Nanoparticles meet electrospinning: recent advances and future prospects

A polymer/metal core–shell nanofiber membrane by electrospinning with an electric field, and its application for catalyst support

PVP/Ag core–shell nanofibers are prepared via electrospinning; electric field induces phase separation, and leads Ag migrate; the nanofiber exhibits a great potential in the field of catalysis.

Mesoporous carbon soft-templated from lignin nanofiber networks: microphase separation boosts supercapacitance in conductive electrodes

Lignin was used to fabricate electrospun fibers with mesopores from a PVA precursor (soft templating). The resultant carbon mat was flexible, conductive and displayed supercapacitance, a remarkable property in a biomass-derived electrode.

Recent advances in electrospun metal-oxide nanofiber based interfaces for electrochemical biosensing

Synthesis of various electrospun metal-oxide nanofibers and their application towards electrochemical enzymatic and enzyme-free biosensor platforms has been critically discussed.

Direct-Write, Self-Aligned Electrospinning on Paper for Controllable Fabrication of Three-Dimensional Structures

Electrospinning, a process that converts a solution or melt droplet into an ejected jet under a high electric field, is a well-established technique to produce one-dimensional (1D) fibers or two-dimensional (2D) randomly arranged fibrous meshes. Nevertheless, the direct electrospinning of fibers into controllable three-dimensional (3D) architectures is still a nascent technology. Here, we apply near-field electrospinning (NFES) to directly write arbitrarily shaped 3D structures through consistent and spatially controlled fiber-by-fiber stacking of polyvinylidene fluoride (PVDF) fibers. An element central to the success of this 3D electrospinning is the use of a printing paper placed on the grounded conductive plate and acting as a fiber collector. Once deposited on the paper, residual solvents from near-field electrospun fibers can infiltrate the paper substrate, enhancing the charge transfer between the deposited fibers and the ground plate via the fibrous network within the paper. Such charge transfer grounds the deposited fibers and turns them into locally fabricated electrical poles, which attract subsequent in-flight fibers to deposit in a self-aligned manner on top of each other. This process enables the design and controlled fabrication of electrospun 3D structures such as grids, walls, hollow cylinders, and other 3D logos. As such, this technique has the potential to advance the existing electrospinning technologies in constructing 3D structures for biomedical, microelectronics, and MEMS/NMES applications.

ZrO2 Nanofiber as a Versatile Tool for Protein Analysis

Phosphorylation is one of the most important post-translational modifications in proteins. Their essential roles in the regulation of cellular processes and alteration of protein-protein interaction networks have been actively studied. However, phosphorylated proteins are present at low abundance in cells, and ionization of the modified peptides is often suppressed by the more abundant species in mass spectrometry. Effective enrichment techniques are needed to remove the unmodified peptides and concentrate the phosphorylated ones before their identification and quantification. Herein, we prepared ZrO2 nanofibers by electrospinning, a straightforward and easy fabrication technique, and applied them to enrich phosphorylated peptides and proteins. The fibers showed good size homogeneity and porosity and could specifically bind to the phosphorylated peptides and proteins, allowing their separation from the unmodified analogues when present in either simple protein digests or highly complex cell lysates. The enrichment performance was superior to that of the commercially available nanoparticles. Moreover, modifying the solution pH could lead to selective adsorption of proteins with different pI values, suggesting the fibers' potential applicability in charge-based protein fractionation. Our results support that the electrospun ZrO2 nanofibers can serve as a versatile tool for protein analysis with great ease in preparation and handling.

Nanofibers Fabricated Using Triaxial Electrospinning as Zero Order Drug Delivery Systems

A new strategy for creating functional trilayer nanofibers through triaxial electrospinning is demonstrated. Ethyl cellulose (EC) was used as the filament-forming matrix in the outer, middle, and inner working solutions and was combined with varied contents of the model active ingredient ketoprofen (KET) in the three fluids. Triaxial electrospinning was successfully carried out to generate medicated nanofibers. The resultant nanofibers had diameters of 0.74 ± 0.06 μm, linear morphologies, smooth surfaces, and clear trilayer nanostructures. The KET concentration in each layer gradually increased from the outer to the inner layer. In vitro dissolution tests demonstrated that the nanofibers could provide linear release of KET over 20 h. The protocol reported in this study thus provides a facile approach to creating functional nanofibers with sophisticated structural features.

Unexpected Enhancement in Antibacterial Activity of N-Halamine Polymers from Spheres to Fibers

Preventing bacterial infections is a main focus of medical care. Antibacterial agents with broad and excellent disinfection capability against pathogenic bacteria are in fact urgently required. Herein, a novel strategy for the development of N-halamine polymers from spheres to fibers using a combined copolymerization-electrospinning-chlorination technique was reported, allowing fight against bacterial pathogen. Optimizing the process conditions, e.g., comonomer molar ratio, concentration of electrospinning solution, chlorination order, and chlorination period, resulted in the formation of N-halamine fibers with controllable morphology. N-Halamine polymers were tested against two common bacterial pathogens, Escherichia coli and Staphylococcus aureus, and were found to be extremely potent against both bacteria, suggesting that they possess powerful sterilizing properties. Remarkably, compared with those with sphere morphology, N-halamine fibers show unexpected enhancement toward both pathogens possibly because of their shape (fiber morphology), surface state (rough surfaces), and surface charge (positive zeta potentials). It is believed that this approach has great potential to be utilized in various fields where antifouling and antibacterial properties are highly required.

Controlled growth of polyhedral and plate-like Ag nanocrystals on a nanofiber mat as a SERS substrate

We report chemical deposition of silver nanocrystals (AgNCs) of different sizes and morphologies, such as polyhedra and plates, on a polyacrylonitrile (PAN) nanofiber mat. High performance surface-enhanced Raman scattering (SERS) substrates are achieved. The effect of the experimental parameters, such as the temperature, concentration and pH of [Ag(NH3)2]OH aqueous solution, on the morphology evolution and density of AgNCs is systematically investigated. The results suggest that the optimized nanofiber mat exhibits a significant SERS performance with superior stability and reproduction, and the SERS enhancement factor (EF) can reach as high as 10(8) for 4-mercaptobenzoic acid (4-MBA). The optimized nanofiber mat also shows high SERS activity for p-aminothiophenol (4-ATP) over the whole nanofiber mat demonstrating the feasibility for detection of both analytes. The detection limit of 4-MBA and 4-ATP is as low as 10(-9) M and 10(-10) M respectively, making the nanofiber mat a promising candidate for SERS detection of chemical pollutants.

Synergetic catalytic effect of Cu2-xSe nanoparticles and reduced graphene oxide coembedded in electrospun nanofibers for the reduction of a typical refractory organic compound

A new heterogeneous catalytic composite composed of nonstoichiometric Cu2-xSe nanoparticles (NPs) with high copper deficiency and graphene oxide (GO) is prepared by coembedding in electrospun nanofibers of a poly(vinylpyrrolidone) (PVP) support, wherein GO in the nanofibers is converted into reduced GO (rGO) via heat treatment. The as-prepared composite Cu2-xSe/rGO/PVP nanofibers have demonstrated superior catalytic activity toward the reduction of a refractory organic compound by taking 4-nitrophenol (4-NP) as an example. In the presence of NaBH4, the Cu2-xSe/rGO/PVP nanofibers display a synergetic effect between Cu2-xSe and rGO in PVP nanofibers compared to their independent components or corresponding nanofibers. Furthermore, the Cu2-xSe/rGO/PVP nanofibers exhibit a favorable water-stable property via heat treatment to solidify the hydrophilic PVP matrix, which makes the composite display good reusability, stability in aqueous solution, and separability from a water medium. This work not only presents a direct, convenient, and effective approach to doping semiconductor nanomaterials into polymer nanofibers but also provides fundamental routes for further investigations about the synergetic effect between different materials based on the platform of electrospun nanofibers.

Electrospun porous carbon nanofiber@MoS2 core/sheath fiber membranes as highly flexible and binder-free anodes for lithium-ion batteries

Self-standing membranes of porous carbon nanofiber (PCNF)@MoS2 core/sheath fibers have been facilely obtained through a combination of electrospinning, high-temperature carbonization and the solvothermal reaction. PCNF fibers with porous channels are used as building blocks for the construction of hierarchical PCNF@MoS2 composites where thin MoS2 nanosheets are uniformly distributed on the PCNF surface. Thus, a three-dimensional open structure is formed, which provides a highly conductive pathway for rapid charge-transfer reactions, as well as greatly improving the surface active sites of MoS2 for fast lithiation/delithiation of Li(+) ions. The highly flexible PCNF@MoS2 composite membrane electrode exhibits synergistically improved electrochemical performance with a high specific capacity of 954 mA h g(-1) upon the initial discharge, a high rate capability of 475 mA h g(-1) even at a high current density of 1 A g(-1), and good cycling stability with almost 100% retention after 50 cycles, indicating its potential application as a binder-free anode for high-performance lithium-ion batteries.

Facile synthesis of electrospun MFe2O4 (M = Co, Ni, Cu, Mn) spinel nanofibers with excellent electrocatalytic properties for oxygen evolution and hydrogen peroxide reduction

Designing and preparing porous transition metal ferrites without using any template, shape-directing agent, and surfactant is a challenge. Herein, heterojunction MFe2O4 (M = Co, Ni, Cu, Mn) nanofiber (NF) based films with three-dimensional configurations were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed show the 3D net-like textural structures of the electrospun spinel-type MFe2O4 NFs. In particular, the resulting MFe2O4 NFs have lengths up to several dozens of micrometers with an average diameter size of about 150 nm and possess abundant micro/meso/macropores on both the surface and within the films. The hierarchically porous structures and high surface areas of these MFe2O4 NFs (for example, the CoFe2O4 NFs possess a larger BET specific surface area (61.48 m(2) g(-1)) than those of the CoFe2O4 NPs (5.93 m(2) g(-1))) can afford accessible transport channels for effectively decreasing the mass transport resistances, enhancing the electrical conductivity, and increasing the density and reactivity of the exposed catalytic active sites. All these advantages will be responsible for the better electrocatalytic performances of these MFe2O4 NFs compared with their structural isomers (i.e. the MFe2O4 NPs) for the oxygen evolution reaction (OER) and H2O2 reduction in alkaline solution. Meanwhile, both the OER and H2O2 reduction catalytic activities for these MFe2O4 NFs obey the order of CoFe2O4 NFs > CuFe2O4 NFs > NiFe2O4 NFs > MnFe2O4 NFs > Fe2O3 NFs. The CoFe2O4 NFs represent a new class of highly efficient non-noble-metal catalysts for both OER and H2O2 reduction/detection in alkaline media.

Antimicrobial activity and cytotoxicity of nanofibrous mats immobilized with polysaccharides-rectorite based nanogels

Rectorite (REC)-encapsulated lysozyme (LY)-alginate (ALG) nanogels (NGs) were prepared by adding ALG-REC composites suspensions into LY solutions at the mass ratio of 1:2. The morphology of the NGs and the NGs-assembled nanofibrous mats were studied by transmission electron microscope and field emission scanning electron microscopy, respectively. The composition of NGs-immobilized nanofibrous mats was detected by X-ray photoelectron spectroscopy. The NGs-assembled nanofibrous mats with the addition of REC could enhance the inhibition against Escherichia coli and Staphylococcus aureus. Additionally, NGs-coated mats reduced the toxicity of cellulose mats on mouse lung fibroblasts using MTT assay. Besides, the addition of REC in the NGs improved the cell compatibility of NGs-assembled nanofibrous mats.

Nanotubular structured Si-based multicomponent anodes for high-performance lithium-ion batteries with controllable pore size via coaxial electro-spinning

We demonstrate a simple but straightforward process for the synthesis of nanotube-type Si-based multicomponents by combining a coaxial electrospinning technique and subsequent metallothermic reduction reaction. Si-based multicomponent anodes consisting of Si, alumina and titanium silicide show several advantages for high-performance lithium-ion batteries. Alumina and titanium silicide, which have high mechanical properties, act as an effective buffer layer for the large volume change of Si, resulting in outstanding volume suppression behavior (volume expansion of only 14%). Moreover, electrically conductive titanium silicide layers located at the inner and outer layers of a Si nanotube exhibit a high initial coulombic efficiency of 88.5% and an extraordinary rate capability. Nanotubular structured Si-based multicomponents with mechanically and electrically improved components can be used as a promising alternative to conventional graphite anode materials. This synthetic route can be extended to other high capacity lithium-ion battery anode materials.

Electrospun microfiber membranes embedded with drug-loaded clay nanotubes for sustained antimicrobial protection

Guided tissue regeneration/guided bone regeneration membranes with sustained drug delivery were developed by electrospinning drug-loaded halloysite clay nanotubes doped into poly(caprolactone)/gelatin microfibers. Use of 20 wt % nanotube content in fiber membranes allowed for 25 wt % metronidazole drug loading in the membrane. Nanotubes with a diameter of 50 nm and a length of 600 nm were aligned within the 400 nm diameter electrospun fibers, resulting in membranes with doubling of tensile strength along the collector rotating direction. The halloysite-doped membranes acted as barriers against cell ingrows and have good biocompatibility. The metronidazole-loaded halloysite nanotubes incorporated in the microfibers allowed for extended release of the drugs over 20 days, compared to 4 days when directly admixed into the microfibers. The sustained release of metronidazole from the membranes prevented the colonization of anaerobic Fusobacteria, while eukaryotic cells could still adhere to and proliferate on the drug-loaded composite membranes. This indicates the potential of halloysite clay nanotubes as drug containers that can be incorporated into electrospun membranes for clinical applications.

Ionic liquid assisted electrospun cellulose acetate fibers for aqueous removal of triclosan

The cellulose acetate (CA) membrane prepared via electrospun was innovatively utilized as fiber-adsorbent for the separation of aqueous triclson (TCS). It was found that the presence of the room temperature ionic liquid (RTIL) in the precursor amplified electric force toward the CA-solution, thereby benefiting the formation of CA fibers. The as-spun CA fibers exhibit excellent adsorptive performance toward TCS, with fast adsorption kinetics, and the maximum adsorption capacity achieved to 797.7 mg g(-1), which established much better performance in contrast to conventional adsorbents. We proposed that the adsorption of TCS onto CA fibers was primarily facilitated by the hydrogen bonding between the abundant carbonyl, hydroxyl groups of CA surface, and the hydrogen atoms of phenol functional groups in TCS molecular.

Co3O4 nanoparticles decorated carbon nanofiber mat as binder-free air-cathode for high performance rechargeable zinc-air batteries

An efficient, durable and low cost air-cathode is essential for a high performance metal-air battery for practical applications. Herein, we report a composite bifunctional catalyst, Co3O4 nanoparticles-decorated carbon nanofibers (CNFs), working as an efficient air-cathode in high performance rechargeable Zn-air batteries (ZnABs). The particles-on-fibers nanohybrid materials were derived from electrospun metal-ion containing polymer fibers followed by thermal carbonization and a post annealing process in air at a moderate temperature. Electrochemical studies suggest that the nanohybrid material effectively catalyzes oxygen reduction reaction via an ideal 4-electron transfer process and outperforms Pt/C in catalyzing oxygen evolution reactions. Accordingly, the prototype ZnABs exhibit a low discharge-charge voltage gap (e.g. 0.7 V, discharge-charge at 2 mA cm(-2)) with higher stability and longer cycle life compared to their counterparts constructed using Pt/C in air-cathode. Importantly, the hybrid nanofiber mat readily serves as an integrated air-cathode without the need of any further modification. Benefitting from its efficient catalytic activities and structural advantages, particularly the 3D architecture of highly conductive CNFs and the high loading density of strongly attached Co3O4 NPs on their surfaces, the resultant ZnABs show significantly improved performance with respect to the rate capability, cycling stability and current density, promising good potential in practical applications.

Hydrogen-bond-mediated in situ fabrication of AgNPs/agar/PAN electrospun nanofibers as reproducible SERS substrates

Reproducibility in surface enhanced Raman scattering (SERS) measurements is a challenge. This work developed a facile way to make highly dispersed uniform silver nanoparticles (AgNPs) loaded in the agar/polyacrylonitrile (PAN) nanofibers by the coupling the electrospinning technology from metal complex-containing polymer solution and in situ photoreductive technique. Agar, as hydrophilic component, was introduced into the electrospinning solution considering that its abundant hydroxyl group sites could greatly improve the contents of silver ions in the polymers because of the rich silver ion chelated with the hydroxyl group, whereas hydrophilic agar was integrated with hydrophobic PAN by -OH···N≡C- hydrogen bonds as a bridge. Meanwhile, the in situ photoreductive reaction was made under different light irradiations such as desk lamp, 365 nm UV-lamp, and 254 nm UV-lamp. High yield of stable AgNPs with highly uniform and dispersion are available in the agar/PAN nanofibers after the in situ photoreductive reaction, supplying the possibility of reproducible SERS signals. To identify that concept of proof, a facile approach for the determination of malachite green (MG) in three environmental practical samples was demonstrated by using the composite nanofibrous material irradiated by 365 nm UV-lamp, giving the minimum detection concentration of MG as low as 0.1 μmol/L with a good linear response ranging from 0.1-100 μmol/L (R(2) = 0.9960).

Preparation and evaluation of nanocellulose–gold nanoparticle nanocomposites for SERS applications

We present a gold nanoparticle/bacterial cellulose nanocomposite SERS substrate that accumulates analytes in hydrogel form and then exhibits strong Raman signal enhancements after drying.

Binder free and free-standing electrospun membrane architecture for sensitive and selective non-enzymatic glucose sensors

Novel free standing and binder free non-enzymatic electrochemical sensors were fabricated using in situ grown copper (Cu) nanoparticles on polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP) nanofibers.

Catalyst-loaded porous WO3 nanofibers using catalyst-decorated polystyrene colloid templates for detection of biomarker molecules

A new facile catalyst loading method assisted by layer-by-layer self-assembly as well as pore formation on electrospun nanofibers (NFs) can generate in-depth research for establishing high performance gas sensing composites by exploring diverse catalyst-loaded porous NF composites.

One-dimensional Bi2O3 QD-decorated BiVO4 nanofibers: electrospinning synthesis, phase separation mechanism and enhanced photocatalytic performance

In this work, we design and successfully fabricate novel Bi₂O₃ quantum dot (QD)-decorated BiVO₄ nanofibers by electrospinning. Furthermore, it exhibits enhanced photocatalytic activities by promoting the separation of photoinduced electrons and holes.

Improving the electrochemical properties of polyamide 6/polyaniline electrospun nanofibers by surface modification with ZnO nanoparticles

ZnO nanoparticles adsorbed onto electrospun nanofiber surfaces improve the electron transfer kinetics and increase the electrode electroactive area. The modified electrodes can be a potential platform for electrochemical applications.

Self-assembly of various silver nanocrystals on PmPD/PAN nanofibers as a high-performance 3D SERS substrate

The AgNCs (AgNPs, AgNTs and AgNDs) decorated-PmPD/PAN nanofiber mats were obtained as highly sensitive 3D SERS substrates.

Three-dimensional Porous Networks of Ultra-long Electrospun SnO2 Nanotubes with High Photocatalytic Performance

Recent progress in nanoscience and nanotechnology creates new opportunities in the design of novel SnO₂ nanomaterials for photocatalysis and photoelectrochemical. Herein, we firstly highlight a facile method to prepare three-dimensional porous networks of ultra-long SnO₂ nanotubes through the single capillary electrospinning technique. Compared with the traditional SnO₂ nanofibers, the as-obtained three-dimensional porous networks show enhancement of photocurrent and photocatalytic activity, which could be ascribed to its improved light-harvesting efficiency and high separation efficiency of photogenerated electron-hole pairs. Besides, the synthesis route delivered three-dimensional sheets on the basis of interwoven nanofibrous networks, which can be readily recycled for the desirable circular application of a potent photocatalyst system.

A simply prepared flexible SiBOC ultrafine fiber mat with enhanced high-temperature stability and chemical resistance

A simply prepared flexible SiBOC ultrafine fiber mat with high-temperature stability and chemical resistance. I: A typical SiBOC material composed of Si, B, O and C. II: A comparison of SiBOC fibers and SiOC fibers treated under different conditions.

Dual-compartment nanofibres: separation of two highly reactive components in close vicinity

Nanofibers based on polyvinyl alcohol encapsulating epoxy and amine colloids in close vicinity as reactive compartments are investigated. Their crosslinking can be initiated upon thermal or mechanical stimuli and enables self-healing applications.

Green fabrication of antibacterial polymer/silver nanoparticle nanohybrids by dual-spinneret electrospinning

Nanohybrids from waterborne polyurethane, poly(vinyl alcohol) and silver nanoparticles of ultrasmall sizes (5.1 ± 0.6 nm) are facilely obtained by directly one-step dual-spinneret electrospinning fabrication in water without additional chemicals.

Redox reaction mediated direct synthesis of hierarchical flower-like CuO spheres anchored on electrospun poly(vinylidene difluoride) fiber surfaces at low temperatures

Flower-like CuO spheres anchored on electrospun PVDF fiber surfaces as catalytic membranes for the photodegradation of rhodamine B aqueous solutions.

Green catalyst: magnetic La0.7Sr0.3MnO3 hollow microspheres

Compared with nanoparticles, the rugged microspherical structure makes the magnetic La_0.7Sr_0.3MnO₃ more favorable for photocatalytic water oxidation.

A new sensing platform based on electrospun copper oxide/ionic liquid nanocomposite for selective determination of risperidone

A copper oxide nanoparticle/ionic liquid nanocomposite modified electrode exhibits excellent electrocatalytic activity towards the oxidation of risperidone.

Preparation of Rh–SiO2 fiber catalyst with superior activity and reusability by electrospinning

Rh–SiO₂ fiber catalyst prepared by electrospinning for room temperature hydrogenation of alkenes with superior catalytic activity and reusability.

Electrospun acid–base pair solid dispersions of quercetin

An electrospun acid–base pair solid dispersion in the form of core–shell nanofibers was developed for improving the dissolution of quercetin.