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Proton-exchange-membrane hydrogen fuel cells (PEMFCs) are an important energy device for achieving a sustainable hydrogen society. Carbon-based catalysts used in PEMFCs' cathode can degrade significantly during operation-voltage shifts due to the carbon deterioration. The longer lifetime of the system is necessary for the further wide commercialization of PEMFCs. Therefore, carbon-free catalysts are required for PEMFCs. In this study, highly crystallized conducting Sb-doped SnO2 (Sb-SnO2) nanoparticles (smaller than 7 nm in size) were synthesized using an ozone-assisted hydrothermal synthesis. Pt nanoparticles were loaded on Sb-SnO2 supporting particles by polyol method to be "Pt/Sb-SnO2 catalyst". The Pt/Sb-SnO2 catalyst showed a high oxygen reduction reaction (ORR) mass activity (178.3 A g−1-Pt @ 0.9 V), compared to Pt/C (149.3 A g−1-Pt @ 0.9 V). In addition, the retention ratio from the initial value of electrochemical surface area (ECSA) during 100,000-voltage cycles tests between 1.0 V and 1.5 V, Pt/SnO2 and Pt/Sb-SnO2 catalyst exhibited higher stability (90% and 80%), respectively, than that of Pt/C catalyst (47%). Therefore, the SnO2 and Sb-SnO2 nanoparticles synthesized using this new ozone-assisted hydrothermal method are promising as carbon-free catalyst supports for PEMFCs. [ABSTRACT FROM AUTHOR]

The charging effect often complicates photoemission spectroscopy and x-ray absorption spectroscopy of an insulating material. Here, monolayer graphene was used as a conductive layer to prevent the charging effect of insulating substrates such as glass and LiNbO3. Charging-free spectra were obtained with various photon energies ranging from vacuum ultraviolet light to hard x-rays. This method could also be applied to photoemission spectroscopy of epoxy adhesives and to photoemission electron microscopy of an insulating film. Photoelectron transmissivities for the transferred graphene film were evaluated over a wide kinetic energy range from 29 to 7910 eV. A minimum transmissivity of ∼0.1 was found at a kinetic energy of ∼60 eV, which rose to 0.86 at 7910 eV. In terms of the kinetic energy dependence of the transmissivity, this method is especially suitable for conventional and hard x-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

This work demonstrates an enhancement of the external quantum efficiency (ηex) associated with the bulk photovoltaic effect (BPVE) resulting from the ballistic conduction of hot carriers in indium tin oxide/Mn-doped BiFeO3 (BFMO)/SrRuO3 capacitors in response to a blue–violet laser (λ = 405 nm). The effect of the BFMO film thickness on the short circuit current showed an abnormal trend in the case of films less than 100 nm thick. This result established that ballistic conduction was the dominant BPVE mechanism, although an effect of the BFMO/electrode interface on the photovoltaic properties may also have been a factor. BFMO films with thicknesses less than 100 nm also exhibited enhanced external quantum efficiency, demonstrating that the ballistic conduction of hot carriers enhanced ηex. [ABSTRACT FROM AUTHOR]

Immunoelectron microscopy was utilized to determine the protein products of atl gene to determine the role of the bacterolytic enzyme gene in wall perforation in penicillin G (PNG)-treated Staphylococcus aureus. Analysis of atl gene products during the autolytic process in PNG-treated Staphylococcus aureus indicated the presence of atl-generated wall hydrolases that promoted the formation of wall defects due to PNG. The wall defects created by atl gene products during the autolytic process released internal pressure which led to the formation of murosomes.

This study experimentally investigated the atomic structure of a single-crystalline Mn-doped BiFeO3 (BFO) thin film using X-ray fluorescence holography with synchrotron radiation. Bi atoms can be reconstructed from both Fe Kβ and Mn Kα fluorescence X-ray holograms, indicating Mn doping at B sites in ABO3-type perovskite structure. The fluorescence intensity of the 1st to 4th nearest Bi atoms around target Fe atoms was lower than those around Mn atoms, confirming the selective formation of Bi vacancies around Fe atoms. In contrast, the 5th to 8th nearest Bi atoms around Fe atoms showed higher intensities than those around Mn atoms, indicating that the Mn-doped BFO thin film had a double-perovskite-like structure. These results provide important information that helps elucidate the mechanism by which Mn doping modifies the conductivity of BFO. [ABSTRACT FROM AUTHOR]

Bismuth-layer-structured multiferroic Bi5Ti3FeO15 (BTFO15) (number of pseudoperovskite blocks, m=4) and natural-superlattice-structured Bi4Ti3O12-Bi5Ti3FeO15 (BIT-BTFO15) (m=3 or 4) thin films were prepared on (001)-oriented and (110)-oriented La-doped (3.73 wt %) SrTiO3 (La-STO) single-crystal substrates using pulsed laser deposition. X-ray diffraction patterns of these thin films on (001) La-STO single crystals indicated that the obtained thin films were single-phase (00l)-oriented layered perovskite, and that the BIT-BTFO15 (m=3 or 4) natural-superlattice structure was also obtained. On (110) La-STO single crystal, layered perovskite (11l)-oriented thin films were also obtained. Moreover, cross-sectional transmission electron microscope images of these thin films revealed four pseudoperovskite blocks (m=4) in the BTFO15 thin films, and an intergrowth structure of three and four pseudoperovskite blocks (m=3 or 4) in BIT-BTFO15 sandwiched by two (Bi2O2)2+ layers. In ferroelectric D-E hysteresis loop measurements, BTFO15 (m=4) and BIT-BTFO15 (m=3 or 4) thin films on (110) La-doped STO single crystals produced clear ferroelectric hysteresis loops with double remanent polarizations (2Pr) of 49 μC/cm2 and 44 μC/cm2, respectively. However, BTFO15 and BIT-BTFO15 thin films on (001) La-doped STO single crystals had paraelectric characteristics. These results demonstrate that the spontaneous polarization vectors of the BTFO15 and BIT-BTFO15 thin films were parallel to the a axis of their unit cells. [ABSTRACT FROM AUTHOR]

The stress influence of the structural and ferroelectric properties of polycrystalline BiFeO3 (BFO) thin films has been investigated using a membrane substrate for relaxing stress. Reciprocal space mapping (RSM) measurement has been performed to confirm the stress dependence of the crystal structure of polycrystalline BFO thin films on the Pt (200 nm)/TiO2 (50 nm)/SiO2 (600 nm)/Si (625 μm) substrate (stress-constrained BFO film) and the Pt (200 nm)/TiO2 (50 nm)/SiO2 (600 nm)/Si (15 μm) membrane substrate (stress-relaxed BFO film). The BFO thin films prepared by pulsed laser deposition were polycrystalline and mainly exhibit a texture with (001) and (110) plane orientations. From the RSM results, the crystal structure of the (001)-oriented domain changes from Pm monoclinic to Cm monoclinic or to R3c rhombohedral due to stress relaxation. Moreover, at room temperature as well as at 150 K, remanent polarization (Pr) increases and double coercive field (2Ec) decreases (in the latter case from 88 to 94 μC/cm2 and from 532 to 457 kV/cm, respectively) due to relaxing stress. The enhancement of ferroelectricity is attributed to the crystal structural deformation and/or transition and angle change between the polarization direction and film plane. [ABSTRACT FROM AUTHOR]

We have investigated effects of the postmetallization annealing and the electric field application on ferroelectric properties of BiFeO3 thin films prepared by chemical solution deposition. The leakage current is reduced after the postmetallization annealing although the crystallinity of the polycrystalline BiFeO3 is unchanged. In addition, double coercive field is reduced at about 90 kV/cm after the postmetallization annealing, while remanent polarization of 90 μC/cm2 is almost the same at 80 K. The postmetallization annealing is considered to lead the improvement of contact between the BiFeO3 film and the Pt electrode or the reduction in defects near the interface between the BiFeO3 film and the Pt electrode. Moreover, once a high electric field of 2.8 MV/cm is applied, the ferroelectric property of BiFeO3 thin films is dramatically improved. This effect may be due to the relaxation of pinned domains or locked polarizations in the BiFeO3 film. The postmetallization annealing and the electric field application are effective to improve ferroelectric properties of BiFeO3 thin films. [ABSTRACT FROM AUTHOR]

Bismuth-layer-structured multiferroic [Bi.sub.5][Ti.sub.3]Fe[O.sub.15] (BTFO15) and natural-superlattice-structured [Bi.sub.4][Ti.sub.3][O.sub.12]-[Bi.sub.5][Ti.sub.3]Fe[O.sub.15] (BIT-BTFO15) thin films are prepared on (001)-oriented and (110)-oriented La-doped SrTi[O.sub.3] (La-STO) single-crystal substrates by using pulsed laser deposition. The results have shown that the spontaneous polarization vectors of the BTFO15 and BIT-BTFO15 thin films are parallel to the a axis of their unit cells.

The stress influence of the structural and ferroelectric properties of polycrystalline BiFe[O.sub.3] (BFO) thin films is examined by using a membrane substrate for relaxing stress. The increase in the ferroelectricity is attributed to the crystal structural deformation and transition and angle change between the polarization direction and film plane.

The effects of the postmetallization annealing and the electric field application on ferroelectric properties of BiFe[O.sub.3] thin films prepared by chemical solution deposition are examined. The improvement in the ferroelectric property is due to the relaxation of pinned domains or locked polarizations in the BiFe[O.sub.3] film along with the application of postmetallization annealing and the electric field.