Engineering Internal and External Low-Coordination Atoms in Nickel-Organic Framework Nanoarrays to Promote the Electrochemical Oxygen Evolution Reaction.

Monometallic nickel-organic frameworks based on a carboxylated ligand [2,6-naphthalenedicarboxylic acid (Ni-NDC)] have abundant and uniformly distributed single-atom Ni sites, enabling superior oxygen evolution reaction (OER) activity. In theory, most of the Ni atoms inside Ni-NDC microcrystals are coordinatively saturated except for the surface. Therefore, there are no accessible low-coordination atoms (LCAs) as electrocatalytic sites for the OER. One effective way is to expose more LCAs by preparing self-supporting Ni-NDC nanoarrays (Ni-NDC NAs) with hierarchical secondary structural units. Another effective method is to create more internal LCAs by removing partial ligands or coordination atoms attached to the Ni atoms. Herein, by combining the two strategies, we engineered LCAs in the interior and exterior of Ni-NDC to synergistically accelerate the OER. In brief, ultrathick "brick-like" Ni-NDC NAs were first prepared with dissolution and coordination effects of NDC on self-sacrificial templates of "agaric-like" nickel hydroxide nanoarrays [Ni(OH)2 NAs]. Subsequently, dual-coordinated NDC was partially replaced by monocoordinated 2-naphthoic acid (NA). The Ni-NDC NAs were further tailed into ultrathin "liner leaf-like" nanoneedle arrays (LCAs-Ni-NDC NAs). As a consequence, the LCAs-Ni-NDC NAs have more internal and external LCAs, which can deliver an OER performance that is superior to that of Ni-NDC NAs.

Aerogel-Involved Triple-State Gels Resemble Natural Living Leaves in Structure and Multi-Functions.

Natural plant leaves with multiple functions, for example, spectral features, transpiration, photosynthesis, etc., have played a significant role in the ecosystem, and artificial synthesis of plant leaves with multiple functions of natural ones is still a great challenge. Herein, this work presents an aerogel-involved living leaf (AL), most similar to natural ones so far, by embedding super-hydrophobic SiO2 aerogel microparticles in polyvinyl alcohol hydrogel in the presence of hygroscopic salt and chlorophyllin copper sodium to form solid-liquid-vapor triple-state gel. The AL shows a high spectral similarity with all sampled 15 species of natural leaves and exhibits ≈4-7 times transpiration speed higher than natural leaves. More importantly, AL can achieve several times higher photosynthesis than natural leaves without the energy provided by the respiratory action of natural ones. This work demonstrates the feasibility of creating ALs with natural leaf-like triple-state gel structures and multiple functions, opening up new avenues for energy conversion, environmental engineering, and biomimetic applications.

Transparent Silica Aerogels: Optical and Chemical Design, Controlled Synthesis, and Emerging Applications.

Transparent silica aerogel, serving as one typical porous and transparent material, possesses various unique features (e.g., large amounts of pores and interfaces, super-lightweight, super thermal insulation, low refractive index similar to gas), and it has attracted great attention in the fields of science, technology, engineering, art, and others. Transparency is one important evaluation index of transparent silica aerogel, and it was influenced by various factors such as raw materials, sol-gel reactions, phase separation, and drying methods. The structure design and fabrication of transparent silica aerogel is one huge and fine engineering. In this review, the optical/chemical guidance and design for the preparation of transparent silica aerogels are discussed, and typical applications, such as Cherenkov detectors, solar energy collection, lighting systems, and transparent fabric, also were discussed. Finally, a future outlook on the opportunities and challenges of transparent silica aerogels was proposed.

Tunable Light-Responsive Polyurethane-urea Elastomer Driven by Photochemical and Photothermal Coupling Mechanism.

Light-driven soft actuators based on photoresponsive materials can be used to mimic biological motion, such as hand movements, without involving rigid or bulky electromechanical actuations. However, to our knowledge, no robust photoresponsive material with desireable mechanical and biological properties and relatively simple manufacture exists for robotics and biomedical applications. Herein, we report a new visible-light-responsive thermoplastic elastomer synthesized by introducing photoswitchable moieties (i.e., azobenzene derivatives) into the main chain of poly(ε-caprolactone) based polyurethane urea (PAzo). A PAzo elastomer exhibits controllable light-driven stiffness softening due to its unique nanophase structure in response to light, while possessing excellent hyperelasticity (stretchability of 575.2%, elastic modulus of 17.6 MPa, and strength of 44.0 MPa). A bilayer actuator consisting of PAzo and polyimide films is developed, demonstrating tunable bending modes by varying incident light intensities. Actuation mechanism via photothermal and photochemical coupling effects of a soft-hard nanophase is demonstrated through both experimental and theoretical analyses. We demonstrate an exemplar application of visible-light-controlled soft "fingers" playing a piano on a smartphone. The robustness of the PAzo elastomer and its scalability, in addition to its excellent biocompatibility, opens the door to the development of reproducible light-driven wearable/implantable actuators and lightweight soft robots for clinical applications.

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.

Mimicking polar bear hairs in aerogel fibers.

Encapsulated aerogel fibers offer thermal insulation, breathability, and strength.

Folk arts-inspired twice-coagulated configuration-editable tough aerogels enabled by transformable gel precursors.

Aerogels, as famous lightweight and porous nanomaterials, have attracted considerable attention in various emerging fields in recent decades, however, both low density and weak mechanical performance make their configuration-editing capability challenging. Inspired by folk arts, herein we establish a highly efficient twice-coagulated (TC) strategy to fabricate configuration-editable tough aerogels enabled by transformable gel precursors. As a proof of concept, aramid nanofibers (ANFs) and polyvinyl alcohol (PVA) are selected as the main components of aerogel, among which PVA forms a flexible configuration-editing gel network in the first coagulation process, and ANF forms a configuration-locking gel network in the second coagulation process. TC strategy guarantees the resulting aerogels with both high toughness and feasible configuration editing capability individually or simultaneously. Altogether, the resulting tough aerogels with special configuration through soft to hard modulation provide great opportunities to break through the performance limits of the aerogels and expand application areas of aerogels.

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.

Ratio-Tuning of Silica Aerogel Co-Hydrolyzed Precursors Enables Broadband, Angle-Independent, Deformation-Tolerant, Achieving 99.7% Reflectivity.

The super-white body might be defined as its reflectivity exceeding 98% at any angle in the visible light spectrum, which can be used in a variety of emerging fields including optics, energy, environment, aerospace, etc. However, elaborate synthesis of a light-weight, highly reflective super-white aerogel body remains a great challenge. In this work, fine-tuning of silica aerogel co-hydrolyzed precursor ratios, 99.7% reflectivity with angle-independence in the visible light spectrum has been successfully achieved when the areal density is only 0.129 g cm-2 , which breaks through the theoretical bandwidth limit of photonic crystals as well as the measured reflectivity limit of conventional porous materials. Furthermore, the reflectivity of super-white silica aerogel remains unchanged after various harsh deformations including compression and bending 1000 times, solar (≈800 W m-2 ), ultraviolet (≈0.68 W m-2 ), and humidity (100%) aging for 100 days, liquid nitrogen (-196 °C) and high-temperature (300 °C) thermal shock 100 times. As proofs of performance, the resulting super-white silica aerogels have been used as the novel standard white plate  for better spectrum calibration, as the flexible projector curtains for optical display, as well as the transmitted light reflective layer in the photovoltaic cell for improving the relative power conversion efficiency of 5.6%.

Smart Energy-Absorbing Aerogel-Based Honeycombs with Selectively Nanoconfined Shear-Stiffening Gel.

Aerogels, shaped as fibers, films, as well as monoliths, have demonstrated a plethora of applications in both academia and industry due to charming properties including ultralow density, large specific surface area, high porosity, etc., however studies on more complicated aerogel forms (e.g., honeycombs) with more powerful applications have not been fully explored. Herein, the Kevlar aerogel honeycomb is firstly constructed through a dry ice-assisted 3D printing method, where the Kevlar nanofiber ink is printed directly in dry ice freezing atmosphere, followed by supercritical fluid drying. The subsequent 3D Kevlar/shear-stiffening gel (SSG) honeycomb (3D-KSH) can be obtained by selective nanoconfining of SSG into nanopores of the aerogel skeleton wall (with the loading amount of 93 wt%) rather than into open honeycomb channels, solving the leakage, creep deformation, and shape design infeasibility of the SSG. Combining the advantages of Kevlar, honeycomb and SSG, the fabricated 3D-KSH shows obvious smart responsive behavior to external stimulus. Additionally, the 3D-KSH has high strain rate sensitivity (sensitivity factor of 4.16 × 10-4 ) and excellent impact protection performance (energy absorption value up to 176 J g-1 at the strain rate of 6300 s-1 ), which will significantly broaden application prospect in some intelligent protection fields.

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.

3D Printed Hybrid Aerogel Gauzes Enable Highly Efficient Hemostasis.

Hemostatic materials have played a significant role in mitigating traumatic injury by controlling bleeding, however, the fabrication of the desirable material's structure to enhance the accumulation of blood cells and platelets for highly efficient hemostasis is still a great challenge. In this work, directed assembly of poly(vinyl alcohol) (PVA) macromolecules covering the rigid Kevlar nanofiber (KNF) network during 3D printing process is utilized to fabricate hydrophilic, biocompatible, and mechanically stable KNF-PVA aerogel filaments for effective enriching blood components by fast water absorption. As such, KNF-PVA aerogel gauzes demonstrate remarkable water permeability (338 mL cm-2 s-1 bar-1 ), water absorption speed (as high as 9.64 g g-1 min-1 ) and capacity (more than ten times of self-weight), and ability to enrich micron-sized particles when contacting aqueous solution. All these properties favor efficient hemostasis and the resulting KNF-PVA aerogel gauzes significantly outperform the commercial product Quikclot Gauze (Z-Medica) during in vivo experiments with the rat liver laceration model, reducing the hemostasis time by half (60 ± 4 s) and the blood loss by two thirds (0.07 ± 0.01 g). These results demonstrate a robust strategy to design various aerogel gauzes for hemostasis applications.

Case report: Apalutamide-induced severe lethal cutaneous adverse effects in China.

Introduction: Apalutamide is a novel agent for castration-resistant prostate cancer while skin rashes are the most common untoward reactions. Up to now, most of the reported dermatologic adverse events (dAEs) allocated to mild and moderate with a fair prognosis. Herein, we report a case series of severe dAEs in China caused by apalutamide. Case presentation: The four patients all developed severe and lethal drug eruptions including Stevens-Johnson syndrome and toxic epidermal necrolysis with a mean incubation period of 40 days. On the basis of the medical condition, all the patients were suggested to withdraw apalutamide and three of them recovered. Of note, attempts of rechallenges of apalutamide may be fatal. Discussion: The incidence of dAEs in previously conducted clinical trials exceeded 20%, with maculopapular rashes being the most common feature. However, the incidence and severity varied in different geographic regions and ethnicities. Inadequate attention was paid to severe cutaneous adverse reactions. Long latency may easily lead to the misdiagnosis of dAEs, and immediate withdrawal of apalutamide is the cornerstone of therapies. Conclusion: Special and adequate attention should be paid to apalutamide-attributed severe cutaneous adverse effects. Besides, the prognosis of severe drug eruptions may be disappointing, and in-time withdrawal is vital.

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.

Laminated Structural Engineering Strategy toward Carbon Nanotube-Based Aerogel Films.

Aerogel films with a low density are ideal candidates to meet lightweight application and have already been used in a myriad of fields; however, their structural design for performance enhancement remains elusive. Herein, we put forward a laminated structural engineering strategy to prepare a free-standing carbon nanotube (CNT)-based aerogel film with a densified laminated porous structure. By directional densification and carbonization, the three-dimensional network of one-dimensional nanostructures in the aramid nanofiber/carbon nanotube (ANF/CNT) hybrid aerogel film can be reconstructed to a laminated porous structure with preferential orientation and consecutively conductive pathways, resulting in a large specific surface area (341.9 m2/g) and high electrical conductivity (8540 S/m). Benefiting from the laminated porous structure and high electrical conductivity, the absolute specific shielding effectiveness (SSE/t) of a CNT-based aerogel film can reach 200647.9 dB cm2/g, which shows the highest value among the reported aerogel-based materials. The laminated CNT-based aerogel films with an adjustable wetting property also exhibit exceptional Joule heating performance. This work provides a structural engineering strategy for aerogel films with enhanced electric conductivity for lightweight applications, such as EMI shielding and wearable heating.