Supramolecular Synthesis of Solid‐State Tapes Through Molecular Facial Self‐Recognition

Four heterocyclic compounds are presented which exhibit specific self‐recognition of identical Donor–Acceptor (D–A) H‐bonding arrays, resulting in solid‐state tapes with the same, but anti‐parallel functional‐group distribution on opposite sides. A detailed X‐ray‐crystallographic analysis of these supramolecular structures is described.     

Optical properties of sol-gel fabricated Ni/SiO2 glass nanocomposites

Nickel nanoparticles were grown in silica glass by annealing of the sol-gel prepared silicate matrices doped with nickel nitrate. TEM characterization of Ni/SiO₂ glass proves the formation of isolated spherical nickel nanoparticles with mean sizes 6.7 and 20 nm depending on annealing conditions. The absorption and photoluminescence spectra of Ni/SiO₂ glasses were measured. In the absorption spectra, we observed the band related to the surface plasmon resonance (SPR) in Ni nanoparticles. The broadening of SPR was observed with decrease of Ni nanoparticle size. The width of the surface plasmon band decreases 1.5 times at the lowering of temperature from 293 to 2 K because of strong electron-phonon interaction. The spectra proved the creation of nickel oxide NiO clusters and Ni²⁺ ions in silica glass as well.     

Continuous paranematic-to-nematic ordering transitions of liquid crystals in tubular silica nanochannels

The optical birefringence of rodlike nematogens (7CB, 8CB), imbibed in parallel silica channels with 10 nm diameter and 300 microm length, is measured and compared to the thermotropic bulk behavior. The orientational order of the confined liquid crystals, quantified by the uniaxial nematic ordering parameter, evolves continuously between paranematic and nematic states, in contrast to the discontinuous isotropic-to-nematic bulk phase transitions. A Landau-de Gennes model reveals that the strength of the orientational ordering fields, imposed by the silica walls, is beyond a critical threshold, that separates discontinuous from continuous paranematic-to-nematic behavior. Quenched disorder effects, attributable to wall irregularities, leave the transition temperatures affected only marginally, despite the strong ordering fields in the channels.     

HyperKähler and quaternionic Kähler manifolds with S -symmetries

We study relations between quaternionic Riemannian manifolds admitting different types of symmetries. We show that any hyperKähler manifold admitting hyperKähler potential and triholomorphic action of S¹$S^1$ can be constructed from another hyperKähler manifold (of lower dimension) with an action of S¹$S^1$ that fixes one complex structure and rotates the other two and vice versa. We also study the corresponding quaternionic Kähler manifolds equipped with a quaternionic Kähler action of the circle. In particular we show that any positive quaternionic Kähler manifolds with S¹$S^1$-symmetry admits a Kähler metric on an open everywhere dense subset.     

On Banach–Mazur distance between planar convex bodies

Upper estimates of the diameter and the radius of the family of planar convex bodies with respect to the Banach–Mazur distance are obtained. Namely, it is shown that the diameter does not exceed \(\tfrac{19-\sqrt{73}}{4}\approx 2.614\), which improves the previously known bound of 3, and that the radius does not exceed \(\frac{117}{70}\approx 1.671\).     

Reactive Hydrogel Networks for the Fabrication of Metal–Polymer Nanocomposites

In this study, highly stable gold and silver nanoparticles evenly distributed within a crosslinked poly(acrylamide)/poly(N‐(hydroxymethyl)acrylamide) (PAAm‐PHMAAm) network have been fabricated without addition of a reducing agent. Remarkably, the same chemical hydrogel composition has been involved in the successful fabrication of spherical gold and silver nanoparticles within the hydrogel template. The hydrogel network acts simultaneously as an efficient reducing agent and stabilizer. The PAAm–PHMAAm hydrogel network binds metal ions and, following reduction of bound to crosslinked template metal ions, proceeds via oxidation of hydroxymethyl hydrogel fragments. A one‐electron mechanism is proposed for the formation of the silver and gold nanoparticles.

     

Clustering of Iron Oxide Nanoparticles with Amphiphilic Invertible Polymer Enhances Uptake and Release of Drugs and MRI Properties

A functionalization of iron oxide nanoparticles (NPs) of different diameters by the amphiphilic invertible polymer, (PEG600‐alt‐PTHF650)_k (PEG and PTHF stand for poly(ethylene glycol) and poly(tetrahydrofuran), respectively), leads to different NP/polymer architectures for dye/drug uptake and release, as is reported here for the first time. It is demonstrated that 18.6 ± 1.4 and 11.9 ± 0.6 nm NPs are individually coated by this polymer, while 5.9 ± 0.6 nm NPs form nanoparticle clusters (NPCs) which could be isolated by either ultracentrifugation or magnetic separation. This phenomenon is most likely due to the character of the (PEG600‐alt‐PTHF650)_k macromolecule with alternating hydrophilic and hydrophobic fragments and its dimensions sufficient to cause NP clustering. Utilizing Rhodamine B base (RBB) and doxorubicin (DOX), the data on uptake upon mixing and further release via inversion into octanol (mimicking the penetration of the cell biomembrane) are presented. The magnetic NPCs display enhanced uptake and release of both RBB and DOX most likely due to the higher retained polymer amount. The NPCs also display exceptional magnetic resonance imaging properties. This and the high uptake/release efficiency of the NPCs combined with easy magnetic separation make them promising for theranostic probes for magnetically targeted drug delivery.     

In situ X-ray photoelectron spectroscopy investigation of the solid electrolyte interphase in a Li/Li6.4Ga0.2La3Zr2O12/LiFePO4 all-solid-state battery

Journal of Solid State Electrochemistry - The fundamental understanding of the solid electrolyte/electrode interphase during charge and discharge is promising for the development of all-solid-state...     

A method for prompt in situ uranium assay and free acidity determination in uranyl nitrate solutions by density and Raman measurements

A precise and accurate compositional characterization methodology using wavelength dispersive X-ray fluorescence (WDXRF) spectrometry for mixed oxide nuclear fuels is reported. The methodology involves pelletization of standards and samples. The calibration plots were made by plotting the percent intensity of analyte X-ray lines against their amount percent. The relative standard deviation were 0.4% and 0.25%, respectively for uranium and thorium, having U ranging from 2.85 to 4.2 (wt%). The analytical results were compared with chemical analysis method and were in good agreement. The developed WDXRF method is non-destructive, fast and better in comparison to chemical analysis methods.