To date, thousands of publications have reported chemical vapor deposition growth of “single layer” graphene, but none of them has described truly single layer graphene over large area because a ...fraction of the area has adlayers. It is found that the amount of subsurface carbon (leading to additional nuclei) in Cu foils directly correlates with the extent of adlayer growth. Annealing in hydrogen gas atmosphere depletes the subsurface carbon in the Cu foil. Adlayer‐free single crystal and polycrystalline single layer graphene films are grown on Cu(111) and polycrystalline Cu foils containing no subsurface carbon, respectively. This single crystal graphene contains parallel, centimeter‐long ≈100 nm wide “folds,” separated by 20 to 50 µm, while folds (and wrinkles) are distributed quasi‐randomly in the polycrystalline graphene film. High‐performance field‐effect transistors are readily fabricated in the large regions between adjacent parallel folds in the adlayer‐free single crystal graphene film.
Adlayer‐free large‐area single‐crystal graphene film is grown on Cu(111) foil by chemical vapor deposition. Such graphene film contains parallel long graphene folds up to centimeters in length, with a separation of ≈20–50 µm and a width of ≈80–100 nm, which allows straightforward fabrication of integrated high‐performance electronic devices within the regions between the folds.
Recent graphene research has triggered enormous interest in new two-dimensional ordered crystals constructed by the inclusion of elements other than carbon for bandgap opening. The design of new ...multifunctional two-dimensional materials with proper bandgap has become an important challenge. Here we report a layered two-dimensional network structure that possesses evenly distributed holes and nitrogen atoms and a C2N stoichiometry in its basal plane. The two-dimensional structure can be efficiently synthesized via a simple wet-chemical reaction and confirmed with various characterization techniques, including scanning tunnelling microscopy. Furthermore, a field-effect transistor device fabricated using the material exhibits an on/off ratio of 10(7), with calculated and experimental bandgaps of approximately 1.70 and 1.96 eV, respectively. In view of the simplicity of the production method and the advantages of the solution processability, the C2N-h2D crystal has potential for use in practical applications.
The formation of 2D polyaniline (PANI) has attracted considerable interest due to its expected electronic and optoelectronic properties. Although PANIwas discovered over 150 y ago, obtaining an ...atomically well-defined 2D PANI framework has been a longstanding challenge. Here, we describe the synthesis of 2D PANI via the direct pyrolysis of hexaaminobenzene trihydrochloride single crystals in solid state. The 2D PANI consists of three phenyl rings sharing six nitrogen atoms, and its structural unit has the empirical formula of C₃N. The topological and electronic structures of the 2D PANI were revealed by scanning tunneling microscopy and scanning tunneling spectroscopy combined with a first-principle density functional theory calculation. The electronic properties of pristine 2D PANI films (undoped) showed ambipolar behaviors with a Dirac point of −37 V and an average conductivity of 0.72 S/cm. After doping with hydrochloric acid, the conductivity jumped to 1.41 × 10³ S/cm, which is the highest value for doped PANI reported to date. Although the structure of 2D PANI is analogous to graphene, it contains uniformly distributed nitrogen atoms for multifunctionality; hence, we anticipate that 2D PANI has strong potential, from wet chemistry to device applications, beyond linear PANI and other 2D materials.
The structure of graphene grown in chemical vapor deposition (CVD) is sensitive to the growth condition, particularly the substrate. The conventional growth of high‐quality graphene via the ...Cu‐catalyzed cracking of hydrocarbon species has been extensively studied; however, the direct growth on noncatalytic substrates, for practical applications of graphene such as current Si technologies, remains unexplored. In this study, nanocrystalline graphene (nc‐G) spirals are produced on noncatalytic substrates by inductively coupled plasma CVD. The enhanced out‐of‐plane electrical conductivity is achieved by a spiral‐driven continuous current pathway from bottom to top layer. Furthermore, some neighboring nc‐G spirals exhibit a homogeneous electrical conductance, which is not common for stacked graphene structure. Klein‐edge structure developed at the edge of nc‐Gs, which can easily form covalent bonding, is thought to be responsible for the uniform conductance of nc‐G aggregates. These results have important implications for practical applications of graphene with vertical conductivity realized through spiral structure.
Nanocrystalline graphene spirals are successfully produced by the direct growth on noncatalytic substrates, which exhibits excellent out‐of‐plane electrical conductivity for interconnect technology. The superior vertical conductivity is achieved by covalently connecting one atomic layer and the local density of states developed in the spiral's core.
The interfacial dipolar polarization in inverted structure polymer solar cells, which arises spontaneously from the absorption of ethanolamine end groups, such as amine and hydroxyl groups on ...ripple‐structure zinc oxide (ZnO‐R), lowers the contact barrier for electron transport and extraction and leads to enhanced electron mobility, suppression of bimolecular recombination, reduction of the contact resistance and series resistance, and remarkable enhancement of the power conversion efficiency.
Polycyclic aromatic hydrocarbons (PAHs) are key components of organic electronics. The electronic properties of these carbon‐rich materials can be controlled through doping with heteroatoms such as B ...and N, however, few convenient syntheses of BN‐doped PAHs have been reported. Described herein is the rationally designed, two‐step syntheses of previously unknown ixene and BN‐doped ixene (B2N2‐ixene), and their characterizations. Compared to ixene, B2N2‐ixene absorbs longer‐wavelength light and has a smaller electrochemical energy gap. In addition to its single‐crystal structure, scanning tunneling microscopy revealed that B2N2‐ixene adopts a nonplanar geometry on a Au(111) surface. The experimentally obtained electronic structure of B2N2‐ixene and the effect of BN‐doping were confirmed by DFT calculations. This synthesis enables the efficient and convenient construction of BN‐doped systems with extended π‐conjugation that can be used in versatile organic electronics applications.
A forgotten curiosity: Ixene, a compound that was previously named but never prepared, and its BN‐doped derivative (B2N2‐ixene) were synthesized in two steps from simple intermediates. The effect of BN‐doping, or substitution of carbon–carbon bonds with isoelectronic boron–nitrogen bonds, was elucidated both experimentally and theoretically.
Although the presence of ischemia is a key prognostic factor in patients with coronary artery disease, the presence of high-risk plaque characteristics (HRPC) is also associated with increased risk ...of cardiovascular events. Limited data exist regarding the prognostic implications of combined information on physiological stenosis severity assessed by fractional flow reserve (FFR) and plaque vulnerability by coronary computed tomography angiography (CTA)–defined HRPC.
The current study aimed to evaluate the: 1) association between physiological stenosis severity and coronary CTA-defined HRPC; and 2) prognostic implications of coronary CTA-defined HRPC according to physiological stenosis severity in patients with coronary artery disease.
A total of 772 vessels (299 patients) evaluated by both coronary CTA and FFR were analyzed. The presence and number of HRPC (minimum lumen area <4 mm2, plaque burden ≥70%, low attenuating plaque, positive remodeling, napkin-ring sign, or spotty calcification) were assessed using coronary CTA images. The risk of vessel-oriented composite outcome (VOCO) (a composite of vessel-related ischemia-driven revascularization, vessel-related myocardial infarction, or cardiac death) at 5 years was compared according to the number of HRPC and FFR categories.
The proportion of lesions with ≥3 HRPC was significantly decreased according to the increase in FFR values (58.6%, 46.5%, 36.8%, 15.7%, and 3.5% for FFR ≤0.60, 0.61 to ≤0.70, 0.71 to ≤0.80, 0.81 to ≤0.90, and >0.90, respectively; overall p value <0.001). Both FFR and number of HRPC showed significant association with the estimated risk of VOCO (p = 0.008 and p = 0.023, respectively). In the FFR >0.80 group, lesions with ≥3 HRPC showed significantly higher risk of VOCO than those with <3 HRPC (15.0% vs. 4.3%; hazard ratio: 3.964; 95% confidence interval: 1.451 to 10.828; p = 0.007). However, there was no significant difference in the risk of VOCO according to HRPC in the FFR ≤0.80 group. By multivariable analysis, the presence of ≥3 HRPC was independently associated with the risk of VOCO in the FFR >0.80 group.
Physiological stenosis severity and the number of HRPC were closely related, and both components had significant association with the risk of clinical events. However, the prognostic implication of HRPC was different according to FFR. Integration of both physiological stenosis severity and plaque vulnerability would provide better prognostic stratification of patients than either individual component alone, especially in patients with FFR >0.80. (Clinical Implication of 3-vessel Fractional Flow Reserve 3V FFR-FRIENDS study; NCT01621438)
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Abstract Background The prognostic impact of microvascular status in patients with high fractional flow reserve (FFR) is not clear. Objectives The goal of this study was to investigate the ...implications of coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) in patients who underwent FFR measurement. Methods Patients with high FFR (>0.80) were grouped according to CFR (≤2) and IMR (≥23 U) levels: group A, high CFR with low IMR; group B, high CFR with high IMR; group C, low CFR with low IMR; and group D, low CFR with high IMR. Patient-oriented composite outcome (POCO) of any death, myocardial infarction, and revascularization was assessed. The median follow-up was 658 days (interquartile range: 503.8 to 1,139.3 days). Results A total of 313 patients (663 vessels) were assessed with FFR, CFR, and IMR. Correlation ( r = 0.201; p < 0.001) and categorical agreement (kappa value = 0.178; p < 0.001) between FFR and CFR were modest. Low CFR was associated with higher POCO than high CFR (p = 0.034). There were no significant differences in clinical and angiographic characteristics among groups. Patients with high IMR with low CFR had the highest POCO (p = 0.002). Overt microvascular disease (p = 0.008), multivessel disease (p = 0.033), and diabetes mellitus (p = 0.033) were independent predictors of POCO. Inclusion of a physiological index significantly improved the discriminant function of a predictive model (relative integrated discrimination improvement 0.467 p = 0.037; category-free net reclassification index 0.648 p = 0.007). Conclusions CFR and IMR improved the risk stratification of patients with high FFR. Low CFR with high IMR was associated with poor prognosis. (Clinical, Physiological and Prognostic Implication of Microvascular Status; NCT02186093 )
Interactions between monatomic ions and water molecules are fundamental to understanding the hydration of complex polyatomic ions and ionic process. Among the simplest and well-established ...ion-related reactions is dissolution of salt in water, which is an endothermic process requiring an increase in entropy. Extensive efforts have been made to date; however, most studies at single-ion level have been limited to theoretical approaches. Here, we demonstrate the salt dissolution process by manipulating a single water molecule at an under-coordinated site of a sodium chloride film. Manipulation of molecule in a controlled manner enables us to understand ion-water interaction as well as dynamics of water molecules at NaCl interfaces, which are responsible for the selective dissolution of anions. The water dipole polarizes the anion in the NaCl ionic crystal, resulting in strong anion-water interaction and weakening of the ionic bonds. Our results provide insights into a simple but important elementary step of the single-ion chemistry, which may be useful in ion-related sciences and technologies.
Nickel coating of reinforcing fibers via electroless plating can provide superior properties to polymer composites, particularly for radar stealth, although its effect on thermomechanical properties ...and thermal cycling response are relatively unverified. Thermal cycling of strained nickel‐coated glass fiber epoxy laminates was performed to evaluate its effect through in‐plane shear mechanical testing and fiber‐matrix interface region microscopic observations. Laminates were subjected to 4000 cycles of thermal conditioning (regular and strained). Subsequent in‐plane shear tensile tests revealed a ~10% increase in their ultimate shear strength, which was credited to polymer relaxation and increased plastic energy storage capacity. Atomic force microscopy in force modulation mode showed the most significant fiber‐matrix interface region changes for strained thermal cycled specimens, which we attribute to their higher stress during conditioning and plastic deformation. A relatively short fiber‐matrix interface region length was observed, which we attribute to the lower surface energy of Ni‐glass fiber. Thermomechanical analysis (TMA) revealed a glass‐transition temperature range of 71–110°C, and coefficients of thermal expansion (CTE) were evaluated for several laminate configurations.
Nickel‐coated glass fiber epoxy laminates were subjected to 4000 cycles of thermal conditioning (regular and strained). In‐plane shear tensile tests on conditioned specimens revealed a 10% increase in ultimate shear strength. Changes to the fiber‐matrix region were observed with atomic force microscopy in force modulation mode.
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