Control of optical bandgap energy and optical absorption coefficient by geometric parameters in sub-10 nm silicon-nanodisc array structure

A sub-10 nm, high-density, periodic silicon-nanodisc (Si-ND) array has been fabricated using a new top-down process, which involves a 2D array bio-template etching mask made of Listeria-Dps with a 4.5 nm diameter iron oxide core and damage-free neutral-beam etching (Si-ND diameter: 6.4 nm). An Si-ND array with an SiO(2) matrix demonstrated more controllable optical bandgap energy due to the fine tunability of the Si-ND thickness and diameter. Unlike the case of shrinking Si-ND thickness, the case of shrinking Si-ND diameter simultaneously increased the optical absorption coefficient and the optical bandgap energy. The optical absorption coefficient became higher due to the decrease in the center-to-center distance of NDs to enhance wavefunction coupling. This means that our 6 nm diameter Si-ND structure can satisfy the strict requirements of optical bandgap energy control and high absorption coefficient for achieving realistic Si quantum dot solar cells.     

Amorphous nanosilicas induce consumptive coagulopathy after systemic exposure

We previously reported that well-dispersed amorphous nanosilicas with particle size 70 nm (nSP70) penetrate skin and produce systemic exposure after topical application. These findings underscore the need to examine biological effects after systemic exposure to nanosilicas. The present study was designed to examine the biological effects. BALB/c mice were intravenously injected with amorphous nanosilicas of sizes 70, 100, 300, 1000 nm and then assessed for survival, blood biochemistry, and coagulation. As a result, injection of nSP70 caused fatal toxicity, liver damage, and platelet depletion, suggesting that nSP70 caused consumptive coagulopathy. Additionally, nSP70 exerts procoagulant activity in vitro associated with an increase in specific surface area, which increases as diameter reduces. In contrast, nSP70-mediated procoagulant activity was absent in factor XII-deficient plasma. Collectively, we revealed that interaction between nSP70 and intrinsic coagulation factors such as factor XII, were deeply related to nSP70-induced harmful effects. In other words, it is suggested that if interaction between nSP70 and coagulation factors can be suppressed, nSP70-induced harmful effects may be avoided. These results would provide useful information for ensuring the safety of nanomaterials (NMs) and open new frontiers in biological fields by the use of NMs.     

Improvement of dry float–sink separation of smaller sized spheres by reducing the fluidized bed height

In this study, the influence of the fluidized bed height on the float–sink of different sized spheres in a gas–solid fluidized bed was investigated. Fluidized beds with heights h = 200, 150, 100 and 50 mm were prepared using a cylindrical column of inner diameter = 290 mm and a mixture of zircon sand and iron powder as the fluidized medium. Float–sink experiments were carried out using density adjusted spheres of diameter D_sp = 40, 30, 20 and 10 mm. It was found that the float–sink performance at D_sp ?20 mm is not affected by the height of the bed, and the sharpness of separation (the density range where spheres neither float nor sink completely) is less than or equal to 200 kg/m³. In the case of D_sp = 10 mm, the sharpness of separation is a larger value (1100 kg/m³ at h = 200 mm), whereas it decreases with decreasing h and is 400 kg/m³ at h = 50 mm. The fluctuation of the surface height of the fluidized bed was visually recorded. The fluctuation is reduced by reducing h. The fluctuation vs. h correlates with the sharpness of separation at D_sp = 10 mm vs. h. These results indicate that the dry float–sink separation of smaller sized spheres is improved as the fluctuation of fluidized bed surface is decreased by reducing the fluidized bed height.     

Crystal growth and scintillation properties of Ce-doped sodium calcium lutetium complex fluoride

0.1%, 0.5%, 1% and 3% Ce doped scintillation crystals based on NaF-CaF₂-LuF₃ solid solutions were grown from the melt using Micro-Pulling-Down (μ-PD) method. The grown crystals were transparent and their transmittance was approximately 80% for the wavelengths longer than 320 nm. Concerning the scintillation properties, radio-luminescence peaks of the crystals were detected at approximately 330 nm. The light yield of the crystals was also measured using γ-ray (¹³⁷Cs and ²²Na) as the excitation source.     

Electronic structure of the buried interface between an organic semiconductor, N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), and metal surfaces

The electronic structures of buried interfaces between an organic semiconductor, N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) and metal surfaces of Au, Ag, Al and Ca were examined by the new experimental method that we have developed recently. In this method the energy levels at the organic/metal interface can be examined without changing the film thickness and related physical parameters e.g., the vacuum levels of the sample in contrast to the widely-used thickness-dependent photoemission experiments. The results were discussed in view of large interfacial dipole moment of the TPD and metal (Au and Ag) contacts.     

Nickel-free stainless steel avoids neointima formation following coronary stent implantation

SUS316L stainless steel and cobalt–chromium and platinum–chromium alloys are widely used platforms for coronary stents. These alloys also contain nickel (Ni), which reportedly induces allergic reactions in some subjects and is known to have various cellular effects. The effects of Ni on neointima formation after stent implantation remain unknown, however. We developed coronary stents made of Ni-free high-nitrogen austenitic stainless steel prepared using a N₂-gas pressurized electroslag remelting (P-ESR) process. Neointima formation and inflammatory responses following stent implantation in porcine coronary arteries were then compared between the Ni-free and SUS316L stainless steel stents. We found significantly less neointima formation and inflammation in arteries implanted with Ni-free stents, as compared to SUS316L stents. Notably, Ni²⁺ was eluted into the medium from SUS316L but not from Ni-free stainless steel. Mechanistically, Ni²⁺ increased levels of hypoxia inducible factor protein-1α (HIF-1α) and its target genes in cultured smooth muscle cells. HIF-1α and their target gene levels were also increased in the vascular wall at SUS316L stent sites but not at Ni-free stent sites. The Ni-free stainless steel coronary stent reduces neointima formation, in part by avoiding activation of inflammatory processes via the Ni-HIF pathway. The Ni-free-stainless steel stent is a promising new coronary stent platform.     

Fabrication of dielectric nanocubes in ordered structure by capillary force assisted self-assembly method and their piezoresponse properties

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT/ST nanocubes mixture were directly fabricated on Si and Pt-coated Si substrates using a capillary force assisted assembly method. The morphology of self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop multilayer and monolayer regions at the surface of substrates. The elemental mapping of the structure consisting of the nanocubes mixture was also investigated by transmission electron microscopy (TEM) with an energy dispersive X-ray spectroscopy (EDX). It was revealed that BT and ST nanocubes coexisted homogeneously in the structure and had possibility to be arranged in order to each other. The piezoresponse properties obtained by scanning probe microscopy (SPM) indicated that the hetero-interface between BT and ST nanocubes would introduce anomaly in piezoelectric properties.     

Capacitance distribution of Ni-Nb-Zr-H glassy alloys

Capacitance distribution of {(Ni(0.6)Nb(0.4)(1-x)Zrx}(100-y)-Hy (x = 0.30, 0.35, 0.40, 0.45 and 0.50, 0 < or = y < or = 20) glassy alloy ribbons was carried out by ac impedance analysis at frequency of 1 kHz, in terms of a distributed constant equivalent circuit. The capacitance can be represented by oblique contour lines. The highest capacitance (1-11 microF) could be found near the point when x = 0.40, y = 10, which is a composition occurring room-temperature Coulomb oscillation, while capacitance of the composition (x = 0.35, y = 4) occurring ballistic transport was around 0.8 microF. The capacitance difference would be explained by an effect of hydrogen localization derived from morphology of distorted Zr-centered icosahedral Zr5Ni5Nb3 clusters and ideal Ni-centered clusters. The electrocapillarity equation showed that the specific capacitance between two electrodes increases parabolic with decreasing the distance, as a polarized glutinous liquid.     

Enhancing the Humidity Sensitivity of Ga2O3/SnO2 Core/Shell Microribbon by Applying Mechanical Strain and Its Application as a Flexible Strain Sensor

The humidity sensitivity of a single β‐Ga₂O₃/amorphous SnO₂ core/shell microribbon on a flexible substrate is enhanced by the application of tensile strain and increases linearly with the strain. The strain‐induced enhancement originates from the increase in the effective surface area where water molecules are adsorbed. This strain dependence of humidity sensitivity can be used to monitor the external strain. The strain sensing of the microribbon device under various amounts of mechanical loading shows excellent reliability and reproducibility with a gauge factor of ?41. The flexible device has high potential to detect both humidity and strain at room temperature. These findings and the mechanism involved are expected to pave the way for new flexible strain and multifunctional sensors.