Induction and Acceleration of Bonelike Apatite Formation on Tantalum Oxide Gel in Simulated Body Fluid

Untreated tantalum metal forms bonelike apatite layer on its surface in a simulated body fluid (SBF) after a long period. The apatite formation on the tantalum metal is significantly accelerated, when the metal was previously subjected to NaOH and heat treatments to form an amorphous sodium tantalate on its surface. The fast formation of the apatite on the NaOH- and heat-treated tantalum metal was explained as follows. The sodium tantalate on the surface of the metal releases the Na⁺ ion via exchange with H₃O⁺ ion in SBF to form a lot of Ta-OH groups on its surface. Thus formed Ta-OH groups induce the apatite nucleation and the released Na⁺ ion accelerates the apatite nucleation by increasing ionic activity product of the apatite in SBF due to increase in OH^– ion concentration. In the present study, in order to confirm this explanation, apatite formations on sodium tantalate gels with different Na/Ta atomic ratios, which were prepared by a sol-gel method were investigated. It was found that even Na₂O-free tantalum oxide gel forms the apatite on its surface in SBF. This proves that the Ta-OH groups abundant on the gel can induce the apatite nucleation. The apatite-forming ability of the gels increased with increasing Na/Ta atomic ratios of the gels. The sodium-containing tantalum oxide gels released the Na⁺ ion, the amount of which increased with increasing Na/Ta atomic ratios of the gels. The released Na⁺ ion gave an increase in pH of SBF. These results prove that the apatite nucleation induced by the Ta-OH groups is accelerated with the released Na⁺ ion by increasing ionic activity product of the apatite in SBF.     

Determination of estrogens in river water by gas chromatography-negative-ion chemical-ionization mass spectrometry.

A method for the determination of estrogens (17alpha-estradiol, 17beta-estradiol, estrone, ethynyl estradiol, and estriol) as pentafluorobenzyl-trimethylsilyl (PFB-TMS) derivatives by gas chromatography-mass spectrometry (GC-MS) with negative-ion chemical-ionization (NICI) is described. The NICI of all the derivatives produced an intense [M-PFB]- ion as the base peak. The reagent gas (methane) flow-rate and the ion source temperature were determined to be 2.0 ml/min and 240 degrees C, respectively, for the optimized NICI-selected ion monitoring (SIM) conditions. The sensitivities of the PFB-TMS derivatives in the NICI mode were 8.0-130 times higher than those of the PFB-TMS derivatives in electron ionization (EI) mode, and 12-25 times higher than those of all the TMS derivatives in the EI mode. This method was applied to the analysis of estrogens in river water using a solid-phase extraction as the sample preparation. The recoveries of the target chemicals from a river-water sample spiked with standards at 2 ng/l level were 85.8-126.5% (RSD, 6.2-13.0%). The methodical detection limits ranged from 0.10 to 0.28 ng/l.     

原位Raman光谱揭示中性条件下硫化钼结构变化对其电催化析氢反应的促进作用（英文）

硫化钼是析氢反应(HER)有前途的电催化剂.S-或Mo物种均被认为是形成吸附氢触发HER反应的活性位,但Mo中心和S配体间相互作用的本质仍不清楚.另外,采用中性的水作为质子源用于产氢,来开发低成本的水裂解催化剂体系为研究者高度关注,但人们很少研究中性水条件下HER反应的机理.本文采用原位电化学Raman光谱对所合成的硫化钼中Mo–Mo和S–S物种在中性条件下的结构变化进行了监测.结果显示,归属于端位S–S物种的谱带随着和Mo–S振动谱带频率而同步变化,表明Mo–Mo键与端位S–S键起着协同作用,从而有利于氢气的生成.这可能是通过三核物种的内部重组而确认的.本文所揭示的HER反应中金属-配体相互作用的本质与作用表明了一个不同的反应机理,而以往的机理认为,S或Mo活性位独立起作用而促进HER反应的进行.     

Temperature dependent control of the solubility of gallium nitride in supercritical ammonia using mixed mineralizer

Using a mass-loss method, we investigated the solubility change of gallium nitride (GaN) in supercritical ammonia with mixed mineralizers [ammonium chloride (NH₄Cl)?+?ammonium bromide (NH₄Br) and NH₄Cl?+?ammonium iodide (NH₄I)]. The solubilities were measured over the temperature range 450–550 °C, at 100 MPa. The solubility increased with NH₄Cl mole fraction at 450 °C and 100 MPa. The temperature dependence of the solubility curve was then measured at an equal mole ratio of the two mineralizers. The slope of the solubility–temperature relationship in the mixed mineralizer was between those of the individual mineralizers. These results show that the temperature dependence of the solubility of GaN can be controlled by the mineralizer mixture ratio. The results of the van’t Hoff plot suggest that the solubility species were unchanged over the investigated temperature range. Our approach might pave the way to realizing large, high-quality GaN crystals for future gallium-nitride electronic devices, which are increasingly on demand in the information-based age.     

Controlled Radical Polymerization of Ethylene Using Organotellurium Compounds

The first successfully controlled radical polymerization (CRP) of ethylene is reported using several organotellurium chain‐transfer agents (CTAs) under mild conditions (70 °C, 200 bar of ethylene) within the concept of organotellurium‐mediated radical polymerization (TERP). In contrast to preceding works on CRPs of ethylene applying reversible addition–fragmentation chain‐transfer (RAFT), the TERP system provided a high livingness and chain‐end functionalization of polyethylene chains. Molar‐mass distributions with dispersities between 1.3 and 2.1 were obtained up to average molar masses of 5000 g mol^?1. As in the RAFT system, the high reactivity of the growing polyethylenyl radical led to an inherent side reaction. For the presented TERP systems, however, this side reaction did not result in dead chains, while it could even be effectively suppressed by a good choice of the CTA.     

Recent advances in the integrated micro-flow synthesis containing photochemical reactions

Micro-flow photochemical reactions have great advantage over batch photochemical reactions due to its high light-penetration efficiency. Integrated micro-flow reaction enables efficient synthesis of structurally complex compounds from simple starting materials and it can avoid handling of explosive, toxic, unstable, or odorous intermediates. Combination of micro-flow photochemical reactions with integrated micro-flow synthesis enhances their benefits. Here we summarize recently reported integrated multi-step micro-flow synthesis containing various photochemical reactions.     

Regioselective allylzincation of alkenylboronate

[reaction: see text] Boryl substitution on an olefin activates the olefinic double bond toward addition of an organozinc reagent. Addition of an allylic zinc reagent to an alkenylboronate thus takes place smoothly to afford a variety of gem-zincio/boryl species. Theoretical studies with density functional calculations on the reaction pathway revealed that the reaction proceeds via a zincio-ene reaction rather than a bora-Claisen rearrangement.     

Enantioselective ring cleavage of dioxane acetals mediated by a chiral Lewis acid: application to asymmetric desymmetrization of meso-1,3-diols

[reaction: see text]. Phenylalanine-derived B-aryl-N-tosyloxazaborolidinones selectively activate one of two enantiotopic oxygen atoms in prochiral anti dioxane acetals derived from meso-1,3-diols, leading to enantioselective formation of ring-cleavage products. The reaction is utilized as a key step in asymmetric desymmetrization of meso-1,3-diols.     

Cationic dye-sensitized degradation of sodium hyaluronate through photoinduced electron transfer in the upper excited state

The formation of ground-state complexes of methylene blue (MB) and thionine (TN) with sodium hyaluronate (NaHA) was clearly observed by means of absorption spectra in aqueous solution. Irradiation of the complexes using 313 nm light caused significant degradation of NaHA under oxygen and argon. However, the use of visible light over 400 nm, which gives the lowest excited singlet state of the cationic dyes, caused no degradation. MB and TN were more efficient sensitizers for the degradation of NaHA than rose bengal (RB), although RB is a more efficient singlet oxygen (1O2) sensitizer than the cationic dyes. Under similar conditions the polysaccharides with carboxyl groups, such as alginic acid and polygalacturonic acid, also photodecomposed. However, the polysaccharides without carboxyl groups, such as pullulan and methyl cellulose, did not. The irradiation of the polysaccharides in the presence of powdered titanium dioxide as a photocatalyst to generate the hydroxyl radical (.OH) in aerated aqueous solution caused the fragmentation of all the polymers. It was confirmed that methyl viologen, an electron-accepting sensitizer, formed a charge-transfer complex with NaHA, the irradiation of which caused the efficient degradation of NaHA. In the presence of beta- and gamma-cyclodextrins the MB- and TN-sensitized photodegradation of NaHA was markedly suppressed. This was probably due to the formation of the inclusion complexes comprising the cationic dyes and the cyclodextrins. On the basis of the results obtained we propose that the cationic dye-sensitized degradation of NaHA involves a photoinduced electron-transfer process between the upper excited dyes and the ground-state NaHA and that .OH and 1O2 do not participate in the degradation.