One-Step Synthesis of Luminescent Nanoparticles of Complex Oxide, Strontium Aluminate

An organic aqueous solution of metal acetylacetonate precursors was subjected to spray pyrolysis in order to fabricate SrAl₂O₄:Eu (SAO) nanoparticles. Non-agglomerated luminescent SAO nanoparticles, having a spherical shape with a size of 10–30 nm, were achieved in a single step, while only submicrometer-sized SAO particles were obtained from the conventional ultrasonic pyrolysis of the metal nitrates. Without any post-annealing process, the as-prepared SAO nanoparticles were observed to exhibit a strong photoluminescence, which is comparable with that of the submicrometer-sized SAO particles. A mechanism for the formation of the nanoparticles is also discussed.     

Fracture- and Indentation-Induced Structural Changes of Sodium Borosilicate Glasses

It is known that indentation using a diamond indenter induces permanent densification to result in plastic or inelastic deformation of glass. However, it is still unclear whether a high tensile stress causes such a structural change or not. In this study, fracture- and indentation-induced structural changes of glasses with the compositions of 20 Na₂O − 40x B₂O₃ – (80−40x) SiO₂ (in mol%, x = 0, 0.5, 1, 1.5) are investigated. Two-point bending tests of the glass fibers are performed to apply a high tensile stress to the glasses, and Vickers indentation tests of the glasses are also carried out for comparison. The structural change of the glass is evaluated by using Raman spectroscopy. It is elucidated that a tensile side of the fractured fiber for every composition shows a permanent structural change, which is characterized by a lower wave number shift of Raman peak assigned to the Si-O-Si bending vibration mode. It is also found that the behaviors of Raman peaks of the fractured fiber are opposite to those of the indented glass under a high compressive stress.     

Thermoresponsive Emission Switching via Lower Critical Solution Temperature Behavior of Organic–Inorganic Perovskite Nanoparticles

Lead halide perovskites have shown much promise for high‐performing solar cells due to their inherent electronic nature, and though the color of bright‐light emitters based on perovskite nanoparticles can be tuned by halide mixing and/or size control, dynamic switching using external stimuli remains a challenge. This article reports an unprecedented lower critical solution temperature (LCST) for toluene solutions containing methylammonium lead bromide (MAPbBr₃), oleic acid, alkylamines, and dimethylformamide. The delicate interplay of these molecules and ions allows for the reversible formation and decomposition of MAPbBr₃ nanoparticles upon heating and cooling, which is accompanied by green and blue photoemissions at each state. An intermediate 1D crystal with PbBr₂‐amine coordination is found to play pivotal role in this, and a mechanistic insight is provided based on a three‐state model. In addition to a high quantum yield (up to 85%), this system allows for control over the cloud point (30?80 °C) through compositional engineering and the luminescent color (blue to red) via halogen exchange, thus making it a versatile solution for developing functional molecular organic–inorganic LCST quantum dots.     

A novel synthesis of reactive polyethers with pendant chloromethyl group by polyaddition of bis(epoxide)s with aromatic dichlorides

New polyethers with pendant chloromethyl groups were successfully synthesized by a polyaddition of bisepoxides with 4,4′-dichloro-3,3′-dinitrodiphenyl sulfone (DCNS) using quaternary onium salts or crown ether complexes as catalysts. The polyaddition of DCNS with diglycidyl ether of bisphenol A (DGEBA) was enhanced efficiently by the addition of tetrabutylammonium chloride (TBAC), tetrabutylammonium bromide (TBAB), or tetrabutylphosphonium chloride (TBPC) as catalysts. It was also found that the reaction proceeded smoothly in amide-type polar solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP) to give a high molecular weight polyether P-1. The polyaddition of DCNS with diglycidyl ether of ethylene glycol (DGEEG) using TBAB in DMAc also proceeded to give the polyether P-2 in good yield. The resulting polyethers contain reactive chloromethyl groups in a side chain, which was introduced during main chain formation.     

Photosensitivities and rates of photocrosslinking of poly(vinyl α-cyanocinnamate) and poly(vinyl α-cyanocinnamoxy acetate)

The photosensitivities and the rates of photocrosslinking of poly(vinyl α-cyanocinamate) and poly(vinyl α-cyanocinnamoxyacetate) were investigated. The photocrosslinkings of these polymers proceeded mainly through radical addition, and these polymers showed higher photosensitivities than poly(vinyl cinnamate) and poly(vinyl cinnamoxyacetate), in spite of lower rates of photocrosslinking of the former polymers.     

Kaposi's sarcoma-associated herpesvirus infection of bone marrow dendritic cells from multiple myeloma patients

Kaposi's sarcoma-associated herpesvirus (KSHV) was found in the bone marrow dendritic cells of multiple myeloma patients but not in malignant plasma cells or bone marrow dendritic cells from normal individuals or patients with other malignancies. In addition the virus was detected in the bone marrow dendritic cells from two out of eight patients with monoclonal gammopathy of undetermined significance (MGUS), a precursor to myeloma. Viral interleukin-6, the human homolog of which is a growth factor for myeloma, was found to be transcribed in the myeloma bone marrow dendritic cells. KSHV may be required for transformation from MGUS to myeloma and perpetuate the growth of malignant plasma cells.     

A novel reaction of epoxy resins with polyfunctional active esters

Addition reactions of commercial epoxy resins such as bisphenol-A diglycidylether (BADGE), ethylene glycol diglycidylether (EGGE), and N,N-diglycidylaniline (GAN) with various active esters such as di[S-(benzothizolyl)] thioadipate (BTAD), di(4-nitrophenyl) adipate (NPAD), di(S-phenyl) thioadipate (PTAD), and 4-nitrobenzoyl esters of polyfunctional phenols were carried out in neat using quaternary salts or crown ether-salts complexes as a catalyst at 50–130°C. The rate of addition reaction of BTAD was faster than that with other esters under the same reaction conditions. Furthermore, it was found that the rate of addition reaction of the epoxy resins with some active esters was strongly affected by the kind of epoxy resin, the structural formula of carboxylic acid, and the kind of catalyst. The reaction of epoxy resins with polyfunctional active esters proceeded quantitatively at the elevated temperatures. However, some of the mixtures of epoxy resin, polyfunctional active ester and the catalyst showed excellent storage stability at 30°C.     

Photocrosslinking reactions of polyfunctional monomers with vinyl ether or propargyl ether groups

Photocrosslinking reactions of di(2-vinyloxy)ethyl ether of bisphenol-A (BPAEVE), dipropargyl ether of bisphenol-A (BPAPE), and diglycidy ether of bisphenol-A (BPAGE) were carried out using various cationic photoinitiators in 1,2-dichloroethane. The reaction of BPAEVE occurred with high conversion to give the gel products, and the reaction rate of BPAEVE was higher than that of BPAGE. While, the photocrosslinking reaction of BPAPE did not take place under the same conditions. Photoinitiated Michael addition reactions of BPAEVE, BPAPE, and other dipropargyl ethers or ester with pentaerythritol (2-tetramercapto)propionate (PETMP) also proceeded very smoothly to give the gel products by using benzophenone as a photosensitizer in THF. Although the rate of addition reaction of BPAEVE was strongly influenced by the photosensitizer concentration, the addition reaction of BPAEVE with PETMP propagated effectively to give the gel products even without the presence of photosensitizer when irradiated with UV light in THF or toluene solution.