were well distributed. The study showed that the thermal stability was enhanced by silver nanoparticle and carbon nanotube each, while carbon nanotube also increased tensile strength of the multi-composite. It was also found that the fabricated poly(vinyl alcohol)/silver nanoparticle composite nanofiber mat demonstrated antibacterial activity, which was intensified due to inclusion of carbon nanotube.

ADVANCES IN AIR FILTERS BASED ON ELECTROSPUN NANOFIBERS

This paper reviews the background and developments of air filters based on electrospun nanofiber materials. Methods of electrospinning in the production of filter materials and their advantages are discussed in detail. Researchers around the globe are working hard to get highly efficient filters at low cost. Famous approaches to build most effective air filters include electrospun nanofiber mats, composite nanofiber mats, and antibacterial nanofiber mats for micro to nano level filtration at a higher rate. Properties like high temperature, alkali, acid, and flame resistance are still constraining the use of nanofiber filters in many industries. Future research should be focused on producing nanofiber mats capable of undergoing extreme conditions.

Polyacrylonitrile nanofiber mats containing titania/AgNP composite nanoparticles for antibacterial applications

Here in we present our research on electrospun polyacrylonitrile nanofiber films embedded with titania/AgNP nanoparticles for sustained antibacterial applications. Although silver possesses excellent antimicrobial characteristics and have been extensively exploited in applications where protection from microbial species and bacterial colonization is needed. Recently, it was discovered that silver may be allergic to skin and may induce detrimental side-effects such as argyria and argyrosis. Excess utilization of silver may even cause carcinoma. In continuation of our research on preparation of biologically safe antibacterial materials producing longer timed protection, here we proposed electrospun polyacrylonitrile nanofiber mats containing titania/AgNP composite nanoparticles. The titania/AgNP nanoparticles were prepared using polydopamine hydrochloride (pdopa) as adhesive and reducing agent. The nanoparticles were then added into polyacrylonitrile polymer solution and electrospun to fabricate polyacrylonitrile/titania/AgNP composite nanofiber mats (PTAgNP). The samples were characterized with XRD, TEM, SEM, FT-IR, SEM-EDX and antibacterial assays. Synthesis of the titania/AgNP was confirmed by XRD, TEM and EDX analysis. The nanofibers were studied with SEM, XRD, TEM and antibacterial tests. The SEM observations confirmed regular morphology of the nanofibers. The XRD and TEM analysis evidenced titania/AgNP contents in the polyacrylonitrile nanofibers. The antibacterial assays demonstrated excellent bacterial growth inhibition on agar plates and in the liquid medium. The samples were observed to inhibit growth of E. coli and S. aureus bacteria for up to 120 h. The quantitative bactericidal assay (relative cell viability, %) demonstrated 0% bacteria cell viability by polyacrylonitrile nanofibers containing 10 wt% of titania/AgNP nanoparticles.

Additive Manufacturing with Cellulose Nano-fiber Composite Materials

Additive Manufacturing with Cellulose Nano-fiber Composite Materials

Preparation of novel morning glory structure γ-MnO2/carbon nanofiber composite materials with the electrospinning method and their high electrochemical performance.

A novel γ-MnO2/carbon nanofiber composite electrode material with a morning glory structure was prepared for the first time by electrospinning a mixture solution of Mn(CH3COO)2 salt and polyacrylonitrile and subsequently treating it with NH3 atmosphere. The resultant materials were applied in supercapacitors, exhibiting a high voltage of 2 V and high energy density of 15.7 W h kg−1 at the current density of 0.5 A g−1 in 1 M Na2SO4 solution. In this study, precisely controlling the concentration and time of the reaction resulted in the novel morning glory structure. And the morning glory structure at the surface of the carbon nanofibers increased the specific surface area and shortened the diffusion path for charge transport, increasing the Na+/H+ ion intercalation capacity, accounting for the high voltage and energy density of the present supercapacitors. These results demonstrated that this new-type of carbon nanofiber with morning glory structure electrode material is potentially superior in obtaining a high voltage for electrode materials and supercapacitors. We hope that these novel materials can expand to different applications in the energy or catalytic field.

Regulating the integrity of diverse composite nanofiber membranes using an organoclay

An organoclay (up to 10 wt%) is incorporated into polymer nanofibers by optimizing the electrospinning conditions. A heat press treatment readily converts the resulting composite nanofiber mats into membranes without notable defects, allowing for the examination of the role of the clay in regard to the type of polymers possessing different hydrophilicity as a function of the content. The systematic loading of clay into the nanofiber membranes and their structural features are examined by various analytical techniques. The influence of the clay filler on the water wettability, thermal stability, and mechanical property of the membranes is also evaluated. Furthermore, the pore properties (e.g., pore size, porosity, tortuosity, etc.) and water flux patterns of the membranes are investigated to understand the relationships between the amount of the clay content and the hydrophilicity degree of the polymers. Hydrophilic polymers loaded with any amount of clay and hydrophobic polymers with low clay content generally render a positive impact on the overall properties of the membranes. However, high clay loading into hydrophobic polymers induces the detrimental effect of the clay on the performance of the membranes, except for their mechanical strength. These findings suggest the importance of the proper selection of polymers and fillers to regulate the overall properties of nanofiber-derived composite membranes.

Synthesis and characterization of SiO2/C composite nanofibers as free-standing anode materials for Li-ion batteries

One dimensional SiO2/C composite nanofibers were successfully synthesized from precursor solutions with polyvinylpyrrolidone (PVP) as a carbon source by electrospinning with two-step heat treatment, comprising preoxidation at 280 °C in the air followed by annealing at 700 °C for 1 h in a reduced atmosphere. The effects of the preoxidation treatment on the morphology, chemical structure, and electrochemical properties of the synthesized materials were studied by scanning electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. The two-step heat treatment had strong positive impacts not only on the morphology but also on the structure and electrochemical performance of the materials. Furthermore, free-standing SiO2/C composite nanofiber mats (FS–SiO2/C-CNFMs) were prepared from precursor solutions with different PVP concentrations by electrospinning with the two-step heat treatment. The FS-SiO2/C-CNFM obtained from the precursor solution with 5 wt.% PVP had a geometric mean diameter of 79 nm and a specific surface area of 642 m2 g−1. It exhibited high initial discharge and charge capacities of 1800 and 984 mA h (SiO2-g)−1, respectively, and finally retained a charge capacity of 754 mA h (SiO2-g)−1 after 200 cycles with 100% Coulombic efficiency.

Fabrication of a Novel Electrospun Polyacrylonitrile/Giant Ball {Mo132} Composite Nanofibrous Mats in Adsorption of 2-CEES

Background: Polyacrylonitrile/Mo132 composite nanofibers mats was synthesized by an electrospinning technique using PAN and giant ball nano-polyoxomolybdateMo132. The nanocluster Mo132 was mixed with PAN solution and then electrospun to produce bead-free nanofibers. The aim of this study is to evaluate the adsorption ability of electrospun composite nanofibers against sulfur mustard stimulants and assess the possibility of using the electrospun nanofibers as protective membranes in chemical masks and warfare clothing. Adsorption of sulfur mustard stimulants was investigated on the surface of PAN nanofibers embedded with keplerate nano-polyoxomolybdate. Methods: In order to study the 2-CEES adsorption ability, the prepared PAN/Mo132 nanofibers composite was further prepared and exposed to 2-CEES solution. The surface morphology and other properties of the PAN/Mo132 nanofibers composite were characterized by various techniques, including SEM, TEM, FT-IR, UV-Vis. SEM images which showed that the average diameter of the fibers was found to be between 100-120 nm. Results: The adsorption efficiency of PAN/Mo132 composite in adsorption of 2-CEES was obtained 89% after 7h at room temperature. The results showed that composite nanofibers PAN/Mo132 will have a good ability as protective clothing and chemical masks against chemical warfare agents. Conclusion: PAN/Mo132 nanofibers were prepared by electrospinning method. The leaching of Mo132 from the nanofibers was not observed, meaning that the catalyst had excellent stability and could be used as a heterogeneous structure against the adsorption of sulfur mustard stimulant at room temperature. This composite nanofibers membrane exhibited good performance to adsorb 2-CEES in comparison with pure PAN. The adsorption rate of 2-CEES increases with increasing the amount of Mo132 embedded in the PAN nanofibers.

Preparation of PVDF-TrFE based electrospun nanofibers decorated with PEDOT-CNT/rGO composites for piezo-electric pressure sensor

We developed a high-performance electrically conductive and transparent PVDF-TrFE based electrode for piezoelectric pressures sensor using the electrospinning technique. The electrode was produced by depositing the reduced graphene oxide (rGO), multiwall carbon nanotubes (rGO-MCNTs) via spray coating. Various concentration of rGO and MCNTs were used and optimized for improved electrical performance of the resultant electrode. The deposition of poly (3,4-ethylenedioxythiophene) (PEDOT) was successfully achieved by using vapor phase polymerization (VPP). The morphological characteristics of the as-prepared hybrid composite nanofiber mats were analyzed by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (X-RD), and UV–visible spectroscopy. The electrical performance of the fabricated composite nanofibers was measured by using a four-point probe device. The results showed significant enhancement in electrical conductivity of the hybrid nanocomposite which increased up to 3916 S cm−1 and sensitivity of the developed pressure sensor was achieved 67.4 kPa−1. This work suggests that the hybrid nanocomposite can be used for the transparent electrodes in a piezoelectric pressure sensor.

Multi-walled carbon nanotube-incorporating electrospun composite fibrous mats for controlled drug release profile.

The fabrication of electrospun composite nanofiber mats used as drug delivery systems with controlled release property is of general interest in biomaterial sciences. The aim of this study was to investigate the effect of MWCNTs on the release profile of the hydrophilic drug. For this aim, tetracycline hydrochloride (TCH) loaded poly (lactic acid) (PLA)/polyvinylpyrrolidone (PVP)/TCH-multiwall carbon nanotubes (MWCNTs) composite fibrous mats were fabricated by electrospinning process, and the drug release profile, release kinetics and cytotoxicity were evaluated to determine the potential for utilization as drug delivery systems. Furthermore, the morphological and physicochemical properties of the composite PLA/PVP/TCH-MWCNTs fibrous mats were characterized. The results demonstrated that TCH and MWCNTs were successfully loaded into the PLA/PVP biopolymeric matrix and the addition of TCH or MWCNTs did not alter the uniform and beadless fibrous structure of the PLA/PVP fibers, resulting in increased Young's modulus and maintained the fibrous structure of the composite mats. Moreover, MWCNTs loaded electrospun mats showed much more controlled drug release manner, increased significantly the drug encapsulation efficiency and reduced the burst release of TCH. In vitro cytotoxicity assay showed that the PLA/PVP/TCH-MWCNTs composite mats did not have a toxic effect on the human umbilical vein endothelial cells (HUVECs). With the improved physicochemical and mechanical properties, controlled drug release-profile and cytocompatibility, the fabricated composite nanofiber mats may be used as therapeutic materials for the biomedical applications as drug delivery systems.

Flexible and porous TiO2/SiO2/carbon composite electrospun nanofiber mat with enhanced interfacial charge separation for photocatalytic degradation of organic pollutants in water

Semiconductor photocatalysis has long been considered as a promising approach for remediation of polluted water. However, the high recombination rate of electrons and holes, as well as a low reaction rate, have impeded its large-scale applications. Therefore, it is of great importance to develop appropriate photocatalysts for promoting its practical application. In this study, a novel TiO2/SiO2/carbon electrospun nanofiber mat (TSC NFM) with flexibility and porous hierarchy has been successfully designed and fabricated by a facile method of electrospinning and carbonization. Characterization results show that the TSC NFM consists of closely-packed and well-distributed anatase (TiO2) nanocrystals, amorphous SiO2 nanoparticles, and carbon with interconnected meso- and macro-pores. The photocatalytic performance of the TSC NFM was evaluated by degrading rhodamine B and 4-nitrophenol in batch systems. The results show that TSC NFM exhibits a higher photocatalytic activity than TiO2/SiO2 nanofiber mat, which does not contain carbon. The enhanced performance of the TSC NFM can be attributed to the improved adsorption capacity toward the organic pollutants due to the presence of carbon and to the enhanced interfacial charge separation between TiO2 nanoparticles and carbon. Besides, the as-prepared TSC NFM displays good stability and reusability. Notably, the flexible TSC NFM can be used in a continuous-flow reactor to efficiently treat wastewater. Our work provides new insights into the fabrication of carbon-based inorganic nanofiber mats, which have great potential in water treatment.

Cobalt, copper and nickel-embedded chitosan/PAAS composite nanofiber mats as efficient heterogeneous catalysts for air oxidation of benzoin to benzil

We have applied electrospinning technique to embed cobalt, copper and nickel catalysts inside chitosan (CS) and polyacrylic acid sodium salt (PAAS) composite nanofiber mats (M@CS/PAAS) (M = Co2+, Cu2+ and Ni2+) as stable heterogeneous catalysts. Scanning electron microscopic analysis shows that the resultant M@CS/PAAS composite mats are bead-free and cylindrical nanofibers with mean diameter ranging from 474 to 504 nm, and the incorporated transition metal catalysts are homogeneously distributed inside the nanofibers in tight chelation with the chitosan amine groups. The M@CS/PAAS nanofiber mats exhibited excellent catalytic activity for atmospheric air oxidation of benzoin to benzil, and are much more stable than those prepared by conventional wetness impregnation (M-CS/PAAS nanofiber mats). Moreover, their catalytic activities and stabilities could be further enhanced by introduction of additional ligands through Schiff base transformation of the chitosan pendant amine groups. The free volume holes of the nanofibers were estimated to be considerably larger than the reactant and product molecules, allowing them to freely migrate around the internal catalytic sites. Taken together, we have demonstrated a straightforward approach to prepare efficient and recyclable heterogeneous catalysts derived from the first-row transition metal catalysts by entrapping them inside the chitosan/PAAS composite nanofibers.

The effect of nanoscale architecture on ionic diffusion in rGo/aramid nanofiber structural electrodes

Structural energy storage is a rapidly emerging area with tantalizing applications such as integrated devices in textiles, smart suits, and uniforms. Due to several outstanding properties, graphene oxide (rGO)/aramid nanofiber (ANF) composite material has emerged as a compelling choice as a structural electrode for supercapacitors and batteries. A key question of significant technological relevance pertains to what kind of nanoscale architecture motifs may lead to enhanced ionic diffusivity—the key characteristic dictating the overall performance of the electrode. In this study, we attempt to address precisely this question, through multiphysics simulations, in the context of several “experimentally realizable, layered” architectures. We investigate different arrangements (staggered and aligned) and various degrees of waviness of the rGO nanosheets inside the ANF polymer matrix. Our results indicate that decreasing waviness of the rGO sheets can enhance the ion diffusivity in the staggered and aligned arrangements of the electrode material, while this effect is stronger in the staggered arrangements than in the aligned arrangements. The insights obtained from this study can lead to a more effective design of electrode architectures.

Poly(3,4‐ethylenedioxythiophene) Polymer Composite Bioelectrodes with Designed Chemical and Topographical Cues to Manipulate the Behavior of PC12 Neuronal Cells

AbstractControlled extracellular chemical and topographical cues can generate physicochemical changes that influence the proliferation and differentiation of neural cells; external electrical stimulation (ES) via conductive bioelectrodes can promote neural differentiation by increasing neurite outgrowth. Rat pheochromocytoma (PC12) cells are used as a neuron‐like model cells to explore the possibility of using a well‐designed poly(ethylene oxide) (PEO)/poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) blend solution to fabricate functional bioelectrodes presenting biological fouling/antifouling surfaces, thereby regulating the cell adhesion, proliferation, and differentiation properties. In this study, it is found that a flat PEO/PEDOT:PSS composite film fabricates through spin‐coating, operates through a contact repulsion mechanism that limits cell attachment and proliferation; in contrast, the aligned and random PEO/PEDOT:PSS nanofibers fabricates through electrospinning promoted neuron adhesion efficiently and allows manipulation of the cell morphology. Furthermore, ES of PC12 cells is performed to investigate the influence of the conductive random and aligned PEO/PEDOT:PSS composite nanofiber mats on the enhancement of neurite outgrowth, as well as the relative gene expression of Nestin, Tuj1, and MAP2. Therefore, combining this unique PEDOT:PSS blend solution with various fabrication processes appears to be a facile approach toward bioelectronic interface coatings displaying tunable surface properties for manipulating the cellular behavior of neurons during ES.

The Construction of Fe-Compounds Doped Porous Carbon Nanofiber and Carbon Nanotube Composite Material by One-Step Carbonization and CVD for Li-Ion Capacitor

In this paper, the Fe-Compounds (FeF2 and Fe2O3) doping porous carbon nanofiber & carbon nanotube (FeCD-PCNF&CNT) composite material is firstly prepared by electro-blown spinning followed by pretreatment and one-step carbonization & chemical vapor deposition (CVD) processes. The CNTs are uniformly growing on the PCNF skeleton which deeply increased specific surface area (from 334.066 to 743.402 m2 g−1) and enhanced electrical conductivity (from 42.22 to 149.48 S cm−1) comparing to those of PCNF, and large number of hierarchical-pores are existed. In addition, the Fe-Compounds are uniformly distributed on the PCNF skeleton which provided numerous active sites. The obtained FeCD-PCNF&CNT as an anode material for Li-ion capacitors exhibited high energy density and power density (76.1 Wh kg−1 at 0.075 kW kg−1, 15.4 Wh kg−1 at 7.5 kW kg−1), which had broad application prospect in the energy storage field. Moreover, the composite materials with special structure and excellent properties may realize the other applications in the fields of adsorption, water treatment, etc., and the prepared method has a great industrialization potentiality.

Preparation and characterization of polyvinylidene fluoride/polysulfone-amide composite nanofiber mats

The polyvinylidene fluoride/polysulfone-amide (PVDF/PSA) composite nanofiber mats were prepared via electrospinning method and characterized systematically by means of scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-Ray diffraction (XRD) and Thermogravimetric analyzer (TGA). In this study, five PVDF/PSA composite spinning solutions with the setting of different mass ratio were mixed by using mechanical agitation method. The mechanical property, wettability and the air permeability of the PVDF/PSA composite nanofiber mats were also measured and discussed. The results show that the addition of PSA has tuned the composite nanofiber mats from hydrophobic to hydrophilic. It is also found that the mechanical property, thermal stability could be improved with the increasing percentage of PVDF component. The PVDF/PSA composite nanofiber mats with the mass ratio of 5/5 gives the best air permeability. In this work, the newly developed composite nanofiber mats have the potential applications in the development of filtration membranes, protective materials, lithium battery diaphragms, etc.

Removal of heavy metal chromium using cross-linked chitosan composite nanofiber mats

Uniform chitosan composite nanofiber mats (CS/PAAS) containing 4.0 wt% polyacrylic acid sodium loading have been prepared by electrospinning, followed by annealing at elevated temperature to improve solvent resistance and mechanical strength. The CS/PAAS nanofiber mats have been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and tensile strength analysis. The prepared nanofiber mats have been shown to be much better than the pristine chitosan powder to adsorb the chromium (VI) ion. SEM-Energy dispersive X-ray spectroscopic (SEM-EDS) and positron annihilation lifetime spectroscopic (PALS) analysis show that Cr(VI) ion can freely permeate into the composite nanofiber and coordinate with the internal chitosan chain molecules. The adsorption abilities of these cross-linked CS/PAAS nanofiber mats are dependent on the chitosan contents as well as N-atom basicity of the chitosan chain. The adsorption capacity toward Cr(VI) ion was improved to 78.92 mg/g after modification of the chelating ligands for the cross-linked CS/PAAS composite nanofibers.

Flexible and binder-free electrospun Co3O4 nanoparticles/carbon composite nanofiber mats as negative electrodes for sodium-ion batteries

Transition metal oxides applied as anode material for sodium-ion batteries have been widely investigated due to their high specific capacity, especially for Co3O4-related nanomaterials. However, its intrinsic low electronic conductivity and the aggregation phenomenon of commercial Co3O4 nanoparticles result in a low initially coulombic efficiency and the fading of cycle performance. In this paper, commercial Co3O4 nanoparticles/carbon composite nanofiber mats were synthesized by sol–gel electrospinning. When directly applied, such flexible negative electrodes as sodium-ion batteries, revealed high specific capacity and excellent rate performance simultaneously, which are not only attributed to the high electronic conductivity of carbon nanofiber mats that could enhance the ionic and electronic transport property, but also attributed to its three-dimensional fibrous network that could prevent the aggregation of commercial Co3O4 nanoparticles. Such a flexible, binder-free and high electronic conductivity negative electrode enables promising applications for large-scale energy storage and conversion.

UV-Triggered Transient Electrospun Poly(propylene carbonate)/Poly(phthalaldehyde) Polymer Blend Fiber Mats.

This work reports the first transient electrospun nanofiber mat triggered by UV-irradiation using poly(propylene carbonate) (PPC)/poly(phthalaldehyde) (cPPA) polymer blends. The ability to trigger room temperature transience of nanofiber mats without the need for additional heat or solvent expands its utility in nonbiological fields, especially for transient electronic devices. The addition of a photo-acid-generator to the system, working in combination with UV light, provides an acid source to enhance degradation because both polymer backbones are acid-sensitive. Electrospinning enables the production of PPC/cPPA composite nanofiber mats capable of significant degradation upon exposure to UV radiation while maintaining relatively high mechanical properties. An acid amplifier, an autocatalytically decomposing compound triggered by acid, was used to generate more acid and accelerate nanofiber degradation. The electrospun fiber mats can be post-annealed to achieve an improved mat with a mechanical strength of ∼170 MPa.