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Author

Hitoshi Ohtaki

Other affiliations: Kumamoto University
Bio: Hitoshi Ohtaki is an academic researcher from National Institutes of Natural Sciences, Japan. The author has contributed to research in topics: Aqueous solution & X-ray crystallography. The author has an hindex of 26, co-authored 153 publications receiving 4456 citations. Previous affiliations of Hitoshi Ohtaki include Kumamoto University.


Papers
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TL;DR: Extended x-ray absorption fine structure (EXAFS) measurements were performed for concentrated aqueous rare earth perchlorate solutions in the liquid state at room temperature and in the glassy state at liquid nitrogen temperature as discussed by the authors.
Abstract: Extended x‐ray absorption fine structure (EXAFS) measurements were performed for concentrated aqueous rare earth perchlorate solutions (R=28; R is the moles of water per mole of salt) in the liquid state at room temperature and in the glassy state at liquid nitrogen temperature. The quantitative analysis of the EXAFS data has revealed that the hydration number changes from about nine for light rare earth ions to about eight for heavy rare earth ions through the intermediate ions of Sm3+ ∼Eu3+ in both liquid and glassy states. The average Ln3+ –OH2 distances were determined and they are in agreement with previously reported values from x‐ray and neutron diffraction. The Debye–Waller factor of the average Ln3+ –OH2 bonds for the light rare earth ions was larger than that for the heavy ions, suggesting that the hydration shell of the light rare earth ions is statically disordered, consisting of different Ln3+ –OH2 bonds.

161 citations

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TL;DR: In this article, the stability constants of bivalent metal complexes with monocarboxylic acids and dicarboxylated acids were determined at 25°C and ionic strength of 0.1.
Abstract: Stability constants of the bivalent metal complexes formed with several mono- and dicarboxylic acids were determined at 25°C and ionic strength of 0.1. For monocarboxylic acids and several dicarboxylic acids having no double bond or forming larger chelate rings than six membered rings the following stability order held: Pb>Cu>Cd>Zn>Ni. It is very remarkable that lead showed the highest stability among bivalent metals.

121 citations

Journal ArticleDOI
TL;DR: The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H2O)−1], KCI [4.56 mol ( kg H 2O) −1], KF [16.15 mol (kH 2 O)−2] and CsF [31.96 mol (h 2 O ) was investigated by means of solution X-ray diffraction at 25°C.
Abstract: The structure of nearly saturated or supersaturated aqueous solutions of NaCI [6.18 mol (kg H2O)−1], KCI [4.56 mol (kg H2O)−1], KF [16.15 mol (kg H2O)−1] and CsF [31.96 mol (kg H2O)−1] has been investigated by means of solution X-ray diffraction at 25°C. In the NaCI and KCI solutions about 30% and 60%, respectively, of the ions form ion pairs and the Na+−Cl− and K+−Cl− distances have been determined to be 282 and 315 pm, respectively. The average hydration numbers of Na+ and Cl− ions are 4.6 and 5.3, respectively, in the NaCI solution and those of K+ and Cl− ions in the KCI solution are both 5.8. In the KF solution, clusters containing some cations and anions, besides 1:1 (K+−F−) ion pairs, are formed. The K+−F− interatomic distance has been determined to be 269 pm, and nonbonding K+...K+ and F−...F− distances in the clusters are 388 and 432 pm, respectively, and the average coordination numbers n KF , n KK and n FF have been estimated to be 2.3, 1.9, and 1.6, respectively. In the highly supersaturated CsF solution an appreciable amount of clusters containing several caesium and fluoride ions are formed. The Cs+−F− distance in the cluster has been determined to be 312 pm, while the nonbonding Cs+...Cs+ and F−...F− distances are estimated to be 442 and 548 pm, respectively, the distances being about $$\sqrt 2 $$ and $$\sqrt 3 $$ times the Cs+−F− distance, respectively. The coordination numbers n CsF , n CsCs , and n FF in the first coordination sphere of each ion are 3.3, 2.3 and 5.3, respectively, and the result shows the formation of clusters of higher order than 1:1 and 2:2 ion pairs. These ion pairs and clusters may be regarded as embryos for the formation of nuclei of crystals and the results obtained in the present diffraction study support observations for the nucleation of the alkali halide crystals studied by molecular dynamics simulations previously examined.

110 citations


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TL;DR: A. Relaxivity 2331 E. Outerand Second-Sphere relaxivity 2334 F. Methods of Improving Relaxivity 2336 V. Macromolecular Conjugates 2336.
Abstract: A. Water Exchange 2326 B. Proton Exchange 2327 C. Electronic Relaxation 2327 D. Relaxivity 2331 E. Outerand Second-Sphere Relaxivity 2334 F. Methods of Improving Relaxivity 2336 V. Macromolecular Conjugates 2336 A. Introduction 2336 B. General Conjugation Methods 2336 C. Synthetic Linear Polymers 2336 D. Synthetic Dendrimer-Based Agents 2338 E. Naturally Occurring Polymers (Proteins, Polysaccharides, and Nucleic Acids) 2339

4,125 citations

Journal ArticleDOI
20 Nov 2015-Science
TL;DR: A highly concentrated aqueous electrolyte whose window was expanded to ~3.0 volts with the formation of an electrode-electrolyte interphase, which could potentially be replaced with a safer aQueous alternative to lithium-ion batteries.
Abstract: Lithium-ion batteries raise safety, environmental, and cost concerns, which mostly arise from their nonaqueous electrolytes. The use of aqueous alternatives is limited by their narrow electrochemical stability window (1.23 volts), which sets an intrinsic limit on the practical voltage and energy output. We report a highly concentrated aqueous electrolyte whose window was expanded to ~3.0 volts with the formation of an electrode-electrolyte interphase. A full lithium-ion battery of 2.3 volts using such an aqueous electrolyte was demonstrated to cycle up to 1000 times, with nearly 100% coulombic efficiency at both low (0.15 C) and high (4.5 C) discharge and charge rates.

2,229 citations

Journal ArticleDOI
TL;DR: Results from Diffraction Experiments 1351 and results from Spectroscopic Measurements 1354 4.3.1.
Abstract: 4. Structure of Ionic Hydration Shells 1351 4.1. Results from Diffraction Experiments 1351 4.1.1. X-ray Diffraction 1351 4.1.2. Neutron Diffraction 1351 4.2. Results from Computer Simulations 1352 4.3. Results from Spectroscopic Measurements 1354 4.3.1. Vibrational Spectroscopic Measurements 1354 4.3.2. EXAFS Spectroscopy 1354 4.3.3. NMR Relaxation Studies 1355 4.3.4. Dielectric Relaxation Studies 1355 4.4. Summary of the Structure of Ionic Hydration Shells 1355

1,445 citations