Gas-Blows-Liquid Spinning Strategy Toward Mechanically Strong, Thermally Protective, Efficiently Hemostatic Aerogel Fibers/Fabrics.

Nanoporous aerogel fibers enjoy the luxury of being one of the most attractive nanomaterials. However, the representative fabrication pathways have faced up with low production rates due to significant speed mismatch between slow sol-gel transition and as fast as possible spinning in the same period. Herein, a novel gas-blows-liquid spinning (GS) strategy with a spinning speed of 300-700 m s-1 is developed to get the high-speed and high-efficiency production of aerogel fibers/fabrics. The spinning speed of the GS strategy is 900 times higher than various techniques reported for aerogel fibers. The resulting aerogel fibers exhibit a high specific surface area (180 m2 g-1). In comparison, the aerogel fiber possesses the highest tensile strength (58.7±3.9 MPa) among its counterparts and aerogel fabric with surprising water-absorption and microparticle-blocking performances exhibits the application prospect for better hemostasis than that of commercial gauze and cotton ball. Besides, the GS aerogel fabrics with hierarchical aligned structures show better thermal insulation (≈0.035 Wm-1K-1) than wet spinning aerogel fabric and commercial insulation felts. This work has provided inspiration for fast fabricating more aerogel fibers/fabrics with this GS strategy, and the resulting aerogel fibers/fabrics may find significant application in the fields of 5G smart phones, wound hemostasis, etc.

Visible Microfluidic Deprotonation for Aramid Nanofibers as Building Blocks of Cascade-Microfluidic-Processed Colloidal Aerogels.

 Microfluidic deprotonation approach is proposed to realize continuous, scalable, efficient, and uniform production of aramid nanofibers (ANFs) by virtue of large specific surface area, high mixing efficiency, strong heat transfer capacity, narrow residence time distribution, mild laminar-flow process, and amplification-free effect of the microchannel reactor. By means of monitoring capabilities endowed by the high transparency of the microchannel, the kinetic exfoliation process of original aramid particles is in situ observed and the corresponding exfoliation mechanism is established quantificationally. The deprotonated time can be reduced from the traditional several days to 7 min for the final colloidal dispersion due to the synergistic effect between enhanced local shearing/mixing and the rotational motion of aramid particles in microchannel revealed by numerical simulations. Furthermore, the cascade microfluidic processing approach is used to make various ANF colloidal aerogels including aerogel fibers, aerogel films, and 3D-printed aerogel articles. Comprehensive characterizations show that these cascade-microfluidic-processed colloidal aerogels have identical features as those prepared in batch-style mode, revealing the versatile use value of these ANFs. This work achieves significant progress toward continuous and efficient production of ANFs, bringing about appreciable prospects for the practical application of ANF-based materials and providing inspiration for exfoliating any other nano-building blocks.

Ionic Liquid Directed Spinning of Cellulose Aerogel Fibers with Superb Toughness for Weaved Thermal Insulation and Transient Impact Protection.

Aerogel fibers, combining the nanoporous characteristics of aerogels with the slenderness of fibers, have emerged as a rising star in nanoscale materials science. However, endowing nanoporous aerogel fibers with good strength and high toughness remains elusive due to their high porosity and fragile mechanics. To address this challenge, this paper reports supertough aerogel fibers (SAFs) initially started from ionic-liquid-dissociated cellulose via wet-spinning and supercritical drying in sequence. The supertough nanoporous aerogel fibers assembled with cellulose nanofibers exhibit a high specific surface area (372 m2/g), good mechanical strength (30 MPa), and large elongation (107%). Benefiting from their high strength and elongation, the resultant cellulose nanoporous aerogel fibers show ultrahigh toughness up to 21.85 MJ/m3, much outperforming the known aerogel materials in the literature. Moreover, the toughness of this nanoporous aerogel fiber is 7.4 times higher than that of human knee ligaments, and its specific toughness is comparable to that of commonly used solid polyester fibers. In addition, we also verified the weavability, desirable thermal insulation performance, and supertoughness to resist the transient impact of SAFs. The long-sought strategy to simultaneously resolve the strength and toughness of nanoporous aerogel fibers, in combination with the biodegradable nature of the cellulose, provides multifaceted opportunities for broad potential applications, including lightweight wearable textiles and beyond.

Liquid-in-Aerogel Porous Composite Allows Efficient CO2 Capture and CO2 /N2 Separation.

The pursuit of efficient CO2 capture materials remains an unmet challenge. Especially, meeting both high sorption capacity and fast uptake kinetics is an ongoing effort in the development of CO2 sorbents. Here, a strategy to exploit liquid-in-aerogel porous composites (LIAPCs) that allow for highly effective CO2 capture and selective CO2 /N2 separation, is reported. Interestingly, the functional liquid tetraethylenepentamine (TEPA) is partially filled into the air pockets of SiO2 aerogel with left permanent porosity. Notably, the confined liquid thickness is 10.9-19.5 nm, which can be vividly probed by the atomic force microscope and rationalized by tailoring the liquid composition and amount. LIAPCs achieve high affinity between the functional liquid and solid porous counterpart, good structure integrity, and robust thermal stability. LIAPCs exhibit superb CO2 uptake capacity (5.44 mmol g-1 , 75 °C, and 15 vol% CO2 ), fast sorption kinetics, and high amine efficiency. Furthermore, LIAPCs ensure long-term adsorption-desorption cycle stability and offer exceptional CO2 /N2 selectivity both in dry and humid conditions, with a separation factor up to 1182.68 at a humidity of 1%. This approach offers the prospect of efficient CO2 capture and gas separation, shedding light on new possibilities to make the next-generation sorption materials for CO2 utilization.

The Rising Aerogel Fibers: Status, Challenges, and Opportunities.

Aerogel fibers garner tremendous scientific interest due to their unique properties such as ultrahigh porosity, large specific surface area, and ultralow thermal conductivity, enabling diverse potential applications in textile, environment, energy conversion and storage, and high-tech areas. Here, the fabrication methodologies to construct the aerogel fibers starting from nanoscale building blocks are overviewed, and the spinning thermodynamics and spinning kinetics associated with each technology are revealed. The huge pool of material choices that can be assembled into aerogel fibers is discussed. Furthermore, the fascinating properties of aerogel fibers, including mechanical, thermal, sorptive, optical, and fire-retardant properties are elaborated on. Next, the nano-confining functionalization strategy for aerogel fibers is particularly highlighted, touching upon the driving force for liquid encapsulation, solid-liquid interface adhesion, and interfacial stability. In addition, emerging applications in thermal management, smart wearable fabrics, water harvest, shielding, heat transfer devices, artificial muscles, and information storage, are discussed. Last, the existing challenges in the development of aerogel fibers are pointed out and light is shed on the opportunities in this burgeoning field.

Nanoscale Kevlar Liquid Crystal Aerogel Fibers.

Aerogel fibers, the simultaneous embodiment of aerogel porous network and fiber slender geometry, have shown critical advantages over natural and synthetic fibers in thermal insulation. However, how to control the building block orientation degree of the resulting aerogel fibers during the dynamic sol-gel transition process to expand their functions for emerging applications is a great challenge. Herein, nanoscale Kevlar liquid crystal (NKLC) aerogel fibers with different building block orientation degrees have been fabricated from Kevlar nanofibers via liquid crystal spinning, dynamic sol-gel transition, freeze-drying, and cold plasma hydrophobilization in sequence. The resulting NKLC aerogel fibers demonstrate extremely high mechanical strength (41.0 MPa), excellent thermal insulation (0.037 W·m-1·K-1), and self-cleaning performance (with a water contact angle of 154°). The superhydrophobic NKLC aerogel fibers can cyclically transform between aerogel and gel states, while gel fibers involving different building block orientation degrees display distinguishable brightness under polarized light. Based on these performances, digital textiles woven or embroidered with high- and low-orientated NKLC aerogel fibers enable up to 6.0 Gb information encryption in one square meter and on-demand decryption. Therefore, it can be envisioned that the tuning of the building blocks' orientation degree will be an appropriate strategy to endow performance to the liquid crystal aerogel fibers for potential applications beyond thermal insulation.

Bending Stiffness-Directed Fabricating of Kevlar Aerogel-Confined Organic Phase-Change Fibers.

Smart and functional fibers have demonstrated great potentials in a wide range of applications including wearable devices and other high-tech fields, but design and fabrication of smart fibers with manageable structures as well as versatile functions are still a great challenge. Herein, an ingenious bending-stiffness-directed strategy is developed to fabricate smart phase-change fibers with different bending stiffnesses for diverse applications. Specifically, the hydrophobic Kevlar aerogel-confined paraffin wax fibers (PW@H-KAF) are fabricated by employing hydrophobic Kevlar aerogel fibers (H-KAFs) as the porous host and paraffin as the functional guest, where the H-KAF is obtained by applying a two-step process to functionalize Kevlar nanofibers (KNFs) with a special coagulation bath containing a mixture of ethanol and n-bromobutane. The prepared PW@H-KAFs exhibit high latent heat (135.1-172 J/g), outstanding thermal cyclic stability and satisfactory mechanical properties (30 MPa in tensile strength and 30% in tensile strain). In addition, the PW@H-KAFs with bending stiffness was lower than the critical one (1.22 × 10-9 N·m2) even in a solid state of paraffin wax exhibits high flexibility, washable performance, and high thermal management capability, showing great potential for smart temperature-regulating fabrics. PW@H-KAFs with a bending stiffness higher than the critical one at a solid state of paraffin wax can be utilized as shape memory materials, attributed to the transition between rigidity and flexibility caused by the phase transition. As a proof of concept, a dynamic gripper is designed based on the PW@H-KAF (400 µm in diameter) for transporting items by gripping in the rigid state and releasing in the flexible state. This work realizes versatile applications with the PW@H-KAFs through the bending stiffness-directed method, providing ideas for the application of phase-change composites.

Polyimide Aerogel Fibers with Superior Flame Resistance, Strength, Hydrophobicity, and Flexibility Made via a Universal Sol-Gel Confined Transition Strategy.

Aerogel fibers with ultrahigh porosity, large specific surface area, and ultralow density have shown increasing interest due to being considered as the next generation thermal insulation fibers. However, it is still a great challenge to fabricate arbitrary aerogel fibers via the traditional wet-spinning approach due to the obvious conflict between the static sol-gel transition of the aerogel bulks and the dynamic wet-spinning process of aerogel fibers. Herein, a sol-gel confined transition (SGCT) strategy was developed for fabricating various mesoporous aerogel fibers, in which the aerogel precursor solution was first driven by the surface tension into the capillary tubes, then the gel fibers were easily formed in the confined space after static sol-gel process, and finally the mesoporous aerogel fibers were obtained via the supercritical CO2 drying process. As a typical case, the polyimide (PI) aerogel fiber prepared via the SGCT approach has exhibited a large specific surface area (up to 364 m2/g), outstanding mechanical property (with elastic modulus of 123 MPa), superior hydrophobicity (with contact angle of 153°), and excellent flexibility (with curvature radius of 200 µm). Therefore, the aerogel woven fabric made from PI aerogel fibers has possessed an excellent thermal insulation performance in a wide temperature window, even under the harsh environment. Besides, arbitrary kinds of aerogel fibers, including organic aerogel fibers, inorganic aerogel fibers, and organic-inorganic hybrid aerogel fibers, have been fabricated successfully, suggesting the universality of the SGCT strategy, which not only provides a way for developing aerogel fibers with different components but also plays an irreplaceable role in promoting the upgrading of the fiber fields.

Reaction-Spun Transparent Silica Aerogel Fibers.

Aerogel fibers, the simultaneous embodiment of aerogel 3D network and fibrous geometry, have shown great advantages over natural and synthetic fibers in thermal insulation. However, as a fast gelation to ensure aerogel fiber spinning generally induces rapid local clustering of precursor particles (i.e., phase separation) and unavoidably results in nontransparency and nonuniformity in the gel state, a severe challenge remains in remedying the spinning to make transparent aerogel fibers come true. Herein, we report a reaction spinning toward highly porous silica aerogel fibers, where the Brownian motion (i.e., diffusion) of colloidal particles is hampered during spinning to allow the maintaining of the fiber shape, while a rapid gelation reaction is activated by concentrated ammonia to solidify the fiber. The aggregation degree of the primary particles can be precisely controlled by pH-dependent hydrolyzation, and thus, the final aerogel fiber can be either transparent or opaque, as dominated by Rayleigh or Mie scattering. The resulting transparent silica aerogel fibers with low density, high specific surface area, and flexibility can inherit advanced features including excellent thermal insulation, wide temperature stability, and optional hydrophobic functionalization and, thus, be suitable for wearable applications.

Nanofibrous Kevlar Aerogel Threads for Thermal Insulation in Harsh Environments.

Aerogel with low density, high porosity, and large surface area is a promising structure for the next generation of high-performance thermal insulation fibers and textiles. However, aerogel fibers suffer from weak mechanical properties or complex fabricating processes. Herein, a facile wet-spinning approach for fabricating nanofibrous Kevlar (KNF) aerogel threads ( i.e., aerogel fibers) with high thermal insulation under extreme environments is demonstrated. The aerogel fibers made from nanofibrous Kevlar render a high specific surface area (240 m2/g) and wide-temperature thermal stability. The flexible and strong KNF aerogel fibers are woven into textiles to illustrate the excellent thermal insulation property under extreme temperature (-196 or +300 °C) and at room temperature. COMSOL simulation is applied to calculate the thermal conductivity of a single aerogel fiber and find an effective way to improve the thermal insulation property of the aerogel fiber. Furthermore, a series of functionalized fibers or textiles based on KNF aerogel fibers, such as phase-change fibers, conductive fibers, and hydrophobic textiles, have been prepared. Such KNF aerogel fibers represent a promising direction for the next generation of high-performance fibrous thermal-insulation materials.

Nanofibrous Kevlar Aerogel Films and Their Phase-Change Composites for Highly Efficient Infrared Stealth.

Infrared (IR) stealth is essential not only in high technology and modern military but also in fundamental material science. However, effectively hiding targets and rendering them invisible to thermal infrared detectors have been great challenges in past decades. Herein, flexible, foldable, and robust Kevlar nanofiber aerogel (KNA) films with high porosity and specific surface area were fabricated first. The KNA films display excellent thermal insulation performance and can be employed to incorporate with phase-change materials (PCMs), such as polyethylene glycol, to fabricate KNA/PCM composite films. The KNA/PCM films with high thermal management capability and infrared emissivity comparable to that of various backgrounds demonstrate high performance in IR stealth in outdoor environments with solar illumination variations. To further realize hiding hot targets from IR detection, combined structures constituted of thermal insulation layers (KNA films) and ultralow IR transmittance layers (KNA/PCM) are proposed. A hot target covered with this combined structure becomes completely invisible in infrared images. Such KNA/PCM films and KNA-KNA/PCM combined structures hold great promise for broad applications in infrared thermal stealth.

[Treatment of hepatic cancer in mice by beta-elemene combined DC/Dribble vaccine: an immune mechanism research].

OBJECTIVE: To observe the therapeutic effects of beta-elemene combined DC/Dribble vaccine in treating mice with hepatic cancer, thus exploring their anti-tumor mechanisms. METHODS: Dentritic cells were derived from Balb/c mice's spleen and their phenotypes were identified. Using hepatic cancer cell line BNL1MEA.7R.1 (abbreviated as BNL) originated from Balb/c mice as target cell, DC/Dribble vaccine was prepared via raising the antigen representing carrier autophagosomes (DRips in Blebs, DRibbles), which were rich in tumor antigen information. The mice previously immunized were divided into 4 groups, i.e., the control group, the beta-elemene group, the vaccine group, and the combined group. The PBS was subcutaneously and intraperitoneally injected to mice in the control group. The beta-elemene was intraperitoneally injected at the daily dose of 50 mg/kg to mice in the beta-elemene group and the combined group for 7 successive days. DC/Dribble vaccine was injected into the lymph node of mice in the vaccine group and the combined group on the 1st day, and DC/Dribble vaccine was subcutaneously injected on the 3rd day and the 5th day. All the mice were sacrificed on the 10th day. Their spleens were obtained sterilely, and the suspension was incubated with or without Dribble. The cells were inoculated for 72 h. The contents of IFN-gamma in the supernatant were measured by ELISA. In addition, the spleen cells obtained from the combined group were incubated with different stimulations for 72 h, which were then divided into the control group, the DRibble group, the DC group, and the DC/Dribble vaccine group. The supernatant of cultured cells were collected and the contents of IFN-gamma were measured by ELISA. The liver tumor-bearing mouse model was established, and then the BNL bearing mice were randomly divided into 4 groups, i.e., the control group, the beta-elemene group, the vaccine group, and the combined group. The treatment ways were the same as the immune ways. The tumor size and the survival period were observed in each group. On the 23rd day the mice were sacrificed. The tumor tissue was stripped and stained by HE staining. The pathomorphological manifestations of the tumor tissue were observed by light microscope. RESULTS: In vitro detection of mice immunized previously by different ways showed that the secretion of IFN-gamma was significantly higher in the combined group than in the rest groups (P < 0.01). The secretion of IFN-gamma was significantly higher in the beta-elemene group and the vaccine group than in the control group (P < 0.01). The spleen cells could be stimulated to secrete a large amount of IFN-gamma in the vaccine group and the Dribble group (P < 0.01). When the beta-elemene was 10 microg/mL as the stimulating dose, the secretion of IFN-gamma obviously increased (P < 0.01). In vivo observation showed that the growth velocity of tumors in mice of the combined group was slowed down. There was statistical difference in the tumor area or the survival period of mice in the combined group, when compared with the other groups (P < 0.01). In HE staining, the surrounding connective tissues of the tumor were wrapped tightly and compactedly, with infiltration of a large amount of inflammatory cells. CONCLUSIONS: beta-elemene combined DC/Dribble vaccine could induce specific immune cells to secrete secretory cells, thus exerting its anti-tumor effect. Its immunological effects might be associated with enhancing the DC antigen presenting function.

Synthesis, structure, photo-responsive properties of 4-(2-fluorobenzylideneamino)antipyrine: a combined experimental and theoretical study.

In this work, 4-(2-fluorobenzylideneamino)antipyrine (FBIAAP) was synthesized and characterized by elemental analysis, XRD, FT-IR, FT-Raman and UV-Vis techniques as well as density functional calculations. The studied molecule adopts a trans configuration about the imine CN bond, and adjacent molecules are linked through two kinds of weak hydrogen bonds to form supramolecular layered structures along the ab plane. Vibrational spectral analyses show that the benzene moiety directly attached to the central pyrazoline shows good vibrational isolation from the other moiety of pyrazole-imino-benzene presenting good vibrational resonances. UV-vis absorption bands mainly belong to n→π and π→π according to the electron transfer orbital assignments for the electron absorption spectrum of FBIAAP. The first-order hyperpolarizability of FBIAAP is 44.9 times that of urea theoretically. In addition, the thermodynamic properties were also obtained theoretically from the harmonic frequencies of the optimized structure.

Structural, proton-transfer, thermodynamic and nonlinear optical studies of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate.

Recently, the study of imine-bridged organics is interested in proton-transfer and photo-responsive material fields. Herein, we make a investigation on the structural, thermodynamic and nonlinear optical properties of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate (HPIMP). The structural varieties of the studied compound are characterized by the X-ray single crystal diffraction and vibrational spectral techniques, as well as the vibrational spectral bands are precisely ascribed to the studied structure with the aid of DFT theoretical calculations. The experimental results of the FT-IR and X-ray measurements supply good proofs to reveal the proton-transfer procedures of HPIMP, and exhibit that the studied compound is a good proton-transfer model. In addition, the thermodynamic properties are obtained from the theoretical vibrations of the optimized HPIMP. The linear polarizability (α(0)) and first-order hyperpolarizabilities (ß(0)) respectively present the values of 26.28 Å(3) and 7.41×10(-30) cm(5)/esu predicated theoretically by the DFT-B3lYP method at 6-31G(d) level, which indicates that the studied compound is a promising nonlinear optical material candidate.