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In this study, we used the lock-in thermography technique (LIT) to successfully visualize the single-walled carbon nanotube (CNT) networks during the tensile deformation of CNT/fluoro-rubber (FKM) composites.

Single-walled carbon nanotubes (CNTs) are promising candidates for near-infrared (NIR) fluorescent labels in diagnostic fields. We report a complex of oxygen-doped CNT (o-CNT) and streptavidin (SA) for preparing CNT-based NIR labels with a high reaction efficiency in immunoassays. This complex specifically binds to biotin molecules by conjugating a linker molecule of phospholipid polyethylene glycol (PL-PEG) to SA (o-CNT-SA). The immunoprecipitation reaction efficiency between o-CNT-SA and biotin reaches 79.3% when the surface of o-CNTs is uniformly covered with SA-conjugated PL-PEG. The strong affinity between SA and biotin is useful for preparing CNT-based sensitive NIR fluorescent labels.

Electrically conductive porous structures are required to design high-performance supercapacitor electrodes; however, the sophisticated control has been challenging. We propose a facile fabrication...

Artificial intelligence relying on structure-property databases is an emerging powerful tool to discover new materials with targeted properties. However, this approach cannot be easily applied to tangible structures, such as plastic composites and fabrics, because of their high structural complexity. Here, we propose a deep learning computational framework that can implement virtual experiments on tangible structures. Structural representations of complex carbon nanotube films were conducted by multiple generative adversarial networks of scanning electron microscope images at four levels of magnifications, enabling a deep learning prediction of multiple properties such as electrical conductivity and surface area. 1716 virtual experiments were completed within an hour, a task that would take years for real experiments. The data can be used as a versatile database for material science, in analogy to databases of molecules and solids used in cheminformatics. Useful examples are the investigation of correlations between electrical conductivity, specific surface area, wall number phase diagrams, economic performance, and inversely designed supercapacitors. Artificial intelligence may significantly accelerate the discovery of new materials but is not easily applicable to non-periodic structures. Here, a deep learning framework is proposed to predict properties of tangible carbon nanotubes by generating virtual structures at different scales and compositions.

Utilizing the nanoscale space created by carbon nanotubes (CNTs) is of importance for applications like energy storage devices, sensors, and functional materials. Gas adsorption is a versatile, quantitative characterization method to analyze nanoscale pore sizes and volumes. Here, we inspected N2 adsorption to the nanospace formed by the bundles of single-walled CNTs with an average nanotube diameter of ca. 2.0 nm and its distributions of 0.7-4.1 nm. Based on comparisons among the as-grown, purified (opened), and heat-treated (closed) CNTs with similar geometric bundle structures, we found that the interstitial channels emerged from a very low relative pressure of approximately 10-8 by removing the impurities from the CNT bundles, which is the first empirical demonstration. These findings can not only be utilized to understand the structures of CNT films, fibers, and bulks but also applied to porous materials science.

The mortality of coronavirus disease 2019 (COVID-19) is strongly correlated with pulmonary vascular pathology accompanied by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection–triggered immune dysregulation and aberrant activation of platelets. We combined histological analyses using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy analyses of the lungs from autopsy samples and single-cell RNA sequencing of peripheral blood mononuclear cells to investigate the pathogenesis of vasculitis and immunothrombosis in COVID-19. We found that SARS-CoV-2 accumulated in the pulmonary vessels, causing exudative vasculitis accompanied by the emergence of thrombospondin-1–expressing noncanonical monocytes and the formation of myosin light chain 9 (Myl9)–containing microthrombi in the lung of COVID-19 patients with fatal disease. The amount of plasma Myl9 in COVID-19 was correlated with the clinical severity, and measuring plasma Myl9 together with other markers allowed us to predict the severity of the disease more accurately. This study provides detailed insight into the pathogenesis of vasculitis and immunothrombosis, which may lead to optimal medical treatment for COVID-19.

Controlling the alignment of single-walled carbon nanotubes (SWCNTs) on the macroscopic scale is critical for practical applications because SWCNTs are extremely anisotropic materials. One efficient technique is to create an effective SWCNT dispersion, which shows a liquid crystal (LC) phase. A strong acid treatment can realize SWCNT liquid crystalline dispersions. However, strong acids pose a substantial safety risk, which renders the process unfit for mass production. Herein, an isolated SWCNT dispersion displaying an LC behavior is prepared using sodium cholate without an acid treatment, and its phase transition behaviors are systematically investigated across the isotropic to biphasic to nematic phases. As the SWCNT concentration increases, the dispersion undergoes an isotropic-to-nematic phase transition in which the spindle-shaped LC droplets, or the so-called tactoids, and the Schlieren textures can be observed in the intermediate biphasic state and the nematic phase, respectively. The arrangements of SWCNTs in the tactoids and the Schlieren structures are directly investigated by polarized optical microscopy. The clear LC behaviors of the CNT dispersion suggest that the CNT orientations can be controlled by the normal surfactant-assisted method, which is a crucial advantage for the liquid-phase processing of CNT fibers and films.

Multi-walled carbon nanotube networks were confirmed to exhibit a linear decrease in resistivity with increasing temperature from 100 to above 400 K. The linearity was explained using a defect scattering model that involved Friedel oscillations (that is, electron-electron interactions). The applicability of this model, which was originally proposed for graphene, to carbon nanotubes was assessed based on a comparison of various experimental data. Increases in the slopes of the resistivity-temperature plots following the introduction of defects, as well as an effect of charge concentration on the slope were key predictions of this model. The results obtained from few-walled carbon nanotube networks are also shown. In the literature, linear resistivity-temperature plots were obtained from other graphene derivatives, indicating that the linearity originates from the hexagonal symmetry of these materials. The present work also indicated a relationship between the appearance of linearity and negative magnetoresistance above 100 K. Based on a mechanism incorporating scattering in association with Friedel oscillations and conventional electron conduction models, the universality of resistivity-temperature plots obtained from carbon nanotube networks is introduced.

We studied the charge-state stabilization of shallow nitrogen-vacancy (NV) centers in (111) diamond using graphene/diamond junctions. Measurement of the fluorescence stability and evaluation of the charge-state stability were conducted on the NV centers at the graphene and the graphene-free region. The results revealed that about half of the total NV centers (NV0 + NV−) at the graphene-free region were unstable, while over 90% of the measured NV centers at the graphene region were stabilized as NV− centers. Graphene/diamond junctions contribute significantly to charge-state stabilization of shallow NV− centers in (111) diamond.

Electrically conductive nano-fillers, such as carbon nanotubes (CNT), carbon black (CB) and carbon fibers (CF), have been of great interest to polymer scientists because their reinforcement into polymer matrices gives rise to conductive thermoplastics. However, it is found that their orientation distributions after the injection molding process reduce the interparticle contacts between particles and thus decreases the electrical conductivity. In this study, it is shown that electrically conductive networks can be re-tailored through post-processing annealing at a temperature higher than the glass-rubber transition temperature of the polymer. We demonstrate these results for polycarbonate (PC) composites produced by injection molding using different fillers including single-walled CNT (SWCNT), multi-walled CNT (MWCNT), CB and CF. The annealing-induced increase in the electrical network path is proved by electrical conductivity improvement. It can be explained by a transition from aligned, unconnected particles before annealing to an interconnected network after annealing through the viscoelastic relaxation of the polymer. Compared with CB- and CF-based PC composites, CNT-based PC composites at low contents exhibited outstanding conductivity improvement after isothermal annealing for several minutes. Moreover, the CNT network helps to keep the composite shape and strength after annealing. Especially, SWCNT nanocomposites have potential to rapid the tailoring process of the electrical network without significant size extension and strength reduction. The post-processing annealing may exploit the future applications of injection-molded CNT polymer composites.

Single-walled carbon nanohorns (CNHs) have great potential in diverse applications such as gas storage, catalyst support, and drug carriers. Although chemical functionalization of CNHs is critical ...

Preserving the quality of carbon nanotubes (CNTs) is essential to fully utilize the characteristics in dispersions and other forms. To fabricate CNT dispersions retaining the quality, we propose to...

Carbon nanotubes (CNTs) are potentially important biomaterials because of their chemical, physical, and biological properties. Our research indicates that CNTs exhibit high compatibility with bone tissue. The guided bone regeneration (GBR) technique is commonly applied to reconstruct alveolar bone and treat peri-implant bone defects. In GBR, bone defects are covered with a barrier membrane to prevent the entry of nonosteogenic cells such as epithelial cells and fibroblasts. The barrier membrane also maintains a space for new bone formation. However, the mechanical and biological properties of materials previously used in clinical practice sometimes delayed bone regeneration. In this study, we developed a CNT-based membrane for GBR exhibiting high strength to provide a space for bone formation and provide cellular shielding to induce osteogenesis. The CNT membrane was made via the dispersion of single-walled CNTs (SWCNTs) in hyaluronic acid solution followed by filtration. The CNT membrane assumed a nanostructure surface due to the bundled SWCNTs and exhibited high strength and hydrophilicity after oxidation. In addition, the membrane promoted the proliferation of osteoblasts but not nonosteogenic cells. CNT membranes were used to cover experimental bone defects made in rat calvaria. At 8 weeks after surgery, more extensive bone formation was observed in membrane-covered defects compared with bone defects not covered with membrane. Almost no diffusion of CNTs was observed around the membrane. These results indicate that the CNT membrane has adequate strength, stability, and surface characteristics for osteoblasts, and its shielding properties promote bone formation. Demonstration of the safety and osteogenic potential of the CNT membranes through further animal studies should facilitate their clinical application in GBR.

We investigate the liquid crystal (LC) phase behaviors of the sodium cholate stabilized single-walled carbon nanotube (SWCNT) aqueous dispersions with different SWCNT aspect ratios. The isotropic-to-nematic phase transition occurs at a lower concentration for the SWCNT dispersion with a larger aspect ratio, which is expected by the Onsager theory. The well-aligned film is successfully fabricated from the dispersion with the higher SWCNT aspect ratio by the simple blade coating. We also prepare the SWCNT dispersions with different surfactants, sodium deoxycholate, and sodium taurodeoxycholate, changing the surface condition of SWCNTs, which may affect the LC transition concentrations.

Here, we propose a novel attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy method for simultaneously monitoring the curing reaction and the diffusion behavior of curing agents at the surface of rubber in real-time. The proposed scheme was demonstrated by fluorine rubber (FKM) and FKM/carbon nanotube (CNT) nanocomposites with a target curing agent of triallyl-isocyanurate (TAIC). The broadening and the evolution of the C=O stretching of TAIC were quantitatively analyzed to characterize the reaction and the diffusion. Changes in the width of the C=O stretching indicated the reaction rate at the surface was even faster than that of the bulk as measured by a curemeter. The diffusion coefficient of the curing agent in the course of heating was newly calculated by the initial increase in the absorbance and our model based on Fickian diffusion. The diffusion coefficients of TAIC during curing were evaluated, and its temperature and filler dependency were identified. Cross-sectional ATR-FTIR imaging and in situ ATR-FTIR imaging measurements supported the hypothesis of the unidirectional diffusion of the curing agent towards the heated surface. It was shown that our method of in situ ATR-FTIR can monitor the degrees of cure and the diffusion coefficients of curing agents simultaneously, which cannot be achieved by conventional methods, e.g., rheological measurements.

Utilizing the nanoscale space created by carbon nanotubes (CNTs) is of importance for applications like energy storage devices, sensors, and functional materials. Gas adsorption is a versatile, quantitative characterization method to analyze nanoscale pore sizes and volumes. Here, we inspected N

Fibres composed of carbon nanotubes (CNT) can be used to make lightweight materials with high mechanical strength and electrical conductivity. However, the reported properties have been much poorer than those of the individual CNT. To address this discrepancy, it is necessary to elucidate the relationship between the fibres' structure and their properties. Here, we systematically investigated the CNT length and fibre density dependences of the electrical and the mechanical properties of CNT fibres produced by the wet-spinning method. The obtained specific conductivities of the fibres were almost proportional to the effective CNT lengths, whereas such correlations were less apparent for the fracture strengths and Young's moduli.

To realize the potential applications of carbon nanotube (CNT) polymer composites produced using injection molding, the CNT networks in composite parts need to be tailored and controlled by processing conditions. In this study, microinjection-molded polycarbonate matrix composite filled with multi-walled carbon nanotubes were prepared from twin-crew extruded pellets using plate-shaped double-cavity. The CNT electrical network in these microinjection-molded parts was observed directly in both cross-section and longitudinal-section using the lock-in thermography technique (LIT). The results showed the skin/shell-core structure with the high degree of inter-connected CNT in the core region, the inhomogeneous conductivity along the injection direction and the lower conductivity near the gate. This is confirmed by inspecting the scanning electron microscopy and polarized Raman mapping images. The effect of total injection molding time, mold temperature and melt temperature on the electrical network and conductivity were also investigated. The observed conductivity variations were explained in term of the processing conditions that induced the CNT network structures in the skin and core regions.

This paper describes methods and evaluation results of predicting the number of defects in image sensors using equipment QC data. Virtual metrology (VM) models are mainly used for measurable values such as dimensions and electrical characteristics. Herein, to predict countable values, we used a regression tree and stepwise AIC for variable selection as well as the “hockey-stick regression model” and generalized linear model for regression, instead of the partial least squares (PLS) regression. The results showed an improved prediction performance in comparison with the conventional method. This method can be used to predict other countable values such as defects or dust particles.

Dispersion of carbon nanotubes (CNTs) in liquids is a crucial process in the fabrication of advanced CNT-based materials. However, quantitative evaluation of the dispersed CNTs remains one of the l...

We propose a general guideline for the application of commercialized carbon nanotubes (CNTs) by making correlations between the structures and properties for various single-walled, double-walled, a...

Understanding the biodegradation profiles of various types of carbon nanotubes (CNTs) is important for their safe use according to their structural characteristics. To investigate the relationship between the biodegradation and the physicochemical properties of CNTs, sodium hypochlorite was used to degrade CNTs because it is believed to be a key oxidizer of CNTs inside macrophages and neutrophils. The complete degradation of CNTs in response to sodium hypochlorite was confirmed, and the half-lives of 11 different types of commercially available single-wall CNTs (SWNTs), carbon nanohorns (CNHs), and multiwall CNTs (MWNTs) in sodium hypochlorite were determined. The degradation of CNTs generally correlated with diameter, as follows: SWNTs ≥ CNHs > thinner MWNTs > thicker MWNTs. In addition, defects and the degree of dispersion also affected the degradation rate, but these were not the primary factors determining CNT degradation.

Introduction and objective: With the increase in carbon nanotube-based products on the commercial market, public concern regarding the possible toxicity of these nanomaterials has attracted much attention. Although previous studies found no obvious toxicity related to carbon nanotubes (CNTs), their safety has not been established because long-term evaluation is still needed. In vitro assays are used to understand the toxicity of nanomaterials. However, the data published so far were generated in short-term assays in which cells are continuously exposed to CNTs. Therefore, the objective of this study is to quantitatively assess the relative long-term cytotoxicity and degradation of CNTs after uptake by macrophages. Methods: We used macrophage cell line of RAW 264.7 and primary rat Kupffer cells to investigate macrophage uptake of CNTs as well as their quantity changes up to a relatively late time point after uptake (7 days) by measuring optical absorbance in the near infrared region and Raman spectra of CNTs in the cell lysates. The time-dependent cytotoxicity was evaluated by measuring reactive oxygen species (ROS), glutathione, cell viability, and caspase 3/7 activity in 1–7 days. Results: CNTs were degraded by approximately 25–30% within first 4 days after uptake; however, and no additional degradation occurred for the remainder of the 7-day test period. Generation of ROS by macrophages decreased as CNT degradation occurred, returning to control levels by Day 7. In the meantime, the glutathione level gradually recovered over time. There were no changes in cell viability or caspase 3/7 activation during CNT degradation. Conclusion: These results confirm that degradation of CNTs by macrophages is associated with ROS generation. The data also suggest that CNT cytotoxicity decreases as they are degraded.

Cellulose nanofibers (CNFs) with different degrees of fibrillation are prepared by the mechanical fibrillation of kraft pulp using wet disk milling, and dispersions of the prepared CNFs were subjected to differential centrifugal sedimentation (DCS) in order to estimate the diameter distributions of the CNFs. The low-fibrillated CNFs (fiber diameter (d):10 μm) had a weak reinforcing effect on natural rubber (NR), while the medium-fibrillated CNFs (d: 0.1-10 μm) dramatically improve the initial modulus and decrease the elongation at break. The high-fibrillated CNFs (d:0.1 μm) enhanced the tensile strength even further while maintaining the elongation at break. The reinforcing mechanism of the NR composites reinforced by the CNFs (NR-CNFs) was confirmed by field-emission scanning electron microscopy imaging, dynamic mechanical analysis, and toluene uptake measurements. It was concluded that these characteristic mechanical properties of the NR-CNFs were determined by the morphologies of the CNFs. The branching structure of the medium-fibrillated CNFs affected high improvement of the initial modulus, and the network formed by the high-fibrillated CNFs were involved in enhancement of the tensile strength without compromising viscoelastic properties. Understanding the effect of their diameter distribution can potentially reduce the production cost of CNFs and thus expand their applicability.

Hexagonal boron nitride (h-BN), an insulating two-dimensional (2D) layered material, has attracted increasing interest due to its electrical screening effect, high-temperature-resistant gas barrier properties, and other unique applications. However, the presence of grain boundaries (GBs) in h-BN is a hindrance to obtain these properties. Here, we demonstrate the epitaxial growth of monolayer h-BN by chemical vapor deposition (CVD) on Ni(111) thin films deposited on c-plane sapphire. The Ni(111) films showed higher thermal stability than Cu(111) and Cu-Ni(111) alloy films, allowing us to perform CVD growth at a high temperature of 1100 °C. This resulted in an increase of the h-BN grain sizes to up to 0.5 millimeter, among the highest reported so far, and in a well-defined triangular grain shape. Low-energy electron microscopy (LEEM) revealed the epitaxial relationship between h-BN and the underlying Ni(111) lattice, leading to a preferential alignment of the h-BN grains. Both the large grain size and the alignment are expected to facilitate the synthesis of h-BN with a low density of GBs. We also found that the addition of N2 gas during the CVD improves the crystalline shape of the h-BN grains, changing from an irregular, truncated to a sharp triangle. The growth behavior of monolayer h-BN is further discussed in terms of the dependences on growth temperature and pressure, as well as on the structural evolution of the Ni metal catalyst. Our findings not only help understand the h-BN growth mechanism but also offer a new route to grow high-quality, monolayer h-BN films.

Functionalization is a key technique to improving the dispersibility of carbon nanotubes (CNTs) in solvents and polymer matrices for producing versatile CNT-based materials. Therefore, a robust and efficient characterization method is required to confirm that the functionalization on the CNT surface is spatially uniform. Although several imaging techniques for transmission electron microscopes can characterize the spatial localization of elements chemically bound to an isolated CNT surface, they are unsuitable for examinations on a practical scale because of their limited scanning area. Here, we present high spatially resolved energy dispersive X-ray spectrometry (EDS) imaging of functionalized single-walled CNTs (SWCNTs) in scanning electron microscopy (SEM). Highly sensitive EDS detection and drift-free operation enables our technique to image the light elements of SWCNTs with sufficient spatial resolution (

Graphene patterning via etching is important for enhancing or controlling the properties of devices and supporting their applications in micro- and nano-electronic fields. Herein, we present a simple, low-cost, and scalable wet etching method for graphene patterning. The technique uses hypochlorite solution combined with ultraviolet light irradiation to rapidly remove unwanted graphene areas from the substrate. Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and optical microscopy results showed that well-patterned graphene with micrometer scale regions was successfully prepared. Furthermore, graphene field effect transistor arrays were fabricated, and the obtained devices exhibited good current-voltage characteristics, with maximum mobility of ~1600 cm2/Vs, confirming the feasibility of the developed technique.

The electronic properties of various carbon nanotube (CNT) fibers that were produced by dry spinning from multi-walled CNT (MWCNT) forests, direct spinning from a CVD furnace and wet spinning of CNTs, are systematically investigated. The electrical conductivity of the fibers is significantly correlated with the effective CNT length [1], yarn density, and CNT alignment in the yarns. In contrast, the tensile strength depends more on the yarn density and the CNT alignment. The temperature dependence of the electronical properties of the CNT fibers are also investigated. Even though the constituent CNTs are very similar, the CNT fibers produced by the wet spinning of the acid treated CNT dispersion and the micelle CNT solution show different temperature dependences in the lower temperature region. The difference can be explained by the different conduction paths in the two wet-spinning fibers. Further, the iodide doping effect on the electronic property of the wet-spinning fiber produced by the acid treated dispersion is also discussed. This work was supported by a project (JPNP16010) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). [1] T. Morimoto et al., ACS Nano, 8, 9897–9904 (2014).

Single-walled carbon nanotubes (CNTs) are promising candidates for near-infrared (NIR) fluorescent labels in diagnostic fields. We here report a complex of oxygen-doped CNT (o-CNT) and streptavidin (SA) to prepare CNT-based NIR labels with a high reaction efficiency in immunoassays [1]. This complex specifically binds to biotin molecules by conjugating a linker molecule of phospholipid polyethylene glycol (PL-PEG) to SA (o-CNT-SA). The immunoprecipitation (IP) reaction efficiency between o-CNT-SA and biotin reaches 79.3% by uniformly covering the surface of o-CNTs with SA conjugated PL-PEG (SA-PEG). Further, we also report the biodistribution and toxicity of oxidized super-growth single-wall carbon nanotubes (oxSG) injected intravenously into mice over 3months [2]. [1] K. Kojima, Y. Iizumi, M. Zhang, T. Okazaki, submitted. [2] M. Zhang, Y. Xu, M. Yang, M. Yudasaka, T. Okazaki, 15, 798-811 (2021).