Thermal and chemical methods for producing zinc silicate (willemite): A review

Thermal and chemical methods for producing zinc silicate, Zn₂SiO₄ phosphor on industrial and laboratory scales are reviewed. Zinc silicate has a promising future in advanced materials as a highly versatile luminescent material due to the wide range of multi-colors that can be obtained from various guest ions. Candidates for future industrial methods of producing zinc silicate are critically reviewed from the point of view of phase formation and compared with the conventional solid-state reaction. Conventional methods require calcination at temperatures higher than 1000 °C and long reaction times to form Zn₂SiO₄ phase and these processes limit particle shape and size. Sol–gel methods are performed in a solvent at ambient pressure, while hydrothermal and solvothermal methods tend use high temperatures and high pressures, and especially supercritical water methods tend use conditions higher than 400 °C and 25 MPa. Hydrothermal and sol–gel literature shows that crystallization of Zn₂SiO₄ requires at least temperatures of around 100 °C. Of all the growth methods, supercritical water is able to bring about phase formation in the shortest reaction time. Vapor methods are performed with a gas phase as the reaction medium. Vapor and sol–gel methods require post-calcination for crystallization and have the advantage of providing characteristic particles such as uniform shapes, spherical particles, or nano-sized particles by varying the experimental conditions; they may be combined with the other crystallization routes in the future.     

Lewis acid-promoted rearrangement of 2,3-epoxy alcohol derivatives: stereochemical control and selective formation of two types of chiral quaternary carbon centers from the single carbon skeleton

The Lewis acid-promoted rearrangement of 2,2,3,3-tetrasubstituted 2,3-epoxy alcohols with several kinds of protecting groups was investigated. When SnCl4 is used as a Lewis acid, the reaction proceeds in a regio- and stereo-controlled manner to afford two types of carbonyl compounds selectively from a single 2,3-epoxy alcohol only by changing the protecting group of the alcohol. The method was then applied to the formation of two types of acyclic and cyclic quaternary carbon centers from the single compound in optically active forms.     

Infrared spectroscopic study of thermal annealing effects of hydrocarbon species on a Si surface exposed to methane plasma

We have investigated the thermal annealing effects of hydrocarbon species on the methane-plasma exposed silicon surface, investigated by in situ infrared absorption spectroscopy (IRAS) in multiple internal reflection (MIR) geometry. The proportion of types of hydrocarbon species is not remarkably changed in the hydrocarbon network that consists of sp-, sp²- and sp³-CH_X species by annealing at moderate temperatures. On the other hands, the proportion is drastically changed in the network that is mainly composed of sp³-CH_X species by annealing at moderate temperatures. It suggests that excess CH₃ species in the film is not stable against thermal annealing and would be converted to sp³-CH_1-2 species by annealing at moderate temperatures. And the data also show that sp²-CH species is more stable against the thermal annealing than sp³-hydrocarbon species.     

Reaction of Acetals with Various Carbon Nucleophiles under Non‐Acidic Conditions: C?C Bond Formation via a Pyridinium‐Type Salt

Mild substitution reactions of acetals with carbon nucleophiles via the pyridinium‐type salts generated by the treatment of acetals with TESOTf‐2,4,6‐collidine or 2,2′‐bipyridyl have been developed. Various carbon nucleophiles, such as organocuprates, silyl enol ethers, enamines, etc., reacted with the pyridinium‐type salts to give the corresponding substituted products in good yields. The reactions proceeded under very mild conditions (non‐acidic conditions) and thus acid‐sensitive functional groups can be tolerated during the reaction. In addition, only an acetal can form the pyridinium‐type salt and react with nucleophiles in the presence of a ketal. This unusual selectivity is in contrast to general methods conducted under acidic conditions.     

The Core Fucose on an IgG Antibody is an Endogenous Ligand of Dectin‐1

The core fucose, a major modification of N‐glycans, is implicated in immune regulation, such as the attenuation of the antibody‐dependent cell‐mediated cytotoxicity of antibody drugs and the inhibition of anti‐tumor responses via the promotion of PD‐1 expression on T cells. Although the core fucose regulates many biological processes, no core fucose recognition molecule has been identified in mammals. Herein, we report that Dectin‐1, a known anti‐β‐glucan lectin, recognizes the core fucose on IgG antibodies. A combination of biophysical experiments further suggested that Dectin‐1 recognizes aromatic amino acids adjacent to the N‐terminal asparagine at the glycosylation site as well as the core fucose. Thus, Dectin‐1 appears to be the first lectin‐like molecule involved in the heterovalent and specific recognition of characteristic N‐glycans on antibodies.     

Reaction of β-aminocrotonamide with dibasic acid derivatives

Reaction of β-aminocrotonamide ( 1 ) with succinic anhydride gave β-succinaminocrotonamide ( 3a ), which was treated with base to cyclize to 3,4-dihydro-6-methyl-4-oxo-2-pyrimidinepropanoic acid ( 4a ). Similarly, pyrimidinepentanoic acid derivative 4b was prepared from compound 1 and glutaric anhydride. Reaction of compound 1 with glutarate, adipate, and phthalate gave the corresponding pyrimidines 4b, 4c and 4d , while reaction of compound 1 with malonate gave 2-hydroxypyridine derivative 11 and dimethylpyrimidinone 4e . Reaction of dimethyl fumarate with compound 1 in the presence of methoxide gave a poor yield of pyrrolo[3,4-c]pyridine derivative 13 .     

Effects of Phosphorus Substituents on Reactions of α-Alkoxyphosphonium Salts with Nucleophiles

The effects of phosphorus substituents on the reactivity of α-alkoxyphosphonium salts with nucleophiles has been explored. Reactions of α-alkoxyphosphonium salts, prepared from various acetals and tris(o-tolyl)phosphine, with a variety of nucleophiles proceeded efficiently. These processes represent the first examples of high-yielding nucleophilic substitution reactions of α-alkoxyphosphonium salts. The reactivity of these salts was determined by a balance between steric and electronic factors, respectively, represented by cone angles θ and CO stretching frequencies ν (steric and electronic parameters, respectively). In addition, a novel reaction of α-alkoxyphosphonium salts derived from Ph(3) P with Grignard reagents was observed to take place in the presence of O(2) to afford alcohols in good yields. A radical mechanism is proposed for this process that has gained support from isotope-labeling and radical-inhibition experiments.     

Infrared diode laser spectroscopy of the deltanu=2 band of AlF

A vibrational-rotational spectrum of the deltanu=2 transitions of a high-temperature molecule AlF was observed between 1,490 and 1,586 cm(-1) with a diode laser spectrometer. Measurements were made on the nu=3-1, 4-2, 5-3 and 8-6 bands at a temperature of 900 degrees C. Measured spectral lines were fitted to effective band constants nu(0), B(nu) and D(nu) for each band. Present measurements were made with only one Pb-salt laser diode. Physical significance of the effective band constants is discussed.