Efficient Synthesis of Carbon Nanotube–Nanoparticle Hybrids

A simple and versatile approach has been developed to synthesize different carbon nanotube (CNT)–nanoparticle hybrid materials. The strategy is based on the nondestructive (noncovalent) functionalization of pristine CNTs and the subsequent in situ synthesis of a variety of different nanoparticles, including metal, semiconductor, and insulator particles, on the modified CNTs. This strategy has been demonstrated here with Pt, CdS, and silica nanoparticles. It is believe that this technique will provide a simple and convenient route to efficiently assemble a wide variety of nanoscale particles/clusters on the surfaces of CNTs, and will enable the construction of nanoscale heterostructures with novel functionalities in nanotechnology.     

Carbon Nanotube–Graphitic Carbon Nitride Hybrid Films for Flavoenzyme‐Catalyzed Photoelectrochemical Cells

In green plants, solar‐powered electrons are transferred through sophistically arranged photosystems and are subsequently channelled into the Calvin cycle to generate chemical energy. Inspired by the natural photosynthetic scheme, a photoelectrochemical cell (PEC) is constructed configured with protonated graphitic carbon nitride (p‐g‐C₃N₄) and carbon nanotube hybrid (CNT/p‐g‐C₃N₄) film cathode, and FeOOH‐deposited bismuth vanadate (FeOOH/BiVO₄) photoanode for the production of industrially useful chiral alkanes using an old yellow enzyme homologue from Thermus scotoductus (TsOYE). In the biocatalytic PEC platform, photoexcited electrons provided by the FeOOH/BiVO₄ photoanode are transferred to the robust and self‐standing CNT/p‐g‐C₃N₄ hybrid film that electrocatalytically reduces flavin mononucleotide (FMN) mediator. The p‐g‐C₃N₄ promotes a two‐electron reduction of FMN coupled with an accelerated electron transfer by the conductive CNT network. The reduced FMN subsequently delivers the electrons to TsOYE for the highly enantioselective conversion of ketoisophorone to (R)‐levodione. Under light illumination (>420 nm) and external bias, (R)‐levodione is synthesized with the enantiomeric excess value of above 83%, not influenced by the scale of applied bias, simultaneously exhibiting stable and high current efficiency. The results suggest that the biocatalytic PEC made up of economical materials can selectively synthesize high‐value organic chemicals using water as an electron donor.     

Catalytic and Electron Conducting Carbon Nanotube–Reinforced Lysozyme Crystals

Novel reinforced cross‐linked lysozyme crystals containing homogeneous dispersions of single‐walled carbon nanotubes bundles (SWCNTs) are produced and characterized. The incorporation of SWCNTs inside lysozyme crystals gives rise to reinforced composite materials with tunable mechanical strength and electronic conductivity, while preserving the crystal quality and morphology. These reinforced crystals show increased catalytic activity at higher temperatures, being active even above the denaturation temperature. The electron transport through the crystals is linked to the content and distribution of SWCNT bundles inside the crystals. The electron conduction through the crystals is isotropic and very efficient, presenting high conductivity values up to 600 nS at very low (0.05 wt%) SWCNT concentration. To obtain these crystals, a new protocol based on the in situ crystallization of lysozyme in composite SWCNT–peptide hydrogels is developed. These peptide hydrogels are able to homogeneously disperse bundles of hydrophobic SWCNTs allowing first, the crystallization of the enzyme lysozyme and second, transferring the new properties of the inorganic component to the crystals. Taken together, these composite crystals represent an example of the versatility of proteins as biological substrates in the generation of novel functional materials, opening the door to use them in catalysis and bioelectronics at macroscale.     

Tailoring the Electrical Properties of Carbon Nanotube–Polymer Composites

Advances in functionality and reliability of nanocomposite materials require careful formulation of processing methods to ultimately realize the desired properties. An extensive study of how the variation in fabrication process would affect the mechanism of conductivity and thus the final electrical properties of the carbon nanotube–polymer composite is presented. Some of the most widely implemented procedures are addressed, such as ultrasonication, melt shear mixing, and addition of surfactants. It is hoped that this study could provide a systematic guide to selecting and designing the downstream processing of carbon nanocomposites. Finally, this guide is used to demonstrate the fabrication and performance of a stretchable (pliable) conductor that can reversibly undergo uniaxial strain of over 100%, and other key applications are discussed.     

Hard–Soft Carbon Composite Anodes with Synergistic Sodium Storage Performance

A series of hard–soft carbon composite materials is produced from biomass and oil waste and applied as low‐cost anodes for sodium‐ion batteries to study the fundamentals behind the dependence of Na storage on their structural features. A good reversible capacity of 282 mAh g^?1 is obtained at a current density of 30 mA g^?1 with a high initial Coulombic efficiency of 80% at a carbonization temperature of only 1000 °C by adjusting the ratio of hard to soft carbon. The performance is superior to the pure hard or soft carbon anodes produced at the same temperatures. This synergy between hard and soft carbon resulting in an excellent performance is due to the blockage of some open pores in hard carbon by the soft carbon, which suppresses the solid electrolyte interface formation and increases the reversible sodium storage capacity.     

Highly Conductive Redox Protein–Carbon Nanotube Complex for Biosensing Applications

The integration of redox proteins with nanomaterials has attracted much interest in the past years, and metallic single‐walled carbon nanotubes (SWNTs) have been introduced as efficient electrical wires to connect biomolecules to metal electrodes in advanced nano‐biodevices. Besides preserving biofunctionality, the protein–nanotube connection should ensure appropriate molecular orientation, flexibility, and efficient, reproducible electrical conduction. In this respect, yeast cytochrome c redox proteins are connected to gold electrodes through lying‐down functionalized metallic SWNTs. Immobilization of cytochromes to nanotubes is obtained via covalent bonding between the exposed protein thiols and maleimide‐terminated functional chains attached to the carbon nanotubes. A single‐molecule study performed by combining scanning probe nanoscopies ascertains that the protein topological properties are preserved upon binding and provides unprecedented current images of single proteins bound to carbon nanotubes that allow a detailed I–V characterization. Collectively, the results point out that the use as linkers of suitably functionalized metallic SWNTs results in an electrical communication between redox proteins and gold electrodes more efficient and reproducible than for proteins directly connected with metal surfaces.     

Synthesis and Characterization of a Composite Zeolite–Metglas Carbon Dioxide Sensor

The synthesis of a faujasite–Metglas composite material that can be used in gas‐sensing applications is presented. A continuous faujasite film was synthesized on a Metglas magnetoelastic strip using the secondary growth method. The ability of the new composite to remotely sense carbon dioxide in a nitrogen atmosphere at room temperature over a wide range of concentrations is demonstrated by monitoring the changes in the resonance frequency of the strip. The novel sensor combines the electromagnetic properties of the magnetoelastic material with the adsorption properties of the faujasite crystals. Experiments performed over a period of a few months showed that the composite sensor remained fully operational, thus indicating its long‐term stability. Furthermore, the present work demonstrates that a zeolite–Metglas composite can be used as a sensor of an analyte in a mixture as long as it adsorbs selectively larger amounts of the particular analyte than other compounds present in the mixture.     

Hydrophilic Nanotube Supported Graphene–Water Dispersible Carbon Superstructure with Excellent Conductivity

In this work, it is shown that the hydrophilic functionalized multiwall carbon nanotubes (MWCNs) can stabilize a large amount of pristine graphene nanosheets in pure water without the assistance of surfactants, ionic liquids, or hydrophilic polymers. Role of stabilizer is conveyed by highly hydrophilic carbon nanotubes, functionalized by dihydroxy phenyl groups, affording a stable dispersion at concentrations as high as 15 mg mL^?1. Such multidimensional (2D/1D) graphene/MWCN hybrid is found to be dispersible also in other polar organic solvents such as ethanol, isopropanol, N,N‐dimethylformamide, ethylene glycol, and their mixtures. High‐resolution transmission microscopy and atomic force microscopy (AFM) including a liquid mode AFM manifest several types of interaction including trapping of multiwalled carbon nanotubes between the graphene sheets or the modification of graphene edges. Molecular dynamic simulations show that formation of an assembly is kinetically controlled. Importantly, the hybrid can be deposited on the paper by drop casting or dispersed in water‐soluble polymers resulting in record values of electrical conductivity (sheet resistance up to R_s ≈ 25 Ω sq^?1 for free hybrid material and R_s ≈ 1300 Ω sq^?1 for a polyvinilalcohol/hybrid composite film). Thus, these novel water dispersible carbon superstructures reveal a high application potential as conductive inks for inkjet printing or as highly conductive polymers.     

Hierarchical Graphene–Carbon Fiber Composite Paper as a Flexible Lateral Heat Spreader

As a low dimensional crystal, graphene attracts great attention as heat dissipation material due to its unique thermal transfer property exceeding the limit of bulk graphite. In this contribution, flexible graphene–carbon fiber composite paper is fabricated by depositing graphene oxide into the carbon fiber precursor followed by carbonization. In this full‐carbon architecture, scaffold of one‐dimensional carbon fiber is employed as the structural component to reinforce the mechanical strength, while the hierarchically arranged two‐dimensional graphene in the framework provides a convenient pathway for in‐plane acoustic phonon transmission. The as‐obtained hierarchical carbon/carbon composite paper possesses ultra‐high in‐plane thermal conductivity of 977 W m^?1 K^?1 and favorable tensile strength of 15.3 MPa. The combined mechanical and thermal performances make the material highly desirable as lateral heat spreader for next‐generation commercial portable electronics.     

Quantum Dot–Carbon Nanotube Hybrid Phototransistor with an Enhanced Optical Stark Effect

Enhanced carrier–carrier interactions in hybrid nanostructures exhibit exceptional electronic and optoelectronic properties. Carbon nanotubes demonstrate excellent switching behavior with high on/off ratio and high mobility but do not show photoresponse in the visible range, whereas quantum dots (QDs) shows excellent optical response in various optical ranges which can be tuned with diameter. Here, a simple and effective way to develop hybrid phototransistors with extraordinary optoelectronic properties is presented by decorating semiconducting QDs on the surface of a single‐walled carbon nanotube (SWCNT). This hybrid structure demonstrates clear negative photoresponse and optical switching behavior, which could be further tuned by applying external gate bias in the future. A clear type conversion of SWCNT transistor from p‐type to n‐type caused by a charge transfer from attached QDs to CNT is demonstrated. Moreover, this hybrid structure also demonstrates an enhancement in ‘optical Stark effect’ without applying any external electric field. Charged SWCNT surface plays a key role behind the enhancement of optical Stark effect in QDs. The carrier dynamics of the QD and CNT heterostructures system highlights the potential application opportunity of the quantum dot systems, which can be adaptable to the current technologies.