Pt/WO3 Nanoparticle-Dispersed Polydimethylsiloxane Membranes for Transparent and Flexible Hydrogen Gas Leakage Sensors.

Hydrogen gas is a promising, clean, and highly efficient energy source. However, to use combustible H2 gas safety, high-performance and safe gas leakage sensors are required. In this study, transparent and flexible platinum-catalyst-loaded tungsten trioxide (Pt/WO3) nanoparticle-dispersed membranes were prepared as H2 gas leakage sensors. The nanoparticle-dispersed membrane with a Pt:W compositional ratio of 1:13 was transparent and exhibited a sufficient color change in response to H2 gas. The membrane containing 0.75 wt.% of Pt/WO3 nanoparticles exhibited high transparency over a wide wavelength range and the largest transmittance change in response to H2 gas among the others. The heat treatment of the particles at 573 K provided sufficient crystallinity and an accessible area for a gasochromic reaction, resulting in a rapid and sensitive response to the presence of H2 gas. The lower limit of detection of the optimized Pt/WO3 nanoparticle-dispersed membrane by naked eye was 0.4%, which was one-tenth of the minimum explosive concentration. This novel membrane was transparent as well as flexible and exhibited a clear and rapid color response to H2. Therefore, it is an ideal candidate sensor for the safe and easy detection of H2 gas leakage.

Construction of Multilayer Films and Superlattice- and Mosaic-like Heterostructures of 2D Metal Oxide Nanosheets via a Facile Spin-Coating Process.

This study reports a design of a variety of nanostructured films of 2D oxide nanosheets. We systematically examined the deposition of perovskite-type Ca2Nb3O10- nanosheets by spin-coating their dimethyl sulfoxide dispersion. Neat and homogeneous monolayer tiling was attained on various substrates by selecting an optimum rotation speed, which was dependent on the nanosheet concentration. Repeating the optimized spin-coating process allowed for layer-by-layer deposition of the nanosheets into multilayer films with a designed layer number. Vertical superlattice heterostructures could also be assembled by alternately spin-coating the suspensions of Ca2Nb3O10- and Ti0.87O20.52- nanosheets. Furthermore, spin-coating of a mixed suspension of Ca2Nb3O10- and Ti0.87O20.52- nanosheets led to a mixed mosaic-like monolayer of these two nanosheets. The present study thus demonstrated spin-coating as a facile and powerful route to construct various nanostructures based on 2D oxide nanosheets.

Afterglow Properties and Trap-Depth Control in ZrO2:Ti, M (M = Ca2+, Y3+, Nb5+, W6+).

Ti-doped ZrO2 is a chemically stable and persistent luminescence material. Doping and co-doping is an effective approach for improving the afterglow properties of phosphors, but few studies have investigated the co-doping of ZrO2:Ti systems. This study aimed to synthesize ZrO2:Ti, M (M = Ca2+, Y3+, Ti single-doped, Nb5+, W6+) and evaluate the luminescent properties of the resulting materials, with a specific focus on the relationship between trap depth and the valence state of the co-doped cation. The ratio of the luminescent center to co-doped ion was optimized using the combinatorial approach, where 0.09 mol % Ti led to the best afterglow duration. The emission decay curves of each co-doped sample differed significantly, where a change in curvature was observed in the Ti single-doped and W6+ co-doped samples due to the presence of multiple traps. From the thermoluminescence glow curves, the trap originating in an oxygen vacancy with a peak at around 270 K was observed. The trap depth was dependent on electrostatic interactions between the trapped electrons and their surrounding cations, and thus related to the valence of the co-dopant. Overall, co-doping with high-valent cations led to improved afterglow duration.

Development of Measurement Tools for High-Throughput Experiments of Synchrotron Radiation XRD and XAFS on Powder Libraries.

We propose to minimize the sampling time for high-throughput measurements of powder X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) in synchrotron radiation. The conventional synchrotron radiation powder X-ray diffraction method requires filling of a capillary tube, but a structure-refining diffraction pattern could be obtained by transferring the crushed powder to a tape and rotating the cassette-tape tool by ±5° around the sample position. XAFS spectra could also be measured with the sample attached to the tape. The time required for sample preparation was greatly reduced, which made high-throughput experiments with powders in synchrotron radiation experiments more accessible.

Ethanol Gas Sensing by a Zn-Terminated ZnO(0001) Bulk Single-Crystalline Substrate.

Metal oxide semiconductor gas sensors have been widely studied for the selective detection of various gases with trace concentrations. The identification of the reaction scheme governing the gas sensing response is crucial for further development; however, the mechanism of ethanol (EtOH) gas sensing by ZnO is still controversial despite being one of the most intensively studied target gas and sensing material combinations. In this work, for the first time, the detailed mechanism of EtOH sensing by ZnO is studied by using a bulk single-crystalline substrate, which has a well-defined stoichiometry and atomic arrangement, as the sensing material. The sensing response is substantial on the ZnO substrate even with a millimeter-size thickness, and it becomes larger with resistance of the substrate. The large sensing response is described in terms of the adsorption/desorption of the oxygen species on the substrate surface, namely, oxygen ionosorption. The valence state of the ionosorbed oxygen involved in EtOH sensing is identified to be O2- regardless of the temperature. The increase in the sensing response with the temperature is attributed to the enhanced oxidation rate of the EtOH molecule on the surface as analyzed by pulsed-jet temperature-programmed desorption mass spectrometry, which has been newly developed for analyzing surface reactions in simulated working conditions.

Development of an Automatic, High-Throughput Structural Refinement Method Using Rietveld Analysis.

Automated structural analysis techniques are required to accelerate materials research. In this study, we developed an algorithm to automate Rietveld analysis, which is a method for crystal structure refinement using powder diffraction patterns. This algorithm features the repeated generation of a set of initial values, followed by one-shot refinement. Accurate results were obtained without any strategy for the sequence of refinement, as is often used in manual analysis. Implementation and testing of the automated algorithm provided fitting results that were comparable to those of manual analysis, even when inaccurate initial values for structural parameters were input. Moreover, the much shorter time was required for the developed automatic analysis method than for manual analysis. The developed method will likely facilitate the analysis of large amounts of diffraction data, allowing the accumulation of structural data that can enhance the efficacy of materials research.

Low-Temperature Spark Plasma Sintering of ZrW2-xMoxO8 Exhibiting Controllable Negative Thermal Expansion.

Molybdenum-doped zirconium tungstate (ZrW2-xMoxO8) has been widely studied because of its large isotropic coefficient of negative thermal expansion (NTE). However, low density and poor sinterability limit its production and application. In this study, relative density greater than 90% single-phase ZrW2-xMoxO8 (0.0 ≤ x ≤ 1.0) sintered bodies were fabricated by spark plasma sintering (500⁻600 °C for 10 min) using ZrW2-xMoxO7(OH)2·2H2O precursor powders as the starting material. High-temperature X-ray diffraction and thermomechanical analysis were used to investigate the change in the order⁻disorder phase transition temperature of the sintered materials; it gradually dropped from 170 °C at x = 0.0 to 78 °C at x = 0.5, and then to below room temperature at x ≥ 0.7. In addition, all sintered bodies exhibited NTE behavior. The NTE coefficient was controllable by changing the x value as follows: from -7.85 × 10-6 °C-1 (x = 0) to -9.01 × 10-6 °C-1 (x = 0.6) and from -3.22 × 10-6 °C-1 (x = 0) to -2.50 × 10-6 °C-1 (x = 1.0) before and after the phase transition, respectively. Rietveld structure refinement results indicate that the change in the NTE coefficient can be straightforwardly traced to the thermodynamic instability of the terminal oxygen atoms, which only have one coordination.

Elastocaloric effect in CuAlZn and CuAlMn shape memory alloys under compression.

This paper reports the elastocaloric effect of two Cu-based shape memory alloys: Cu68Al16Zn16 (CuAlZn) and Cu73Al15Mn12 (CuAlMn), under compression at ambient temperature. The compression tests were conducted at two different rates to approach isothermal and adiabatic conditions. Upon unloading at a strain rate of 0.1 s(-1) (adiabatic condition) from 4% strain, the highest adiabatic temperature changes (ΔTad) of 4.0 K for CuAlZn and 3.9 K for CuAlMn were obtained. The maximum stress and hysteresis at each strain were compared. The stress at the maximum recoverable strain of 4.0% for CuAlMn was 120 MPa, which is 70% smaller than that of CuAlZn. A smaller hysteresis for the CuAlMn alloy was also obtained, about 70% less compared with the CuAlZn alloy. The latent heat, determined by differential scanning calorimetry, was 4.3 J g(-1) for the CuAlZn alloy and 5.0 J g(-1) for the CuAlMn alloy. Potential coefficients of performance (COPmat) for these two alloys were calculated based on their physical properties of measured latent heat and hysteresis, and a COPmat of approximately 13.3 for CuAlMn was obtained.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

Combinatorial Synthesis of Epitaxial LiCoO2 Thin Films on SrTiO3(001) via On-Substrate Sintering of Li2CO3 and CoO by Pulsed Laser Deposition.

High-quality single-phase epitaxial LiCoO2 thin films are synthesized on 0.5 wt % Nb-doped SrTiO3(001) substrates by nanoscale alternate deposition of Li2CO3 and CoO as Li and Co sources, respectively, using a combinatorial pulsed laser deposition (PLD) technique. The formation of LiCoO2 thin films from these two sources results from the sintering reaction between Li2CO3 and CoO, which is commonly used in a bulk ceramics process, but simultaneously takes place on the substrate during the deposition at a temperature of 550 °C. Electrochemical characterization reveals that the charge/discharge property of LiCoO2 thin films as a cathode is severely sensitive to the nominal Li:Co composition ratio. The best-quality film shows an excellent discharge capacity comparable with the characteristic capacity of LiCoO2.

Design of seebeck coefficient measurement probe for powder library.

A thermoelectric evaluation system, attachable to our developed materials exploration system "M-ist Combi" based on the electrostatic spray deposition method, was designed and established for high-throughput to explore new candidate thermoelectric materials. The developed Seebeck coefficient measurement probe consists of two chromel-alumel thermocouples, and one of thermocouples is able to control its own temperature to ensure a temperature difference between thermocouples. The measurement time for each sample was about 5 s. This provides a stabilized time for the thermoelectric power for each sample. And, it was found that the Seebeck coefficient measurement probe could be used as a high-throughput screening tool for exploring candidate thermoelectric materials.

Establishment of pseudoternary LiO0.5-NiO-MnO2 phase diagram by combinatorial wet process.

A pseudoternary LiO0.5-NiO-MnO2 reaction phase diagram was established using a combinatorial high-throughput materials exploration process to find candidate electrode materials for lithium ion secondary batteries. Each powder library was prepared using our combinatorial wet process based on the electrostatic spray deposition method and results obtained at various firing temperatures in an air atmosphere and an oxide atmosphere. In the air atmosphere, newly composed single phase regions of a layered rock salt-type structure were only found around Li2MnO3 at 800 °C. On the other hand, in the oxide atmosphere, most of the powder library showed the multiphase of the spinel and layered rock salt type structure.

High-pressure combinatorial process integrating hot isostatic pressing.

A high-pressure combinatorial process integrating hot isostatic pressing (HIP) was developed by providing a reaction vessel with a high-pressure tightness based on a commercial flange. The reaction vessel can be used up to 200 MPa and 500 °C under HIP processing condition. Preparation of spinel-type MgAl2O4 from Mg(OH)2, Al(OH)3 and AlOOH was performed using the reaction vessel under 200 MPa and 500 °C as demonstration. The entire powder library was characterized using powder X-ray diffraction patterns, and the single phase of spinel-type MgAl2O4 was obtained from Mg(OH)2+Al(OH)3. These assessments corresponded with previously published data.

Effect of copper stress on cup lichens Cladonia humilis and C. subconistea growing on copper-hyperaccumulating moss Scopelophila cataractae at copper-polluted sites in Japan.

We investigated lichen species in the habitats of the copper (Cu)-hyperaccumulating moss Scopelophila cataractae and found that the cup lichens Cladonia subconistea and C. humilis grow on this moss. We performed X-ray fluorescence and inductively coupled plasma mass (ICP-MS) analysis of lichen samples and measured the visible absorption spectra of the pigments extracted from the samples to assess the effect of Cu stress on the cup lichens. The chlorophyll a/b ratio and degradation of chlorophyll a to pheophytin a were calculated from the spectral data. X-ray fluorescence analysis indicated that Cu concentrations in cup lichens growing on S. cataractae were much higher than those in control samples growing on non-polluted soil. Moreover, Cu microanalysis showed that Cu concentrations in parts of podetia of C. subconistea growing on S. cataractae increased as the substrate (S. cataractae) was approached, whereas those of C. humilis growing on S. cataractae decreased as the substrate was approached. This reflects the difference in the route of Cu ions from the source to the podetia. Furthermore, ICP-MS analysis confirmed that C. subconistea growing on S. cataractae was heavily contaminated with Cu, indicating that this lichen is Cu tolerant. We found a significant difference between the visible absorption spectra of pigments extracted from the Cu-contaminated and control samples. Hence, the spectra could be used to determine whether a cup lichen is contaminated with Cu. Chlorophyll analysis showed that cup lichens growing on S. cataractae were affected by Cu stress. However, it also suggested that the areas of dead moss under cup lichens were a suitable substrate for the growth of the lichen. Moreover, it suggested that cup lichens had allolepathic effects on S. cataractae; it is likely that secondary metabolites produced by cup lichens inhibited moss growth.

Spectral properties of the Cu-hyperaccumulating moss Scopelophilacataractae.

To determine the characteristics of a Cu-hyperaccumulating moss Scopelophilacataractae and the influence of Cu on its structure and on chlorophyll (Chl), we measured reflectance and fluorescence (FL) spectra of S.cataractae samples with different Cu concentrations before and after wetting and the absorption spectra of Chl extracted from these samples. We found relationships between the spectral properties and Cu concentration. These relationships can be explained as follows. The higher the Cu concentration is, the lower is the plasticity of the cell wall, and the smaller is the increase in illuminated area due to the opening of the leaves after wetting. This results in a smaller increase in absorption and smaller decrease in reabsorption of the FL by Chl itself, and accordingly, a smaller increase in the FL band of Chl after wetting. Moreover, we found that the Chl concentration in S.cataractae is much higher than that in other common mosses and is correlated with an increase in the FL band of Chl after wetting. The remarkable increase in FL seen in S.cataractae and the slight increase in FL observed in other common mosses after wetting can be explained based on these findings.

Charge-discharge properties of a layered-type Li(Ni,Co,Ti)O2 powder library.

A powder library of layered Li(Ni,Co,Ti)O2 (Ni ≤ 0.8, Ti ≤ 0.2) compounds was prepared by electrostatic spray deposition. From powder x-ray diffraction patterns, most of the powder library sintered at 700 ○C was indexed as a single phase belonging to the space group R[Formula: see text]m. These results were almost identical to those obtained from a study by combinatorial exploration. We investigated the charge-discharge characteristics of the Li(Ni,Co,Ti)O2 powder library in a voltage range from 4.2 to 2.8 V at 1 C and found favorable cycling properties in the LiNi x Co0.9-x Ti0.1O2 (0 ≤x ≤ 0.6) compounds.

A comparison of the efficacy and tolerability of tadalafil 10 mg and 20 mg in Japanese patients with severe erectile dysfunction.

INTRODUCTION: Tadalafil is a phosphodiesterase type 5 inhibitor with documented efficacy in the treatment of erectile dysfunction (ED). AIM: To compare the efficacy and tolerability of tadalafil 10 mg and 20 mg in men with severe ED. METHODS: A prespecified subgroup analysis was conducted to compare the efficacy of tadalafil 10 and 20 mg measured by the International Index of Erectile Function (IIEF) erectile function (EF) domain and Sexual Encounter Profile (SEP) among patients with severe ED (EF domain score = 1-10) in a Japanese placebo-controlled study (PCT). We also analyzed the efficacy of the two doses in men with severe ED post hoc by pooling data from three tadalafil clinical trials that evaluated these doses using a similar study design (three placebo-controlled trials), and evaluated (post hoc) the presence of organic comorbidities in patients with different levels of response to tadalafil 10 or 20 mg. MAIN OUTCOME MEASURES: Mean change in the IIEF-EF domain and mean per-patient changes in percent "yes" responses to SEP Question 2 (SEP2) and Question 3 (SEP3). RESULTS: Patients with severe ED in the Japanese study experienced numerically greater increases (improvements) when taking tadalafil 20 mg compared with 10 mg in the IIEF-EF domain (14.3 vs. 12.4; P = 0.355), SEP2 (60% vs. 57%; P = 0.781), and SEP3 (61% vs. 49%, P = 0.196). When sufficiently powered, these observations reached statistical significance in the three PCTs: patients with severe ED experienced greater increases when taking tadalafil 20 mg compared with 10 mg in the IIEF-EF domain (13.6 vs. 10.4; P = 0.014) and SEP3 (56% vs. 43%, P = 0.019). Both doses were well tolerated. CONCLUSIONS: Patients with severe ED, and especially those with an organic comorbidity, may derive greater clinical benefits from tadalafil 20 mg compared with 10 mg.