Electrospun nanofibers are widely used in air-filtration materials because of their fine fiber diameter, small pore size, and high porosity. However, nanofiber membranes exhibit a dense structure, ...such that they present a large resistance to any air flow. In this study, we set out to design and develop composite nanofiber materials with fluffy structures, as well as blended structures of coarse and fine fibers, through electrospinning technology. These materials could be used in air filtration applications, given that they offer high efficiency and low resistance. The results show that, compared with pure PAN nanofibers, the diameter of PAN nanofibers doped with CNT decreased from 192.36 to 124.37 nm; when the spinning ratio of PS coarse fiber (1053 nm) and PAN/CNT fine fiber is 3:1, the resulting nanofiber membrane materials has an obvious three-dimensional structure, with a specific surface area of 103.16 m
2
/g, a pore size of 2.25 µm, and a quality factor of 0.0947 Pa
−1
. Under test conditions featuring an air flow of 32 L/min, and 0.3 µm NaCl aerosol particles, the filtration efficiency was 99.37 % and the resistance was 35 Pa. Furthermore, the dust-holding capacity of the nanofiber air-filter paper was found to be almost the same as that of melt-blown air-filter papers. Even after being water-soaked 50 times, the filtering efficiency of the nanofiber air-filter paper was still higher. Interestingly, the nanofiber membrane materials doped with CNT also exhibited excellent sound-absorption abilities. Thus, the composite nanofiber material could potentially be applied to areas with serious air pollution and high noise pollution.
A considerable amount of aramid non-woven fabrics (i.e., leftover materials, defective goods, etc.) is produced during the processing of products, leading to waste of resources as well as ...environmental pollution. Herein, a new strategy was proposed to fabricated multi-scale poly(m-phenylene isophthalamide) nanofiber membranes (mPMIAs) based on high-value-added application of aramid non-woven fabrics for high-temperature resistance filters. First, ultrafine PMIA nanofibers with a diameter of 17.87±8 nm (uPMIAs) and conventional PMIA nanofibers with a diameter of 112±38 nm (cPMIAs) were produced using electrospinning, and mPMIAs with different ratios of cPMIAs to uPMIAs (4:0,3:1,2:2,1:3, and 0:4) were then fabricated by adjusting the number of spin units. The results show that when the ratio of cPMIAs to uPMIAs is 2:2 (mPMIAs (2:2)), the nanofiber membrane exhibits excellent mechanical properties (fracture strength of 61.778 MPa) and thermal stability (up to 340 °C). More importantly, the mPMIAs (2:2) maintained a filtration efficiency of 98.05% for PM0.3−10 at 300 °C. A particle vehicle exhaust filter was used to capture particles with a filtration efficiency that exceeded 97.51%. Hence, mPMIAs can potentially be utilized in high-temperature air filtration and industry filtration fields.
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•A true-nanoscale PLA nanofiber with an average size of 37 ± 4 nm was fabricated.•The multi-scale structured nanofiber membrane was designed by one-step method, and the performance ...parameters were optimized.•The mask filter made of multi-scale structured nanofiber membrane showed high filtration efficiency and breathability.•The resultant mask filter has biodegradability and would be a great substitute for existing commercial masks in the future.
The usage of single-use face masks (SFMs) has increased since the outbreak of the coronavirus pandemic. However, non-degradability and mismanagement of SFMs have raised serious environmental concerns. Moreover, both melt-blown and nanofiber-based mask filters inevitably suffer from poor filtration performance, like a continuous decrease in the removal efficiency for particulate matter (PM) and weak breathability. Herein, we report a new method to create biodegradable and reusable fibrous mask filters. The filter consists of a true nanoscale bio-based poly(lactic acid) (PLA) fiber (an average size of 37 ± 4 nm) that is fabricated via electrospinning of an extremely dilute solution. Furthermore, we designed a multiscale structure with integrated features, such as low basis weight (0.91 g m−2), small pore size (0.73 μm), and high porosity (91.72%), formed by electrospinning deposition of true nanoscale fibers on large pore of 3D scaffold nanofiber membranes. The resultant mask filter exhibited a high filtration efficiency (PM0.3–99.996%) and low pressure drop (104 Pa) superior to the commercial N95 filter. Importantly, this filter has a durable filtering efficiency for PM and natural biodegradability based on PLA. Therefore, this study offers an innovative strategy for the preparation of PLA nanofibers and provides a new design for high-performance nanofiber filters.
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Indoor air quality (IAQ) has assumed new significance given the extensive amount of time spent indoor due to the coronavirus pandemic and particulate matter (PM) pollution. ...Accordingly, the development of window air filters to effectively intercept PM from outdoor air under natural ventilation conditions is an important research topic. However, most existing filters inevitably suffer from the compromise among filtration capability, transparency, and air permeability. In this study, we fabricate a high-performance transparent air filter to improve IAQ via natural ventilation. polyvinylidene fluoride (PVDF) superfine nanofibers of size 20–35 nm are prepared using extremely dilute solution electrospinning; a multi-scale nanofiber structure is then designed. By adjusting the ratio of PVDF superfine nanofibers (SNs) to PVDF coarse fibers (CNs), we balance the structure–performance relationship. Benefiting from the multiscale structural features that include a small pore size (0.72 μm) and high porosity (92.22%), the resulting filters exhibit excellent performance including high interception efficiency (99.92%) for PM0.3, low air resistance (69 Pa), high transparency (∼80%) and stable filtration after 100 h of UV irradiation. This work describes a new strategy for the fabrication of nanofibers with true-nanoscale diameters and the design of high-performance air filters.
Recently, because of the outbreak of COVID‐19, the demand for various types of filter elements in protective materials has increased globally. Furthermore, new requirements for the filtration ...performance of PM2.5 liquid (oil) particles have been put forward. In this work, Superhydrophobic and superoleophobic composite nanofibers with excellent filtration capacity for oil and salt particles are developed through the modification of polyacrylonitrile (PAN) by fluoro‐polyurethane (FPU) doping. The results show that the PAN/FPU composite nanofibers doped with 9 wt% FPU has a uniform fiber morphology with a diameter of 240 ± 30 nm. Compared to the pure PAN nanofibers, the water‐based contact angle of PAN/FPU increases from 90 ± 5° to 151 ± 5°, and the oil‐based contact angle increases from 58 ± 2° to 152 ± 3°. Importantly, at a high flow rate of 95 L min−1, the filtration efficiency of the PAN/FPU nanofiber membrane for 0.3 µm oil particles increases from 92 ± 1% to 99.2 ± 0.1%. After cyclic loading, the filtration efficiency of 0.3 µm oil particles remains above 98%. Meanwhile, the filtration efficiency for 0.3 µm salt particles remains at 98.23 ± 0.1%. The PAN/FPU nanofiber membrane developed in this work is effective in applications and has good market prospects as a protective filtration material.
Polyacrylonitrile /fluoro‐polyurethane (FPU) composite nanofiber membranes have been prepared by electrospinning. The results show that nanofiber membranes have excellent superhydrophobic and superoleophobic properties when the FPU concentration is 9 wt%. In terms of filtration performance, its superoleophobic performance significantly improves the interception capacity of oily particles, and the reasons for improving the interception capacity are analyzed in detail.
Successful construction of small‐diameter double‐layer vascular scaffolds (SDVSs) whose inner diameters are less than 1.5 mm, especially those with multilayer mimic structures, remains a challenge in ...vascular tissue engineering. In this study, poly(L‐lactide‐co‐caprolactone) (PLCL)/poly(Ɛ‐caprolactone) (PCL)/tussah silk fibroin (TSF) SDVSs with a double‐layer structure are prepared by one‐step method based on friction twisting core‐spun electrospinning technology. The constructed PLCL/PCL SDVSs grafted TSF have an obvious double‐layer structure; tube wall thickness 524 ± 28 µm; and inner tube diameter 1390 ± 40 µm. Compared with traditional nanofiber vascular scaffolds (TS), the axial and radial tensile strengths of PLCL/PCL SDVSs grafted TSF increase by 86% and 34%, respectively. They also show good scaffold elastic recovery and burst pressure (BP) (8505 ± 875 mmHg). Compared with the PLCL/PCL SDVSs, the inner and outer layers of PLCL/PCL SDVSs grafted TSF show good hydrophilicity and protein adsorption performance. The in vitro cell viability results indicate that the inner and outer layers of PLCL/PCL SDVSs grafted TSF show enhanced proliferation and adhesion of vein endothelial cells (VECs) and smooth muscle cells (SMCs), respectively. Therefore, the successful preparation of PLCL/PCL SDVSs grafted TSF provides more possibilities for the clinical transplantation of small‐diameter vascular scaffolds.
Small‐diameter poly(L‐lactide‐co‐caprolactone) (PLCL)/ poly(Ɛ‐caprolactone) (PCL) nanofiber grafted tussah silk fibroin (TSF) vascular scaffolds with a double‐layer structure have been successfully designed and fabricated using one‐step method based on friction twisting core‐spun electrospinning technology. The vascular scaffolds show excellent hydrophilicity, protein adsorption performance, and enhanced blood compatibility. Importantly, they also show excellent mechanical properties and cytocompatibility, and have great potential in vascular tissue engineering.
Owing to the robust scalability, ease of control and substantial industrial applications, the utilization of electrospinning technology to produce piezoelectric nanofiber materials demonstrates a ...significant potential in the development of wearable products including flexible wearable sensors. However, it is unfortunate that the attainment of high-performance piezoelectric materials through this method remains a challenging task. Herein, a high-performance composite nanofiber membrane with a coherent and uniformly dispersed two-dimensional network topology composed of polyvinylidene fluoride (PVDF)/dopamine (DA) nanofiber membranes and ultrafine PVDF/DA nanofibers was successfully fabricated by the electrospinning technique. Based on the evidence obtained from simulations, experimental and theoretical results, it was confirmed that the unique structure of the nanofiber membrane significantly enhances the piezoelectric performance. The present PVDF/DA composite nanofibers demonstrated a remarkable piezoelectric performance such as a wide response range (1.5–40 N), high sensitivity to weak forces (0–4 N, 7.29 V N
−1
), and outstanding operational durability. Furthermore, the potential application of the present PVDF/DA membrane as a flexible wearable sensor for monitoring human motion and subtle physiological signals has also been validated. This work not only introduces a novel strategy for the application of electrospun nanofibers in sensors but also provides new insights into high-performance piezoelectric materials.
Graphical Abstract
Surface area, pore properties, synergistic behavior, homogenous dispersion, and interactions between carbon matrix and metal‐nanostructures are the key factors for achieving the better performance of ...carbon‐metal based (electro)catalysts. However, the traditional hydro‐ or solvothermal preparation of (electro)catalysts, particularly, bi‐ or tri‐metallic nanostructures anchored graphene (G) or carbon nanotubes (CNTs), often pose to poor metal–support interaction, low synergism, and patchy dispersion. At first, bimetallic flower‐like‐CuFeS 2 /NG and cube‐like‐NiFeS 2 /NCNTs nanocomposites were prepared by solvothermal method. The resultant bimetallic nanocomposites were employed to derive the 2D‐nano‐sandwiched Fe 2 CuNiS 4 /NGCNTs‐SW (electro)catalyst by a very simple and green urea‐mediated “mix‐heat” method. The desired physicochemical properties of Fe 2 CuNiS 4 /NGCNTs‐SW such as multiple active sites, strong metal‐support interaction, homogenous dispersion and enhanced surface area were confirmed by various microscopic and spectroscopic techniques. To the best of our knowledge, this is the first urea‐mediated “mix‐heat” method for preparing 2D‐nano‐sandwiched carbon‐metal‐based (electro)catalysts. The Fe 2 CuNiS 4 /NGCNTs‐SW was found to be highly effective for alkaline‐mediated oxygen evolution reaction at low onset potential of 284.24 mV, and the stable current density of 10 mA cm −2 in 1.0 m KOH for 10 h. Further, the Fe 2 CuNiS 4 /NGCNTs‐SW demonstrated excellent catalytic activity in the reduction of 4‐nitrophenol with good k app value of 87.71 × 10 −2 s −1 and excellent reusability over five cycles. Overall, the developed urea‐mediated “mix‐heat” method is highly efficient for the preparation of metal‐nanoarchitectures anchored 2D‐nano‐sandwiched (electro)catalysts with high synergism, uniform dispersion and excellent metal‐support interaction.
A
bstract
Finding out root patterns of quantum integrable models is an important step to study their physical properties in the thermodynamic limit. Especially for models without U(1) symmetry, their ...spectra are usually given by inhomogeneous
T − Q
relations and the Bethe root patterns are still unclear. In this paper with the antiperiodic
XXZ
spin chain as an example, an analytic method to derive both the Bethe root patterns and the transfer-matrix root patterns in the thermodynamic limit is proposed. Based on them the ground state energy and elementary excitations in the gapped regime are derived. The present method provides an universal procedure to compute physical properties of quantum integrable models in the thermodynamic limit.
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