Direct synthesis of ultralight, elastic, high-temperature insulation N-doped TiO2 ceramic nanofibrous sponges via conjugate electrospinning.

The design of three-dimensional ceramic nanofibrous materials with high-temperature insulation and flame-retardant characteristics is of significant interest due to the effectively improved mechanical properties. However, achieving a pure ceramic monolith with ultra-low density, high elasticity and toughness remains a great challenge. Herein, a low-cost, scalable strategy to fabricate ultralight and mechanically robust N-doped TiO2 ceramic nanofibrous sponges with a continuous stratified structure by conjugate electrospinning is reported. Remarkably, the introduction of dopamine into the precursor nanofibers is engineered, which realizes the nitrogen doping to inhibit the TiO2 grain growth, endowing single nanofibers with a smoother, less defective surface. Besides, the self-polymerization process of dopamine allows the construction of bonding points between nanofibers and optimizes the distribution of inorganic micelles on polymer templates. Moreover, a rotating disk receiving device under different rotating speeds is designed to obtain N-doped TiO2 sponges with various interlamellar spacings, further affecting the maximum compressive deformation capacity. The resulting ceramic sponges, consisting of fluffy crosslinked nanofiber layers, possess low densities of 12-45 mg cm-3, which can quickly recover under a large strain of 80% and have only 9.2% plastic deformation after 100 compression cycles. In addition, the sponge also exhibits a temperature-invariant superelasticity at 25-800 °C and a low heat conductivity of 0.0285 W m-1 K-1, with an outstanding thermal insulation property, making it an ideal insulation material for high-temperature or harsh conditions.

Polylactic Acid/Calcium Stearate Hydrocharging Melt-Blown Nonwoven Fabrics for Respirator Applications.

Non-biodegradable polypropylene, which poses a serious threat to the environment, is the most utilized material in air filtration systems. Moreover, under conditions of high temperature and high humidity, the electrostatic charge in melt-blown nonwoven fabrics treated with traditional corona electrets will quickly dissipate. Here, biodegradable polylactic acid, calcium stearate, and an innovative hydrocharging technique are reported to develop environmentally friendly polylactic acid/calcium stearate hydrocharging melt-blown nonwoven fabrics with high charge stability. Compared with polylactic acid melt-blown nonwoven fabrics, the crystallization structure and charge storage of polylactic acid/calcium stearate melt-blown nonwoven fabrics have been greatly improved due to the presence of calcium stearate. In PM0.3, it exhibited a high filtration efficiency (96.78%), a low pressure drop (65.20 Pa), and a good quality factor (0.053 Pa-1), which can meet the N95 respirator standard. Furthermore, it is worth mentioning that the filtration performance remained at a high level (>95.00%) after 2 months. Importantly, based on the test and analysis of surface electrostatic potential, crystallization, and charge storage and distribution, we proposed plausible charge generation and stable storage mechanisms. It demonstrated more potential for electret air filtration and smart respirators as the further possible step of research in the field.

Heat-conducting elastic ultrafine fiber sponges with boron nitride networks for noise reduction.

Industrial and traffic noise has become increasingly serious with the progress of industrialization. Most existing noise-absorbing materials suffer from poor heat dissipation and insufficient low-frequency (<1000 Hz) noise absorption, which not only reduces working efficiency but also leads to safety risks. Herein, heat-conducting elastic ultrafine fiber sponges with boron nitride (BN) networks were prepared by integrating direct electrospinning and impregnation method. The large acoustic contact area of ultrafine fibers and the vibration effect of BN nanosheets in a three-dimensional direction endow fiber sponges with good noise reduction, which can reduce white noise by 28.3 dB with a high noise reduction coefficient of 0.64. Moreover, thanks to good heat-conducting networks composed of BN nanosheets and porous structures, the obtained sponges exhibit superior heat dissipation with thermal conductivity of 0.159 W m-1 K-1. Besides, the introduction of elastic polyurethane and following crosslinking endow the sponges with good mechanical properties, which have almost no plastic deformation after 1000 compressions, and the tensile strength and strain are as high as 0.28 MPa and 75%. The successful synthesis of heat-conducting elastic ultrafine fiber sponges overcomes poor heat dissipation and low-frequency noise reduction of noise absorbers.

Recent progress in TiO2-based microwave absorption materials.

It is particularly important to develop high-performance microwave absorption (MA) materials to remediate the increasingly serious electromagnetic pollution. Recently, titanium dioxide-based (TiO2-based) composites have become a research hotspot owing to their light weight and synergy loss mechanism. In this study, significant research progress in TiO2-based complex-phase microwave absorption materials is reviewed, which involves carbon components, magnetic materials, polymers and so on. First, the research background and limitations of TiO2-based composites are discussed. The design principles for microwave absorption materials are elaborated in the next section. More importantly, TiO2-based complex-phase materials with multi-loss mechanisms are analyzed and summarized in this review. Finally, the conclusions and prospectives are presented, which provide a reference for the understanding of TiO2-based MA materials.

High Toughness Combined with High Strength in Oxide Ceramic Nanofibers.

Traditional oxide ceramics are inherently brittle and highly sensitive to defects, making them vulnerable to failure under external stress. As such, endowing these materials with high strength and high toughness simultaneously is crucial to improve their performance in most safety-critical applications. Fibrillation of the ceramic materials and further refinement of the fiber diameter, as realized by electrospinning, are expected to achieve the transformation from brittleness to flexibility owing to the structural uniqueness. Currently, the synthesis of electrospun oxide ceramic nanofibers must rely on an organic polymer template to regulate the spinnability of the inorganic sol, whose thermal decomposition during ceramization will inevitably lead to pore defects, and seriously weaken the mechanical properties of the final nanofibers. Here, a self-templated electrospinning strategy is proposed for the formation of oxide ceramic nanofibers without adding any organic polymer template. An example is given to show that individual silica nanofibers have an ideally homogeneous, dense, and defect-free structure, with tensile strength as high as 1.41 GPa and toughness up to 34.29 MJ m-3 , both of which are far superior to the counterparts prepared by polymer-templated electrospinning. This work provides a new strategy to develop oxide ceramic materials that are strong and tough.

Fibrous MXene Aerogels with Tunable Pore Structures for High-Efficiency Desalination of Contaminated Seawater.

The seawater desalination based on solar-driven interfacial evaporation has emerged as a promising technique to alleviate the global crisis on freshwater shortage. However, achieving high desalination performance on actual, oil-contaminated seawater remains a critical challenge, because the transport channels and evaporation interfaces of the current solar evaporators are easily blocked by the oil slicks, resulting in undermined evaporation rate and conversion efficiency. Herein, we propose a facile strategy for fabricating a modularized solar evaporator based on flexible MXene aerogels with arbitrarily tunable, highly ordered cellular/lamellar pore structures for high-efficiency oil interception and desalination. The core design is the creation of 1D fibrous MXenes with sufficiently large aspect ratios, whose superior flexibility and plentiful link forms lay the basis for controllable 3D assembly into more complicated pore structures. The cellular pore structure is responsible for effective contaminants rejection due to the multi-sieving effect achieved by the omnipresent, isotropic wall apertures together with underwater superhydrophobicity, while the lamellar pore structure is favorable for rapid evaporation due to the presence of continuous, large-area evaporation channels. The modularized solar evaporator delivers the best evaporation rate (1.48 kg m-2 h-1) and conversion efficiency (92.08%) among all MXene-based desalination materials on oil-contaminated seawater.

Conductivity optimization via intertwined CNTs between TiNb2O7@C microspheres for a superior performance Li-ion battery anode.

Titanium niobate (TiNb2O7, TNO) possesses attractive discharge voltage and reversibility, which is considered to be an ideal anode material of lithium ion battery (LIB). However, its rate capability is strictly limited by their poor conductivity. To improve this issue faced by traditional TNO electrodes, a hierarchical conductive optimization strategy has been proposed and fabricated by a facile spray drying approach. For the construction, TiNb2O7@ultrathin carbon layer (TNO@C) is entangled into carbon nanotubes network to synthesize a highly conductive porous TNO@C/CNTs microsphere. This ultrathin carbon layer and evenly intertwined carbon nanotubes can ensure the superior charge transfer pathway, facilitating the transportation of electrons and Li ions. Additionally, CNTs can provide robust mechanical strength framework, beneficial to the structural stability of composite microspheres. As expected, the TNO@C/CNTs exhibits elevated conductivity and cyclic durability with charge capacities of 343.3 mAh·g-1 at 0.25 C after 300 cycles and 274.9 mAh·g-1 at 10 C after 1000 cycles. This study intends to explore the effect of the attached carbon materials on the TNO-based electrode conductivity and LIBs performances.

Tailoring Nanoporous-Engineered Sponge Fiber Molecular Sieves with Ternary-Nested Architecture for Precise Molecular Separation.

Polymeric fiber molecular sieves (PFMs) with ultrahigh surface areas, well-defined Murray's-law hierarchical nanoporous structures, and superior self-standing properties are of great interest for molecular-level separation applications. However, creating such PFMs has been proven extremely challenging. Herein, we report a cross-scale pore-forming strategy to create intriguing sponge fiber molecular sieves with hierarchical, tailorable, and molecularly defined nanoporosity by nanospace-confined chain-packing modulation at the molecular level. Robust secondary ultramicropores (<7 Å) and micropores (<2 nm) are in situ constructed in the macro/mesoporous skeletons of sponge fibers to realize a tunable pore size distribution. The resultant PFMs exhibit the integrated properties of ultrahigh surface area (860 m2 g-1), large pore volume (0.6 cm3 g-1), self-standing properties, and excellent molecular sieving performance and are widely applied in acetophenone/phenyl ethanol separation, hydrogen peroxide purification, ethyl acetate separation, and CO2 adsorption fields. The fabrication of such PFMs provides a feasible way for the design and development of polymeric fibrous sieves for molecular separation in large-scale chemical, energy, and environmental operation processes.

Ultrathin Zirconium Hydroxide Nanosheet-Assembled Nanofibrous Membranes for Rapid Degradation of Chemical Warfare Agents.

Organophosphorus-based chemical warfare agents (CWAs) are highly poisonous, and recent attacks using nerve agents have stimulated researchers to develop breakthrough materials for their fast degradation. Zr-based materials have been identified as the most effective catalysts for breaking down CWAs, but in their powdered form, their practical application in personal protective equipment is limited. Herein, a surface-confined strategy for the direct growth of vertically aligned zirconium hydroxide (Zr(OH)4 ) nanosheets with ultrathin and tortuous structures on nanofibers is reported. The freestanding Zr(OH)4 nanosheet-assembled nanofibrous membranes (NANMs) show superior catalytic performance to degrade dimethyl methylphosphonate, a nerve agent simulant, with a half-life of 4 min. In addition, intriguing membrane-type NANMs feature integrated properties of exceptional breathability, prominent flexibility, and robust fatigue resistance over one million buckling loads. This facile strategy provides a novel route to manufacture new classes of nanosheet-supported membranes for chemical-protective materials, in particular for gas filters, protective suits, and clothing.

In-situ electrospinning of thymol-loaded polyurethane fibrous membranes for waterproof, breathable, and antibacterial wound dressing application.

Skin-like flexible membrane with excellent water resistance and moisture permeability is an urgent need in the wound dressing field to provide comfort and protection for the wound site. Despite efforts that have been made in the development of waterproof and breathable (W&B) membranes, the in-situ electrospinning of W&B membranes suitable for irregular wound surfaces as wound dressings still faces huge challenges. In the current work, a portable electrospinning device with multi-functions, including adjustable perfusion speed for a large range from 0.05 mL/h to 10 mL/h and high voltage up to 11 kV, was designed. The thymol-loaded ethanol-soluble polyurethane (EPU) skin-like W&B nanofibrous membranes with antibacterial activity were fabricated via the custom-designed device. Ultimately, the resultant nanofibrous membranes composed of EPU, fluorinated polyurethane (FPU), and thymol presented uniform structure, robust waterproofness with the hydrostatic pressure of 17.6 cm H2O, excellent breathability of 3.56 kg m-2 d-1, the high tensile stress of 1.83 MPa and tensile strain of 453%, as well as high antibacterial activity. These results demonstrate that the new-type device has potential as a portable electrospinning apparatus for the fabrication of antibacterial membranes directly on the wound surface and puts a new way for the development of portable electrospinning devices.

Visible-Light-Driven and Self-Hydrogen-Donated Nanofibers Enable Rapid-Deployable Antimicrobial Bioprotection.

The novel coronavirus SARS-CoV-2 has prompted a worldwide pandemic and poses a great threat to public safety and global economies. Most present personal protective equipment (PPE) used to intercept pathogenic microorganisms is deficient in biocidal properties. Herein, we present green nanofibers with effective antibacterial and antiviral activities that can provide sustainable bioprotection by continuously producing reactive oxygen species (ROS). The superiority of the design is that the nanofibers can absorb and store visible light energy and maintain the activity under light or dark environment. Moreover, the nanofibers can uninterruptedly release ROS in the absence of an external hydrogen donor, acting as a biocide under all weather conditions. A facile spraying method is proposed to rapidly deploy the functional nanofibers to existing PPE, such as protective suits and masks. The modified PPE exhibit stable ROS production, excellent capacity for storing activity potential, long-term durability, and high bactericidal (>99.9%) and viricidal (>99.999%) efficacies.

Green-Solvent-Processed Fibrous Membranes with Water/Oil/Dust-Resistant and Breathable Performances for Protective Textiles.

Waterproof and breathable membranes (WBMs) are highly demanded worldwide due to their promising applications in outdoor protective clothing, medical hygiene, and electronic devices. However, the design of such materials integrated with environmental friendliness and high functionality has been considered a long-standing challenge. Herein, we report the green-solvent-processed polyamide fibrous membranes with amphiphobicity and bonding structure via ethanol-based electrospinning and water-based impregnating techniques, endowing the fibrous membranes with outstanding water/oil/dust-resistant and good breathable properties. The developed green smart fibrous membranes exhibit integrated properties with robust water and oil intrusion pressures of 101.2 and 32.4 kPa, respectively, excellent dust removal efficiency of above 99.9%, good water vapor transmission rate of 11.2 kg m-2 d-1, air permeability of 2.6 mm s-1, tensile strength of 15.6 MPa, and strong toughness of 22.8 MJ m-3, enabling the membranes to protect human beings and electronic devices effectively. This work may shed light on designing the next generation green smart fibrous WBMs for protective textiles.

Yolk-Shell Fe/Fe4 N@Pd/C Magnetic Nanocomposite as an Efficient Recyclable ORR Electrocatalyst and SERS Substrate.

A yolk-shell Fe/Fe4 N@Pd/C (FFPC) nanocomposite is synthesized successfully by two facile steps: interfacial polymerization and annealing treatment. The concentration of Pd2+ is the key factor for the density of Pd nanoparticles (Pd NPs) embedded in the carbon shells, which plays a role in the oxygen reduction reaction (ORR) and surface-enhanced Raman scattering (SERS) properties. The ORR and SERS performances of FFPC nanocomposites under different concentrations of PdCl2 are investigated. The optimal ORR performance exhibits that onset potential and tafel slope can reach 0.937 V (vs reversible hydrogen electrode (RHE)) and 74 mV dec-1 , respectively, which is attributed to the synergistic effects of good electrical conductivity, large electrochemically active areas, and strong interfacial charge polarization. Off-axis electron holography reveals that interfacial charge polarization could facilitate the ORR of Pd NPs and defective carbon simultaneously and the shell with low density of Pd NPs is easier to form strong interfacial charge polarization. Moreover, FFPC-3 with maximum EF of 2.3 × 105 results from more hot-spots, local positive charge centers to attract rhodamine 6G molecules, and magnetic cores. This work not only offers a recyclable multifunctional nanocomposite with excellent performance, but also has instructional implications for interfacial engineering for electrocatalysts design.

Two hybrid Au-ZnO aggregates with different hierarchical structures: A comparable study in photocatalysis.

Two hierarchical ZnO micro/nano-materials have been prepared by a short-time (45min) hydrothermal reaction without any surfactants. The different morphologies have been characterized comprehensively by XRD, SEM, TEM and XPS technologies. The hierarchical micro- and nano-structures are respectively consisted by the subordinate nano-pieces and nano-hexagonal-rods. Under the illumination of the simulated solar light, the nano-piece-aggregate spends 40min to degrade the 98% of rhodamine 6G solution (10-5mol/L), whereas the nano-rod-aggregate only degrades the 78% of the solution in the same condition. Moreover, the photocatalytic performances of the two ZnO aggregates are significantly improved by loading with Au nanoparticles (NPs) in the same assembly process. The nano-piece-aggregate decorated with the Au NPs spends 24min to decompose the rhodamine 6G solution completely, while nano-rod-aggregate decorated with the Au NPs needs 28min. The related photocatalytic mechanisms are proposed in this paper.

Self-Assembled 3D Hierarchical Copper Hydroxyphosphate Modified by the Oxidation of Copper Foil as a Recyclable, Wide Wavelength Photocatalyst.

In this work, three-dimensional flower-like and petal-like copper hydroxyphosphate Cu5(OH)4(PO4)2 (CHP) based on the self-assembly of numerous nanosheets has been successfully fabricated on a copper foil by a mild one-pot wet-chemical method without ligand assistance. This research contributes to the development of the method to change the morphology of the CHP active material by varying the degree of substrate oxidation. The two different CHP architectures were used to photocatalytically degrade rhodamine 6G (Rh 6G) under solar light, which can absorb wide-range light wavelength from the UV to the near-infrared region. They all exhibit high photocatalytic activity and good durability, which are potential candidates for high performance and recyclable wide wavelength photocatalysis.

Susceptibilities of Mycoplasma hominis to herbs.

To determine the susceptibilities of Mycoplasma homonis (M. hominis) to Chinese medicinal herbs in vitro, 30 clinical strains of M. hominis were isolated and identified from the clinical specimen. The susceptibilities of M. hominis to 19 herbs were determined by serial dilution methods in vitro. The results showed that M. hominis was susceptible to Radix Isatidis, Radix Angelicae Dahuricae, Cortex Phellodendri, Radix et Rhizoma Rhei, Fructus Kochiae and Herba Houttuyniae. These findings laid a foundation in treating M. hominis infection with Chinese herbs.