Hierarchically aligned heterogeneous core-sheath hydrogels.

Natural materials with highly oriented heterogeneous structures are often lightweight but strong, stiff but tough and durable. Such an integration of diverse incompatible mechanical properties is highly desired for man-made materials, especially weak hydrogels which are lack of high-precision structural design. Herein, we demonstrate the fabrication of hierarchically aligned heterogeneous hydrogels consisting of a compactly crosslinked sheath and an aligned porous core with alignments of nanofibrils at multi-scales by a sequential self-assembly assisted salting out method.

Solvent-adaptive hydrogels with lamellar confinement cellular structure for programmable multimodal locomotion.

Biological organisms can perform flexible and controllable multimodal motion under external stimuli owing to the hierarchical assembly of anisotropic structures across multiple length scales. However, artificial soft actuators exhibit the limited response speed, deformation programmability and movement capability especially in harsh environments because of insufficient anisotropic hierarchy and precision in structural design. Here, we report a programmed assembly directed confinement polymerization method for the fabrication of environmentally tolerant and fast responsive hydrogels with lamellar assembly-confined cellular structure interpenetrated with highly aligned nanopillars by the directional freezing-assisted polymerization in the predesigned anisotropic laminar scaffold.

Nanocomposite Hydrogel Actuators with Ordered Structures: From Nanoscale Control to Macroscale Deformations.

Flexible intelligent actuators with the characteristics of flexibility, safety and scalability, are highly promising in industrial production, biomedical fields, environmental monitoring, and soft robots. Nanocomposite hydrogels are attractive candidates for soft actuators due to their high pliability, intelligent responsiveness, and capability to execute large-scale rapid reversible deformations under external stimuli. Here, the recent advances of nanocomposite hydrogels as soft actuators are reviewed and focus is on the construction of elaborate and programmable structures by the assembly of nano-objects in the hydrogel matrix.

Rapid Printing and Patterning of Tough, Self-Healable, and Recyclable Hydrogel Thin-Films toward Flexible Sensing Devices.

Direct and rapid printing and surface patterning of hydrogel thin films are of great significance in the construction of advanced electronic devices, yet they are greatly underdeveloped due to the intrinsic contradiction between mechanical strength and self-healability as well as recyclability. Here, we present a universal and rapid slipping-directed route with a newly developed water-soluble star polymer hydrogel for direct and reproducible printing and patterning of freestanding functional thin films with precisely controlled thicknesses, components, and surface structures on a large scale. The resulting thin films combine the features of large transmittance (93%), tough mechanical strength (114 MPa), multiresponsive self-healability, recyclability, and remarkable multifunctionality.

Double Confinement Hydrogel Network Enables Continuously Regenerative Solar-to-Hydrogen Conversion.

Soft matter catalyst system allowing controllable manipulation of the organized nanostructure and surface property holds the potential for renewable energy. Here we demonstrate the construction of a continuously regenerative hydrogel photocatalyst that confines the metal-thiolate coordination induced nanocavity into robust micro-sized spongy network for water splitting. Thanks to low vaporization enthalpy and fast proton mobility of water molecules confining in nanocavities, the composite delivers outstanding photocatalytic H production (TOF of 4568 H  h ), nearly 4.

Autonomous Self-Healing of Highly Stretchable Supercapacitors at All Climates.

Realizing autonomous self-healing and high stretchability of flexible supercapacitors over a wide temperature range remains a big challenge because of simultaneous incorporation of self-healing, stretchable and temperature-tolerant elements into a device as well as unfavorable electrochemical kinetics in harsh conditions. Here, we demonstrate for the first time an autonomous self-healing and intrinsically stretchable supercapacitor that can work at all-climate environments assembled by universally self-healing and highly stretchable organohydrogel electrodes with record-high temperature-invariant conductivity of ∼965 S/cm. Benefiting from multiple hydrogen bonding and dynamic metal coordination combined with electrochemistry-favorable components and integrated device configuration, the supercapacitor exhibits outstanding long-term stability, high stretchability, instantaneous and complete capacitive self-healability, and real-time mechanical healing at harsh temperatures from -35 to 80 °C.

Ultrastretchable and Self-Healing Conductors with Double Dynamic Network for Omni-Healable Capacitive Strain Sensors.

Skin-mountable capacitive-type strain sensors with great linearity and low hysteresis provide inspiration for the interactions between human and machine. For practicality, high sensing performance, large stretchability, and self-healing are demanded but limited by stretchable electrode and dielectric and interfacial compatibility. Here, we demonstrate an extremely stretchable and self-healing conductor via both hard and soft tactics that combine conductive nanowire assemblies with double dynamic network based on π-π attractions and Ag-S coordination bonds.

A multi-responsive healable supercapacitor.

Self-healability is essential for supercapacitors to improve their reliability and lifespan when powering the electronics. However, the lack of a universal healing mechanism leads to low capacitive performance and unsatisfactory intelligence. Here, we demonstrate a multi-responsive healable supercapacitor with integrated configuration assembled from magnetic FeO@Au/polyacrylamide (MFP) hydrogel-based electrodes and electrolyte and Ag nanowire films as current collectors.

Anisotropic and self-healing hydrogels with multi-responsive actuating capability.

Inspired by smart biological tissues, artificial muscle-like actuators offer fascinating prospects due to their distinctive shape transformation and self-healing function under external stimuli. However, further practical application is hindered by the lack of simple and general routes to fabricate ingenious soft materials with anisotropic responsiveness. Here, we describe a general in situ polymerization strategy for the fabrication of anisotropic hydrogels composed of highly-ordered lamellar network crosslinked by the metal nanostructure assemblies, accompanied with remarkably anisotropic performances on mechanical, optical, de-swelling and swelling behaviors.

A Highly Stretchable and Real-Time Healable Supercapacitor.

In addition to a high specific capacitance, a large stretchability and self-healing properties are also essential to improve the practicality and reliability of supercapacitors in portable and wearable electronics. However, the integration of multiple functions into one device remains challenging. Here, the construction of a highly stretchable and real-time omni-healable supercapacitor is demonstrated by sandwiching the polypyrrole-incorporated gold nanoparticle/carbon nanotube (CNT)/poly(acrylamide) (GCP@PPy) hydrogel electrodes with a CNT-free GCP (GP) hydrogel as the electrolyte and chemically soldering an Ag nanowire film to the hydrogel electrode as the current collector.

Self-healing and superstretchable conductors from hierarchical nanowire assemblies.

It is still a great challenge to improve deformability and fatigue-resistance of stretchable conductors when maintaining their high-level conductivity for practical use. Herein, a high-performance stretchable conductor with hierarchically ternary network and self-healing capability is demonstrated through in situ polymerizing N-isopropylacrylamide (NIPAM) on well-defined sulfur-containing molecule-modified Ag nanowire (AgNW) aerogel framework. Owing to hierarchical architecture from nanoscale to microscale and further to macroscale and strong interactions of polymer chains and AgNWs, the composite exhibits good conductivity of 93 S cm, excellent electromechanical stability up to superhigh tensile strain of 800% and strong fatigue-resistant ability through well accommodating the applied deformations and sharing external force in the network.

Highly Tough Bioinspired Ternary Hydrogels Synergistically Reinforced by Graphene/Xonotlite Network.

The application fields of hydrogels are often severely limited by their weak mechanical performance. It is therefore highly demanded to develop an effective strategy to fabricate mechanically strong hydrogels. Herein, a kind of bioinspired ternary hydrogel consisting of graphene oxide (GO) nanosheets, xonotlite nanowires, and polyacrylamide (PAM) is constructed under the synergy of hydrogen bonding-induced GO/xonotlite network and the penetrated PAM chain network.

Templating Synthesis of Mesoporous FeC-Encapsulated Fe-N-Doped Carbon Hollow Nanospindles for Electrocatalysis.

Developing cost-efficient alternatives to the noble metal catalysts toward oxygen reduction reaction (ORR) has attracted much attention. Herein, a kind of mesoporous hollow spindlelike Fe-N-C electrocatalysts with iron carbide nanoparticles encased in the N-doped graphitic layers has been synthesized by a novel "reactive hard template" strategy through the Fe-assisted polymerization of dopamine on the FeO cores and the following calcinations. The FeO nanospindles not only as the hard template guide the formation of well-defined shape and structure of the catalyst but also as the reactive template provide Fe reservoir to generate FeC nanoparticles in the catalyst during the thermochemical process.

Stable Lithium Storage in Nitrogen-Doped Carbon-Coated Ferric Oxide Yolk-Shell Nanospindles with Preserved Hollow Space.

Iron oxide (Fe O ) is a promising anode material for next-generation high-energy lithium-ion batteries owing to its high theoretical specific capacity, but it suffers from unstable electrochemistry, as represented by a significant volume variation upon (de)lithiation and unstable solid-electrolyte interface. To target these issues, a double-coating synthetic route has been developed to prepare a yolk-shell-structured γ-Fe O /nitrogen-doped carbon composite, in which spindle-like γ-Fe O cores are encapsulated in the highly conductive carbon shell. Through precisely controlling the void space between the γ-Fe O core and the carbon shell, volume variation in γ-Fe O during (de)lithiation is well accommodated, while the composite maintains an intact and relatively dense structure, which stabilizes the solid-electrolyte interface and is beneficial for improving the practical energy density of the material.

A Bioinspired Interface Design for Improving the Strength and Electrical Conductivity of Graphene-Based Fibers.

Graphene-based fibers (GBFs) are attractive for next-generation wearable electronics due to their potentially high mechanical strength, superior flexibility, and excellent electrical and thermal conductivity. Many efforts have been devoted to improving these properties of GBFs in the past few years. However, fabricating GBFs with high strength and electrical conductivity simultaneously remains as a great challenge.

Graphene Sandwiched by Sulfur-Confined Mesoporous Carbon Nanosheets: A Kinetically Stable Cathode for Li-S Batteries.

The practical use of lithium-sulfur batteries for the next-generation energy storage, especially the automobiles, was hindered by low electronic conductivity of sulfur and the resulting poor rate capabilities. Here, we report a sulfur-carbon composite by confining S into a graphene sandwiched in mesoporous carbon nanosheets with a two-dimensional ultrathin morphology, suitable mesopore size and large pore volume, and excellent electronic conductivity. Serving as cathode material for a Li-S battery, the elaborately designed S/C composite leads to "kinetically stable" transmissions of Li ions and electrons, triggering a stable electrochemistry and a record-breaking rate performance.

Combining Nitrogen-Doped Graphene Sheets and MoS2 : A Unique Film-Foam-Film Structure for Enhanced Lithium Storage.

With a notable advantage in terms of capacity, molybdenum disulfide has been considered a promising anode material for building high-energy-density lithium-ion batteries. However, its intrinsically low electronic conductivity and unstable electrochemistry lead to poor cycling stability and inferior rate performance. We herein describe the scalable assembly of free-standing MoS2 -graphene composite films consisting of nitrogen-doped graphene and ultrathin honeycomb-like MoS2 nanosheets.

Conductive Carbon Network inside a Sulfur-Impregnated Carbon Sponge: A Bioinspired High-Performance Cathode for Li-S Battery.

A highly conductive sulfur cathode is crucial for improving the kinetic performance of a Li-S battery. The encapsulation of sulfur in porous nanocarbons is expected to benefit the Li(+) migration, yet the e(-) conduction is still to be improved due to a low graphitization degree of a conventional carbon substrate, especially that pyrolyzed from carbohydrates or polymers. Aiming at facilitating the e(-) conduction in the cathode, here we propose to use ketjen black, a highly graphitized nanocarbon building block to form a conductive network for electrons in a biomass-derived, hierarchically porous carbon sponge by a easily scaled-up approach at a low cost.

The Electrochemistry with Lithium versus Sodium of Selenium Confined To Slit Micropores in Carbon.

Substitution of selenium for sulfur in the cathode of a rechargeable battery containing Sx molecules in microporous slits in carbon allows a better characterization of the electrochemical reactions that occur. Paired with a metallic lithium anode, the Sex chains are converted to Li2Se in a single-step reaction. With a sodium anode, a sequential chemical reaction is characterized by a continuous chain shortening of Sex upon initial discharge before completing the reduction to Na2Se; on charge, the reconstituted Sex molecules retain a smaller x value than the original Sex chain molecule.

Titanium Dioxide/Upconversion Nanoparticles/Cadmium Sulfide Nanofibers Enable Enhanced Full-Spectrum Absorption for Superior Solar Light Driven Photocatalysis.

In this work, we demonstrate an electrospinning technique to fabricate TiO2 /upconversion nanoparticles (UCNPs)/CdS nanofibers on large scale. In addition, the as-prepared TiO2 nanofibers are incorporated with a high population of UCNPs and CdS nanospheres; this results in Förster resonance energy-transfer configurations of the UCNPs, TiO2 , and CdS nanospheres that are in close proximity. Hence, strong fluorescent emissions for the Tm(3+) ions including the (1) G4 →(3) H6 transition are efficiently transferred to TiO2 and the CdS nanoparticles through an energy-transfer process.

Coupling Microbial Growth with Nanoparticles: A Universal Strategy To Produce Functional Fungal Hyphae Macrospheres.

Macroscale assembly of nanoscale building blocks is an intriguing way to translate the unique characteristics of individual nanoparticles into macroscopic materials. However, the lack of the efficient universal assembly strategy seriously hinders the possibility of macroscale architectures in practical applications. Herein, we develop a general, environment-friendly, and scalable microbial growth method for the construction of macroscopic composite assemblies with excellent mechanical strength by in situ integrating various types of nanoparticles into fungal hyphae (FH) macrospheres.

Iron Oxide with Different Crystal Phases (α- and γ-Fe2O3) in Electroanalysis and Ultrasensitive and Selective Detection of Lead(II): An Advancing Approach Using XPS and EXAFS.

Iron oxide with different crystal phases (α- and γ-Fe2O3) has been applied to electrode coatings and been demonstrated to ultrasensitive and selective electrochemical sensing toward heavy metal ions (e.g., Pb(II)).

Peptide Self-Assembled Biofilm with Unique Electron Transfer Flexibility for Highly Efficient Visible-Light-Driven Photocatalysis.

Inspired by natural photosynthesis, biomaterial-based catalysts are being confirmed to be excellent for visible-light-driven photocatalysis, but are far less well explored. Herein, an ultrathin and uniform biofilm fabricated from cold-plasma-assisted peptide self-assembly was employed to support Eosin Y (EY) and Pt nanoparticles to form an EY/Pt/Film catalyst for photocatalytic water splitting to H2 and photocatalytic CO2 reduction with water to CO, under irradiation of visible light. The H2 evolution rate on EY/Pt/Film is 62.