Polymer-based composites by electrospinning: Preparation & functionalization with nanocarbons

Graphene impregnated electrospun nanofiber sensing materials: a comprehensive overview on bridging laboratory set-up to industry

Owing to the unique structural characteristics as well as outstanding physio-chemical and electrical properties, graphene enables significant enhancement with the performance of electrospun nanofibers, leading to the generation of promising applications in electrospun-mediated sensor technologies. Electrospinning is a simple, cost-effective, and versatile technique relying on electrostatic repulsion between the surface charges to continuously synthesize various scalable assemblies from a wide array of raw materials with diameters down to few nanometers. Recently, electrospun nanocomposites have emerged as promising substrates with a great potential for constructing nanoscale biosensors due to their exceptional functional characteristics such as complex pore structures, high surface area, high catalytic and electron transfer, controllable surface conformation and modification, superior electric conductivity and unique mat structure. This review comprehends graphene-based nanomaterials (GNMs) (graphene, graphene oxide (GO), reduced GO and graphene quantum dots) impregnated electrospun polymer composites for the electro-device developments, which bridges the laboratory set-up to the industry. Different techniques in the base polymers (pre-processing methods) and surface modification methods (post-processing methods) to impregnate GNMs within electrospun polymer nanofibers are critically discussed. The performance and the usage as the electrochemical biosensors for the detection of wide range analytes are further elaborated. This overview catches a great interest and inspires various new opportunities across a wide range of disciplines and designs of miniaturized point-of-care devices.

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance

Membrane distillation (MD) is a thermally induced membrane separation process that utilizes vapor pressure variance to permeate the more volatile constituent, typically water as vapor, across a hydrophobic membrane and rejects the less volatile components of the feed. Permeate flux decline, membrane fouling, and wetting are some serious challenges faced in MD operations. Thus, in recent years, various studies have been carried out on the modification of these MD membranes by incorporating nanomaterials to overcome these challenges and significantly improve the performance of these membranes. This review provides a comprehensive evaluation of the incorporation of new generation nanomaterials such as quantum dots, metalloids and metal oxide-based nanoparticles, metal organic frameworks (MOFs), and carbon-based nanomaterials in the MD membrane. The desired characteristics of the membrane for MD operations, such as a higher liquid entry pressure (LEPw), permeability, porosity, hydrophobicity, chemical stability, thermal conductivity, and mechanical strength, have been thoroughly discussed. Additionally, methodologies adopted for the incorporation of nanomaterials in these membranes, including surface grafting, plasma polymerization, interfacial polymerization, dip coating, and the efficacy of these modified membranes in various MD operations along with their applications are addressed. Further, the current challenges in modifying MD membranes using nanomaterials along with prominent future aspects have been systematically elaborated.

Molybdenum Carbide-Embedded Multichannel Hollow Carbon Nanofibers as Bifunctional Catalysts for Water Splitting

With the environmental pollution and non-renewable fossil fuels, it is imperative to develop eco-friendly, renewable, and highly efficient electrocatalysts for sustainable energy. Herein, a simple electrospinning process used to synthesis Mo₂ C-embedded multichannel hollow carbon nanofibers (Mo₂ C-MCNFs) and followed by the pyrolysis process. As prepared lotus root-like nanoarchitecture could offer rich porosity and facilitate the electrolyte infiltration, the Mo₂ C-MCNFs delivered favourable catalytic activity for HER and OER. The resultant catalysts exhibit low overpotentials of 114 mV and 320 mV at a current density of 10 mA cm^-2 for HER and OER, respectively. Furthermore, using the Mo₂ C-MCNFs catalysts as a bifunctional electrode toward overall water splitting, which only needs a small cell voltage of 1.68 V to afford a current density of 10 mA cm^-2 in the home-made alkaline electrolyzer. This interesting work presents a simple and effective strategy to further fabricating tunable nanostructures for energy-related applications.

Tensile Properties of Composite Reinforced with Three-Dimensional Printed Fibers

This study used melt-electrospinning writing to fabricate three-dimensional fiber constructs by embedding them in a polyvinyl alcohol (PVA) matrix to obtain thin composite films. Fourier transform infrared spectroscopy (FTIR) and dynamic scanning calorimetry (DSC) were used to demonstrate an interaction between the polycaprolactone (PCL) fibrous phase and the PVA matrix phase. Following this, the mechanical deformation behavior of the composite was investigated, and the effect of reinforcement with three-dimensional fibrous constructs was illustrated. The specific strength of the composite was found to be five times higher than the specific strength of the neat PVA matrix. Additionally, the specific toughness of the composite was determined to be roughly four times higher than the specific toughness determined for the neat PVA matrix. These results demonstrate the potential of using melt-electrospinning writing for producing three-dimensional fibrous constructs for composite reinforcement purposes.

Co-incorporation of graphene oxide/silver nanoparticle into poly-L-lactic acid fibrous: A route toward the development of cytocompatible and antibacterial coating layer on magnesium implants

Magnesium (Mg) alloys present great potential for the development of orthopedic implants, whereas, their high degradation rate and poor antibacterial performance have restricted orthopedic applications. In this work, PLLA/GO-AgNP (poly-L-lactic acid/graphene oxide- silver nanoparticle) with different concentration of GO-AgNPs were deposited on Mg alloy via electrospinning method for enhancement of corrosion resistance and antibacterial performance. The result revealed that incorporation of GO into PLLA fibrous considerably slowed down the degradation rate of Mg alloy substrate and reduced the H₂ release rate from the substrate. Also, co-incorporation of GO and AgNPs into PLLA fibrous resulted in substantial escalate in compressive strength after immersion in simulated body fluid (SBF). Antibacterial activity test exhibited that Mg alloy and neat PLLA fibrous presented minimal inhibition area toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In contrast, using PLLA/GO-AgNPs fibrous improved antibacterial performance against both bacteria. Cytocompatibility results indicated that PLLA/GO-AgNPs fibrous with a low amount of GO-AgNPs enhanced cell proliferation and growth while high co-incorporation of GO-AgNPs showed a negative effect on cell proliferation. Taken together, PLLA/1GO-AgNPs fibrous coating shows suitable corrosion resistance, cytocompatibility, and antibacterial function for use in orthopedic applications.

A novel bio-inspired conductive, biocompatible, and adhesive terpolymer based on polyaniline, polydopamine, and polylactide as scaffolding biomaterial for tissue engineering application

A novel electrically conductive nanofibrous scaffold based on polyaniline-co-(polydopamine-grafted-poly(d,l-lactide)) [PANI-co-(PDA-g-PLA)] was fabricated using electrospinning technique and its physicochemical as well as biological characteristics toward bone tissue engineering (TE) were investigated extensively. In detail, PANI-co-PDA was synthesized via a one-step chemical oxidization approach. Then, d,l-lactaide monomer was grafted onto PDA segment using a ring opening polymerization (ROP) to afford PANI-co-(PDA-g-PLA) terpolymer. The successful synthesis of PANI-co-(PDA-g-PLA) terpolymer was confirmed using FTIR spectroscopy as well as TGA analysis. Finally, a solution of the synthesized terpolymer was electrospun to fabricate a conductive nanofibrous scaffold. Some physicochemical features such as mechanical, conductivity, electroactivity, hydrophobicity, and morphology as well as biological characteristics including biocompatibility, biodegradability, as well as enhancing the cells adhesion and proliferation were investigated. According to the above-mentioned experimental results, the fabricated electrospun nanofibers can be considered as a potential scaffold for TE application, mainly due to its proper physicochemical and biological properties.

Data on effect of electrospinning conditions on morphology and effect of heat-treatment temperature on the cycle and rate properties of core-shell LiFePO4/FeS/C composite fibers for use as cathodes in Li-ion batteries

The data in this study are related to the research article "Core-shell electrospun and doped LiFePO₄/FeS/C composite fibers for Li-ion batteries" [1]. Core-shell LiFePO₄/FeS/C composites fiber were prepared via an electrospinning method for use as cathodes in Li-ion batteries. The data presented in this paper showed the effect of electrospinning parameters, including applied voltage, solution flow rate, the concentration of polyvinylpyrrolidone (PVP) (wt%) and a mixed PVP/PEO (polyethylene oxide) (w/w%) polymers on the morphological properties of composites fibers. These data were developed using scanning electron microscopy (SEM). Then, the effect of heat-treatment temperature on fiber morphology was investigated using transmission electron microscopy (TEM). The voltage profile and cycle rate properties of the core-shell LiFePO₄/FeS/C composites obtained after various heat treatments were studied.

Light scattering effect of polyvinyl-alcohol/titanium dioxide nanofibers in the dye-sensitized solar cell

In the present work, polyvinyl-alcohol/titanium dioxide (PVA/TiO2) nanofibers are utilized as a light scattering layer (LSL) on top of the TiO2 nanoparticles photoanode. The TiO2 nanoparticles decorated PVA/TiO2 nanofibers display a power conversion efficiency (PCE) of 4.06%, which is 33% higher than TiO2 nanoparticles without LSL, demonstrating the incorporation of PVA/TiO2 nanofibers as LSL reduces the radiation loss and increases the excitation of the electron that leads to high PCE. The incorporation of PVA/TiO2 nanofibers as LSL also increases the electron life time and charge collection efficiency in comparison to the TiO2 nanoparticles without LSL.

Nanoparticles in an antibiotic-loaded nanomesh for drug delivery

Antibiotic loaded nanomeshes were fabricated by electrospinning polycaprolactone, a biocompatible polymer, with 12.5% w/w Colistin, 1.4% w/w Vancomycin and either cationic or anionic gold nanoparticles in varying combinations. The resulting nanomeshes had different antibiotic release profiles, with citrate capped gold nanoparticles combined with Colistin having the highest sustained release over 14 days for a 4 mg, 1.5 cm2 nanomesh. The electrospinning parameters were optimised to ensure the spinning of a homogenous mesh and the addition of antibiotics was confirmed through 1H NMR and ATR-FTIR. This research, as a proof of concept, suggests an opportunity for fabricating nanomeshes which contain gold nanoparticles as a drug release mechanism for antibiotics.

UV cross-linked polyvinylpyrrolidone electrospun fibres as antibacterial surfaces

Many bacteria become progressively more resistant to antibiotics and it remains a challenging task to control their overall levels. Polymers combined with active biomolecules come to the forefront for the design of antibacterial materials that can address this encounter. In this work, we investigated the photo-crosslinking approach of UV-sensitive benzophenone molecule (BP) with polyvinylpyrrolidone (PVP) polymer within electrospun fibres. The BP and PVP solutions allowed fabricating polymer mats that were subsequently functionalised with antibacterial lysozyme. The physical properties of the crosslinked electrospun fibres were investigated by scanning electron microscopy and atomic force microscopy. The average diameter of the obtained fibres decreased from 290 ± 50 nm to 270 ± 70 nm upon the addition of the crosslinking molecules and then to 240 ± 80 nm and 180 ± 90 nm after subsequent crosslinking reaction at an increasing time: 3 and 5 h, respectively. The peak force quantitative nanomechanical mapping (PF-QNM) indicated the increase of DMT modulus of obtained cross-linked fibres from 4.1 ± 0.8 GPa to 7.2 ± 0.5 GPa. Furthermore, the successful crosslinking reaction of PVP and BP solution into hydrogels was investigated in terms of examining photo-crosslinking mechanism and was confirmed by rheology, Raman, Fourier transform infrared and nuclear magnetic resonance. Finally, lysozyme was successfully encapsulated within cross-linked PVP-BP hydrogels and these were successfully electrospun into mats which were found to be as effective antibacterial agents as pure lysozyme molecules. The dissolution rate of photo cross-linked PVP mats was observed to increase in comparison to pure PVP electrospun mats which opened a potential route for their use as antibacterial, on-demand, dissolvable coatings for various biomedical applications.

Electrospun fibers and their application in drug controlled release, biological dressings, tissue repair, and enzyme immobilization

Electrospinning is a method of preparing microfibers or nanofibers by using an electrostatic force to stretch the electrospinning fluid. Electrospinning has gained considerable attention in many fields due to its ability to produce continuous fibers from a variety of polymers and composites in a simple way. Electrospun nanofibers have many merits such as diverse chemical composition, easily adjustable structure, adjustable diameter, high surface area, high porosity, and good pore connectivity, which give them broad application prospects in the biomedical field. This review systematically introduced the factors influencing electrospinning, the types of electrospun fibers, the types of electrospinning, and the detailed applications of electrospun fibers in controlled drug release, biological dressings, tissue repair and enzyme immobilization fields. The latest progress of using electrospun fibers in these fields was summarized, and the main challenges to be solved in electrospinning technology were put forward.

A Review on Porous Polymeric Membrane Preparation. Part I: Production Techniques with Polysulfone and Poly (Vinylidene Fluoride)

Porous polymeric membranes have emerged as the core technology in the field of separation. But some challenges remain for several methods used for membrane fabrication, suggesting the need for a critical review of the literature. We present here an overview on porous polymeric membrane preparation and characterization for two commonly used polymers: polysulfone and poly (vinylidene fluoride). Five different methods for membrane fabrication are introduced: non-solvent induced phase separation, vapor-induced phase separation, electrospinning, track etching and sintering. The key factors of each method are discussed, including the solvent and non-solvent system type and composition, the polymer solution composition and concentration, the processing parameters, and the ambient conditions. To evaluate these methods, a brief description on membrane characterization is given related to morphology and performance. One objective of this review is to present the basics for selecting an appropriate method and membrane fabrication systems with appropriate processing conditions to produce membranes with the desired morphology, performance and stability, as well as to select the best methods to determine these properties.

Carbon-Based Alloy-Type Composite Anode Materials toward Sodium-Ion Batteries

In the scenario of renewable clean energy gradually replacing fossil energy, grid-scale energy storage systems are urgently necessary, where Na-ion batteries (SIBs) could supply crucial support, due to abundant Na raw materials and a similar electrochemical mechanism to Li-ion batteries. The limited energy density is one of the major challenges hindering the commercialization of SIBs. Alloy-type anodes with high theoretical capacities provide good opportunities to address this issue. However, these anodes suffer from the large volume expansion and inferior conductivity, which induce rapid capacity fading, poor rate properties, and safety issues. Carbon-based alloy-type composites (CAC) have been extensively applied in the effective construction of anodes that improved electrochemical performance, as the carbon component could alleviate the volume change and increase the conductivity. Here, state-of-the-art CAC anode materials applied in SIBs are summarized, including their design principle, characterization, and electrochemical performance. The corresponding alloying mechanism along with its advantages and disadvantages is briefly presented. The crucial roles and working mechanism of the carbon matrix in CAC anodes are discussed in depth. Lastly, the existing challenges and the perspectives are proposed. Such an understanding critically paves the way for tailoring and designing suitable alloy-type anodes toward practical applications.

Improving the Damping Properties of Nanocomposites by Monodispersed Hybrid POSS Nanoparticles: Preparation and Mechanisms

In this work, a series of heptaphenyl siloxane trisilanol/polyhedral oligomeric silsesquioxane (T₇-POSS) modified by polyols with different molecular weights were synthesized into liquid-like nanoparticle⁻organic hybrid materials using the grafted-from method. All grafted POSS nanoparticles changed from solid powders to liquid at room temperature. Polyurethane (PU) nanocomposites with POSS contents ranging from 1.75 to 9.72 wt % were prepared from these liquefied polyols-terminated POSS with polyepichlorohydrin (POSS–PECH). Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the morphology of the POSS–PECH/PU nanocomposites. The results showed that the polyol-terminated POSS particles overcame the nanoagglomeration effect and evenly disperse in the polymeric matrix. The damping factor (tan δ) of resultant nanocomposites increased from 0.90 to 1.16, while the glass transition temperature decreased from 15.8 to 9.4 °C when POSS contents increased from 0 to 9.75 wt %. The gel content, tensile strength and Fourier transform infrared (FTIR) analyses demonstrated that the molecular thermal movement ability of the polyurethane (PU) matrix increased with increasing POSS hybrid content. Therefore, the improvement of the damping properties of the composites was mainly due to the friction-related losses occurring in the interface region between the nanoparticles and the matrix.

Electrospinning of Ethylene Vinyl Acetate/Carbon Nanotube Nanocomposite Fibers

Nanocomposites, based on an ethylene vinyl acetate (EVA) copolymer with a vinyl acetate content of 34 wt % and varying amounts of multiwall carbon nanotubes (MWCNTs), were prepared by an electrospinning method. The dispersibility of the MWCNTs in the solution was improved by using cholesteryl 1-pyrenecarboxylate (PyChol) as a compatibilizer. The transmission electron microscopy images showed that the MWCNTs were aligned inside of the elastomeric matrix by the electrospinning process. The morphologies of the fibers were evaluated by scanning electron microscopy. When the amount of MWCNTs in the polymer solution reached 3 wt %, fibers with a diameter of 846 ± 447 nm were prepared. The chemical composition of the prepared fibers was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). FTIR results confirmed the presence of a carboxyl group, originating from the presence of PyChol. XPS results showed that the EVA fibers produced by electrospinning were oxidized in ethylene units, when comparing the spectra of the original EVA granules, but the presence of MWCNTs enhanced the stability of the EVA. The thermal stabilities of the fibers were tested with thermogravimetric analysis. The results confirmed that the presence of MWCNTs inside the fibers enhanced the thermal stabilities of the prepared nanocomposites.

The assembly of silk fibroin and graphene-based nanomaterials with enhanced mechanical/conductive properties and their biomedical applications

The assembly of silk fibroin and graphene-based nanomaterials would present fantastic properties and functions via optimizing the interaction between each other, and can be processed into various formats to tailor specific biomedical applications.

Non Monotonous Effects of Noncovalently Functionalized Graphene Addition on the Structure and Sound Absorption Properties of Polyvinylpyrrolidone (1300 kDa) Electrospun Mats

Graphene is an attractive component for high-performance stimuli-responsive or 'smart' materials, shape memory materials, photomechanical actuators, piezoelectric materials and flexible strain sensors. Nanocomposite fibres were produced by electrospinning high molecular weight Polyvinylpyrrolidone (PVP-1300 kDa) in the presence of noncovalently functionalised graphene obtained through tip sonication of graphite alcoholic suspensions in the presence of PVP (10 kDa). Bending instability of electrospun jet appears to progressively increase at low graphene concentrations with the result of greater fibre stretching that leads to lower fibre diameter and possibly conformational changes of PVP. Further increase of graphene content seams having the opposite effect leading to greater fibre diameter and Raman spectra similar to the pure PVP electrospun mats. All this has been interpreted on the basis of currently accepted model for bending instability of electrospun jets. The graphene addition does not lower the very high sound absorption coefficient, α, close to unity, of the electrospun PVP mats in the frequency range 200⁻800 Hz. The graphene addition affects, in a non-monotonous manner, the bell shaped curves of α versus frequency curves becoming sharper and moving to higher frequency at the lower graphene addition. The opposite is observed when the graphene content is further increased.

Engineering Surface and Optical Properties of TiO₂-Coated Electrospun PVDF Nanofibers Via Controllable Self-Assembly

Understanding the effect of a porous TiO₂ nanolayer on the optical scattering and absorption through electrospun fibers is of great importance for the design and development of advanced optical extinction materials. Based on electrospinning and controllable self-assembly techniques, pure electrospun poly(vinylidene fluoride) (PVDF) fibers and TiO₂-coated ones with different self-assembly cycles were prepared. The effect of TiO₂ self-assembly cycles on surface parameters, e.g., thickness, assembled content, and porosity of the TiO₂ nanolayer were determined by scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy. With an increase in the self-assembly cycles, the TiO₂-coated electrospun PVDF fibers presented rougher surfaces and greater average diameters. According to the characterized surface parameters, the effects of the controllable self-assembly on the optical refractive index, absorption index, and infrared extinction were investigated to increase the optical properties of electrospun PVDF fibers. The results indicated that an increase of almost 120–130 cm⁻¹ in infrared extinction could be achieved through the controllable self-assembly with only 5.7 wt. % assembled TiO₂ content. This is highly efficient when compared with other coating modes. We believe that this study could give some positive guidance in the design of TiO₂-coated electrospun fibers for improving their surface and optical properties.