Synthesis of nano-polycrystalline diamond from glassy carbon at pressures up to 25 GPa

ABSTRACT

Nano-polycrystalline diamond (NPD) with various grain sizes has been synthesized from glassy carbon at pressures 15–25?GPa and temperatures 1700–2300°C using multianvil apparatus. The minimum temperature for the synthesis of pure NPD, below which a small amount of compressed graphite was formed, significantly increased with pressure from ～1700°C at 15?GPa to ～1900°C at 25?GPa. The NPD having grain sizes less than ～50?nm was synthesized at temperatures below ～2000°C at 15?GPa and ～2300°C at 25?GPa, above which significant grain growth was observed. The grain size of NPD decreases with increasing pressure and decreasing temperature, and the pure NPD with grain sizes less than 10?nm is obtained in a limited temperature range around 1800–2000°C, depending on pressure. The pure NPD from glassy carbon is highly transparent and exhibits a granular nano-texture, whose grain size is tunable by selecting adequate pressure and temperature conditions.     

Changes in the near-edge X-ray absorption fine structure spectra of long-chain diacetylene derivatives through photopolymerization in Langmuir–Blodgett films

Photopolymerization of cadmium 10,12-pentacosadiynoate (CdDA) in Langmuir–Blodgett (LB) films, with the molecular packing well arranged by moderate preannealing, was investigated with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Greenish films of polydiacetylene with an absorption wavelength of 705 nm were obtained through the photopolymerization of preannealed monomer LB films, and this resulted in an extended π-conjugate system based on the well-ordered monomer in a two-dimensional arrangement. The electronic structures of the polydiacetylenes were found to be correlated to the variation of the molecular arrangements in the films from the changes in the NEXAFS spectra through photopolymerization in the LB films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2329–2336, 2004     

Characterization and determination of linear alkylbenzenesulfonates in environmental water samples by high-performance liquid chromatography with a hydrophilic polymer column and electrospray ionization mass spectrometric detection.

A liquid chromatography-mass spectrometry (LC/MS) method was developed for the separation and determination of linear alkylbenzenesulfonates (C10-C14 LAS) in environmental water samples using a hydrophilic polymer column (Shodex Mspak GF-310 4D). This method involves a solid-phase extraction of the LAS samples with a Sep-Pak PS-2 cartridge. The LAS components were separated on the column with a mobile phase of 29% (w/v) acetonitrile-water containing 0.8 mM di-n-butylammonium acetate and 0.2 M acetic acid, and were detected by mass spectrometry with electrospray ionization. Detection limits of the developed method based on selected ion monitoring (SIM) technique for the C10-C14 LAS standards were 13-47 ng L(-1). The concentrations of the C10-C14 LAS in the environmental water samples ranged between 5-317 microg L(-1) for a river water sample and 0.4-6.4 microg L(-1) for a seawater sample. Linear relationships between the logarithms of retention factors and the alkyl chain lengths for each phenyl positional isomer of LAS could successfully be used for the identification of the isomer peaks.     

Convenient synthesis of alkoxyhalosilanes from hydrosilanes

Selective dehydrogenative coupling of di- and trihydrosilanes with alcohols catalyzed by PdCl₂ or NiCl₂ afforded alkoxyhydro- and dialkoxyhydrosilanes in good yield. Further treatment of the resulting alkoxyhydrosilanes with carbon tetrachloride or allyl bromide in the presence of the same catalyst led to the formation of alkoxychloro- and alkoxybromosilanes, respectively. Similar reactions of dialkoxyhydrosilanes with carbon tetrachloride afforded dialkoxychlorosilanes in good yield, although contamination of small amounts of trialkoxysilanes and alkoxydichlorosilanes was detected in the products. Selective substitution of the alkoxyhalosilanes with nucleophiles is also reported.     

Heavy element nuclear chemistry at JAERI

The present status of heavy element nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed. Production of the transactinide nuclei ²⁶¹Rf and ²⁶²Db via the reactions of ²⁴⁸Cm(¹⁸O,5n) and ²⁴⁸Cm(¹⁹F, 5n), respectively, at the JAERI tandem accelerator is reported. Study of the aqueous chemistry of Rf is being carried out with a newly developed rapid ion-exchange separation apparatus. Anion-exchange behavior of Rf in acidic solution is briefly discussed. Recent experimental results on decay studies of neutron-deficient actinide nuclei using the gas-jet coupled JAERI-ISOL are given. We also discuss characteristics of nuclear deformation properties at scission in symmetric and asymmetric fission of actinides. Prospects for studies in the near future are briefly considered.     

Temperature Dependence of the Threshold Current and the Lasing Wavelength in 1.3-μm GalnNAs/GaAs Single Quantum Well Laser Diode

Temperature stability of the threshold current and the lasing wavelength is investigated in a 1.3-μm GaInNAs/ GaAs single quantum-well laser. The measured characteristic-temperature was 88 K. The small wavelength shift per change in temperature of 0.35 nm/°C was obtained, indicating the superior lasing-wavelength stability. Therefore, it is shown experimentally that GaInNAs is very promising material for the fabrication of light source with excellent high-temperature performance for optical fiber communications.     

New Chiral Kemp's Acid Diamides for Chiral Amine Recognition by 1 H NMR

Two Kemp's acid diamides were synthesized and applied to chiral amine recognition using ¹H NMR analysis. One derivative based on 1-(1-naphthyl)ethylamine had good chiral recognition of six amines and was useful to determine the optical purity for three amines, i.e., methylbenzylamine, 1-(1-naphthyl)ethylamine and 1- henylpropylamine,however, the cyclohexylethylamine derivative showed little discrimination for the amines studied. Together with the results for alkylamines, it was shown that aromatic structure was important for aromatic shielding anisotropy and –– interactions between host and guest. The structure of the 1-(1-naphthyl)ethylamine derivative in solution was also considered based on ¹H NMR data and computer simulation.     

Time-resolved fluorescence spectroscopic and scanning near-field optical microscopic studies of rhodamine dye adsorbed in cationic Langmuir-Blodgett films

The fluorescence lifetimes decays and picosecond time-resolved fluorescence spectra were measured to investigate the dynamics of the excited state of sulforhodamine B (SRB) molecules adsorbed in the mono- and multilayered Langmuir-Blodgett (LB) films of octadecylamine. Steady-state and time-resolved fluorescence spectroscopy reveals that the fluorescence lifetimes and contents of the monomer and dimers in the molecular organizates depend upon the concentration of the dye in the solution and the adsorption process. SRB dye molecules adsorbed in LB films have been imaged with scanning near-field optical microscopy (SNOM). This information is exploited to map the distribution with molecular spatial resolution. SNOM provide the visual evidence of the monomers and dimers of SRB in cationic LB films.     

Prompt Gamma-Ray Analysis of Rats

Prompt -ray analysis with the internal monostandard method was used to organs taken from rats. After B or Cd was administered, the B/H and Cd/H contents ratios were determined in the brain, kidney, and liver to study their distribution and metabolism. Boron was distributed in all organs but metabolized quickly. Cd was slowly accumulated in the liver and kidneys during the 65 hours studied but no Cd was detected in the brain.     

Combinatorial synthesis of MUC1 glycopeptides: polymer blotting facilitates chemical and enzymatic synthesis of highly complicated mucin glycopeptides

The chemoselective polymer blotting method allows for rapid and efficient synthesis of glycopeptides based on a "catch and release" strategy between solid-phase and water-soluble polymer supports. We have developed a heterobifunctional linker sensitive to glutamic acid specific protease (BLase). The general procedure consists of five steps, namely (i) the solid-phase synthesis of glycopeptide containing BLase sensitive linker, (ii) subsequent deprotections and the release of the glycopeptide from the resin, (iii) chemoselective blotting of the glycopeptide intermediates in the presence of water-soluble polymers with oxylamino functional groups, (iv) sugar elongations using glycosyltransferases, and (v) the release of target glycopeptides from the polymer platform by selective BLase promoted hydrolysis. The combined use of the solid-phase chemical syntheses of peptides and the enzymatic syntheses of carbohydrates on water-soluble polymers would greatly contribute to the production of complicated glycopeptide libraries, thereby enhancing applicative research. We report here a high-throughput synthetic system for the various types of MUC1 glycopeptides exhibiting a variety of sugar moieties. It is our belief that this concept will become part of the entrenched repertoire for the synthesis of biologically important glycopeptides on the basis of glycosyltransferase reactions in automated and combinatorial syntheses.