Surface antimicrobial modification of polyamide by poly(hexamethylene guanidine) hydrochloride

Antimicrobial polyamide (PA) received much attention for the demand of packaging and biomedical fields. In this paper, an antimicrobial PA6 membrane was prepared via a surface chemical reaction. A highly effective antibacterial component (PHMG‐E) with terminal epoxy group was firstly synthesized via a reaction between polyhexamethylene guanidine hydrochloride (PHMG) and ethylene glycol diglycidyl ether (EGDE). Then, PHMG‐E was bonded on the surface of PA6 membrane with secondary amine reduced by borane‐tetrahydrofuran (BH₃‐THF). The antimicrobial rates of surface‐modified PA6 membrane (PA6‐PHMG) against Escherichia coli and Staphylococcus aureus were both higher than 99.99%, and the PHMG was non‐leaching due to the chemical bonding. The hydrophilicity of antibacterial PA6 membrane was also significantly improved and the mechanical performance became better.     

Paper spray tandem mass spectrometry: A rapid approach for the assay of parabens in cosmetics and drugs

A fast methodology for the assay of parabens in drug and cosmetic preparations has been presented. The procedure developed is based on paper spray tandem mass spectrometry and isotope dilution approach. For each investigated paraben, the corresponding labeled standard has been used in order to improve the accuracy and reproducibility of the analyses. The MS experiments have been performed under MRM conditions, monitoring the transitions [M‐H]^? → m/z 92 and [M‐H]^? → m/z 98, respectively, for each analyte and the corresponding labeled internal standard. The quantitative assay has been performed using a calibration curve built from 2 to 15 mg/L. The method accuracy, in all case near 100%, was evaluated using fortified samples at two concentration levels, which are representative of the lower and the higher portion of calibration curve. The good values of LOQ, LOD, and reproducibility confirm the consistency of the developed approach.     

NaGaS2: An Elusive Layered Compound with Dynamic Water Absorption and Wide‐Ranging Ion‐Exchange Properties

Most ternary sulfides belonging to the MGaS₂ structure‐type have been known for many years and are well‐characterized. Surprisingly, there have been no reports of the NaGaS₂ composition, which contains Na, a monovalent cation slightly larger in size than Li, found in LiGaS₂, a compound known for its non‐linear optical properties. Now it is demonstrated for the first time that the unique reversible water absorption in NaGaS₂ has resulted in its absence from previous reports owing to difficulties encountered when characterizing this compound by SC XRD. The layered structure of this compound coupled with uniquely easy migration of water molecules between the layers allows for ion exchange with 3d and 5f metal cations. Some cations, for example, Ni²⁺, facilitate exfoliation of the layers, providing a facile synthetic route to a new class of 2D chalcogenide materials and furthermore demonstrating that NaGaS₂ can readily uptake uranyl species from aqueous solutions.     

Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids

As a key element in the construction of complex organic scaffolds, the formation of C?C bonds remains a challenge in the field of synthetic organic chemistry. Recent advancements in single‐electron chemistry have enabled new methods for the formation of various C?C bonds. Disclosed herein is the development of a novel single‐electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium in situ followed by a radical–radical coupling was made possible merging N‐heterocyclic carbene (NHC) and photoredox catalysis. The utility of this protocol in synthesis was showcased in the late‐stage functionalization of a variety of pharmaceutical compounds. Preliminary investigations using chiral NHCs demonstrate that enantioselectivity can be achieved, showcasing the advantages of this protocol over alternative methodologies.     

Perdeuterated Conjugated Polymers for Ultralow‐Frequency Magnetic Resonance of OLEDs

The formation of excitons in OLEDs is spin dependent and can be controlled by electron‐paramagnetic resonance, affecting device resistance and electroluminescence yield. We explore electrically detected magnetic resonance in the regime of very low magnetic fields (<1 mT). A pronounced feature emerges at zero field in addition to the conventional spin‐ Zeeman resonance for which the Larmor frequency matches that of the incident radiation. By comparing a conventional π‐conjugated polymer as the active material to a perdeuterated analogue, we demonstrate the interplay between the zero‐field feature and local hyperfine fields. The zero‐field peak results from a quasistatic magnetic‐field effect of the RF radiation for periods comparable to the carrier‐pair lifetime. Zeeman resonances are resolved down to 3.2 MHz, approximately twice the Larmor frequency of an electron in Earth's field. However, since reducing hyperfine fields sharpens the Zeeman peak at the cost of an increased zero‐field peak, we suggest that this result may constitute a fundamental low‐field limit of magnetic resonance in carrier‐pair‐based systems. OLEDs offer an alternative solid‐state platform to investigate the radical‐pair mechanism of magnetic‐field effects in photochemical reactions, allowing models of biological magnetoreception to be tested by measuring spin decoherence directly in the time domain by pulsed experiments.     

Multicomponent Organic Metal Halide Hybrid with White Emissions

Zero‐dimensional (0D) organic metal halide hybrids, in which organic and metal halide ions cocrystallize to form neutral species, are a promising platform for the development of multifunctional crystalline materials. Herein we report the design, synthesis, and characterization of a ternary 0D organic metal halide hybrid, (HMTA)₄PbMn_0.69Sn_0.31Br₈, in which the organic cation N‐benzylhexamethylenetetrammonium (HMTA⁺, C₁₃H₁₉N₄⁺) cocrystallizes with PbBr₄^2?, MnBr₄^2?, and SnBr₄^2?. The wide band gap of the organic cation and distinct optical characteristics of the three metal bromide anions enabled the single‐crystalline “host–guest” system to exhibit emissions from multiple “guest” metal halide species simultaneously. The combination of these emissions led to near‐perfect white emission with a photoluminescence quantum efficiency of around 73 %. Owing to distinct excitations of the three metal halide species, warm‐ to cool‐white emissions could be generated by controlling the excitation wavelength.     

Molecular Dynamic Simulation of Side-Chain Liquid Crystalline Elastomer

Summary: Molecular dynamic simulation of side chain liquid crystalline elastomer has been carried out. As an initial state a flexible polymer network in a low molecular liquid-crystal (LC) solvent was used. The LC solvent comprises of anisotropic rod-like semiflexible linear molecules (mesogens) composed of particles bonded into the chain by FENE potential. Rigidity of LC molecules was induced by a bending potential. All interactions between nonbonded particles are described by a repulsive Lennard-Jones potential. For the systems with different values of density and order parameter obtained after sufficiently long trajectory the attachment of ends of mesogens to the polymer network was simulated. The kinetic of the process of mesogens attachment to network was studied as well as morphology of attachment. The structural and dynamical behaviour of side chain LC elastomer was studied and compared with systems of polymer network in low molecular LC solvent.