Room-temperature quantum emission from interface excitons in mixed-dimensional heterostructures

The development of van der Waals heterostructures has introduced unconventional phenomena that emerge at atomically precise interfaces. For example, interlayer excitons in two-dimensional transition metal dichalcogenides show intriguing optical properties at low temperatures. Here we report on room-temperature observation of interface excitons in mixed-dimensional heterostructures consisting of two-dimensional tungsten diselenide and one-dimensional carbon nanotubes. Bright emission peaks originating from the interface are identified, spanning a broad energy range within the telecommunication wavelengths. The effect of band alignment is investigated by systematically varying the nanotube bandgap, and we assign the new peaks to interface excitons as they only appear in type-II heterostructures. Room-temperature localization of low-energy interface excitons is indicated by extended lifetimes as well as small excitation saturation powers, and photon correlation measurements confirm antibunching. With mixed-dimensional van der Waals heterostructures where band alignment can be engineered, new opportunities for quantum photonics are envisioned.

Evaluating the Efficiency of Boron Nitride Coating in Single-Walled Carbon-Nanotube-Based 1D Heterostructure Films by Optical Spectroscopy

Single-walled carbon nanotube (SWCNT) films exhibit exceptional optical and electrical properties, making them highly promising for scalable integrated devices. Previously, we employed SWCNT films as templates for the chemical vapor deposition (CVD) synthesis of one-dimensional heterostructure films where boron nitride nanotubes (BNNTs) and molybdenum disulfide nanotubes (MoS2NTs) were coaxially nested over the SWCNT networks. In this work, we have further refined the synthesis method to achieve precise control over the BNNT coating in SWCNT@BNNT heterostructure films. The resulting structure of the SWCNT@BNNT films was thoroughly characterized using a combination of electron microscopy, UV-vis-NIR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. Specifically, we investigated the pressure effect induced by BNNT wrapping on the SWCNTs in the SWCNT@BNNT heterostructure film and demonstrated that the shifts of the SWCNT's G and 2D (G') modes in Raman spectra can be used as a probe of the efficiency of BNNT coating. In addition, we studied the impact of vacuum annealing on the removal of the initial doping in SWCNTs, arising from exposure to ambient atmosphere, and examined the effect of MoO3 doping in SWCNT films by using UV-vis-NIR spectroscopy and Raman spectroscopy. We show that through correlation analysis of the G and 2D (G') modes in Raman spectra, it is possible to discern distinct types of doping effects as well as the influence of applied pressure on the SWCNTs within SWCNT@BNNT heterostructure films. This work contributes to a deeper understanding of the strain and doping effect in both SWCNTs and SWCNT@BNNTs, thereby providing valuable insights for future applications of carbon-nanotube-based one-dimensional heterostructures.

Horizontal Arrays of One-Dimensional van der Waals Heterostructures as Transistor Channels

The nanotube/dielectric interface plays an essential role in achieving superb switching characteristics of carbon nanotube-based transistors for energy-efficient computation. Formation of van der Waals heterostructures with hexagonal boron nitride nanotubes could be an effective means to reduce interface state density, but the need for isolating nanotubes during the formation of coaxial outer layers has hindered the fabrication of their horizontal arrays. Here, we develop a strategy to create isolated heterostructure arrays using aligned carbon nanotubes grown on a quartz substrate as starting materials. Air-suspended arrays of carbon nanotubes are prepared by a dry transfer technique and then used as templates for the coaxial wrapping of boron nitride nanotubes. We then fabricate the transistors, where boron nitride serves as interfacial layers between carbon nanotube channels and conventional gate dielectrics, showing hysteresis-free characteristics owing to the improved interfaces. We have also gained a deeper understanding of the strain applied on inner carbon nanotubes, as well as the inhomogeneity of the outer coating, by characterizing individual heterostructures over trenches and on a substrate surface. The device fabrication and characterization presented here essentially do not require elaborate electron microscopy, thus paving the way for the practical use of one-dimensional van der Waals heterostructures for nanoelectronics.

Formation of organic color centers in air-suspended carbon nanotubes using vapor-phase reaction

Organic color centers in single-walled carbon nanotubes have demonstrated exceptional ability to generate single photons at room temperature in the telecom range. Combining the color centers with pristine air-suspended nanotubes would be desirable for improved performance, but all current synthetic methods occur in solution which makes them incompatible. Here we demonstrate the formation of color centers in air-suspended nanotubes using a vapor-phase reaction. Functionalization is directly verified by photoluminescence spectroscopy, with unambiguous statistics from more than a few thousand individual nanotubes. The color centers show strong diameter-dependent emission, which can be explained with a model for chemical reactivity considering strain along the tube curvature. We also estimate the defect density by comparing the experiments with simulations based on a one-dimensional exciton diffusion equation. Our results highlight the influence of the nanotube structure on vapor-phase reactivity and emission properties, providing guidelines for the development of high-performance near-infrared quantum light sources.

Organic color centers in single-walled carbon nanotubes can act as single-photon sources in the telecom range. Here the authors report the functionalization of air-suspended nanotubes through a vapor-phase photochemical reaction, demonstrating a further tailoring of quantum emitter materials.

Direct Visualization of Ultrastrong Coupling between Luttinger-Liquid Plasmons and Phonon Polaritons

Ultrastrong coupling of light and matter creates new opportunities to modify chemical reactions or develop novel nanoscale devices. One-dimensional Luttinger-liquid plasmons in metallic carbon nanotubes are long-lived excitations with extreme electromagnetic field confinement. They are promising candidates to realize strong or even ultrastrong coupling at infrared frequencies. We applied near-field polariton interferometry to examine the interaction between propagating Luttinger-liquid plasmons in individual carbon nanotubes and surface phonon polaritons of silica and hexagonal boron nitride. We extracted the dispersion relation of the hybrid Luttinger-liquid plasmon-phonon polaritons (LPPhPs) and explained the observed phenomena by the coupled harmonic oscillator model. The dispersion shows pronounced mode splitting, and the obtained value for the normalized coupling strength shows we reached the ultrastrong coupling regime with both native silica and hBN phonons. Our findings predict future applications to exploit the extraordinary properties of carbon nanotube plasmons, ranging from nanoscale plasmonic circuits to ultrasensitive molecular sensing.

Universal Map of Gas-Dependent Kinetic Selectivity in Carbon Nanotube Growth

Single-walled carbon nanotubes have been a candidate for outperforming silicon in ultrascaled transistors, but the realization of nanotube-based integrated circuits requires dense arrays of purely semiconducting species. In order to directly grow such nanotube arrays on wafers, control over kinetics and thermodynamics in tube-catalyst systems plays a key role, and further progress requires a comprehensive understanding of seemingly contradictory reports on the growth kinetics. Here, we propose a universal kinetic model that decomposes the growth rates of nanotubes into the adsorption and removal of carbon atoms on the catalysts, and we provide its quantitative verification by ethanol-based isotope labeling experiments. While the removal of carbon from catalysts dominates the growth kinetics under a low supply of precursors, resulting in chirality-independent growth rates, our kinetic model and experiments demonstrate that chiral angle-dependent growth rates emerge when sufficient amounts of carbon and etching agents are cosupplied. The kinetic maps, as a product of generalizing the model, include five types of kinetic selectivity that emerge depending on the absolute quantities of gases with opposing effects. Our findings not only resolve discrepancies existing in the literature but also offer rational strategies to control the chirality, length, and density of nanotube arrays for practical applications.

Epicardial adipose tissue volume is associated with low-attenuation plaque volume in subjects with or without increased visceral fat: a 3-vessel coronary artery analysis with CT angiography

Background

Low-attenuation plaque (LAP) with a CT value of less than or equal 30 HU on coronary CT angiography (CCTA) is a marker of high-risk plaque features that leads to future acute coronary syndromes. Perivascular and epicardial adipose tissue (EAT) have been shown to be associated with progression of high-risk coronary plaques through metabolic and inflammatory mechanisms. However, association of EAT with LAP volume in three coronary arteries in subjects with or without visceral obesity remain unclear.

Aims

This study aimed to investigate the association of EAT volume (EAV) and coronary 3-vessel LAP volume in subjects with or without visceral obesity who underwent CCTA.

Methods

Patients who underwent CCTA without known coronary artery disease were included in the study (525 patients). Study subjects were classified as having non-obstructive or obstructive coronary artery disease according to the degree of coronary artery stenosis on CCTA. The plaque volume and EAV of the main vessel of the left anterior descending artery, left circumflex artery, and right coronary artery were measured with VINCENT software. Coronary plaque composition was classified as calcified plaque (CP, >150HU), noncalcified plaque (NCP, 30–150HU), and Lap (<30HU). The %LAP volume of the three coronary arteries was classified into quartiles. Multiple logistic regression analysis was used to analyze the factors associated with the %LAP volume.

Results

Compared with subjects without increase visceral fat, subjects with increased visceral fat had a significantly higher BMI, a greater total plaque volume, a greater total %LAP volume, a greater EAV, and a lower mean CT value of EAT. A significant correlation was observed between EAV and %LAP volume (R=0.24, p<0.001). EAV (odds ratio; 1.83, 95% confidence interval 1.071–3.141, p-value 0.027) and type 2 diabetes mellitus (odds ratio 1.76, 95%confidence interval 1.042–3.000, p-value 0.034) appeared to be independent predictors of %LAP volume (Q4), when adjusted by age, gender, BMI>25 kg/m2, visceral fat >100cm2, LogCRP, coronary artery calcium score>300, and obstructive coronary artery disease requiring revascularization.

Conclusion

This study suggests that LAP volume, which reflects the high-risk plaques in the three coronary arteries, is associated with EAV in subjects with or without increased visceral fat. Further research is needed whether pharmacological therapeutic intervention enables the prevention of coronary plaque progression and destabilization through the reduction of EAV in patients.

Funding Acknowledgement

Type of funding sources: None.

Clinical significance of aortic arch plaques simultaneously assessed with coronary atherosclerosis on cardiovascular outcomes in patients undergoing coronary CT angiography

Aims

Computed tomography (CT) coronary angiography is a useful diagnostic imaging modality in assessing presence, severity, and extent of coronary artery disease (CAD). Aortic arch plaques have been shown to be an underlying cause of embolic stroke and also related to increased risk of cardiovascular events. Yet, conventional CTCA imaging protocol does not include aortic arch for the reduction of radiation exposure. This study aimed to investigate prevalence of aortic arch plaques simultaneously assessed by CTCA and their clinical significance in combination with the presence of obstructive CAD for prediction of CVD events in patients with suspected CAD.

Methods

This study consisted of 310 (mean age, 66 years old, 42% female) patients with suspected CAD undergoing CTCA between 2017 and 2019. All CTCA examination was performed with 320-row detector scanner using ECG-triggered prospective gating method. Aortic arch images were simultaneously acquired during CTCA scanning without an increase of contrast media. Using Agatston method, coronary artery calcium score (CACS) was categorized into either of the groups having CACS of 0, 0–99, 100–299, or more than 300. The presence of CAD was reported as non-obstructive or obstructive CAD. High-risk featured aortic plaque was defined as large plaques >4 mm in thickness showing ulceration or protrusion. A composite event of cardiovascular disease, including all-cause mortality, non-fatal myocardial infarction, unplanned hospitalization requiring revascularization or stroke was defined as the primary endpoint.

Results

Patients having CACS of 0, 0–99, 100–299, and >300 were found in 41%, 24%, 15%, 20%%, respectively, where obstructive CAD was diagnosed in 11%. Aortic HRPs in ascending aorta, aortic arch, and thoracic descending aorta were observed in 1.6%, 6.9%, and 15%, respectively. During a mean follow-up period of 2.2 years, the primary endpoint was observed in 27 patients (8.7%). Cox regression hazard model demonstrated an independent association of aortic arch high-risk plaques (HR; 3.2, 95% CI; 1.20–8.64, p=0.02) and obstructive CAD (HR; 3.3, 95% CI; 1.45–7.92, P=0.005) when adjusted by age, CACS, and chronic kidney disease. Kaplan-Meier curve analysis showed a worse outcome of patients with aortic HRP and obstructive CAD compared to those without aortic plaques and obstructive CAD (p<0.001).

Conclusion

This study demonstrated an independent association of aortic arch high-risk featured plaques with CVD events. Further study is warranted whether pharmacological interventional therapies can reduce future CVD risks in patients with CAD and aortic arch plaques.

Funding Acknowledgement

Type of funding sources: None.

Nanotube-Based 1D Heterostructures Coupled by van der Waals Forces

1D van der Waals heterostructures based on carbon nanotube templates are raising a lot of excitement due to the possibility of creating new optical and electronic properties, by either confining molecules inside their hollow core or by adding layers on the outside of the nanotube. In contrast to their 2D analogs, where the number of layers, atomic type and relative orientation of the constituting layers are the main parameters defining physical properties, 1D heterostructures provide an additional degree of freedom, i.e., their specific diameter and chiral structure, for engineering their characteristics. The current state-of-the-art in synthesizing 1D heterostructures are discussed here, in particular focusing on their resulting optical properties, and details the vast parameter space that can be used to design heterostructures with custom-built properties that can be integrated into a large variety of applications. First, the effects of van der Waals coupling on the properties of the simplest and best-studied 1D heterostructure, namely a double-walled carbon nanotube, are described, and then heterostructures built from the inside and the outside are considered, which all use a nanotube as a template, and, finally, an outlook is provided for the future of this research field.

Deterministic transfer of optical-quality carbon nanotubes for atomically defined technology

When continued device scaling reaches the ultimate limit imposed by atoms, technology based on atomically precise structures is expected to emerge. Device fabrication will then require building blocks with identified atomic arrangements and assembly of the components without contamination. Here we report on a versatile dry transfer technique for deterministic placement of optical-quality carbon nanotubes. Single-crystalline anthracene is used as a medium which readily sublimes by mild heating, leaving behind clean nanotubes and thus enabling bright photoluminescence. We are able to position nanotubes of a desired chirality with a sub-micron accuracy under in-situ optical monitoring, thereby demonstrating deterministic coupling of a nanotube to a photonic crystal nanobeam cavity. A cross junction structure is also designed and constructed by repeating the nanotube transfer, where intertube exciton transfer is observed. Our results represent an important step towards development of devices consisting of atomically precise components and interfaces.

As device fabrication reach atomic scales, assembly of atomically defined components becomes crucial. Here, the authors demonstrate a low contamination transfer technique, using single-crystalline anthracene as medium, for placement of structure-specific carbon nanotubes with submicron accuracy.

Intracoronary polarimetry for characterizing coronary plaque vulnerability in patients with coronary artery disease

Background

Intracoronary polarimetry with polarization-sensitive (PS-) optical frequency domain imaging (OFDI) measures polarization properties, including birefringence and depolarization, in parallel with structural features of conventional OFDI (Figure 1A). Collagen, which imparts mechanical integrity to fibrous caps, and collagen-synthesizing smooth muscle cells exhibit elevated birefringence. Depolarization is increased by the presence of macrophages and lipid/necrotic cores.

Purpose

This study aimed to compare conventional OFDI and polarimetric signatures of coronary lesions between patients with acute coronary syndrome (ACS) and chronic coronary syndrome (CCS). Furthermore, we aimed to determine a birefringence cut-off value for identifying which fibrous caps belong to ACS culprit lesions.

Methods

This study consisted of 37 patients with ACS (n=23) or CCS (n=14). ACS culprit lesions (ACS-lesions) and CCS stenotic lesions (CCS-lesions) were included in the analysis (820 mm). Qualitative and quantitative conventional OFDI analysis included the presence of plaque rupture, macrophage infiltration, micro-vessels, thrombus, stenosis severity, fibrous cap thickness (FCT), lipid arc, lipid-burden and calcium-burden index. Birefringence and depolarization of the coronary lesions and fibrous caps were measured in the cross-sectional images showing the minimum FCT or minimum luminal area. Predictors of ACS-lesions were investigated by multivariate regression analysis. Receiver operating characteristic (ROC) analysis was used to determine the birefringence cut-off value identifying ACS fibrous caps (ACS-caps).

Results

There were no significant differences in clinical characteristics between the two groups, except for previous history of coronary artery disease. Compared to CCS-lesions, ACS-lesions featured higher lipid-burden index and maximum lipid arc (both p<0.05). ACS-lesions featured lower birefringence and higher depolarization than CCS-lesions (p<0.05). Multivariable regression demonstrated an independent association of birefringence with ACS-lesions (p<0.05), even after adjusting for the conventional OFDI findings. Limiting the analysis to the fibrous caps, ACS-caps exhibited significantly lower birefringence (p<0.05) and higher depolarization (p<0.05) that CCS-caps. ROC analysis for differentiating ACS-caps from CCS-caps found that a birefringence value of 0.0004 results in a sensitivity and specificity of 88% and 82%, respectively (Figure 1B, AUC = 0.82).

Conclusions

Intracoronary polarimetry provides quantitative assessment of coronary lesions related to their composition. Birefringence was an independent robust predictor of ACS-lesions. Decreased birefringence and pronounced depolarization within the ACS-caps may indicate increased collagenolytic activity and macrophage infiltration, respectively. These results suggest that polarization properties may serve as quantitative imaging markers for assessing plaque vulnerability.

Figure 1

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): This work was supported by the National Institutes of Health and by Terumo Corporation.

Polarization-sensitive OFDI findings of vascular tissue response following drug-eluting stent implantation in patients with coronary artery disease

 

Intravascular polarimetry (IVP) with polarization-sensitive (PS-) optical frequency domain imaging (OFDI) measures polarization properties of the coronary arterial wall in parallel with the conventional OFDI images (Figure 1A). Tissues rich in collagen and smooth muscle cells (SMCs) appear birefringent, while the presence of lipid and macrophages causes depolarization. Because drug-eluting stents (DES) are designed to prevent SMC proliferation and collagen deposition, we hypothesized that neointimal tissue would exhibit low birefringence. The accumulation of lipid-laden macrophages characteristic of neoatherosclerosis should result in notable depolarization.

Methods

This study included 19 DES imaged with PS-OFDI in 13 patients (median follow-up period of 1.5 years). Coronary segments stented >90 days were analyzed every 1 mm. We analyzed polarization properties of the neointima in a total of 455 frames, and in additional 97 frames of native atherosclerosis remote from the stented segments. Neointima, delineated by the lumen and the inner boundary of the stent, was manually segmented in the intensity images using MATLAB. The median birefringence in all areas of the segmented neointima featuring a depolarization of ≤0.2 and the median depolarization across the entire neointima were computed for each frame after masking the guidewire shadow. Frames presenting intensity features of macrophages, lipid or calcifications extending to at least one adjacent frame were classified as neoatherosclerosis (n=112), and otherwise as normal neointima (n=343). For comparison with neoatherosclerosis, polarization properties of native atherosclerosis (n=97) were measured. We also categorized all frames of a stented segment according to the presence of in-stent restenosis (ISR) and/or stent thrombosis (ST) (204 frames from 5 patients). A generalized linear model using a generalized estimating equation or one-way ANOVA was used for statistical analysis.

Results

The major findings of the present study are: 1) neoatherosclerosis exhibited lower birefringence than native atherosclerosis (p<0.001, Figure-1B); 2) depolarization was positively associated with neoatherosclerosis (β=0.86, p<0.001) and ISR/ST (β=0.72, p=0.002), while birefringence was not (Figure 1C); 3) birefringence was positively correlated with the duration after DES implantation (β=5.22×10–3, p<0.001, Figure 1D). For the detection of neointimas within stents with ISR, the best cut-off value for depolarization was 0.033 with a sensitivity of 77% and a specificity of 57% (AUC=0.72). For comparison, using only conventional OFDI parameters to detect stents with ISR, the AUC were 0.52 for calcium area, 0.62 for lipid arc, and 0.63 for macrophage accumulations.

Conclusions

This study suggests that IVP provides quantitative assessment of vascular healing after DES implantation and may help clinical decision making in patients at high risk of stent failure.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): This work was supported by the National Institutes of Health.

P176 Left ventricular diastolic function by gated myocardial perfusion SPECT strongly reflects NT-ProBNP

Background

The importance of left ventricle diastolic dysfunction (LVDD) has been recognized widely, as it is well established that heart failure with preserved ejection fraction has a poor prognosis. Furthermore, N-terminal pro–B-type natriuretic peptide (NT-ProBNP) is used as a marker of heart failure. However, the association between LVDD and NT-proBNP is unclear. 

Purpose

The aim of this study was to clarify the association between LVDD and NT-ProBNP. 

Methods

In this study, an index based on gated myocardial perfusion SPECT using CardioREPO software for the diagnosis of LVDD was used. Out of the 171 patients who underwent myocardial perfusion imaging (MPI) between January 2015 and December 2018, 163 individuals (116 men and 47 women) completed MPI and NT-ProBNP. Patients were classified into 4 groups: NT-ProBNP levels below 125 pg/ml (n = 52), NT-ProBNP levels 125 to 400 pg/ml (n = 33), NT-ProBNP levels 400 to 900 pg/ml (n = 23), and NT-ProBNP levels over 900 pg/ml (n = 37). CardioREPO parameters (peak filling rate　(PFR), 1/3 mean filling rate (MFR), and time to peak filling rate/R-R (TTPFR)) were compared between the 4 NT-ProBNP groups. 

Results

Of the 163 patients, 55 had LVDD. The PFR and 1/3MFR were associated with LVDD. There was a statistically significant difference in PFR and 1/3 MFR between the NT-ProBNP levels below 125 pg/ml group and the NT-ProBNP levels 400 to 900 pg/ml group (PFR = 2.51+/-1.11 vs. 1.80+/-0.65, p = 0.001; 1/3 MFR = 1.41+/-0.55 vs. 1.06+/-0.47, p = 0.006, Table).

Conclusions

The MPI indices obtained by CardioREPO software were useful in the diagnosis of LVDD. The evaluation of LVDD by MPI correlated with NT-Pro BNP level is thought to have a clinical utility in the diagnosis and management of LVDD.

Variable: NT-ProBNP 　 0-125 (n = 52) 125-400 (n = 33) 400-900 (n = 23) 900- (n = 37) p Age 66 ± 11 72 ± 11 68 ± 17 70 ± 12 0.133 Male 40 (77%) 22 (12%) 18 (78%) 23 (62%) 0.36 Left ventricular diastolic dysfunction 8 (15%) 4 (12%) 10 (43%) 27 (73%) <0.001 E/A 0.9 ± 0.3 0.8 ± 0.2 1.1 ± 0.7 1.4 ± 0.9 (35) <0.001 E/e" 10.27 ± 3.69 (20) 8.83 ± 3.56 (10) 12.46 ± 3.75 (12) 20.25 ± 8.30 (25) <0.001 rest-PFR /s 2.51 ± 1.11 2.06 ± 0.58 2.16 ± 0.65 1.80 ± 0.65 0.001 rest-1/3 MFR /s 1.41 ± 0.55 1.19 ± 0.41 1.16 ± 0.50 1.06 ±0.47 0.008 rest-TTPFR ms 177 ± 53 181 ± 69 198 ± 80 166 ± 85 0.38 rest-TTPFR / R-R 　 0.19 ± 0.06 0.20 ± 0.11 0.21 ±0.09 0.21 ± 0.15 0.92

Super-resolution fluorescence imaging of carbon nanotubes using a nonlinear excitonic process

Highly efficient exciton-exciton annihilation process unique to one-dimensional systems is utilized for super-resolution imaging of air-suspended carbon nanotubes. Through the comparison of fluorescence signals in linear and sublinear regimes at different excitation powers, we extract the efficiency of the annihilation processes using conventional confocal microscopy. Spatial images of the annihilation rate of the excitons have resolution beyond the diffraction limit. We investigate excitation power dependence of the annihilation processes by experiment and Monte Carlo simulation, and the resolution improvement of the annihilation images can be quantitatively explained by the superlinearity of the annihilation process. We have also developed another method in which the cubic dependence of the annihilation rate on exciton density is utilized to achieve further sharpening of single nanotube images.

Atomic-scale structural identification and evolution of Co-W-C ternary SWCNT catalytic nanoparticles: High-resolution STEM imaging on SiO2

Recently, W-based catalysts have provided a promising route to synthesize single-walled carbon nanotubes (SWCNTs) with specific chirality, but the mechanism of the growth selectivity is vaguely understood. We propose a strategy to identify the atomic structure as well as the structure evolution of the Co-W-C ternary SWCNT catalyst. The key is to use a thin SiO2 film as the catalyst support and observation window. As the catalyst is uniformly prepared on this SiO2 film and directly used for the SWCNT synthesis, this method has an advantage over conventional methods: it creates an opportunity to obtain original, statistical, and dynamic understanding of the catalyst. As a technique, atomic-scale imaging directly on SiO2 serves as a powerful and versatile tool to investigate nanocrystals and high-temperature reactions; for the synthesis of SWCNTs, this work successfully visualizes the structure and evolution of the catalyst and illuminates the possible nucleation sites of the chirality-specific growth.

Digital Isotope Coding to Trace the Growth Process of Individual Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) are attracting increasing attention as an ideal material for high-performance electronics through the preparation of arrays of purely semiconducting SWCNTs. Despite significant progress in the controlled synthesis of SWCNTs, their growth mechanism remains unclear due to difficulties in analyzing the time-resolved growth of individual SWCNTs under practical growth conditions. Here we present a method for tracing the diverse growth profiles of individual SWCNTs by embedding digitally coded isotope labels. Raman mapping showed that, after various incubation times, SWCNTs elongated monotonically until their abrupt termination. Ex situ analysis offered an opportunity to capture rare chirality changes along the SWCNTs, which resulted in sudden acceleration/deceleration of the growth rate. Dependence on growth parameters, such as temperature and carbon concentration, was also traced along individual SWCNTs, which could provide clues to chirality control. Systematic growth studies with a variety of catalysts and conditions, which combine the presented method with other characterization techniques, will lead to further understanding and control of chirality, length, and density of SWCNTs.

Fabrication, characterization, and high temperature surface enhanced Raman spectroscopic performance of SiO2 coated silver particles

We present a systematic study on the fabrication, characterization and high temperature surface enhanced Raman spectroscopy (SERS) performance of SiO₂ coated silver nanoparticles (Ag@SiO₂) on a flat substrate, aiming to obtain a thermally robust SERS substrate for monitoring high temperature reactions. We confirm that a 10-15 nm SiO₂ coating provides a structure stability up to 900 °C without significantly sacrificing the enhancement factor, while the uncoated particle cannot retain the SERS effect above 500 °C. The finite difference time domain (FDTD) simulation results supported that the SiO₂ coating almost has no influence on the distribution of the electric field but only physically trapped the most enhanced spot inside the coating layer. On this thermally robust substrate, we confirmed that the SERS of horizontally aligned single walled carbon nanotubes is stable at elevated temperatures, and demonstrate an in situ Raman monitoring of the atmosphere of the annealing process of nanodiamonds, in which the interconverting process of C-C bonds is unambiguously observed. We claim that this is a first experimental proof that the high temperature SERS effect can be preserved and applied in a chemical reaction at temperature above 500 °C. This versatile substrate also enables novel opportunities for observing growth, etching, and structure transformation of many 0D and 2D nano-materials.

On-Chip Sorting of Long Semiconducting Carbon Nanotubes for Multiple Transistors along an Identical Array

Ballistic transport and sub-10 nm channel lengths have been achieved in transistors containing one single-walled carbon nanotube (SWNT). To fill the gap between single-tube transistors and high-performance logic circuits for the replacement of silicon, large-area, high-density, and purely semiconducting (s-) SWNT arrays are highly desired. Here we demonstrate the fabrication of multiple transistors along a purely semiconducting SWNT array via an on-chip purification method. Water- and polymer-assisted burning from site-controlled nanogaps is developed for the reliable full-length removal of metallic SWNTs with the damage to s-SWNTs minimized even in high-density arrays. All the transistors with various channel lengths show large on-state current and excellent switching behavior in the off-state. Since our method potentially provides pure s-SWNT arrays over a large area with negligible damage, numerous transistors with arbitrary dimensions could be fabricated using a conventional semiconductor process, leading to SWNT-based logic, high-speed communication, and other next-generation electronic devices.

Stability of cervical esophagogastrostomy via hand-sewn anastomosis after esophagectomy for esophageal cancer

The aim of the present study is to evaluate the outcome of hand-sewn esophagogastric anastomosis during radical esophagectomy for esophageal cancer. The outcomes of 467 consecutive esophageal cancer patients who underwent cervical esophagogastric anastomosis using interrupted and double-layered sutures after radical esophagectomy via right thoracotomy or thoracoscopic surgery were retrospectively reviewed. Anastomotic leakage, including conduit necrosis, occurred in 11 of 467 patients (2.4%); 7 of 11 (63.6%) cases experienced only minor leakage, whereas the other four (36.4%) patients had major leakage that required surgical or radiologic intervention, including two patients of conduit necrosis. Anastomotic leakages were more frequently observed after retrosternal reconstruction compared with the posterior mediastinal route (P < 0.0001). The median time to healing of leakage was 40 days (range: 14-97 days). Two patients (2/467, 0.4%) died in the hospital due to sepsis caused by the leakage and conduit necrosis. Twelve patients (2.6%) developed anastomotic stenosis, which was improved by dilatation in all patients. Hand-sewn cervical esophagogastric anastomosis is a stable and highly safe method of radical esophagectomy for esophageal cancer.

IL4Rα and ADAM33 as genetic markers in asthma exacerbations and type-2 inflammatory endotype

BACKGROUND

Genetic markers of susceptibility to asthma exacerbations in adults remain unclear.

OBJECTIVE

To identify genetic markers of asthma exacerbations, particularly in patients with type-2 inflammatory endotype.

METHODS

In this observational study of patients enrolled in the Kinki Hokuriku Airway disease Conference multicenter study, frequency of exacerbations requiring systemic corticosteroids during 2 years after enrolment and associated risk factors was determined. For genetic marker analysis, interleukin-4 receptor α (IL4RA) rs8832 and a disintegrin and metalloprotease 33 (ADAM33) S_2 (rs528557), T_1 (rs2280091), T_2 (rs2280090), and V_4 (rs2787094) variants were included. Elevated serum periostin levels at enrolment (≥95 ng/mL, defined as type-2 inflammatory endotype) were considered in the analysis.

RESULTS

Among 217 patients who were successfully followed up for 2 years after enrolment, 60 patients showed at least one asthma exacerbation during the 2 years. Airflow limitation (%FEV₁ <80%) and recent exacerbations but not genetic variants were identified as risk markers of exacerbations. A total of 27 patients showed type-2 inflammatory endotype (serum periostin ≥95 ng/mL at enrolment) and subsequent exacerbations; risk factors in these patients were airflow limitation (odds ratio, 6.51; 95% confidence interval (CI): 2.37-18.6; P=.0003), GG genotype of IL4RA rs8832 (odds ratio, 4.01; 95% CI: 1.47-11.0; P=.007), and A allele of ADAM33 T_2 (odds ratio, 2.81; 95% CI: 1.05-7.67; P=.04) by multivariate analysis. In addition, GG genotype of IL4RA rs8832 was associated with type-2 endotype, whereas A allele of ADAM33 T_2 was associated with mixed type of eosinophilic/type-2 and neutrophilic inflammations.

CONCLUSIONS AND CLINICAL RELEVANCE

IL4RA and ADAM33 variants may be risk markers of asthma exacerbations in type-2 inflammatory endotype. Precise endotyping may facilitate the identification of genetic risk markers of asthma exacerbations.

Field emission and anode etching during formation of length-controlled nanogaps in electrical breakdown of horizontally aligned single-walled carbon nanotubes

We observe field emission between nanogaps and voltage-driven gap extension of single-walled carbon nanotubes (SWNTs) on substrates during the electrical breakdown process. Experimental results show that the gap size is dependent on the applied voltage and humidity, which indicates high controllability of the gap size by appropriate adjustment of these parameters in accordance with the application. We propose a mechanism for the gap formation during electrical breakdown as follows. After small gaps are formed by Joule heating-induced oxidation, SWNTs on the anode side are electrochemically etched due to physically-adsorbed water from the air and the enhanced electric field at the SWNT tips. Field emission is measured in a vacuum as a possible mechanism for charge transfer at SWNT gaps. The relationship between the field enhancement factor and geometric features of SWNTs explains both the voltage dependence of the extended gap size and the field emission properties of the SWNT gaps. In addition, the similar field-induced etching can cause damage to adjacent SWNTs, which possibly deteriorates the selectivity for cutting metallic pathways in the presence of water vapor.

Selective synthesis of large diameter, highly conductive and high density single-walled carbon nanotubes by a thiophene-assisted chemical vapor deposition method on transparent substrates

Selective synthesis of single-walled carbon nanotubes (SWNTs) with controlled properties is an important research topic for SWNT studies. Here we report a thiophene-assisted chemical vapor deposition (CVD) method to directly grow highly conductive SWNT thin films on substrates, including transparent ones. By adding low concentration thiophene into the carbon feedstock (ethanol), the as-prepared carbon nanotubes demonstrate an obvious up-shift in the diameter distribution while the single-walled structure is still retained. In the proposed mechanism, the change in the diameter is sourced from the increase in the carbon yield induced by the sulfur-containing compound. Such SWNTs are found to possess high conductivity with 95% SWNTs demonstrating on/off ratios lower than 100 in transistors. More importantly, it is further demonstrated that this method can be used to directly synthesize dense SWNT networks on transparent substrates which can be utilized as transparent conductive films (TCFs) with very high transparency. Such TCFs can be applied to fabricate a light modulating window as a proof-of-concept. The present work provides important insights into the growth mechanism of SWNTs and great potential for the preparation of TCFs with high scalability, easy operation and low cost.

Observation of motion of colloidal particles undergoing flowing Brownian motion using self-mixing laser velocimetry with a thin-slice solid-state laser

We achieved a highly sensitive method for observing the motion of colloidal particles in a flowing suspension using a self-mixing laser Doppler velocimeter (LDV) comprising a laser-diode-pumped thin-slice solid-state laser and a simple photodiode. We describe the measurement method and the optical system of the self-mixing LDV for real-time measurements of the motion of colloidal particles. For a condensed solution, when the light scattered from the particles is reinjected into the solid-state laser, the laser output is modulated in intensity by the reinjected laser light. Thus, we can capture the motion of colloidal particles from the spectrum of the modulated laser output. For a diluted solution, when the relaxation oscillation frequency coincides with the Doppler shift frequency, f_d, which is related to the average velocity of the particles, the spectrum reflecting the motion of the colloidal particles is enhanced by the resonant excitation of relaxation oscillations. Then, the spectral peak reflecting the motion of colloidal particles appears at 2×f_d. The spectrum reflecting the motion of colloidal particles in a flowing diluted solution can be measured with high sensitivity, owing to the enhancement of the spectrum by the thin-slice solid-state laser.

Selective removal of metallic single-walled carbon nanotubes in full length by organic film-assisted electrical breakdown

An organic film-assisted electrical breakdown technique is proposed to selectively remove metallic (m-) single-walled carbon nanotubes (SWNTs) in full length towards creation of pure semiconducting SWNT arrays which are available for the large-scale fabrication of field effect transistors (FETs). The electrical breakdown of horizontally aligned SWNT arrays embedded in organic films resulted in a maximum removal length of 16.4 μm. The removal of SWNTs was confirmed using scanning electron microscopy and Raman mapping measurements. The on/off ratios of FETs were improved up to ca. 10,000, similar to that achieved for in-air breakdown. The experimental results suggest that exothermic oxidation of organic films induces propagation of oxidation reaction, hence the long-length removal of m-SWNTs.

Effect of 34 kinds of traditional Japanese herbal medicines on prolongation of cardiac allograft survival

Herbal medicines have been used for over 3,000 years in Asian as alternative therapy for their variety effects and have recently become popular in Europe and the United States. In the last 30 years, Japanese herbal medicines were widely used for treatment of diseases after been recognized officially by Japanese government. In this study, we investigated the effect of 34 kinds of traditional Japanese herbal medicines on alloimmune responses in a murine model of cardiac allograft transplantation. CBA mice (H2(k)) underwent transplantation of a C57BL/6 (H2(b)) heart and received oral administration of 2 g/kg/d of the 34 kinds of herbal medicines from the day of transplantation until 7 days afterward. Naïve CBA mice rejected B6 cardiac grafts acutely (median survival time [MST], 7 days). CBA transplant recipients given 2 g/kg/d of Sairei-to (TJ-114) and Tokishakuyaku-san (TJ-23) had prolonged C57BL/6 allograft survival indefinitely (both MSTs > 100 days). Moreover, CBA transplant recipients given Seisinrensiin (TJ-111), Tokishigyakukagoshuyushokyoto (TJ-38), Rikkunshito (TJ-43), Maobushisaishinto (TJ-127), Ninjin-yoei-to (TJ-108), Ryokan-kyomi-shinge-nin-to (TJ-119), Inchingorei-san (TJ-117), Hochuekkito (TJ-41), Kihi-to (TJ-65), and Sinbu-to (TJ-30) had also prolonged C57BL/6 allograft survival significantly (MSTs of 28, 22, 16, 14, 14, 13, 12, 9.5, 9 and 9 days, respectively). However, none of other 22 kinds of herbal medicines could prolong the allograft survival. Furthermore, oral administration of 2 g/kg/d of Daikenchuto (TJ-100) induced sudden death (within 1 minute) in CBA mice. In conclusion, 12 kinds of Japanese herbal medicines prolonged allograft survival and one showed toxic effect in mice.

GLCCI1 variant accelerates pulmonary function decline in patients with asthma receiving inhaled corticosteroids

BACKGROUND

In steroid-naive patients with asthma, several gene variants are associated with a short-term response to inhaled corticosteroid (ICS) treatment; this has mostly been observed in Caucasians. However, not many studies have been conducted for other ethnicities. Here, we aimed to determine the relationship between the annual decline in forced expiratory flow volume in one second (FEV1 ) and the variant of the glucocorticoid-induced transcript 1 gene (GLCCI1) in Japanese patients with asthma receiving long-term ICS treatment, taking into account the effect of high serum periostin levels, a known association factor of pulmonary function decline and a marker of refractory eosinophilic/Th2 inflammation.

METHODS

In this study, 224 patients with asthma receiving ICS treatment for at least 4 years were enrolled. The effects of single-nucleotide polymorphisms (SNPs) in GLCCI1, stress-induced phosphoprotein 1 (STIP1), and T gene on the decline in FEV1 of 30 ml/year or greater were determined.

RESULTS

Besides the known contributing factors, that is, the most intensive treatment step, ex-smoking, and high serum periostin levels (≥95 ng/ml), the GG genotype of GLCCI1 rs37973, and not other SNPs, was independently associated with a decline in FEV1 of 30 ml/year or greater. When patients were stratified according to their serum periostin levels, the GG genotype of rs37973 was significantly associated with blood eosinophilia (≥250/μl) in the high serum periostin group.

CONCLUSIONS

A GLCCI1 variant is a risk factor of pulmonary function decline in Japanese patients with asthma receiving long-term ICS treatment. Thus, GLCCI1 may be associated with response to ICS across ethnicities.