Well‐Controlled Biodegradable Nanocomposite Foams: From Microcellular to Nanocellular

Via a batch process in an autoclave, the foam processing of neat polylactide (PLA) and two different types of PLA/layered silicate nanocomposites has been conducted using supercritical carbon dioxide as a foaming agent. The morphological correlation between the dispersed silicate particles with nanometer dimensions in the bulk and the obtained closed‐cell structure of the foam is discussed. This is the first report that deals with the possibility of preparing biodegradable nanocellular polymeric foams via nanocomposite technology.

SEM image of the freeze‐fracture surface of a PLA/layered silicate foam, exhibiting closed‐cell structure.     

Continuum background reduction in orthogonal-acceleration time-of-flight mass spectrometry with continuous ion sources

The continuum ion background in an inductively coupled plasma time-of-flight mass spectrometer (TOFMS) has been reduced by 2 orders of magnitude by using energy discrimination (ED). A potential barrier placed in front of the ion detector effectively discriminates between higher-energy signal ions and the lower-energy background ions. The signal-to-noise ratio was increased tenfold and detection limits of 0.4–4.2 ppt were achieved for 11 elements ranging from Li to U. The resolving power was observed to degrade from 1520 to 1230 with the addition of the potential barrier. The residual background count rate was found to be limited by neutrals formed after exiting the ion reflectron via charge exchange with the background gas. This ED method can be employed to effectively reduce the continuum ion background in any TOFMS that uses orthogonal acceleration with a continuous ion source.     

Entrapment of a Pseudo‐Tetrahedral CoII Center by Thioether Sulfur Bound {Co2(μ‐L)} Fragments: Synthesis,Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity

Simultaneous incorporation of both Co^II and Co^III ions within a new thioether S‐bearing phenol‐based ligand system, H₃L (2,6‐bis‐[{2‐(2‐hydroxyethylthio)ethylimino}methyl]‐4‐methylphenol) formed [Co₅] aggregates [Co^IICo^III₄L₂(μ‐OH)₂(μ_1,3‐O₂CCH₃)₂](ClO₄)₄?H₂O ( 1 ) and [Co^IICo^III₄L₂(μ‐OH)₂(μ_1,3‐O₂CC₂H₅)₂](ClO₄)₄?H₂O ( 2 ). The magnetic studies revealed axial zero‐field splitting (ZFS) parameter, D/hc=?23.6 and ?24.3 cm^?1, and E/D=0.03 and 0.00, respectively for 1 and 2 . Dynamic magnetic data confirmed the complexes as SIMs with U_eff/k_B=30 K ( 1 ) and 33 K ( 2 ), and τ₀=9.1×10^?8 s ( 1 ), and 4.3×10^?8 s ( 2 ). The larger atomic radius of S compared to N gave rise to less variation in the distortion of tetrahedral geometry around central Co^II centers, thus affecting the D and U_eff/k_B values. Theoretical studies also support the experimental findings and reveal the origin of the anisotropy parameters. In solutions, both 1 and 2 which produce {Co^III₂(μ‐L)} units, display solvent‐dependent catechol oxidation behavior toward 3,5‐di‐tert‐butylcatechol in air. The presence of an adjacent Co^III ion tends to assist the electron transfer from the substrate to the metal ion center, enhancing the catalytic oxidation rate.     

Aqueous Phase Sensing of Fe3+ and Ascorbic Acid by a Metal–Organic Framework and Its Implication in the Construction of Multiple Logic Gates

A new Hf^IV‐based metal‐organic framework with UiO‐66 topology was synthesized via a one‐step solvothermal method by using 3‐methyl‐4‐phenylthieno[2,3‐b]thiophene‐2,5‐dicarboxylic acid (H₂MPTDC) as a ligand. The MOF material showed a high stability in a broad pH range (from pH 2 to pH 12) in an aqueous medium. The presence of hydrophobic methyl and phenyl substituents in the carboxylic acid ligand and strong Hf?O bond play crucial roles in its stability. The new MOF material was systematically characterized by various techniques such as XRPD, N₂ sorption, thermogravimetric analyses and FT‐IR spectroscopy. The photophysical properties of the MOF material were also examined by steady‐state and time‐resolved fluorescence studies. It was observed that the blue fluorescence of the MOF material was selectively quenched in the presence of Fe³⁺ ion in pure aqueous medium. A mechanistic study disclosed that quenching occurs via a strong inner filter effect (IFE) arising from Fe³⁺ ion in aqueous medium. Interestingly, the fluorescence of the MOF material can be recovered by elimination of the IFE of Fe³⁺ ion via reduction of Fe³⁺ ion by ascorbic acid (AA). Based on the fluorescence recovery by AA, a MOF based on‐off‐on probe was developed for the sensing of Fe³⁺ ion and AA in aqueous medium. Inspired by this reversible sensing event, we demonstrate basic (NOT, OR, YES, INHIBIT and IMP) and higher integrated logic operations utilizing this fluorescent MOF. This MOF‐based logic systems could be potentially used for next‐generation logic‐gate based analytical applications as well as for the detection and discrimination of targeted molecules in various complex domains.     

The crystal and molecular structures of three copper‐containing complexes and their activities in mimicking galactose oxidase

The structures of three copper‐containing complexes, namely (benzoato‐κ²O,O′)[(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O]copper(II) dihydrate, [Cu(C₇H₅O₂)(C₁₃H₁₉N₂O)]·2H₂O, 1 , [(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O](2‐phenylacetato‐κ²O,O′)copper(II), [Cu(C₈H₇O₂)(C₁₃H₁₉N₂O)], 2 , and bis[μ‐(E)‐2‐({[3‐(diethylamino)propyl]imino}methyl)phenolato]‐κ⁴N,N′,O:O;κ⁴O:N,N′,O‐(μ‐2‐methylbenzoato‐κ²O:O′)copper(II) perchlorate, [Cu₂(C₈H₇O₂)(C₁₂H₁₇N₂O)₂]ClO₄, 3 , have been reported and all have been tested for their activity in the oxidation of d ‐galactose. The results suggest that, unlike the enzyme galactose oxidase, due to the precipitation of Cu₂O, this reaction is not catalytic as would have been expected. The structures of 1 and 2 are monomeric, while 3 consists of a dimeric cation and a perchlorate anion [which is disordered over two orientations, with occupancies of 0.64 (4) and 0.36 (4)]. In all three structures, the central Cu atom is five‐coordinated in a distorted square‐pyramidal arrangment (τ parameter of 0.0932 for 1 , 0.0888 for 2 , and 0.142 and 0.248 for the two Cu centers in 3 ). In each species, the environment about the Cu atom is such that the vacant sixth position is open, with very little steric crowding.     

New double-periodic solutions of fractional Drinfeld–Sokolov–Wilson equation in shallow water waves

Nonlinear Dynamics - In the present article, the new exact solutions of time-fractional coupled Drinfeld–Sokolov–Wilson equations have been derived by using a new reliable analytical...     

New Exact Solutions of Fractional Zakharov–Kuznetsov and Modified Zakharov–Kuznetsov Equations Using Fractional Sub-Equation Method

In the present paper, we construct the analytical exact solutions of some nonlinear evolution equations in mathematical physics; namely the space-time fractional Zakharov–Kuznetsov(ZK) and modified Zakharov–Kuznetsov(m ZK) equations by using fractional sub-equation method. As a result, new types of exact analytical solutions are obtained. The obtained results are shown graphically. Here the fractional derivative is described in the Jumarie's modified Riemann–Liouville sense.     

Electrical characteristics of BaTiO3/ Bi0.5K0.5TiO3 multilayered thin films synthesized via metalloorganic decomposition

Multilayered BaTiO₃(BTO)/Bi_0.5K_0.5TiO₃ (BKT) thin films have been fabricated on Pt/Ti/SiO₂/Si substrates using a metalloorganic decomposition process. XRD investigation of the resultant BTO/BKT multilayered thin films shows that they retain a perovskite-related structure type. They also exhibit a well-defined, polarization–electric field hysteresis loop with a measured remnant polarization (2P_r) of 5 µC/cm² at an applied electric field of 250 kV/cm. The measured dielectric constant and dielectric loss at 10 kHz is 470 and 0.07 respectively. These multilayer BTO/BKT films maintain an excellent fatigue-free character even after 10⁹ switching cycles. The mechanism associated with the enhancement of the electrical properties of the synthesized BTO/BKT films is also discussed.