Hexahistidine‐Tagged Single‐Walled Carbon Nanotubes (His6‐tagSWNTs): A Multifunctional Hard Template for Hierarchical Directed Self‐Assembly and Nanocomposite Construction

While a hexahistidine affinity tag can be introduced at protein termini or internal sites by standard molecular biology procedures for purification, immobilization, or labeling of proteins, here the versatility of this concept is exploited for the chemical preparation of novel hexahistidine‐tagged single‐walled carbon nanotubes (His₆‐tagSWNTs), a novel hard template useful for solubilizing, assembling, processing, and interfacing SWNTs in aqueous conditions. Water‐soluble and exfoliated His₆‐tagSWNTs are prepared and fully characterized. This functional molecular module is able to interact via robust physisorption (π?π stacking) with the sidewall of SWNTs and combines the versatility of small, water‐soluble reporters (His₆) for hierarchical directed self‐assembly (HDSA) and construction of nanocomposites. It is demonstrated that metal coordination bonds with Ni(II) can be used for the supramolecular self assembly of His₆‐tagSWNTs, generating complex reticulated networks and architectures. The His₆‐tagSWNTs hard template nanohybrid is further utilized for directed self‐assembly with silica nanoparticles. The versatility of the novel hybrids opens a new era for the rational design, smart (bio)functionalization, processing, interfacing, and self assembling of carbon nanotubes for the construction of multicomposites and more complex systems with controllable spatial organization and programmable properties for a wide range of applications in biology, nanoelectronics, and catalysis.     

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.     

Self‐Assembling Nanotubes Consisting of Rigid Cyclic γ‐Peptides

Self‐assembling cyclic peptide nanotubes (SPNs) have been extensively studied due to their potential applications in biology and material sciences. Cyclic γ‐peptides, which have a larger conformational space, have received less attention than the cyclic α‐ and β‐peptides. The self‐assembly of cyclic homo‐γ‐tetrapeptide based on cis‐3‐aminocyclohexanecarboxylic acid (γ‐Ach) residues, which can be easily synthesized by a one‐pot process is investigated. Fourier transform infrared (FTIR) and NMR analysis along with density functional theory (DFT) calculations indicate that the cyclic homo‐γ‐tetrapeptide, with a non‐planar conformation, can self‐assemble into nanotubes through hydrogen‐bond‐mediated parallel stacking. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) experiments reveal the formation of bundles of nanotubes in CH₂Cl₂/hexane, but individual nanotubes and bundles of only two nanotubes are obtained in water. The integration of TEG (triethylene glycol) monomethyl ether chains and cyclopeptide backbones may allow the control of width of single nanotubes.     

General Method for Large‐Area Films of Carbon Nanomaterials and Application of a Self‐Assembled Carbon Nanotube Film as a High‐Performance Electrode Material for an All‐Solid‐State Supercapacitor

Rational assembly of carbon nanostructures into large‐area films is a key step to realize their applications in ubiquitous electronics and energy devices. Here, a self‐assembly methodology is devised to organize diverse carbon nanostructures (nanotubes, dots, microspheres, etc.) into homogeneous films with potentially infinite lateral dimensions. On the basis of studies of the redox reactions in the systems and the structures of films, the spontaneous deposition of carbon nanostructures onto the surface of the copper substrate is found to be driven by the electrical double layer between copper and solution. As a notable example, the as‐assembled multiwalled carbon nanotube (MWCNT) films display exceptional properties. They are a promising material for flexible electronics with superior electrical and mechanical compliance characteristics. Finally, two kinds of all‐solid‐state supercapacitors based on the self‐assembled MWCNT films are fabricated. The supercapacitor using carbon cloth as the current collector delivers an energy density of 3.5 Wh kg^?1 and a power density of 28.1 kW kg^?1, which are comparable with the state‐of‐the‐art supercapacitors fabricated by the costly single‐walled carbon nanotubes and arrays. The supercapacitor free of foreign current collector is ultrathin and shows impressive volumetric energy density (0.58 mWh cm^?3) and power density (0.39 W cm^?3) too.     

Amphiphilic Poly(p‐phenylene)s for Self‐Organized Porous Blue‐Light‐Emitting Thin Films

Micro‐ and nanostructuring of conjugated polymers are of critical importance in the fabrication of molecular electronic devices as well as photonic and bandgap materials. The present report delineates the single‐step self‐organization of highly ordered structures of functionalized poly(p‐phenylene)s without the aid of either a controlled environment or expensive fabrication methodologies. Microporous films of these polymers, with a honeycomb pattern, were prepared by direct spreading of the dilute polymer solution on various substrates, such as glass, quartz, silicon wafer, indium tin oxide, gold‐coated mica, and water, under ambient conditions. The polymeric film obtained from C₁₂PPPOH comprises highly periodic, defect‐free structures with blue‐light‐emitting properties. It is expected that such microstructured, conjugated polymeric films will have interesting applications in photonic and optoelectronic devices. The ability of the polymer to template the facile micropatterning of nanomaterials gives rise to hybrid films with very good spatial dispersion of the carbon nanotubes.     

Probing the Dynamic Nature of Self‐Assembling Cyclic Peptide–Polymer Nanotubes in Solution and in Mammalian Cells

Self‐assembling cyclic peptide–polymer nanotubes have emerged as a fascinating supramolecular system, well suited for a diverse range of biomedical applications. Due to their well‐defined diameter, tunable peptide anatomy, and ability to disassemble in situ, they have been investigated as promising materials for numerous applications including biosensors, antimicrobials, and drug delivery. Despite this continuous effort, the underlying mechanisms of assembly and disassembly are still not fully understood. In particular, the exchange of units between individual assembled nanotubes has been overlooked so far, despite its knowledge being essential for understanding their behavior in different environments. To investigate the dynamic nature of these systems, cyclic peptide–polymer nanotubes are synthesized, conjugated with complementary dyes, which undergo a Förster resonance energy transfer (FRET) in close proximity. Model conjugates enable to demonstrate not only that their self‐assembly is highly dynamic and not kinetically trapped, but also that the self‐assembly of the conjugates is strongly influenced by both solvent and concentration. Additionally, the versatility of the FRET system allows studying the dynamic exchange of these systems in mammalian cells in vitro using confocal microscopy, demonstrating the exchange of subunits between assembled nanotubes in the highly complex environment of a cell.     

Facile Nondestructive Assembly of Tyrosine‐Rich Peptide Nanofibers as a Biological Glue for Multicomponent‐Based Nanoelectrode Applications

Achieving the nondestructive assembly of carbon nanoelectrodes with multiple components in a scalable manner enables effective electrical interfaces among nanomaterials. Here, a facile nondestructive multiscale assembly of multicomponent nanomaterials using self‐assembled tyrosine‐rich peptide nanofibers (TPFs) as a biological glue is reported. The versatile functionalities of the rationally devised tyrosine‐rich short peptide allow for (1) self‐assembly of the peptide into nanofibers using noncovalent interactions, followed by (2) immobilization of spatially distributed metal nanoparticles on the nanofiber surface, and (3) subsequent assembly with graphitic nanomaterials into a percolated network‐structure. This percolated network‐structure of silver nanoparticle (AgNP)‐decorated peptide nanofibers with imbedded single‐walled carbon nanotubes (SWNTs) proves to be a versatile nanoelectrode platform with excellent processability. The SWNT–TPF–AgNP assembly, when utilized as a flexible and transparent multicomponent electronic film, was quite effective for enhancing direct electron transfer (DET) as verified for a third‐generation glucose sensor composed of this film. The simple solution process used to produce the functional nanomaterials could provide a new platform for scalable manufacturing of novel nanoelectrode materials forming effective electrical contacts with molecules from diverse biological systems.     

High‐Yield Fabrication,Activation, and Characterization of Carbon Nanotube Ion Channels by Repeated Voltage‐Ramping of Membrane‐Capillary Assembly

The interior channels of carbon nanotubes are promising for studying transport of individual molecules in a 1D confined space. However, experimental investigations of the interior transport have been limited by the extremely low yields of fabricated nanochannels and their characterization. Here, this challenge is addressed by assembling nanotube membranes on glass capillaries and employing a voltage‐ramping protocol. Centimeter‐long carbon nanotubes embedded in an epoxy matrix are sliced to hundreds of 10 µm‐thick membranes containing essentially identical nanotubes. The membrane is attached to glass capillaries and dipped into analyte solution. Repeated ramping of the transmembrane voltage gradually increases ion conductance and activates the nanotube ion channels in 90% of the membranes; 33% of the activated membranes exhibit stochastic pore‐blocking events caused by cation translocation through the interiors of the nanotubes. Since the membrane‐capillary assembly can be handled independently of the analyte solution, fluidic exchange can be carried out simply by dipping the capillary into a solution of another analyte. This capability is demonstrated by sequentially measuring the threshold transmembrane voltages and ion mobilities for K⁺, Na⁺, and Li⁺. This approach, validated with carbon nanotubes, will save significant time and effort when preparing and testing a broad range of solid‐state nanopores.     

Clay‐Graphene Nanoplatelets Functional Conducting Composites

An approach to functionalize graphene‐based materials has been developed by assembling graphene nanoplatelets (GNP) with clay minerals. Under convenient sonomechanical treatment, clay–GNP mixtures may produce very stable water dispersions in particular using sepiolite fibrous clay. While in the absence of clay a rapid decantation of GNP in water is observed, in the presence of sepiolite the resulting dispersions remain stable during months without syneresis effects. Rigid but flexible self‐supported films are easily obtained by filtering of these dispersions. As the electrical percolation threshold corresponds to sepiolite/GNP composites of 0.5:1 in weight, doping these systems with multiwalled carbon nanotubes (MWCNTs) significantly enhances their electrical conductivity. The particular microporosity of the sepiolite component allows interactions with molecules, such as organic dyes, as well as polymers, such as biopolymers, opening the way to functional materials for advanced applications due to their inherent conductivity afforded by the GNP and MWCNTs carbonaceous components. In fact, using very small amount of MWCNT together with GNP can obtain composites with significant electrical conductivity, maintaining the enhanced mechanical properties, at a lower cost.     

Ultrafast Self‐Assembly of Graphene Oxide‐Induced Monolithic NiCo–Carbonate Hydroxide Nanowire Architectures with a Superior Volumetric Capacitance for Supercapacitors

The monolithic electrodes with high volumetric capacitance demonstrate a great potential in practical industrial applications for supercapacitors. Herein, a novel strategy for ultrafast self‐assembly of graphene oxides (GO)‐induced monolithic NiCo–carbonate hydroxide (NiCo–CH) nanowire composite films (G–CH) is reported. The oxygen‐containing functional groups on the GO surface help effectively to induce formation of the monodisperse NiCo–CH nanowires. Such a nanowire‐shaped structure further functions as a scaffold and/or support, leading to 25 s of ultrafast self‐assembly for G–CH composite films and a relatively loose and open channel that contributes to fast electrolyte transport. The as‐obtained monolithic G–CH architectures show an excellent supercapacitor performance as binder‐ and conductive agent‐free electrode, evidenced by a superior volumetric capacitance of 2936 F cm^?3 and good electrochemical stability. Combining highly conductive carbon nanotubes (CNTs) into the monolithic composite films can further create well‐interconnected conductive networks within the electrode matrix, thus to improve the reaction kinetics and rate capability. The present strategy that can modulate the growth of the high‐electroactive pseudocapacitive hydroxides and achieve an ultrafast self‐assembly of monolithic composites may pave a promising new way for development of high‐performance supercapacitors and shed a new light on the configuration of carbon‐based electrode materials in energy storage and conversion devices.     

Protein Fragment Reconstitution as a Driving Force for Self‐Assembling Reversible Protein Hydrogels

Due to their potential biomedical applications, protein‐based hydrogels have attracted considerable interest. Although various methods have been developed to engineer self‐assembling, physically‐crosslinked protein hydrogels, exploring novel driving forces to engineer such hydrogels remains challenging. Protein fragment reconstitution, also known as fragment complementation, is a self‐assembling mechanism by which protein fragments can reconstitute the folded conformation of the native protein when split into two halves. Although it has been used in biophysical studies and bioassays, fragment reconstitution has not been explored for hydrogel construction. Using a small protein GL5 as a model, which is capable of fragment reconstitution to reconstitute the folded GL5 spontaneously when split into two halves, GN and GC, we demonstrate that protein fragment reconstitution is a novel driving force for engineering self‐assembling reversible protein hydrogels. Fragment reconstitution between GN and GC crosslinks GN and GC‐containing proteins into self‐assembling reversible protein hydrogels. These novel hydrogels show temperature‐dependent reversible sol‐gel transition, and excellent property against erosion in water. Since many proteins can undergo fragment reconstitution, we anticipate that such fragment reconstitution may offer a general driving force for engineering protein hydrogels from a variety of proteins, and thus significantly expanding the ‘toolbox’ currently available in the field of biomaterials.     

Self‐Assembling Peptides as Cell‐Interactive Scaffolds

Cell and tissue engineering therapies for regenerative medicine as well as cell‐based assays require an understanding of the interactions between cells with the surrounding microenvironment at the nanoscale. Engineering a cell‐interactive scaffold therefore entails control over the nanostructure of the biomaterial. Peptides that are able to self‐assemble into 3D scaffolds have emerged as interesting biomaterials for directing cell behavior, with desirable properties such as the capability of tuning the nanostructure by modulating the amino acid composition. Here, an overview of the development of self‐assembling peptide hydrogels as functional cell scaffolds is presented, highlighting recent work on incorporating features such as bioactive ligands, growth factor delivery, controlled degradation, and formulation into microgels for defined cell microenvironments.     

Silicon‐Based Self‐Assemblies for High Volumetric Capacity Li‐Ion Batteries via Effective Stress Management

Silicon nanoparticles (Si NPs) have been considered as promising anode materials for next‐generation lithium‐ion batteries, but the practical issues such as mechanical structure instability and low volumetric energy density limit their development. At present, the functional energy‐storing architectures based on Si NPs building blocks have been proposed to solve the adverse effects of nanostructures, but designing ideal functional architectures with excellent electrochemical performance is still a significant challenge. This study shows that the effective stress evolution management is applied for self‐assembled functional architectures via cross‐scale simulation and the simulated stress evolution can be a guide to design a scalable self‐assembled hierarchical Si@TiO₂@C (SA‐SiTC) based on core–shell Si@TiO₂ nanoscale building blocks. It is found that the carbon filler and TiO₂ layer can effectively reduce the risk of cracking during (de)lithiation, ensuring the stability of the mechanical structure of SA‐SiTC. The SA‐SiTC electrode shows long cycling stability (842.6 mAh g^?1 after 1000 cycles at 2 A g^?1), high volumetric capacity (174 mAh cm^?3), high initial Coulombic efficiency (80.9%), and stable solid‐electrolyte interphase (SEI) layer. This work provides insight into the development of the structural stable Si‐based anodes with long cycle life and high volumetric energy density for practical energy applications.     

Tailored Assembly of Carbon Nanostructures: Tailored Assembly of Carbon Nanotubes and Graphene (Adv. Funct. Mater. 8/2011)

This Feature Article reviews recent progress in the tailored assembly of carbon nanotubes and graphene into three‐dimensional architectures with particular emphasis on our own research employing self‐assembly principles. Carbon nanotubes and graphene can be assembled into macroporous films, hollow spherical capsules, or hollow nanotubes, via directed assembly from solvent dispersion. This approach is cost‐effective and beneficial for large‐scale assembly, but pre‐requests stable dispersion in a solvent medium. Directed growth from a nanopatterned catalyst array is another promising approach, which enables the control of morphology and properties of graphitic materials as well as their assembly. In addition, the aforementioned two approaches can be synergistically integrated to generate a carbon hybrid assembly consisting of vertical carbon nanotubes grown on flexible graphene films. Tailored assembly relying on scalable self‐assembly principles offer viable routes that are scalable for mass production towards the ultimate utilization of graphitic carbon materials in nanoelectronics, displays, sensors, energy storage/conversion devices, and so on, including future flexible devices.     

Self‐Assembly of Polyaniline—From Nanotubes to Hollow Microspheres

By simply changing the molar ratio of the dopant to monomer, the morphology of salicylic acid (SA)‐doped polyaniline (PANI) can be changed from one‐dimensional nanotubes (～ 109–150 nm in diameter) to three‐dimensional hollow microspheres (～ 1.5–3.1 μm in diameter) via a self‐assembly process. Freeze–fracture electron microscopy (FFEM) proved that hollow spherical micelles composed of SA/aniline act as templates in the formation of either nanotubes or hollow spheres. FTIR and X‐ray diffraction measurements suggest that the hydrogen bond of the –OH group of SA with the amine group of PANI might be a driving force for self‐assembling hollow microspheres, while the hydrogen bond through hydrogen and oxygen of the adjacent SA doped on the polymer chains results in short‐range order of the counter‐ions along the polymer chain in the nanotubes.     

Tailored Assembly of Carbon Nanotubes and Graphene

This Feature Article reviews recent progress in the tailored assembly of carbon nanotubes and graphene into three‐dimensional architectures with particular emphasis on our own research employing self‐assembly principles. Carbon nanotubes and graphene can be assembled into macroporous films, hollow spherical capsules, or hollow nanotubes, via directed assembly from solvent dispersion. This approach is cost‐effective and beneficial for large‐scale assembly, but pre‐requests stable dispersion in a solvent medium. Directed growth from a nanopatterned catalyst array is another promising approach, which enables the control of morphology and properties of graphitic materials as well as their assembly. In addition, the aforementioned two approaches can be synergistically integrated to generate a carbon hybrid assembly consisting of vertical carbon nanotubes grown on flexible graphene films. Tailored assembly relying on scalable self‐assembly principles offer viable routes that are scalable for mass production towards the ultimate utilization of graphitic carbon materials in nanoelectronics, displays, sensors, energy storage/conversion devices, and so on, including future flexible devices.     

2D Janus Hybrid Materials of Polymer‐Grafted Carbon Nanotube/Graphene Oxide Thin Film as Flexible,Miniature Electric Carpet

Ultrathin, freestanding polymer hybrid film with macroscopic sizes and molecular thicknesses have received significant interest due to their applications as functional devices, microsensors or nanoactuators. Herein, a 2D Janus hybrid of polymer‐grafted carbon nanotubes/graphene oxide (CNTs/GO) thin film is fabricated using microcontact printed CNTs/GO as photo active surface to grow polymer brushes by self‐initiated photografting and photopolymerization selectively from one side of CNTs/GO film. This achieved 2D Janus hybrid materials with grafted polymer layer as insulative carpet and supported CNTs/GO thin film as conductive element have the potential application as flexible and miniature electric carpet for heating micro‐/nano devices locally.     

Self‐Healing,Flexible, and Tailorable Triboelectric Nanogenerators for Self‐Powered Sensors based on Thermal Effect of Infrared Radiation

Self‐healing triboelectric nanogenerators (TENGs) with flexibility, robustness, and conformability are highly desirable for promising flexible and wearable devices, which can serve as a durable, stable, and renewable power supply, as well as a self‐powered sensor. Herein, an entirely self‐healing, flexible, and tailorable TENG is designed as a wearable sensor to monitor human motion, with infrared radiation from skin to promote self‐healing after being broken based on thermal effect of infrared radiation. Human skin is a natural infrared radiation emitter, providing favorable conditions for the device to function efficiently. The reversible imine bonds and quadruple hydrogen bonding (UPy) moieties are introduced into polymer networks to construct self‐healable electrification layer. UPy‐functionalized multiwalled carbon nanotubes are further incorporated into healable polymer to obtain conductive nanocomposite. Driven by the dynamic bonds, the designed and synthesized materials show excellent intrinsic self‐healing and shape‐tailorable features. Moreover, there is a robust interface bonding in the TENG devices due to the similar healable networks between electrification layer and electrode. The output electric performances of the self‐healable TENG devices can almost restore their original state when the damage of the devices occurs. This work presents a novel strategy for flexible devices, contributing to future sustainable energy and wearable electronics.     

Amino Acid Pairing for De Novo Design of Self‐Assembling Peptides and Their Drug Delivery Potential

Molecular self‐assembly has emerged as the “bottom‐up” engineering route to fabricate functional supramolecules for diverse applications. The design of molecular building units becomes critical in determining the structure, properties, and function of the resulting assemblies. Here, a de novo design principle of amino acid pairing (AAP) to generate new classes of self‐assembling peptides (SAPs) is presented. In this study, the AAP focuses on hydrogen bonding, and ionic and hydrophobic interactions among amino acid pairs. With solely hydrogen bond pairs, SAPs can be constructed with only two amino acids. With all three AAP strategies (hydrogen bonds, ionic and hydrophobic pairs), a short novel SAP is constructed. This peptide can self‐assemble into β‐sheet‐rich nanofibers with a relatively low “critical aggregation concentration (CAC)” of ～10 μM . It also shows the ability to stabilize and deliver the hydrophobic anticancer agent ellipticine in aqueous solution. The peptide‐drug complexes/co‐assemblies exhibit anticancer activity against human lung carcinoma cells A549 and breast cancer cells MCF‐7, and have good dilution stability. The presented AAP design provides a new strategy to fabricate functional supramolecules with potential applications in nanomedicine.