A Rapid-Ab/Desorption and Portable Photothermal MIL- 101(Cr) Nanofibrous Composite Membrane Fabricated by Spray-Electrospinning for Atmosphere Water Harvesting

MIL-101(Cr)is a promising moisture absorbent for solar-driven water harvesting from moisture to tackle the worldwide water shortage issue.However,the MIL-101(Cr)powder suffers from a long ab/desorption cycle due to the crystal aggregation caused by its inherent powder properties.Here,we demonstrate a MIL-101(Cr)nanofibrous composite membrane with a nanofibrous matrix where MIL-101(Cr)is monodisperse in the 3D porous nanofibrous matrix through a simple spray-electrospinning strategy.The continuous porous nanofibrous matrix not only offers sufficient sites for MIL-101(Cr)loading but also provides rapid moisture transport channels,resulting in a super-rapid ab/desorption duration of 50 min(including an absorption process for 40 min and a desorption process for 10 min)and multicycle daily water production of 15.9 L kg^(−1) d^(−1).Besides,the MIL-101(Cr)nanofibrous composite membrane establishes a high solar absorption of 92.8%,and excellent photothermal conversion with the surface temperature of 70.7°C under one-sun irradiation.In addition,the MIL-101(Cr)nanofibrous composite membrane shows excellent potential for practical application due to its flexibility,portability,and use stability.This work provides a new perspective of shortening MOF ab/desorption duration by introducing a porous nanofibrous matrix to improve the specific water production for the solar-driven ab/desorption water harvesting technique.

Fabrication of High-Efficiency Polyvinyl Alcohol Nanofiber Membranes for Air Filtration Based on Principle of Stable Electrospinning

A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages and injection rates to figure out their influence on steadily fabricating polyvinyl alcohol(PVA)nanofibers prepared from PVA spinning solutions with two different mass fractions(10%and 16%).The results revealed that during the stable electrospinning,the influence resulted from the change of the injection rate approximately canceled out the impact brought by adjusting the applied voltage,leading to almost the same morphology as that of the PVA nanofibers.And the mass fraction of PVA in the spinning solution dominated the structure and the diameter distribution of the electrospun nanofibers.Under stable electrospinning conditions,the composite membrane was produced by depositing PVA nanofibers on the polyethylene terephthalate(PET)nonwoven substrate for an air filtration test.Furthermore,the prepared composite membrane exhibited a high air filtration efficiency(99.97%)and a low pressure drop(120 Pa)for 300-500 nm neutralized polystyrene latex(PSL)aerosol particles,demonstrating its potential as an alternative for a variety of commercial applications in air filtration.

An energetic nano-fiber composite based on polystyrene and 1,3,5-trinitro-1,3,5-triazinane fabricated via electrospinning technique

Electrospinning is a simple technique used to fabricate polymeric nano-fibrous membranes.These nano-fibers have found a wide range of valuable applications in the biomedical field.However,it has not been utilized with solid high explosives yet.Herein,the electrospinning technique has been used to fabricate polystyrene(PS)/1,3,5-trinitro-1,3,5-triazinane(RDX)composite nanofibers.The governed electrospinning parameters,voltage,distance from the collector,flow rate,mandrel rotating speed,time,and solution concentration,that greatly affect the morphology of the obtained nanofibers were optimized.The fabricated PS/RDX nano-fibers were characterized using scanning electron microscopy(SEM),X-ray diffractometer(XRD),and Fourier Transform Infrared(FTIR)spectroscopy.The impact and friction sensitivities of PS/RDX were also measured.The thermal behavior of the prepared composite and the pure materials were studied by the thermal gravimetric analysis technique(TGA).SEM results proved the fabrication of PS/RDX fibers in the nano-size via electrospinning.FTIR spectroscopy confirmed the existence of the characteristic functional groups of both PS and RDX in the composite nano-fibers.XRD sharp peaks showed the conversion of amorphous PS into crystalline shape via electrospinning and also confirmed the formation of PS/RDX composite.The PS fibers absorbed the heat and increased the onset decomposition of the pure RDX from 181.5 to 200.7℃in the case of PS/RDX fibers.Interestingly,PS/RDX nano-fibers showed the relatively low impact and friction sensitivities of 100 J and 360 N respectively.These results could introduce PS/RDX nanofibrous composite in the field of explosives detection with high levels of safety.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

Microporous carbon nanofibers prepared by combining electrospinning and phase separation methods for supercapacitor

Microporous carbon nanofibers(MCNFs) derived from polyacrylonitrile nanofibers were fabricated via electrospinning technology and phase separation in the presence of polyvinylpyrrolidone(PVP).PVP together with a mixed solvent of N,N-Dimethylformamide and dimethyl sulfoxide was used as poreforming agent.The influences of PVP content in casting solution on the structure and electrochemical performance of the MCNFs were also investigated.The highest capacitance of 200 F/g was obtained on a three-electrode system at a scan rate of 0.5 A/g.The good performance was owing to the high specific surface area and the large amount of micro-pores,which enhanced the absorption and the transportation efficiency of electrolyte ion during charge/discharge process.This research indicated that the combination of electrospinning and phase separation technology could be used to fabricate microporous carbon nanofibers as electrode materials for supercapacitors with high specific surface area and outstanding electrochemical performance.

Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue Engineering Applications

The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.

Research progress in electrospinning engineering for all-solid-state electrolytes of lithium metal batteries

Owing to safety issue and low energy density of liquid lithium-ion batteries(LIBs),all-solid-state lithium metal batteries(ASLMBs)with unique all-solid-state electrolytes(SEs)have attracted wide attentions.This arises mainly from the advantages of the SEs in the suppression of lithium dendrite growth,long cycle life,and broad working temperature range,showing huge potential applications in electronic devices,electric vehicles,smart grids,and biomedical devices.However,SEs suffer from low lithiumion conductivity and low mechanical integrity,slowing down the development of practical ASLMBs.Nanostructure engineering is of great efficiency in tuning the structure and composition of the SEs with improved lithium-ion conductivity and mechanical integrity.Among various available technologies for nanostructure engineering,electrospinning is a promising technique because of its simple operation,cost-effectiveness,and efficient integration with different components.In this review,we will first give a simple description of the electrospinning process.Then,the use of electrospinning technique in the synthesis of various SEs is summarized,for example,organic nanofibrous matrix,organic/inorganic nanofibrous matrix,and inorganic nanofibrous matrix combined with other components.The current development of the advanced architectures of SEs through electrospinning technology is also presented to provide references and ideas for designing high-performance ASLMBs.Finally,an outlook and further challenges in the preparation of advanced SEs for ASLMBs through electrospinning engineering are given.

Recent Progress on the Fabrication of Ultrafine Polyamide-6 Based Nanofibers Via Electrospinning: A Topical Review

Electrospinning is a highly versatile technique to prepare continuous fibers with diameters of the order of nanometers. The remarkable high aspect ratio and high porosity bring electrospun nanofibers highly attractive to various nanotechnological applications such as filtration membranes, protective clothing, drug delivery, tissue-engineering, biosensors, catalysis, fuel cells and so on. In this review, we collectively summarized the recent progress in developments of the electrospun ultrafine polyamide-6 based nanofibers preparation,characterization and their applications. Information of this polyamide-6 and composites together with their processing conditions for electrospinning of ultrafine nanofibers has been summarized in this review. The recent developments made during last few years on these materials are addressed in this review. We are anticipating that this review certainly drive the researchers for developing more intensive investigation for exploring in many technological areas.

Controllable Fabrication of Spider-Web-Like Structured Anaphe Panda Regenerated Silk Nanofibers / Nets via Electrospinning / Netting

An Anaphe panda silk nanofibers / nets( NFN) membrane with attractive structures consisting of common electrospun nanofibers and two-dimensional( 2D) spider-web-like structured nano-nets were successfully fabricated via electrospinning / netting technology. The unique structures of NFN membranes such as extremely small diameter( < 20 nm),high porosity,large specific surface area. and biocompatibility make this Anaphe panda silk NFN membrane a promising candidate for biomedical applications. In the present study, field emission scanning electron microscopy( FESEM) was used to investigate the influence of polymer solution and humidity on nano-nets coverage and morphology. The FE-SEM images revealed that nano-net coverage area increased with increase in concentration of solution while lowering the humidity increased the nano-nets formation. Moreover,the mechanical properties of the membrane were also tested and the result showed that the silk NFN membrane displayed a breaking stress of 3. 7 MPa and breaking strain of 13. 8%. For further structural elucidation, Fourier transform infrared spectroscopy( FT-IR) was used to analyze the structural conformation changes from random coil to β-sheet in the NFN membrane which was an important factor effecting the usability of membrane. Thus,the results above confirmed the feasibility of Anaphe panda NFN structures applicability in cell tissue culture and other biomedical applications.

Electrospinning Preparation and Mechanical Properties of Polymethyl Methacrylate (PMMA)/Halloysite Nanotubes (HNTs) Composite Nanofibers

The paper was aimed at the PMMA/HNTs composite nanofibers with well enhanced mechanical properties prepared by electrospinning technique for the first time. A series of characterizations were used to illustrate the structure and properties of the composite nanofibers by SEM, XRD, FTIR and DSC techniques. The effect of the PMMA/HNTs composite nanofibers in relationship to the mass percentage of HNTs was investigated. The results indicated that HNTs wrapped in polymer matrix were highly oriented and dispersed by the electrospinning technique, resulting in improved thermal stability of the polymer. Moreover, the mechanical properties of the PMMA/HNTs composite nanofibers which were dependent on HNTs mass content were measured, and good enhanced mechanical properties were obtained.

Synthesis and Electrical Properties of TiO_2 Nanoparticles Embedded in Polyamide-6 Nanofibers Via Electrospinning

We report on the synthesis and characterizations of TiO2 nanoparticles embedded in polyamide-6composite nanofibers by using electrospinning technique. The influence of substrate on the electrical characteristics of polyamide-6/TiO2 composite nanofibers was investigated. The resultant nanofibers exhibit good incorporation of TiO2 nanoparticles. The doping of TiO2 nanoparticles into the polyamide-6 nanofibers were confirmed by high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Photoluminescence（PL） and cathodoluminescence（CL） spectroscopy were also used to characterize the samples.The PL and CL spectra reveal that the as-spun polyamide-6/TiO2 composite nanofibers consisted of overlapping of two broad emission bands due to the contribution of polyamide-6（centered at about 475 nm）, which might originate from organic functional groups of polyamide-6 and TiO2 nanoparticles（centered around 550 nm）. The electrical conductivity of the polyamide-6/TiO2 composite nanofibers on different substrates was carried out.It was found that the electrical conductivity of the polyamide-6/TiO2 composite nanofibers on silicon substrate was in the range of 13 μA, and about 1 to 20 p A for the paper and glass substrates.

Progress and perspectives on electrospinning techniques for solid-state lithium batteries

Abstract Solid-state electrolytes(SSEs),being the key component of solid-state lithium batteries,have a significant impact on battery performance.Rational materials structure and composition engineering on SSEs are promising to improve their Li+conductivity,interfacial contact,and mechanical integrity.Among the fabrication approaches,the electrospinning technique has attracted tremendous attention due to its own merits in constructing a three-dimensional framework of SSEs with precise porosity structure,tunable materials composition,easy operation,and superior physicochemical properties.To this end,in this review,we provide a comprehensive summary of the recent development of electrospinning techniques for high-performance SSEs.Firstly,we introduce the historical development of SSEs and summarize the fundamentals,including the Li+transport mechanism and materials selection principle.Then,the versatility of electrospinning technologies in the construction of the three main types of SSEs and stabilization of lithium metal anodes is comprehensively discussed.Finally,a perspective on future research directions based on previous work is highlighted for developing high-performance solid-state lithium batteries based on electrospinning techniques.

Influence of Sorbitan Monooleate on Morphology and Drug Release Behavior of Emulsion Electrospinning Polycaprolactone Nanofibers

Ultrafine polycaprolactone(PCL)fibers containing watersoluble drug tetracycline hydrochloride(Tet)were prepared by emulsion electrospinning.Sorbitan monooleate(Span80)was added as an essential additive to form stable water/oil emulsions and fabricate fibers with core-sheath structure.Different concentrations of Span80(0-40 g/L)were used to investigate the stability of emulsion and size of dispersed droplets.The scanning electron microscope(SEM)images indicated that the morphology of the fibers with Span80 were beaded-free with diameters of 200-400 nm,and Span80 enhanced the spinnability of electrospinning solution.The laser scanning confocal microscope(LSCM)images indicated that Tet was well encapsulated into the core region of the PCL fibers.The transmission electron microscope(TEM)image showed the formation of core-sheath structure.The loading efficiency(LE)and entrapment efficiency(EE)of Tet were calculated and release profiles in artificial saliva buffer solution(pH=6.8)were also analyzed.The results revealed that LE and EE of fibers with Span80decreased with the increase of its concentration.Fibers with coresheath structure had a longer effective release lifetime than without Span80.The increase of Span80 resulted in higher hydrophilicity of fibers and faster release rate of Tet.

Microstructural Changes of Graphene/PLA/PBC Nanofibers by Electrospinning during Tensile Tests

This study focuses on the nanostructure and nanostructural changes of novel graphene/poly(lactic acid)(PLA)/poly(butylene carbonate)(PBC)nanofibers via electrospinning,which are characterized by differential scanning calorimetry(DSC),scanning electron microscopy(SEM),tensile test and in situ small angle x-ray scattering.DSC indicates that the endothermic peak at 295℃ of pure PLA/PBC nanofibers shifted from 317℃ to lower 290℃with the increasing graphene content.SEM observations reveal a fine dispersion of graphene in the nanofiber matrices.The graphene/PLA/PBC nanofibers exhibit good improvements in mechanical property.The tensile strength of nanofibers increases with the addition of 0.01 g graphene but reduces with further addition of 0.04 g graphene.The scattering intensities increase dramatically when the strain levels are higher than the yield point due to the nucleation and growth of nanovoids or crystals.However,the increasing content of graphene in the PLA/PBC matrix provokes a strong restriction to the deformation-induced crystals.

Electrospinning of Gelatin Functionalized with Silver Na-noparticles for Nanofiber Fabrication

The present paper deals with gelatin nanofibres functionalized with silver nanoparticles, prepared by electrospinning using solutions of gelatin mixed with silver nitrate (AgNO3). As a common solvent for gelatin and silver nitrate (AgNO3), a mixture of acetic acid and water (70:30 v/v) was selected. In this system, acetic acid was used as a solvent for gelatin, and at the same time reducing agent for silver ions in solution. Silver nanoparticles (nAg) were stabilized through a mechanism that involves an interaction of the oxygen atoms of the carbonyl groups of gelatin. The viscosity and the conductivity of the gelatinous solutions were found to increase with the solution concentration. There is an observed decrease in the viscosity of the nAg containing gelatin solutions with the aging time increasing, whereas the conductiity of the AgNO3—containing gelatin solutions was greater than that of the base gelatin solution. The gelatin nanofibres functionalized with silver nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and antimicrobial test. The results of investigations by TEM and XRD confirmed the presence of silver nanoparticles with diameters in the range of (2 - 10 nm), uniformly distributed over the surface of smooth nanofibres with an average diameter of 70 nm. The release of silver ions from both the 2- and 4-hrs crosslinked nAg containing gelatin fiber mats by a total immersion method in buffer and distilled water occurred rapidly during the first 60 minutes, and increased gradually afterwards. Lastly, the tests demonstrated that gelatin/Ag nanofibers have a good antimicrobial activity against some common bacteria found on burned wounds. The anti-bacterial activity of these materials was greatest against Staphylococcus aureus, followed by Escherichia coli, and Pseudomonas aeroginosa ≈ Candida albicans.

Structure Changes of Silk Fibroin(SF) by Blending with Poly(ε-caprolactone)(PCL):Characterization of SF and PCL Blended Electrospinning Films

The mechanical properties and water solubility of electrospinning SF films limit their use as biomaterials. In order to develop a tissue engineering biomaterial with both satisfying biological properties and sufficient biomechanical properties,blended films composed of silk fibroin( SF) and poly( ε-caprolactone)( PCL) were fabricated by electrospinning in this study. Scanning electron microscope( SEM), X-ray diffraction( XRD),thermal analysis,Fourier transform-infrared( FT-IR),Raman spectra,mechanical testing,and water solubility were used to characterize the morphological, structural and mechanical properties of the blended electrospinning films. Results showed that the diameter of the blended fiber was distributed between 600 and1000 nm,and the fiber diameter increased as the PCL content increased. There is no obvious phase separation due to the similarity and intermiscibility,as well as the interactions( mainly hydrogen bonds), between the two polymers. Meanwhile, the secondary structures of SF changed from random coils and Silk I to Silk II because of the interactions between SF and PCL. For this reason,the tensile strength and elongation at break of the electrospinning films improved significantly,and the water solubility decreased. In conclusion,the blended electrospinning films fabricated in this study showed satisfying mechanical properties and water insolubilities,and they may be promising biomaterials for applications in tissue engineering for blood vessels,nerve conduits,tendons,ligaments and other tissues.

Effect of Solution Concentration on the Electrospray/Electrospinning Transition and on the Crystalline Phase of PVDF

A study was conducted regarding the effect of concentration of poly (vinylidene fluoride) (PVDF)/N,N-dimethylformamide (DMF) and PVDF/DMF/acetone solutions on the transition between electrospray and electrospinning and on the formation of the ? and ? crystalline phases of PVDF. The crystalline phases present in the samples, crystallinity and morphology were determined by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. Low concentration solutions resulted in films consisting of small droplets (electrospray) containing predominantly the ? phase. High concentration solutions resulted in a non-woven mesh of nano-to-micron diameter fibers (electrospinning) containing exclusively the ? phase. These results showed that, the formation of this phase in the electrospinning is related mainly to the solvent evaporation rate, and not to drawing experienced by the polymer during the process. Solvent type affected the amount of crystalline phase present, the boundary concentration between the two processes and the average diameter of fibers. Meshes processed by electrospinning display a degree of crystallinity higher than the films obtained by electrospray.

ELECTROSPRAYING/ELECTROSPINNING OF POLY(γ-STEARYL-LGLUTAMATE):FORMATION OF SURFACES WITH SUPERHYDROPHOBICITY

Electrospraying/electrospinning of poly(γ-stearyl-L-glutamate) (PSLG) was investigated on a series solutions with different concentrations in chloroform.Field emission scanning electron microscopy (FESEM) and attenuated Iotal reflectance Fourier transform infrared spectroscopy (FT-IR/ATR) were used to characterize the morphology and structure of the electrosprayed/electrospun polypeptide mats.It was found that electrospraying of PSLG with concentrations lower than 16 wt% afforded beads,while microfibers ...

Origami meets electrospinning:a new strategy for 3D nanofiber scaffolds

Inspired by the constitution of things in the natural world,three-dimensional (3D)nanofiber scaffold/cells complex was constructed via the combination of electrospinning technology and origami techniques.The nanofiber boxes prepared by origami provided a limited space for the layer-by-layer nanofiber films,and the human fetal osteoblasts (hFOBs)seeded on the both sides of the nanofiber films were expected to facilitate the bonding,of the adjacent nanofiber films through the secretion of extracellular matrix.Specifically,the hFOBs presented 3D distribution in the nanofiber scaffold,and they can stretch across the gaps between the adjacent nanofiber films,forming the cell layers and filling the whole 3D nanofiber scaffold.Eventually,a 3D block composed of electrospun nanofiber scaffold and cells was obtained',which possesses potential applications in bone tissue engineering.Interestingly,we also created 3D nanofiber structures that range from simple forms to intricate architectures via origami,indicating that the combination of electrospinning technology and origami techniques is a feasible method for the 3D construction of tissue engineering scaffolds.

Fabrication of Multi-layered Composite Scaffolds by Bi-directional Electrospinning Method

A multi-layered composite scaffolds consisting of poly （ L- ne） （ P （LLA-CL） ）, collagen （COL） and chitosan （CS） were fabricated by a bi-directional electrospinnlng method. Synthetic P （LLA-CL） was used as the middle layer to enhance the strength, while natural COL/CS blending （9： 1, v/v） was used as the bioactive surfaces （inner and outer layers ） to improve the biocompatibility. Each three transitional layers were set between inner/outer layer and middle layer for delamination resistance. Scanning electron microscopy （SEM） was used to observe the fiber morphology. The Fourier transform infrared attenuated total reflectance spectroscopy （FTIR-ATR） spectra, X- ray diffraction （XRD） and thermogravimetry （TG） tests were used to analyze the physical properties of the scaffolds. The results showed that the modified clectrospinning method bad no negative effect on the components, crystal structure and thermostability of the scaffolds, but could effectively combine the mechanical property of synthetic material and biocompatibility of natural materials. Such method could be applied to the fabrication of composite scaffolds for vascular, skin. and nerve tissue engineering.