Hierarchical Composites of Single/Double‐Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double Hydroxides

Three‐dimensional hierarchical nanocomposites consisting of one‐dimensional carbon nanotubes (CNTs) and two‐dimensional lamellar flakes (such as clay, layered double hydroxides) show unexpected properties for unique applications. To achieve a well‐designed structure with a specific function, the uniform distribution of CNTs into the used matrix is a key issue. Here, it is shown that a hierarchical composite of single/double‐walled CNTs interlinked with two‐dimensional flakes can be constructed via in‐situ CNT growth onto layered double hydroxide (LDH) flakes. Both the wall number and diameter of the CNTs and the composition of the flakes can be easily tuned by changing the proportion of the transition metal in the LDH flakes. Furthermore, a structure with continuously interlinked CNT layers alternating with lamellar flakes is obtained after compression. The hierarchical composite is demonstrated to be an excellent filler for strong polyimide films. This study indicates that LDH is an extraordinary catalyst for the fabrication of hierarchical composites with high‐quality single/double‐walled CNTs. The as‐obtained CNTs/calcined LDHs nanocomposite is a novel structural platform for the design of mechanically robust materials, catalysts, ion‐transportation, energy‐conversion, and other applications.     

Hierarchical Nanowire Arrays Based on ZnO Core−Layered Double Hydroxide Shell for Largely Enhanced Photoelectrochemical Water Splitting

Well‐aligned hierarchical nanoarrays containing ZnO core and layered double hydroxide (LDH) nanoplatelets shell have been synthesized via a facile electrosynthesis method. The resulting ZnO@CoNi–LDH core?shell nanoarray exhibits promising behavior in photoelectrochemical water splitting, giving rise to a largely enhanced photocurrent density as well as stability; much superior to those of ZnO‐based photoelectrodes. This is attributed to the successful integration of photogenerated electron–hole separation originating from the ZnO core and the excellent electrocatalytic activity of LDH shell. This work provides a facile and cost‐effective strategy for the fabrication of multifunctional nanoarrays with a hierarchical structure, which can be potentially used in energy storage and conversion devices.     

Non‐Equilibrium,Light‐Adaptive,Steady‐State Reconfiguration of Mechanical Patterns in Bioinspired Nanocomposites

Bioinspired nanocomposites have made great progress for the fabrication of mechanical high‐performance structural materials, but their properties have thus far been engineered with a focus on static behavior. This contrasts profoundly with the dynamic reconfiguration often observed in living tissues. Here, a first concept is introduced for steady‐state, light‐adaptive reconfiguration of mechanical patterns in bioinspired nanocomposites under dissipative out‐of‐equilibrium conditions. This is realized for green, waterborne cellulose nanofibril/polymer nanopapers by achieving a heterogeneous activation of a photothermal effect. To this end, predefined mechanical patterns are designed by top‐down lamination of bottom‐up engineered bioinspired nanocomposites containing thermoreversible hydrogen bonds, as well as spatially selectively incorporated single‐walled carbon nanotubes for photothermal response. Global irradiation leads to localized photothermal softening by cascading light to heat, and to the dynamization and breakage of the thermoreversible supramolecular bonds, leading to macroscopic reconfiguration and even inversion of mechanical stiff/soft patterns. The altered configuration is only stable in a dissipative steady state and relaxes to the ground state once light is removed. The strategy presents a new approach harnessing the capabilities from top‐down and bottom‐up structuring, and by interfacing it with non‐equilibrium adaptivity concepts, it opens avenues for hierarchical bioinspired materials with anisotropic response in global fields.     

Fatigue‐Resistant Bioinspired Graphene‐Based Nanocomposites

Graphene is an attractive building block for constructing functional materials of flexible electronic devices, due to its extraordinary mechanical and electrical properties. Up to now, large amounts of high‐performance graphene‐based nanocomposites are fabricated. However, the fatigue behavior of graphene‐based nanocomposites, a key parameter for flexible electronic devices, is rarely investigated. According to the fatigue mechanisms of thermosetting polymer composites, the fatigue resistance of graphene‐based nanocomposites can be significantly improved by effectively restricting the crack growth. Natural nacre demonstrates unique multisuppression of crack propagation, which is attributed to its sophisticated interfacial architecture over multiple length scales, resulting in remarkable fracture toughness. The crack suppression mechanisms corresponding to different interfacial design strategies within bioinspired graphene‐based nanocomposites (BGBNs) are summarized in this feature article. The static mechanical properties, electrical conductivity, and fatigue resistance of these BGBNs are compared and discussed. The synergistic effect from various interfacial interactions and building blocks is highlighted to serve as the guidance for constructing novel fatigue‐resistant BGBNs. The promising applications of fatigue‐resistant BGBNs in flexible electronic devices are reviewed, and several challenges and corresponding solutions are proposed. The perspective of fatigue‐resistant BGBNs for fundamental research and commercial application is depicted.     

Size‐Transformable Metal–Organic Framework–Derived Nanocarbons for Localized Chemo‐Photothermal Bacterial Ablation and Wound Disinfection

Severe infectious diseases caused by pathogenic bacteria have become urgent threats to global public health. Antibacterial materials with combined chemo‐photothermal therapeutic capabilities possess distinct advantages when compared with many other antibacterial approaches. However, developing simplified and chemically tunable precursors to synthesize such antibacterial nanoagents for rapidly, safely, and synergistically combating pathogenic bacteria remains a huge challenge. Herein, metal–organic framework (MOF)‐derived nanocarbons with near‐infrared (NIR)‐responsive and size‐transformable capabilities are designed to overcome this challenge. The MOF‐derived nanocarbons with chemo‐photothermal bactericidal capabilities are first synthesized, and then coated with a thermoresponsive gel layer to obtain ON–OFF switching capability for bacterial trapping. The fabricated nanocarbons exhibit high photo‐to‐thermal conversion efficiency and fast size transformation from nanodispersions to micrometer aggregations upon NIR irradiation, thus enabling nanocarbons to generate localized massive heat and abundant Zn²⁺ ions for directly disrupting bacterial membrane and intracellular proteins. Furthermore, these nanocarbons not only exhibit a nearly 100% bactericidal ratio at very low dosage, but also possess highly efficient and safe wound disinfection activities, which are comparable to vancomycin. Overall, these proposed novel nanocarbons display robust and localized chemo‐photothermal bactericidal capability and possess great potential to be used as alternative to antibiotics for broad‐spectrum eradication of pathogenic bacteria.     

3D Nanocomposites of Covalently Interconnected Multiwalled Carbon Nanotubes with SiC with Enhanced Thermal and Electrical Properties

Synthesizing 3D carbon nanotube (CNT) networks with multifunctional characteristics has stimulated the interest from the scientific community since the 1990s. Here, the fabrication of a novel composite material consisting of 3D covalently interconnected multiwalled CNT with silicon carbide (SiC) nano and microparticles is reported. The material is synthesized by a two‐step process involving the coating of CNT with silicon oxide (SiO _x ) via chemical routes, followed by spark plasma sintering (SPS). SPS enables carbothermal reduction of SiO_x and subsequent densification of the material into 3D composite blocks. Covalent interconnections of CNT are facilitated by a carbon diffusion process resulting in SiC formation as SiO_x coated CNT are subjected to high temperatures. The presence of SiC in the sintered composite has been confirmed by Raman spectroscopy, as well as through energy filtered transmission electron microscopy maps. Interestingly, the 3D CNT composite exhibits high thermal conductivity (16.72 W m^?1 K^?1); and also a semiconducting behavior with an electron hopping mechanism associated to a 3D variable range hopping model. These findings demonstrate that it is indeed possible to fabricate SiC–CNT composites with enhanced physical properties that can be used as multifunctional materials.     

Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites

Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC–NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self‐assembly strategy is described for fabrication of complex and well‐defined BC–NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self‐assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near‐field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.     

Reactive Aramid Nanostructures as High‐Performance Polymeric Building Blocks for Advanced Composites

Traditionally, the field of advanced nanocomposites has relied on a fairly limited set of building blocks; many with low reactivity and of limited variability. These limitations have been addressed by the creation of functionalized nanometer‐scale aramid structures, in the form of nanofibers and nanosheets. These were obtained by deprotonating macroscale, commercial Kevlar yarns using potassium hydroxide in dimethyl sulfoxide to yield stable dispersions of nanometer‐scale aramid fibers that were then hydrolyzed using phosphoric acid (PA). To illustrate the use of these functionally‐active nanostructures as building blocks for nanocomposites, they were crosslinked by glutaraldehyde (GA), and formed into macroscopic thin films by vacuum‐assisted filtration. It was shown that the mechanical properties of these PA/GA treated films can be tuned by varying the amounts of PA and GA used during synthesis, adjusting the relative amounts of hydrolysis and polymerization. These results are the first demonstration that aramid nanometer‐scale fibers can be used to form versatile nanometer‐sized building blocks that can then be crosslinked to fabricate a wide variety of nanostructured aramid materials with tailorable properties.     

Bioinspired Nanocomposites: Ordered 2D Materials Within a 3D Lattice

Composites, materials composed of two or more materials—metallic, organic, or inorganic—usually exhibit the combined physical properties of their component materials. The result is a material that is superior to conventional monolithic materials. Advanced composites are used in a variety of industrial applications and therefore attract much scientific interest. Here the formation of novel carbon‐based nanocomposites is described via incorporation of graphene oxide (GO) into the crystal lattice of single crystals of calcite. Incorporation of a 2D organic material into single‐crystal lattices has never before been reported. To characterize the resulting nanocomposites, high‐resolution synchrotron powder X‐ray diffraction, electron microscopy, transmission electron microscopy, fluorescence microscopy and nanoindentation tests are employed. A detailed analysis reveals a layered distribution of GO sheets incorporated within the calcite host. Moreover, the optical and mechanical properties of the calcite host are altered when a carbon‐based nanomaterial is introduced into its lattice. Compared to pure calcite, the composite GO/calcite crystals exhibits lower elastic modulus and higher hardness. The results of this study show that the incorporation of a 2D material within a 3D crystal lattice is not only feasible but also can lead to the formation of hybrid crystals exhibiting new properties.     

2D or Not 2D: Strain Tuning in Weakly Coupled Heterostructures

A route to realize strain engineering in weakly bonded heterostructures is presented. Such heterostructures, consisting of layered materials with a pronounced bond hierarchy of strong and weak bonds within and across their building blocks respectively, are anticipated to grow decoupled from each other. Hence, they are expected to be unsuitable for strain engineering as utilized for conventional materials which are strongly bonded isotropically. Here, it is shown for the first time that superlattices of layered chalcogenides (Sb₂Te₃/GeTe) behave neither as fully decoupled two‐dimensional (2D) materials nor as covalently bonded three‐dimensional (3D) materials. Instead, they form a novel class of 3D solids with an unparalleled atomic arrangement, featuring a distribution of lattice constants, which is tunable. A map to identify further material combinations with similar characteristic is given. It opens the way for the design of a novel class of artificial solids with unexplored properties.     

Novel metal carbon nanocomposites and carbon nanocrystalline material with promising properties for the development of electronics

New materials based on carbon nanocrystalline material and metal carbon nanocomposites, which have specific properties and are promising for the use in the fabrication of electron and electrochemical sensor devices and catalysts, have been suggested for the development of electronics.     

Integrative Self‐Assembly of Graphene Quantum Dots and Biopolymers into a Versatile Biosensing Toolkit

Hybrid self‐assembly has become a reliable approach to synthesize soft materials with multiple levels of structural complexity and synergistic functionality. In this work, photoluminescent graphene quantum dots (GQDs, 2–5 nm) are used for the first time as molecule‐like building blocks to construct self‐assembled hybrid materials for label‐free biosensors. Ionic self‐assembly of disc‐shaped GQDs and charged biopolymers is found to generate a series of hierarchical structures that exhibit aggregation‐induced fluorescence quenching of the GQDs and change the protein/polypeptide secondary structure. The integration of GQDs and biopolymers via self‐assembly offers a flexible toolkit for the design of label‐free biosensors in which the GQDs serve as a fluorescent probe and the biopolymers provide biological function. The versatility of this approach is demonstrated in the detection of glycosaminoglycans (GAGs), pH, and proteases using three strategies: 1) competitive binding of GAGs to biopolymers, 2) pH‐responsive structural changes of polypeptides, and 3) enzymatic hydrolysis of the protein backbone, respectively. It is anticipated that the integrative self‐assembly of biomolecules and GQDs will open up new avenues for the design of multifunctional biomaterials with combined optoelectronic properties and biological applications.     

Dual Support System Ensuring Porous Co–Al Hydroxide Nanosheets with Ultrahigh Rate Performance and High Energy Density for Supercapacitors

Layered double hydroxides (LDHs) are promising supercapacitor electrode materials due to their high specific capacitances. However, their electrochemical performances such as rate performance and energy density at a high current density, are rather poor. Accordingly, a facile strategy is demonstrated for the synthesis of the integrated porous Co–Al hydroxide nanosheets (named as GSP‐LDH) with dual support system using dodecyl sulfate anions and graphene sheets as structural and conductive supports, respectively. Owing to fast ion/electron transport, porous and integrated structure, the GSP‐LDH electrode exhibits remarkably improved electrochemical characteristics such as high specific capacitance (1043 F g^?1 at 1 A g^?1) and ultra‐high rate performance capability (912 F g^?1 at 20 A g^?1). Moreover, the assembled sandwiched graphene/porous carbon (SGC)//GSP‐LDH asymmetric supercapacitor delivers a high energy density up to 20.4 Wh kg^?1 at a very high power density of 9.3 kW kg^?1, higher than those of previously reported asymmetric supercapacitors. The strategy provides a facile and effective method to achieve high rate performance LDH based electrode materials for supercapacitors.     

Bio‐Inspired Synthesis of Minerals for Energy,Environment, and Medicinal Applications

Biomineralization, the natural pathway of assembling biogenic inorganic compounds, inspires us to exploit unique, effective strategies to fabricate functional materials with intricate structures. In this article, the recent advances in bio‐inspired synthesis of minerals—with a focus on those of calcium‐based minerals—and their applications to the design of functional materials for energy, environment, and biomedical fields are reviewed. Biomimetic mineralization is extending its application range to unconventional area such as the design of component materials for lithium‐ion batteries and elaborately structured composite materials utilizing carbon dioxide gas. Materials with highly enhanced mechanical properties are synthesized through emulating the nacre structure. Studies of bioactive minerals‐carbon hybrid materials show an expansion of potential applications to fields ranging from interdisciplinary science to practical engineering such as the fabrication of reinforced bone‐implantable materials.     

Structural Fabrication and Functional Modulation of Nanoparticle–Polymer Composites

This review article summarizes recent progress in the fabrication methodologies and functional modulations of nanoparticle (NP)–polymer composites. On the basis of the techniques of NP synthesis and surface modification, the fabrication methods of nanocomposites are highlighted; these include surface‐initiated polymerization on NPs, in situ formation of NPs in polymer media, and the incorporation through covalent linkages and supramolecular assemblies. In these examples, polymers are foremost hypothesized as inert hosts that stabilize and integrate the functionalities of NPs, thus improving the macroscopic performance of NPs. Furthermore, due to the unique physicochemical properties of polymers, polymer chains are also dynamic under heating, swelling, and stretching. This creates an opportunity for modulating NP functionalities within the preformed nanocomposites, which will undoubtedly promote the developments of optoelectronic devices, optical materials, and intelligent materials.     

Graphene‐Functionalized Natural Microcapsules: Modular Building Blocks for Ultrahigh Sensitivity Bioelectronic Platforms

Natural cellular materials with honeycomb or foam microstructures are excellent inspirations for the biomimetic design of sensitive and robust bioelectronic interfaces. Herein, the fabrication of a hierarchical, self‐assembled platform that combines a natural cellular material (Lycopodium clavatum pollen spores) with an electrically conductive material (reduced graphene oxide, defined as rGO) for the first time is reported. The spores function as natural building blocks which are functionalized with crumpled rGO and then deposited on a silicon oxide surface, yielding a 3D architecture with electroactive properties. The hybrid material design is incorporated into a field‐effect transistor device and employed in an antibody‐based detection scheme in order to measure the concentration of a target protein with a limit of detection of 1 × 10^?15 m , which is five orders of magnitude better than a conventional rGO‐based biosensor tested in comparison. The findings in this work highlight the merit of integrating natural cellular materials with electrically conductive materials, offering a framework to develop high‐sensitivity bioelectronic platforms.     

Atom‐by‐Atom Fabrication of Single and Few Dopant Quantum Devices

Atomically precise fabrication has an important role to play in developing atom‐based electronic devices for use in quantum information processing, quantum materials research, and quantum sensing. Atom‐by‐atom fabrication has the potential to enable precise control over tunnel coupling, exchange coupling, on‐site charging energies, and other key properties of basic devices needed for solid‐state quantum computing and analog quantum simulation. Using hydrogen‐based scanning probe lithography, individual dopant atoms are deterministically placed relative to atomically aligned contacts and gates to build single electron transistors, single atom transistors, and gate‐controlled quantum sensing devices. The key steps required to fabricate and demonstrate the essential building blocks needed for spin selective initialization/readout and coherent quantum manipulation are described.     

Guest‐Molecule‐Directed Assembly of Mesostructured Nanocomposite Polymer/Organoclay Hydrogels

Given the urgent need for soft materials with high functional value, hydrogels based on the integrative assembly of organic polymers and nanoscale inorganic building blocks—so‐called nanocomposite polymer hydrogels—offer a generic approach to swollen hybrid networks with tuneable and synergistic properties. Here, we report a new approach to assembling nanocomposite polymer hydrogels with multiple levels of structural complexity and enhanced functionality by using nanoscale integration of mesostructured inorganic building blocks capable of sequestering and releasing drugs (ibuprofen, aspirin, naproxen) and enzymes (glucose oxidase). The viscoelastic materials are produced by noncovalent crosslinking of poly(vinylpyrrolidone) in the presence of low amounts (1–5 wt%) of an exfoliated synthetic organoclay that undergoes in situ guest‐molecule‐directed self‐assembly. The hydrogels can be moulded into shape‐persistent, free‐standing objects that are stable between pH values of 4 to 11 and self‐heal when damaged. Significantly, the mesostructured nanocomposite polymer hydrogels, which can be reversibly dried and reconstituted in the form of highly swollen materials, exhibit sustained drug release and can be recharged and reused. The results provide important guidelines for developing new multifunctional nanocomposite polymer hydrogels based on the concerted self‐assembly of inorganic building blocks with mesostructured interiors.