Dealloying of Mesoporous PtCu Alloy Film for the Synthesis of Mesoporous Pt Films with High Electrocatalytic Activity

Mesoporous Pt film with highly electrocatalytic activity is successfully synthesized by dealloying of mesoporous PtCu alloy film prepared through electrochemical micelle assembly. The resulting mesoporous electrode exhibits high current density and superior stability toward the methanol oxidation reaction.     

Easy and General Synthesis of Large‐Sized Mesoporous Rare‐Earth Oxide Thin Films by ′Micelle Assembly′

Large‐sized (ca. 40 nm) mesoporous Er₂O₃ thin films are synthesized by using a triblock copolymer poly(styrene‐b‐2‐vinyl pyridine‐b‐ethylene oxide) (PS‐b‐P2VP‐b‐PEO) as a pore directing agent. Each block makes different contributions and the molar ratio of PVP/Er³⁺ is crucial to guide the resultant mesoporous structure. An easy and general method is proposed and used to prepare a series of mesoporous rare‐earth oxide (Sm₂O₃, Dy₂O₃, Tb₂O₃, Ho₂O₃, Yb₂O₃, and Lu₂O₃) thin films with potential uses in electronics and optical devices.     

Unexpected effect of catalyst concentration on photochemical CO2 reduction by trans(Cl)–Ru(bpy)(CO)2Cl2: new mechanistic insight into the CO/HCOO– selectivity

Photochemical CO₂ reduction catalysed by trans(Cl)–Ru(bpy)(CO)₂Cl₂ (bpy = 2,2′-bipyridine) efficiently produces carbon monoxide (CO) and formate (HCOO^–) in N,N-dimethylacetamide (DMA)/water containing [Ru(bpy)₃]²⁺ as a photosensitizer and 1-benzyl-1,4-dihydronicotinamide (BNAH) as an electron donor. We have unexpectedly found catalyst concentration dependence of the product ratio (CO/HCOO^–) in the photochemical CO₂ reduction: the ratio of CO/HCOO^– decreases with increasing catalyst concentration. The result has led us to propose a new mechanism in which HCOO^– is selectively produced by the formation of a Ru(i)–Ru(i) dimer as the catalyst intermediate. This reaction mechanism predicts that the Ru–Ru bond dissociates in the reaction of the dimer with CO₂, and that the insufficient electron supply to the catalyst results in the dominant formation of HCOO^–. The proposed mechanism is supported by the result that the time-course profiles of CO and HCOO^– in the photochemical CO₂ reduction catalysed by [Ru(bpy)(CO)₂Cl]₂ (0.05 mM) are very similar to those of the reduction catalysed by trans(Cl)–Ru(bpy)(CO)₂Cl₂ (0.10 mM), and that HCOO^– formation becomes dominant under low-intensity light. The kinetic analyses based on the proposed mechanism could excellently reproduce the unusual catalyst concentration effect on the product ratio. The catalyst concentration effect observed in the photochemical CO₂ reduction using [Ru(4dmbpy)₃]²⁺ (4dmbpy = 4,4′-dimethyl-2,2′-bipyridine) instead of [Ru(bpy)₃]²⁺ as the photosensitizer is also explained with the kinetic analyses, reflecting the smaller quenching rate constant of excited [Ru(4dmbpy)₃]²⁺ by BNAH than that of excited [Ru(bpy)₃]²⁺. We have further synthesized trans(Cl)–Ru(6Mes-bpy)(CO)₂Cl₂ (6Mes-bpy = 6,6′-dimesityl-2,2′-bipyridine), which bears bulky substituents at the 6,6′-positions in the 2,2′-bipyridyl ligand, so that the ruthenium complex cannot form the dimer due to the steric hindrance. We have found that this ruthenium complex selectively produces CO, which strongly supports the catalytic mechanism proposed in this work.     

Laser-induced pinpoint hydrogen evolution from benzene and water using metal free single-walled carbon nanotubes with high quantum yields

Metal-free photocatalytic hydrogen evolution occurred efficiently in benzene containing single-walled carbon nanotubes under laser irradiation at 532 nm with an extremely high turnover number of 2 000 000 and a high quantum yield of 130%. The rate of hydrogen evolution increased with increasing laser intensity to exhibit a fourth power dependence, suggesting that hydrogen was evolved via four-photon processes in which the coupling of two radical anions derived from benzene is the rate-determining step and the benzene radical anion is produced by electron transfer from benzene to the doubly excited state of single-walled carbon nanotubes, which requires two photons. Polymerisation of benzene was induced by the photogenerated C₆H₆˙^–, accompanied by hydrogen evolution, resulting in a leverage effect to increase the quantum yield of hydrogen evolution to well over the 25% expected for the four-photon process. Laser-induced hydrogen evolution also occurred in water containing single-walled carbon nanotubes. In contrast to the case of benzene, water was not oxidized but hydrogen evolution from water was accompanied by the multi-oxidation of single-walled carbon nanotubes. The yield of hydrogen based on one mole of single-walled carbon nanotubes with 1.4 nm diameter and 1–5 mm length was determined to be 2 700 000%, when oxidations of single-walled carbon nanotubes occurred to produce the polyhydroxylated product.     

A Vasicek-Type Short Rate Model With Memory Effect

We introduce a Vasicek-type short rate model which has two additional parameters representing memory effect. This model presents better results in yield curve fitting than the classical Vasicek model. We derive closed-form expressions for the prices of bonds and bond options. Although the model is non-Markov, there exists an associated Markov process that allows one to apply usual numerical methods to the model. We derive analogs of an affine term structure and term structure equations for the model, and, using them, we present a numerical method to evaluate contingent claims.     

Estimated effects of silicone glue on protein crystal growth

Silicone glue (modified silicone polymer) is widely used for both experiments involving inorganic crystal growth and those involving organic materials like proteins. This material is very useful for building a hand-made experiment setup or for fixing protein crystals to specific locations. Though silicone glue is regarded as harmful to proteins, no systematic verification was performed to investigate its impurity effects on protein crystal growth. We focused on and estimated the impurity effects of silicone glue on protein crystal growth.     

Hydrothermal synthesis of organic hybrid BaTiO3 nanoparticles using a supercritical continuous flow reaction system

Barium titanate (BaTiO₃: BT) nanoparticles were synthesized by the hydrothermal method in the presence of dispersants using a continuous supercritical flow reaction system. The reactants of TiO₂ sol/Ba(NO₃)₂ mixed solution and KOH solution were used as starting materials and that was heated quickly up to 400 °C under the pressure of 30 MPa for 8 ms as reaction time. The dispersant solution such as polyacrylic acid (PAA) and polyoxyethylene(20) sorbitan monooleate (Tween 80) was injected in the cooling process after the reaction. The crystal phase of the obtained particles was identified as perovskite cubic BaTiO₃ by X-ray diffractometry (XRD) and Raman spectroscopy. Raman spectra and thermogravimetric data revealed that PAA and Tween 80 fabricated hybrid BT nanoparicles. Primarily particle size of the BaTiO₃ nanoparticle was determined by means of BET surface area, as small as less than 10 nm irrespective of dispersants. In contrast, dispersed particle size in solution measured by dynamic light scattering (DLS) technique decreased from 282 nm to less than 100 nm depending on the dispersant. Aggregation of BaTiO₃ nanoparticles might be depressed in the presence of dispersants, especially PAA is the most effective among the dispersants examined.     

Predictions of cation and anion effects on solubilities,selectivities and permeabilities for CO2 in ionic liquid using COSMO based activity coefficient model

The solubilities and selectivities for CO₂, N₂ and CH₄ in ionic liquid were predicted using a COSMO based activity coefficient model, COSMO-SAC method. The 1-alkyl-3-methylimidazolium cations were focused in this work. The anion species include tetrafluoroborate [BF₄], hexafluorophosphate [PF₆], triflate [OTf], dicyanamide [dca] and bis(trifluoromethane)-sulfonimide [Tf₂N]. The predicted results of the solubilities of CO₂ in the ionic liquids by COSMO-SAC method are in agreement with the experimental data within the averaged deviation of 0.0017 in mole fraction. The predicted results of selectivities for CO₂/N₂ and CO₂/CH₄ represent the effects of anion species qualitatively. Permeability through supported liquid membrane can be presented by solubility and diffusion coefficients in the liquid. The permeabilities of CO₂ through the ionic liquid membranes were also predicted by a solution-diffusion model with COSMO-SAC method. The predicted results of the CO₂ permeabilities through the ionic liquids represent the experimental data within the order of the permeabilities.     

The Spermine–Bisaryl Conjugate as a Potent Inducer of B‐ to Z‐DNA Transition

DNA containing alternating purine and pyrimidine repeats has the potential to adopt the Z‐DNA structure, one of the well‐studied structures besides A‐ and B‐DNA. Despite a number of molecular models that have been proposed to explain the mechanism for B→Z transition, there is continued discussion on the mechanism and physiological role of this transition. In this study, we have found that the bis(2‐naphthyl)‐maleimide–spermine conjugate ( 3 c ) exhibits a remarkable ability to cause the B→Z transition of d(CGCGCG)₂ at low salt concentrations. Using isothermal titration calorimetry (ITC) we show that the B→Z transition induced by 3 c is both enthalpically and entropically favorable. The ligand might effect the dehydration of B‐DNA, which leads to the B→Z transition. Interestingly, an intermediate CD between the B and Z forms was observed in the pH‐dependent transition in the presence of the ligand. The unique structure and characteristics of the ligand designed in this investigation will be useful for the study of Z‐DNA.