Enhancement of visible light-induced hydrophilicity on nitrogen and sulfur-codoped TiO2 thin films

We fabricated N, S-codoped, N-doped, S-doped TiO₂ anatase thin films by a radio-frequency (RF) sputtering method and evaluated the photoelectrochemical and photoinduced hydrophilic activities. The N, S-codoped TiO₂ thin film showed obviously higher activities than either the N-doped or S-doped TiO₂ under visible light irradiation. The photoinduced hydrophilic activity of the N, S-codoped TiO₂ was also greater than that of the undoped TiO₂ even under fluorescent light bulb, which contained both visible and UV lights. The high activities of the N, S-codoped TiO₂ could be attributed to the hybridization of the introduced N 2p and S 3p, which was supported by the results of ab initio calculations.     

Luminescent properties of ZnCdSe/ZnMnSe superlattices

Zn_0.91Cd_0.09Se/Zn_0.82Mn_0.18Se superlattices were grown by molecular beam epitaxy with well layer thicknesses of 4–35 Å and a barrier layer thickness of 12 Å. Magneto-luminescence was measured in the Faraday geometry in the temperature range of 10–100 K. The Zeeman shifts of the excitonic emissions from the superlattices were analyzed as a function of well layer thickness by using Kronig–Penny model, in which the conduction and valence band offsets were modulated by external magnetic field. Paramagnetism enhancement of ZnMnSe at the interface with nonmagnetic layer and Mn diffusion at the heterointerface were taken into consideration. The Mn diffusion showed a crucial effect on the Zeeman shift of the superlattice system.     

Tailoring organic heterojunction interfaces in bilayer polymer photovoltaic devices

In an ideal model, a p-n junction is formed by two stacked slabs of semiconductors. Although the construction of actual devices is generally more complex, we show that such a simple method can in fact be applied to the formation of organic heterojunctions. Two films of the organic semiconductors poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) can be connected by a simple film-transfer method without disturbing their flat surfaces. Each film can further be modified with a surface-segregated monolayer to tune the strength and direction of the surface dipole moment. Using this method, we fabricated bilayer organic photovoltaic devices with interfacial dipole moments that were selected to align the energy levels at the heterojunction. The open-circuit voltages of the P3HT/PCBM devices could be tuned over a wide range between 0.3 and 0.95 V, indicating that, even if the same combination of bulk materials is used, the interfacial properties drastically alter the performance of organic photovoltaic devices.     

Experimental investigation of charge carrier transport in organic thin-film transistors with "buried surface layers"

We studied how the layers with different transport properties buried inside a semiconductor material affect the characteristics of organic thin film transistors (OTFT) using a well-defined multilayered structure fabricated by a contact film transfer method that we recently developed (ACS Appl. Mater. Interfaces 1, 2660 (2009)). A simple model with the charge distribution in the organic semiconductor film, the mobility dependence on the charge density, and the buried surface layers with a high mobility successfully reproduced the experimental mobility dependence on the thickness of the spin-coated films and the gate voltage. These results demonstrated that charge transport layers located far from the dielectric interface could contribute significantly to the total current in OTFTs.     

Simulation of I–V characteristics of a PV module with shaded PV cells

The authors are studying a diagnostic method of a PV power generating system. We consider that the change of I–V characteristics can be utilized for the diagnosis. However, the report on the change of I–V characteristics is very little. In this paper, we investigate the relation between the output lowering due to shaded PV cells and the change of I–V characteristics, utilizing the computer simulation. It was proven from the simulation that I–V characteristics are changed by the condition of the shadow, which covered the module. The change of I–V characteristics of a PV module with shaded PV cells is discussed by the shift of the avalanche breakdown voltage of shaded PV cells.     

Polyarteritis nodosa (PN) complicated with unilateral exophthalmos

A 58-year-old woman suddenly developed right exophthalmos. A CT scan of her orbit revealed an increase in volume and density of extraocular muscles and intraorbital soft tissues that resembled exophthalmos in Graves' disease. The exophthalmos gradually improved without treatment. Two months later she developed mononeuritis multiplex in her limbs, and then showed a sudden onset of swelling of her right calf. Sural nerve biopsy was performed and the diagnosis of polyarteritis nodosa (PN) was established from the histological findings. A rare case of PN with exophthalmos is herein reported with a review of the literature.     

Magnetic ordering in superconducting YBa2(Cu1−xFex)3Oy oxide

Magnetic susceptibility measurement and the zero-field muon-spin-relaxation experiment have been made for the YBa₂(Cu_1−xFe_x)₃O_y system. The susceptibility has been measured in the field strong enough for the magnetic flux to penetrate the superconductor and the resultant temperature dependence has demonstrated the field cooled effect and a cusp at low temperatures below T_c. The cusp has been observed when the high field has been applied. The dynamical depolarization rate of the muon obtained by the muon-spin-relaxation experiment has shown the maximum at the same temperature as the cusp. The results suggest that the spin glass freezing of localized magnetic moment takes place at the temperature of the cusp, which is consistent with the previous Mössbauer effect experiments. The magnetic phase diagram for the system has been obtained.     

Basic research on aw-AC/PLGA composite scaffolds for bone tissue engineering

Recently, it has become important to develop effective material to be used as scaffolds for bone tissue engineering. Therefore, we fabricated new three-dimensional (3D) scaffolds consisting of biodegradable poly(d,l-lactide-co-glycolic acid)(PLGA)(75/25) with anti-washout type AC (aw-AC) particles. The aim of this study was to evaluate this new scaffold concerning its basic properties and biocompatibility. The obtained scaffolds were observed with scanning electron microscopy (SEM), and measured for porosity, shrinkage and biaxial compressive strengths. It was shown that PLGA with aw-AC composite scaffolds (aw-AC/PL) showed a greater strength and stability than PLGA scaffolds (PL). Also, the mass reduction of aw-AC/PL during incubation decreased compared to that of PL. The number of MC3T3-E1 cell in PL and aw-AC/PL was counted at 5 h, 1 week, and 2 weeks after cell seeding. As a result, aw-AC/PL exhibited a superior performance in terms of attachment and proliferation compared to PL. Histologically, aw-AC/PL showed an excellent response toward soft tissues. Therefore, it was shown that aw-AC/PL was more biocompatible than PL. In conclusion, it was strongly suggested that aw-AC/PL was more useful for cell transplantation than PL in bone tissue engineering.