Pressure-assisted strategy for the synthesis of vinyl pyrrolidone-based macro-star photoiniferters. A route to star block copolymers

Star-shaped 1-vinyl-2-pyrrolidone (VP)-based polymers having four pendant arms were produced via high-pressure RAFT using the trithiocarbonate-functionalized core. The use of compression (p = 250 MPa) significantly reduced or eliminated star-star/star-chain coupling side reactions and termination process characteristics the for “core-first” R-type approach, still allowing for a “pseudo-living” reaction course up to very high monomer conversion (>98%). Consequently, tailored and highly living star-shaped poly(1-vinyl-2-pyrrolidone)s (PVP) in a wide range of molecular weights M _n = 2.0–175.6 kg/mol (Đ = 1.18–1.80) have been obtained. The chain extension of the produced polymer was carried out with methyl methacrylate (MMA) via photo-induced RAFT (λ = 365 nm) in the presence of tertiary amine catalyst, yielding well-defined amphiphilic star-shaped block copolymers. DSC measurements showed that synthesized star-shaped PVP homopolymers revealed much lower glass transition temperature values compared to their commercially supplied linear analogs.     

Dispersion of magnetic nanoparticles in a polymorphic liquid crystal

In order to enhance the phase stability of dispersions of magnetic nanoparticles (NPs) in a polymorphic liquid crystal, new ligands have been designed consisting of a terphenyl-based liquid crystalline core. The most stable dispersions were obtained with 7 nm super-paramagnetic Fe₃O₄ NPs decorated with the new ligands in place of 10 nm ferromagnetic CoFe₂O₄ spherical NPs.     

Recording long-term potentiation of synaptic transmission by three-dimensional multi-electrode arrays

Background  

Multi-electrode arrays (MEAs) have become popular tools for recording spontaneous and evoked electrical activity of excitable tissues. The majority of previous studies of synaptic transmission in brain slices employed MEAs with planar electrodes that had limited ability to detect signals coming from deeper, healthier layers of the slice. To overcome this limitation, we used three-dimensional (3D) MEAs with tip-shaped electrodes to probe plasticity of field excitatory synaptic potentials (fEPSPs) in the CA1 area of hippocampal slices of 129S5/SvEvBrd and C57BL/6J-Tyr^C-Brd mice.     

Formation of InAs quantum dots and wetting layers in GaAs and AlAs analyzed by cross-sectional scanning tunneling microscopy

We have used cross-sectional scanning-tunneling microscopy (X-STM) to compare the formation of self-assembled InAs quantum dots (QDs) and wetting layers on AlAs (1 0 0) and GaAs (1 0 0) surfaces. On AlAs we find a larger QD density and smaller QD size than for QDs grown on GaAs under the same growth conditions (500 °C substrate temperature and 1.9 ML indium deposition). The QDs grown on GaAs show both a normal and a lateral gradient in the indium distribution whereas the QDs grown on AlAs show only a normal gradient. The wetting layers on GaAs and AlAs do not show significant differences in their composition profiles. We suggest that the segregation of the wetting layer is mainly strain-driven, whereas the formation of the QDs is also determined by growth kinetics. We have determined the indium composition of the QDs by fitting it to the measured outward relaxation and lattice constant profile of the cleaved surface using a three-dimensional finite element calculation based on elasticity theory.     

Synthesis of morpholin-2-ones by chemoselective intramolecular rhodium-catalyzed reductive ring expansion of oxazolidines

The rhodium-catalyzed reductive intramolecular ring expansion of N-(ethoxycarboxymethyl)oxazolidines was carried out under an atmosphere of carbon monoxide and hydrogen to afford N-methylmorpholin-2-ones in good to excellent yields.     

Bioactivity Performance of Pure Mg after Plasma Electrolytic Oxidation in Silicate-Based Solutions

The biodegradable metals, including magnesium (Mg), are a convenient alternative to permanent metals but fast uncontrolled corrosion limited wide clinical application. Formation of a barrier coating on Mg alloys could be a successful strategy for the production of a stable external layer that prevents fast corrosion. Our research was aimed to develop an Mg stable oxide coating using plasma electrolytic oxidation (PEO) in silicate-based solutions. 99.9% pure Mg alloy was anodized in electrolytes contained mixtures of sodium silicate and sodium fluoride, calcium hydroxide and sodium hydroxide. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle (CA), Photoluminescence analysis and immersion tests were performed to assess structural and long-term corrosion properties of the new coating. Biocompatibility and antibacterial potential of the new coating were evaluated using U2OS cell culture and the gram-positive Staphylococcus aureus (S. aureus, strain B 918). PEO provided the formation of a porous oxide layer with relatively high roughness. It was shown that Ca(OH)₂ was a crucial compound for oxidation and surface modification of Mg implants, treated with the PEO method. The addition of Ca²⁺ ions resulted in more intense oxidation of the Mg surface and growth of the oxide layer with a higher active surface area. Cell culture experiments demonstrated appropriate cell adhesion to all investigated coatings with a significantly better proliferation rate for the samples treated in Ca(OH)₂-containing electrolyte. In contrast, NaOH-based electrolyte provided more relevant antibacterial effects but did not support cell proliferation. In conclusion, it should be noted that PEO of Mg alloy in silicate baths containing Ca(OH)₂ provided the formation of stable biocompatible oxide coatings that could be used in the development of commercial degradable implants.     

Quantum chemical insight on the uranyl benzoates association with cetylpyridinium

Journal of Radioanalytical and Nuclear Chemistry - The possibility of analytical determination of the uranyl cation UO22+ (taken in the form of the complex uranyl benzoate anion) by using the...     

The Rb7Bi3−3xSb3xCl16 Family: A Fully Inorganic Solid Solution with Room-Temperature Luminescent Members

Low-dimensional ns²-metal halide compounds have received immense attention for applications in solid-state lighting, optical thermometry and thermography, and scintillation. However, these are based primarily on the combination of organic cations with toxic Pb²⁺ or unstable Sn²⁺, and a stable inorganic luminescent material has yet to be found. Here, the zero-dimensional Rb₇Sb₃Cl₁₆ phase, comprised of isolated [SbCl₆]³⁻ octahedra and edge-sharing [Sb₂Cl₁₀]⁴⁻ dimers, shows room-temperature photoluminescence (RT PL) centered at 560 nm with a quantum yield of 3.8±0.2 % at 296 K (99.4 % at 77 K). The temperature-dependent PL lifetime rivals that of previous low-dimensional materials with a specific temperature sensitivity above 0.06 K⁻¹ at RT, making it an excellent thermometric material. Utilizing both DFT and chemical substitution with Bi³⁺ in the Rb₇Bi_3−3xSb_3xCl₁₆ (x≤1) family, we present the edge-shared [Sb₂Cl₁₀]⁴⁻ dimer as a design principle for Sb-based luminescent materials.