Suppressed Lattice Disorder for Large Emission Enhancement and Structural Robustness in Hybrid Lead Iodide Perovskite Discovered by High-Pressure Isotope Effect

The soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. Here, using the methylammonium lead iodide as a representative exploratory platform, it is observed that the pressure-driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By a comprehensive in situ neutron/synchrotron-based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD₃ND₃PbI₃, which also shows much greater structural robustness with retainable PL after high peak-pressure compression–decompression cycle. With the first-principles calculations, an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics is proposed, where the less dynamic CD₃ND₃⁺ cations are vital to maintain the long-range crystalline order through steric and Coulombic interactions. These results also show that CD₃ND₃PbI₃-based solar cell has comparable photovoltaic performance as CH₃NH₃PbI₃-based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope-functionalized perovskite materials for better materials-by-design and more stable photovoltaic application.     

An XPS study of anodic behavior of amorphous nickel-phosphorus alloys containing chromium,molybdenum or tungsten in 1 m CHl

The surfaces of amorphous Ni-18P, Ni-IOCr-20P, Ni-9Mo-19P and Ni-5W-18P alloys immersed or anodically polarized in 1 M HCl solution were analyzed in connection with their corrosion and anodic behavior. All alloys were more corrosion-resistant than crystalline nickel metal because of formation of phosphate-containing surface films on the Ni-18P, Ni-9Mo-19P and Ni-5W-18P alloys and because of spontaneous passivation due to formation of passive hydrated chromium oxyhydroxide film on the Ni-10Cr-20P alloy. The latter alloy was stable up to the transpassive region of chromium although intrusion of phosphate in the film was responsible for the higher passive current density in comparison to the amorphous Fe-Cr-13P-7C alloy of the same chromium content. The formation of thick porous phosphate films containing nickel, and molybdenum or tungsten by anodic polarization was not effective in passivating the Ni-18P, Ni-9Mo-19P and Ni-5W-18P alloys, and they suffered pitting corrosion by anodic polarization.     

Flexible Electronic Substrate Film Fabricated Using Natural Clay and Wood Components with Cross‐Linking Polymer

Requirements for flexible electronic substrate are successfully accomplished by green nanocomposite film fabricated with two natural components: glycol‐modified biomass lignin and Li⁺ montmorillonite clay. In addition to these major components, a cross‐linking polymer between the lignin is incorporated into montmorillonite. Multilayer‐assembled structure is formed due to stacking nature of high aspect montmorillonite, resulting in thermal durability up to 573 K, low thermal expansion, and oxygen barrier property below measurable limit. Preannealing for montmorillonite and the cross‐linking formation enhance moisture barrier property superior to that of industrial engineering plastics, polyimide. As a result, the film has advantages for electronic film substrate. Furthermore, these properties can be achieved at the drying temperature up to 503 K, while the polyimide films are difficult to fabricate by this temperature. In order to examine its applicability for substrate film, flexible electrodes are finely printed on it and touch sensor device can be constructed with rigid elements on the electrode. In consequence, this nanocomposite film is expected to contribute to production of functional materials, progresses in expansion of biomass usage with low energy consumption, and construction of environmental friendly flexible electronic devices.     

Effects of aging on poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet radiation for gas separation

In this study, we investigated the effects of physical aging on the surface and gas‐transport properties of highly gas permeable poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet (VUV) radiation. VUV excimer lamp irradiation was performed on one side of the membrane for 6 or 60 min. The gas permeabilities for carbon dioxide (CO₂) and nitrogen (N₂) were determined through a volumetric measurement method at 23 °C. The gas permeabilities for CO₂ and N₂ increased temporarily at 7 days after 6 and 60 min of VUV irradiation of the membranes. The change in the gas permeability for N₂ was more remarkable than that for CO₂. These changes were related to the C?O or SiO_x ratio. The C?O ratio was related to the gas permeability of the membranes VUV‐irradiated for 6 min, whereas the SiO_x ratio was related to the gas permeability of the membranes VUV‐irradiated for 60 min. These changes affected the gas selectivities of the membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45973.     

Calcium phosphates formation on CaTiO<Subscript>3</Subscript> coated titanium

In this study, performance of calcium phosphate formation of CaTiO₃ coating film on Ti in Hanks’ balanced saline solution (HBSS) was investigated. CaTiO₃ thin films with a thickness of 50 nm were deposited on Ti using radiofrequency (RF) magnetron sputtering. The temperature of Ti substrate was adjusted to room temperature (RT) and 873 K. Thereafter, the specimens deposited at RT were annealed at 873 K in air for 7.2 ks. The films were characterized by grazing incident angle X-ray diffractometry (GI-XRD) and X-ray photoelectron spectroscopy (XPS). After immersion in HBSS for 60 d, on CaTiO₃ coated Ti, the formation of hydroxyapatite (HAP) was observed. Furthermore, HAP layer formed was thicker on the specimen on which CaTiO₃ film was deposited at RT and annealed than that prepared at 873 K. The major difference between both specimens was the chemical properties of the outermost surface. In summary, CaTiO₃ thin film deposited at RT and followed by annealing at 873 K for 7.2 ks in air enhances calcium phosphate formation ability on Ti.     

Isolation of a protease-deficient mutant of Bacillus brevis and efficient secretion of a fungal protein disulfide isomerase by the mutant

The efficient production of a thermostable protein disulfide isomerase (PDI) was successfully achieved using the newly isolated protease-deficient mutant, Bacillus brevis 31-OK. Extracellular protease (exoprotease) activity was about a quarter of that in the parent, and the mutant was deficient in at least one of the major exoproteases. The cDNA encoding the fungal PDI was inserted downstream of the signal peptide-encoding region in an expression-secretion vector for B. brevis. Efficient production of PDI was feasible using B. brevis 31-OK as a host and modified signal sequences composed of three leucine residues inserted in the hydrophobic region of the MWP (middle wall protein) signal sequence. The maximal secretion of PDI into the culture medium was 1.1 g/l, which is about twice that by the parent strain and fifty times greater than the amount of rat and murine PDIs produced by Escherichia coli. The enzymatic properties such as the specific activity and thermal stability of the recombinant PDI are similar to those of natural PDI derived from Humicola insolens mycelia. B. brevis 31-OK was able to maintain its exoprotease activity at a low level throughout the cultivation and is considered to be useful host for production of a protease-sensitive protein and for increase of protein productivity due to stable accumulation.     

Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase

Biodiesel derived from vegetable oils has drawn considerable attention with increasing environmental consciousness. We attempted continuous methanolysis of vegetable oil by an enzymatic process. Immobilized Candida antarctica lipase was found to be the most effective for the methanolysis among lipases tested. The enzyme was inactivated by shaking in a mixture containing more than 1.5 molar equivalents of methanol against the oil. To fully convert the oil to its corresponding methyl esters, at least 3 molar equivalents of methanol are needed. Thus, the reaction was conducted by adding methanol stepwise to avoid lipase inactivation. The first step of the reaction was conducted at 30°C for 10 h in a mixture of oil/methanol (1:1, mol/mol) and 4% immobilized lipase with shaking at 130 oscillations/min. After more than 95% methanol was consumed in ester formation, a second molar equivalent of methanol was added and the reaction continued for 14 h. The third molar equivalent of methanol was finally added and the reaction continued for 24 h (total reaction time, 48 h). This three-step process converted 98.4% of the oil to its corresponding methyl esters. To investigate the stability of the lipase, the three-step methanolysis process was repeated by transferring the immobilized lipase to a fresh substrate mixture. As a result, more than 95% of the ester conversion was maintained even after 50 cycles of the reaction (100 d).     

High‐frequency equivalent circuit of an induction motor driven by a PWM inverter

This paper deals with the high‐frequency equivalent circuits in an induction motor driven by a PWM inverter. The leakage current flows through stray capacitance among stator windings and iron core (frame) of the induction motor at the switching instants of the inverter transistors. The high‐frequency equivalent circuits are derived based on the frequency characteristics of the high‐frequency zero‐phase impedance and line‐to‐line impedance of the induction motor. The validity of the derived equivalent circuits is confirmed by simulation and experimental results. © 2001 Scripta Technica, Electr Eng Jpn, 135(1): 65–76, 2001