High‐Strength Laminated Copper Matrix Nanocomposites Developed from a Single‐Walled Carbon Nanotube Film with Continuous Reticulate Architecture

A critical challenge in nanocomposite fabrication by adding SWCNTs as reinforcement is to realize an effective transfer of the excellent mechanical properties of the SWCNTs to the macroscale mechanical properties of the matrix. Using directly grown SWCNT films with continuous reticulate structure as the template, Cu/SWCNTs/Cu laminated nanocomposites are fabricated by an electrodepositing process. The resulting Cu/SWCNTs/Cu laminated nanocomposites exhibit extremely high strength and Young's modulus. The estimated Young's modulus of the SWCNT bundles in the composite are between 860 and 960 GPa. Such a high strength and an effective load‐transfer capacity are ascribed to the unique continuous reticulate architecture of SWCNT films and the strong interfacial strength between the SWCNTs and Cu matrix. Raman spectroscopy is used to characterize the loading status of the SWCNTs in the strained composite. It provides a route to investigate the load transfer of SWCNTs in the metal matrix composites.     

Additive‐Free Dispersion of Single‐Walled Carbon Nanotubes and Its Application for Transparent Conductive Films

A good dispersion of single‐walled carbon nanotubes (SWCNTs) in liquid media is a prerequisite to fulfill many of their applications. This contribution reports an efficient approach to additive‐free dispersion of SWCNTs with the aid of functionalized carbonaceous byproducts (CBs, e.g., amorphous carbon, carbon nanoparticles, and carbonaceous fragments) in SWCNT products. SWCNT bundles are treated by oleum intercalation and nitric acid oxidation in sequence, which leads to the selective functionalization of the CBs while the structure and properties of the SWCNTs are well preserved. These functionalized CBs can improve the subsequent dispersion of SWCNTs and the majority of SWCNTs in the suspension are present in small bundles or individually. Moreover, SWCNT transparent conductive films (TCFs) are fabricated by using these suspensions. The SWCNT TCFs obtained can achieve a low sheet resistance of 76 and 133 Ω sq^?1, with optical transmittance of 82% and 90% at 550 nm, respectively.     

Wet‐Spun Stimuli‐Responsive Composite Fibers with Tunable Electrical Conductivity

Wet‐spun stimuli‐responsive composite fibers made of covalently crosslinked alginate with a high concentration of single‐walled carbon nanotubes (SWCNTs) are electroconductive and sensitive to humidity, pH, and ionic strength, due to pH‐tunable water absorbing properties of the covalently crosslinked alginate. The conductivity depends on the material swelling in humid atmosphere and aqueous solutions: the greater the swelling, the smaller is the electrical conductivity. The covalently crosslinked fibers reversibly deform during the swelling/shrinking. In the swollen state, the fibers are less conductive, while they return to the same level of conductivity after shrinking. This unique reversible change of electroconductivity of the SWCNT‐alginate fibers is due to the elastic deformation of the alginate network in the area of electrical contacts between SWCNT bundles arrested in the alginate matrix. Fibers of this kind can be used as a simple, robust, disposable, and biocompatible platform for electrotextiles, biosensors, and flexible electronics in biomedical and biotechnological applications.     

Toward Bioelectronic Nanomaterials: Photoconductivity in Protein–Porphyrin Hybrids Wrapped around SWCNT

The development of sophisticated ordered functional materials is one of the important challenges in current science. One of the keys to enhance the properties of these materials is the control of the organization and morphology at different scales. This work presents a novel bioinspired methodology to achieve highly ordered donor/acceptor bio‐nanohybrids using a designed repeat protein as scaffold, endowed with photoactive and electron donating porphyrin (P) units, to efficiently wrap around electron accepting single wall carbon nanotubes (SWCNT). A systematic experimental and theoretical study to evaluate the effect of the length of the protein reveals that longer proteins wrap around the SWCNT in a more efficient manner due to the stronger supramolecular interaction existing between the inner concave surface of the protein (namely Trp and His residues) and the convex surface of the (7,6)‐SWCNT. Interestingly, spectroscopy and X‐ray diffraction data further confirm that the so‐called protein‐P–SWCNT donor–acceptor bio‐nanohybrids retain the original protein structure. Finally, the new bio‐nanohybrids show a remarkable enhancement on the photoconductivity values by flash‐photolysis microwave conductivity (FP‐TRMC technique) demonstrating that the major charge carriers of electrons are injected into the SWCNTs and move along the 1D‐structures.     

Towards nanoreliability of sensors incorporating interfaces between single-walled carbon nanotubes and metals: molecular dynamics simulations and in situ experiments using electron microscopy

In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (SWCNTs) embedded in metal matrices. We conducted experimental pull-out tests of SWCNTs embedded in Pd and found maximum forces in the range F ≈ (10 to 65) nN. These values are in good agreement with forces obtained from molecular dynamics simulations taking into account surface functional groups (SFGs) covalently linked to the SWCNT material. The dominant failure mode in experiment is a SWCNT rupture, which can be explained with the presence of SFGs. For further in depth investigations, we present a tensile actuation test system based on a thermal actuator to perform pull-out tests inside a transmission electron microscope with the objective to obtain in situ images of SWCNT–metal interfaces under mechanical loads at the atomic scale. First experiments confirmed the presence of suspended thin metal electrodes to embed SWCNTs. These suspended thin metal electrodes are electron transparent at the designated SWCNT locations. Actuator movements were evaluated by digital image correlation and we observed systematic actuator movements. Although significant image drifts occured during actuation, we achieved atomic resolution of the metal electrode and stable movement in the focal plane of the electron microscope.     

Gas Diffusion,Energy Transport,and Thermal Accommodation in Single‐Walled Carbon Nanotube Aerogels

The thermal conductivity of gas‐permeated single‐walled carbon nanotube (SWCNT) aerogel (8 kg m^?3 density, 0.0061 volume fraction) is measured experimentally and modeled using mesoscale and atomistic simulations. Despite the high thermal conductivity of isolated SWCNTs, the thermal conductivity of the evacuated aerogel is 0.025 ± 0.010 W m^?1 K^?1 at a temperature of 300 K. This very low value is a result of the high porosity and the low interface thermal conductance at the tube–tube junctions (estimated as 12 pW K^?1). Thermal conductivity measurements and analysis of the gas‐permeated aerogel (H₂, He, Ne, N₂, and Ar) show that gas molecules transport energy over length scales hundreds of times larger than the diameters of the pores in the aerogel. It is hypothesized that inefficient energy exchange between gas molecules and SWCNTs gives the permeating molecules a memory of their prior collisions. Low gas‐SWCNT accommodation coefficients predicted by molecular dynamics simulations support this hypothesis. Amplified energy transport length scales resulting from low gas accommodation are a general feature of CNT‐based nanoporous materials.     

On the Impact of Process Variations for Carbon Nanotube Bundles for VLSI Interconnect

Bundles of single-walled carbon nanotubes (SWCNTs) have been proposed as a possible replacement for on-chip copper interconnect due to their large conductivity and current-carrying capabilities. Given the manufacturing challenges associated with future nanotube-based interconnect solutions, determining the impact of process variations on this new technology relative to standard copper interconnect is vital for predicting the reliability of nanotube-based interconnect. In this paper, we investigate the impact of process variations on future interconnect solutions based on carbon nanotube bundles. Leveraging an equivalent RLC model for SWCNT bundle interconnect, we calculate the relative impact of ten potential sources of variation in SWCNT bundle interconnect on resistance, capacitance, inductance, and delay. We compare the relative impact of variation for SWCNT bundles and standard copper wires as process technology scales and find that SWCNT bundle interconnect will typically have larger overall three-sigma variations in delay. In order to achieve the same percentage variation in both SWCNT bundles and copper interconnect, the percentage variation in bundle dimensions must be reduced by up to 63% in 22-nm process technology     

Covalent Surface Modification Effects on Single‐Walled Carbon Nanotubes for Targeted Sensing and Optical Imaging

Optical nanoscale technologies often implement covalent or noncovalent strategies for the modification of nanoparticles, whereby both functionalizations are leveraged for multimodal applications but can affect the intrinsic fluorescence of nanoparticles. Specifically, single‐walled carbon nanotubes (SWCNTs) can enable real‐time imaging and cellular delivery; however, the introduction of covalent SWCNT sidewall functionalizations often attenuates SWCNT fluorescence. Recent advances in SWCNT covalent functionalization chemistries preserve the SWCNT's pristine graphitic lattice and intrinsic fluorescence, and here, such covalently functionalized SWCNTs maintain intrinsic fluorescence‐based molecular recognition of neurotransmitter and protein analytes. The covalently modified SWCNT nanosensor preserves its fluorescence response towards its analyte for certain nanosensors, presumably dependent on the intermolecular interactions between SWCNTs or the steric hindrance introduced by the covalent functionalization that hinders noncovalent interactions with the SWCNT surface. These SWCNT nanosensors are further functionalized via their covalent handles with a targeting ligand, biotin, to self‐assemble on passivated microscopy slides, and these dual‐functionalized SWCNT materials are explored for future use in multiplexed sensing and imaging applications.     

Quaternized Pyridyloxy Phthalocyanines Render Aqueous Electron‐Donor Carbon Nanotubes as Unprecedented Supramolecular Materials for Energy Conversion

Exploring new properties in known materials, sometimes even achieving behaviors opposite to those traditionally encountered, is a fundamental aspect of innovation in materials science. In the field of energy conversion, for example, the development of water‐processed organic solar cells provides environmentally friendlier materials, which contribute to reduce health risks. Herein, a novel approach is described to produce water‐soluble electron‐donor single wall carbon nanotube (SWCNT) hybrids based on the noncovalent immobilization of quaternized pyridyloxy zinc phthalocyanines (ZnPc) with a varying number of pyridyl substituents. Moreover, the excellent electron‐accepting ability of the latter ZnPcs is reported. The introduction of tert‐butylphenyl groups at the pyridines enables for the first time a complete characterization. The electron‐acceptor nature of the ZnPcs enables switching the role of SWCNTs within the resulting supramolecular hybrids. Finally, a proof‐of‐concept demonstration of the SWCNT/ZnPc hybrids' capacity for energy conversion is presented, paving their way to possible use as active layer material in solar cells processed entirely from aqueous solutions.     

Design of Dispersants for the Dispersion of Carbon Nanotubes in an Organic Solvent

The effect of dispersant structures for dispersing single‐walled carbon nanotubes (SWCNTs) is investigated. The monomer 3‐hexylthiophene is used as the starting material for the development of a series of oligomers that are used to disperse SWCNTs in an organic solvent. The series is obtained by varying the number of head groups, the regioregularity of head groups, and the head‐to‐tail ratios of the hexyl group in the oligomers. The SWCNT solutions are characterized with UV‐vis–near‐IR spectroscopy and transmission electron microscopy. An increase in the number of head groups improves the dispersity of SWCNTs, and a regioregular oligomer plays an important role in dispersing SWCNTs. Furthermore, Raman spectroscopy and X‐ray photoelectron spectroscopy shows that the sulfur atom head groups enhance interactions between the thiophenes and the SWCNT walls. The analysis demonstrated that a well‐designed thiophene oligomer could afford well‐dispersed SWCNT solutions with long‐term dispersion stability, even with an extremely low dispersant concentration (weight ratio of CNTs/dispersant is one and the dispersant concentration is 0.1 g L^–1).     

CuI Encapsulated within Single-Walled Carbon Nanotube Networks with High Current Carrying Capacity and Excellent Conductivity

High current carrying capacity and high conductivity are two important indicators for materials used in microscale electronics and inverters. However, it is challenging to obtain high conductivity and high current carrying capacity at the same time since high conductivity requires a weakly bonded system to provide free electrons, while high current carrying capacity requires a strongly bonded system. In this paper, CuI@SWCNT networks by filling the single-walled carbon nanotubes (SWCNTs) with CuI is ingeniously prepared. CuI@SWCNT shows good stability due to the confinement protection of SWCNTs. Through the host-guest hybridization, CuI@SWCNT networks exhibit a current carrying capacity of 2.04 × 10⁷ A cm⁻² and a conductivity of 31.67 kS m⁻¹. Their current carrying capacity and conductivity are significantly improved compared with SWCNT. The Kelvin probe force microscopy measurements show a drop of surface potential energy after SWCNT filled with CuI, indicating that the CuI guest molecules regulate the position of the Fermi level of SWCNTs, increasing carrier concentration, achieving high conductivity and high current carrying capacity. This study offers ideas and solutions for the regulation of high-performance carbon tube networks, which hold great promise for future applications in carbon-based electronic devices.     

Fast and Ultraclean Approach for Measuring the Transport Properties of Carbon Nanotubes

In this work, a fast approach for the fabrication of hundreds of ultraclean field‐effect transistors (FETs) is introduced, using single‐walled carbon nanotubes (SWCNTs). The synthesis of the nanomaterial is performed by floating‐catalyst chemical vapor deposition, which is employed to fabricate high‐performance thin‐film transistors. Combined with palladium metal bottom contacts, the transport properties of individual SWCNTs are directly unveiled. The resulting SWCNT‐based FETs exhibit a mean field‐effect mobility, which is 3.3 times higher than that of high‐quality solution‐processed CNTs. This demonstrates that the hereby used SWCNTs are superior to comparable materials in terms of their transport properties. In particular, the on–off current ratios reach over 30 million. Thus, this method enables a fast, detailed, and reliable characterization of intrinsic properties of nanomaterials. The obtained ultraclean SWCNT‐based FETs shed light on further study of contamination‐free SWCNTs on various metal contacts and substrates.     

Plasmonic Response of Ag‐ and Au‐Infiltrated Cross‐Linked Lysozyme Crystals

Metal‐infiltrated protein crystals form a novel class of bio‐nanomaterials of great interest for applications in biomedicine, chemistry, and optoelectronics. As yet, very little is known about the internal structure of these materials and the interconnectivity of the metallic network. Here, the optical response of individual Au‐ and Ag‐infiltrated cross‐linked lysozyme crystals is investigated using angle‐ and polarization‐dependent spectroscopy. The measurements unequivocally show that metallic inclusions formed inside the nanoporous solvent channels do not connect into continuous nanowires, but rather consist of ensembles of isolated spheroidal nanoclusters with aspect ratios as high as a value of four, and which exhibit a pronounced plasmonic response that is isotropic on a macroscopic length scale. Fluorescence measurement in the visible range show a strong contribution from the protein host, which is quenched by the Au inclusions, and a weaker contribution attributed to the molecule‐like emission from small Au‐clusters.     

Structure Sorting of Large‐Diameter Carbon Nanotubes by NaOH Tuning the Interactions between Nanotubes and Gel

The structure separation of synthetic single‐wall carbon nanotube (SWCNT) mixture species with diameters larger than 1.2 nm still remains a challenge. Here, an NaOH‐assisted gel chromatography method is used for the structure separation of the SWCNT mixture with a diameter range of 1.2–1.7 nm, in which NaOH is used to tune the interaction between distinct (n, m) SWCNTs and gel. Incrementally increasing NaOH concentration in SWCNT dispersion selectively enhances the adsorbability of different‐structure SWCNTs and enlarges their interaction difference with gel, leading to their structure separation after applying into a gel column system. On this basis, a two‐step method is developed for further improving the structure purity of the separated SWCNTs by combining overloading and stepwise elution. These results are well demonstrated by the optical spectra of the separated SWCNTs. This work paves a way for single‐chirality separation of large‐diameter SWCNTs using gel chromatography technique and is an advanced progress in the structure control of SWCNTs.     

Electron‐Beam Manipulation of Silicon Impurities in Single‐Walled Carbon Nanotubes

The recent discovery that impurity atoms in crystals can be manipulated with focused electron irradiation has opened novel perspectives for top‐down atomic engineering. These achievements have been enabled by advances not only in electron optics and microscope stability but also in the preparation of suitable materials with impurity elements incorporated via ion and electron‐beam irradiation or chemical means. Here it is shown that silicon heteroatoms introduced via plasma irradiation into the lattice of single‐walled carbon nanotubes (SWCNTs) can be manipulated using a focused 55–60 keV electron probe aimed at neighboring carbon sites. Moving the silicon atom mainly along the longitudinal axis of large 2.7 nm diameter tubes, more than 90 controlled lattice jumps are recorded and the relevant displacement cross sections are estimated. Molecular dynamics simulations show that even in 2 nm diameter SWCNTs, the threshold energies for out‐of‐plane dynamics are different than in graphene, and depend on the orientation of the silicon‐carbon bond with respect to the electron beam as well as the local bonding of the displaced carbon atom and its neighbors. Atomic‐level engineering of SWCNTs where the electron wave functions are more strictly confined than in 2D materials may enable the fabrication of tunable electronic resonators and other devices.     

Selective Dispersion of Large‐Diameter Semiconducting Carbon Nanotubes by Functionalized Conjugated Dendritic Oligothiophenes for Use in Printed Thin Film Transistors

Selective dispersion of semiconducting single walled carbon nanotubes (s‐SWCNTs) by conjugated polymer wrapping is recognized as the most promising scalable method for s‐SWCNT separation. Despite a number of linear conjugated polymers being reported for use in s‐SWCNT separation, these linear polymers suffer batch‐to‐batch variation for their undefined molecular structure. Here, it is reported that conjugated dendritic oligothiophenes with multiple diketopyrrolopyrrole groups at the periphery have the capability of selectively dispersing large diameter s‐SWCNTs with high dispersion efficiency and certain chiral selectivity. Printed top‐gated thin film transistors using the dendrimer sorted s‐SWCNTs show high charge carrier mobility of up to 57 cm² V^?1 s^?1 and on/off ratios of ≈10⁶ with high reproducibility, which is ascribed to the defined and monodispersed molecular structure of dendrimers. Moreover, owing to the multiple peripheral anchoring groups of these dendritic molecules, these dendrimer‐s‐SWCNT dispersions display excellent stability. The current work proves that dendritic molecules are excellent dispersion reagents for s‐SWCNT separation.     

Improvement of photovoltaic performance of inverted hybrid solar cells by adding single-wall carbon nanotubes in poly(3-hexylthiophene)

Solution prepared hybrid solar cells show promising low cost technology for electricity generation from sun light, although their power conversion efficiency has to be improved. One of the approaches is to increase the absorbance or charge carrier mobility of organic semiconductors. In this work, pristine single walled carbon nanotubes (SWCNT) were added into poly(3-hexylthiophene) (P3HT) solution to form P3HT:SWCNT composite films with different weight percent (wt%) of SWCNT. It is observed that optical absorbance spectra as well as the morphology of the composite films were modified by the addition of SWCNTs. This phenomenon could be explained by the π-π interaction between the conjugated polymer and carbon nanotubes. Most importantly, the electrical conductivities of the composite films increased with the SWCNT wt%. When these films were used as hole conductor layers in inverted planar hybrid solar cell, with CdS thin films as electron acceptor layers, the fill factor (FF) and open-circuit voltage (Voc) of the corresponding cells were decreased with the increase of the wt% of SWCNT. However, the short-circuit current density (Jsc) and the power conversion efficiency (PCE) showed a maximum value at about 0.4 wt% of SWCNT in P3HT. The transient photovoltage measurements (TPV) revealed that the presence of SWNCT promoted the charge recombination process at P3HT/CdS interface, and as a result, reduced the Voc. The photovoltaic performance of the hybrid solar cells could be optimized by choosing an adequate weight percentage of SWCNT in P3HT to balance the charge carrier transport and charge recombination processes at the donor-acceptor interface.     

Single-Walled Carbon Nanotube Film as an Efficient Conductive Network for Si-Based Anodes

Silicon-based anodes are considered ideal candidate materials for next-generation lithium-ion batteries due to their high capacity. However, the low conductivity and large volume variations during cycling inevitably result in inferior cyclic stability. Herein, a dry method without binders is designed to fabricate Si-based electrodes with single-walled carbon nanotubes (SWCNTs) network and to explore the different mechanisms between SWCNT and multiwalled carbon nanotubes (MWCNTs) as a conductive network. As expected, higher initial discharge capacity (1785 mAh g⁻¹), higher initial Coulombic efficiency (ICE, 81.52%) and outstanding cyclic stability are obtained from the SiO_x@C|SWCNT anodes. Furthermore, its lithium-ion diffusion coefficient (D_Li+) is 3–4 orders of magnitude higher than that of SiO_x@C|MWCNT. The underlying mechanism is clarified by in situ Raman spectroscopy and theoretical analysis. It is found that the SWCNTs can maintain good contact with SiO_x@C even under tensile stresses up to 6.2 GPa, while the MWCNTs lose electrical contact due to alternating compressive stress up to 8.9 GPa and tensile stress up to 2.5 GPa during long-term cycling. Under such very large stresses, the more flexible SWCNTs and their stronger van der Waals forces ensure that SiO_x@C still has good contact with SWCNTs.     

Zwitterionic Osmolyte‐Based Hydrogels with Antifreezing Property,High Conductivity,and Stable Flexibility at Subzero Temperature

Conductive hydrogels have emerged as fascinating materials applied in flexible electronics because of their integrated conductivity and mechanical flexibility. However, the large amounts of water in conductive hydrogels inevitably freeze at subzero temperature, causing a reduction of their ionic transport ability and elasticity. Herein, the bioinspired antifreezing agents—zwitterionic osmolytes (e.g., betaine, proline) are first proposed to prevent ammonium chloride‐containing Ca‐alginate/polyacrylamide hydrogels from freezing. With a facile one‐pot solvent displacement method, the zwitterionic osmolytes can displace the water molecules inside the hydrogels. Due to the excellent freeze tolerance of zwitterionic osmolytes, the resulting zwitterionic osmolyte‐based hydrogels exhibit outstanding ionic conductivity (up to ≈2.7 S m^?1) at ?40 °C, which exceeds the conductivities of most reported conductive hydrogels. Meanwhile, they present stable mechanical flexibility over a wide temperature range (?40 to 25 °C). More importantly, two types of the resulting hydrogel‐based flexible electronics, including a capacitive sensor and a resistive sensor, can maintain their response function at ?40 °C. This work offers a new solution to fabricate conductive hydrogels with antifreezing ability, which can broaden the working temperature range of flexible electronics.     

Array of Single‐Walled Carbon Nanotube Intrajunction Devices Fabricated via Type Conversion by Partial Coating with β‐Nicotinamide Adenine Dinucleotide

The fabrication of aligned single‐walled, carbon nanotube (SWCNT) intratube junction devices by partially coating pristine SWCNTs with a β‐nicotinamide adenine dinucleotide (NADH) solution and subsequent annealing at 150 °C is reported. Gate‐bias‐dependent rectification behavior is observed with a rectification ratio of >10³ at ±1 V. A comparative study with p–n‐junction devices of randomly networked SWCNTs confirms the advantage of using aligned SWCNTs with substantially better rectifying characteristics due to the selective removal of metallic tubes by electrical breakdown. The gate dependence of the intratube p–n‐junction in the forward and backward directions is attributed to the difference in the shift of the Fermi levels (forward bias) and the enhanced direct tunneling (reverse bias), as suggested by band‐diagram modeling. This work suggests a potential application of aligned SWCNT intratube p–n‐junction devices in the future of nanoelectronic circuits.