Responsive hyperbranched poly(formyl-1,2,3-triazole)s toward quadruple-modal information security protection

Science China Chemistry - Secrecy has received tremendous attention in modern information society. Innovative polymer-based fluorescent materials with multiple mode emission are quite desirable to...     

Influence of Substitutional Defects in ZIF-8 Membranes on Reverse Osmosis Desalination: A Molecular Dynamics Study

In this study, molecular dynamics simulation is used to investigate the effects of water-based substitutional defects in zeolitic imidazolate frameworks (ZIF)-8 membranes on their reverse osmosis (RO) desalination performance. ZIF-8 unit cells containing up to three defect sites are used to construct the membranes. These substitutional defects can either be Zn defects or linker defects. The RO desalination performance of the membranes is assessed in terms of the water flux and ion rejection rate. The effects of defects on the interactions between the ZIF-8 membranes and NaCl are investigated and explained with respect to the radial distribution function (RDF) and ion density distribution. The results show that ion adsorption on the membranes occurs at either the nitrogen atoms or the defect sites. Complete NaCl rejection can be achieved by introducing defects to change the size of the pores. It has also been discovered that the presence of linker defects increases membrane hydrophilicity. Overall, molecular dynamics simulations have been used in this study to show that water-based substitutional defects in a ZIF-8 structure reduce the water flux and influence its hydrophilicity and ion adsorption performance, which is useful in predicting the type and number of defect sites per unit cell required for RO applications. Of the seven ZIF-8 structures tested, pristine ZIF-8 exhibits the best RO desalination performance.     

Two mononuclear molybdenum(VI) oxo complexes with tridentate hydrazone ligands: Synthesis and crystal structures

Reaction of [MoO₂(Acac)₂] (Acac = acetylacetonate) with two similar hydrazone ligands in methanol yielded two mononuclear molybdenum(VI) oxocomplexes with general formula [MoO₂(L)(CH₃OH)], where L = L¹ = (4-nitrophenoxy)acetic acid [1-(3-ethoxy-2-hydroxyphenyl)methylidene]hydrazide (H₂L¹) and L = L² = (4-nitrophenoxy)acetic acid [1-(5-bromo-2-hydroxyphenyl)methylidene]hydrazide (H₂L²). Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction method. All investigated compounds were further characterized by elemental analysis and FT-IR spectra. Single crystal X-ray structural studies indicate that the hydrazone ligands coordinate to the MoO₂ cores through enolate oxygen, phenolate oxygen, and azomethine nitrogen. The Mo atoms in both complexes are in octahedral coordination.     

miR-98 suppresses melanoma metastasis through a negative feedback loop with its target gene IL-6

Dysregulated microRNA (miRNA) expression has a critical role in tumor development and metastasis. However, the mechanism by which miRNAs control melanoma metastasis is unknown. Here, we report reduced miR-98 expression in melanoma tissues with increasing tumor stage as well as metastasis; its expression is also negatively associated with melanoma patient survival. Furthermore, we demonstrate that miR-98 inhibits melanoma cell migration in vitro as well as metastatic tumor size in vivo. We also found that IL-6 is a target gene of miR-98, and IL-6 represses miR-98 levels via the Stat3-NF-κB-lin28B pathway. In an in vivo melanoma model, we demonstrate that miR-98 reduces melanoma metastasis and increases survival in part by reducing IL-6 levels; it also decreases Stat3 and p65 phosphorylation as well as lin28B mRNA levels. These results suggest that miR-98 inhibits melanoma metastasis in part through a novel miR-98-IL-6-negative feedback loop.     

SO2–ethanol–water (SEW) fractionation process: production of dissolving pulp from spruce

SO₂–ethanol–water (SEW) fractionation process is a highly attractive platform for future lignocellulosic Biorefineries. Its governing advantages include high flexibility in the selection of the raw material, simple and efficient recovery of fractionation chemicals, absence of carbohydrate degradation (both cellulose and hemicelluloses), and high reaction rates. The process is suitable for production of various carbohydrate- and lignin-based products including papermaking pulp, glucose, bioalcohols and lignosulfonates. The present paper addresses the possibility of producing dissolving pulp from spruce using SEW fractionation followed by ECF bleaching with and without hot caustic extraction. Comprehensive characterisation of chemical and macromolecular properties of the SEW dissolving pulps was complemented by determining the quality of viscose. The comparison with conventional viscose-grade acid sulfite pulps revealed close proximity in all properties. Therefore, considering the advantages of SEW process, it is suggested as a possible replacement for acid sulfite process in dissolving pulp manufacturing.     

Oxygen- and Nitrogen-Embedded Zigzag Hydrocarbon Belts

Despite the aesthetically appealing structures and tantalizing physical and chemical properties, zigzag hydrocarbon belts and their heteroatom-embedded analogues remain challenging synthetic targets. We report herein the synthesis of diverse O/N-doped zigzag hydrocarbon belts based on selective bridging of the fjords of resorcin[4]arene derivatives through intramolecular S_NAr and palladium-catalyzed intermolecular C−N bond formation reactions. Preorganized conformations of mono-macrocyclic, half-belt and quasi-belt compounds were revealed to facilitate cyclization reactions to construct heteroatom-linked octahydrobelt[8]arenes. The acquired products had strained square-prism-shaped belt structures in which all six-membered heterocyclic rings adopted an unusual boat conformation with equatorially configured alkyl groups. The unprecedented heteroatom-bearing belts also exhibited different photophysical and redox properties to those of octahydrobelt[8]arene analogues.     

Lattice Distortion in Hollow Multi-Shelled Structures for Efficient Visible-Light CO2 Reduction with a SnS2/SnO2 Junction

Precise control of the micro-/nanostructures of nanomaterials, such as hollow multi-shelled structures (HoMSs), has shown its great advantages in various applications. Now, the crystal structure of building blocks of HoMSs are controlled by introducing the lattice distortion in HoMSs, for the first time. The lattice distortion located at the nanoscale interface of SnS₂/SnO₂ can provide additional active sites, which not only provide the catalytic activity under visible light but also improve the separation of photoexcited electron–hole pairs. Combined with the efficient light utilization, the natural advantage of HoMSs, a record catalytic activity was achieved in solid–gas system for CO₂ reduction, with an excellent stability and 100 % CO selectivity without using any sensitizers or noble metals.     

Orthogonal Cationic and Radical RAFT Polymerizations to Prepare Bottlebrush Polymers

An orthogonal combination of cationic and radical RAFT polymerizations is used to synthesize bottlebrush polymers using two distinct RAFT agents. Selective consumption of the first RAFT agent is used to control the cationic RAFT polymerization of a vinyl ether monomer bearing a secondary dormant RAFT agent, which subsequently allows side‐chain polymers to be grafted from the pendant RAFT agent by a radical‐mediated RAFT polymerization of a different monomer, thus completing the synthesis of bottlebrush polymers. The high efficiency and selectivity of the cationic and radical RAFT polymerizations allow both polymerizations to be conducted in one‐pot tandem without intermediate purification.     

A Molecular Thermochromic Ferroelectric

Molecular ferroelectrics have attracted considerable interests because of their easy and environmentally friendly processing, low acoustical impedance and mechanical flexibility. Herein, a molecular thermochromic ferroelectric, N,N′‐dimethyl‐1,4‐diazoniabicyclo[2.2.2]octonium tetrachlorocuprate(II) ([DMe‐DABCO]CuCl₄) is reported, which shows both excellent ferroelectricity and intriguing thermochromism. [DMe‐DABCO]CuCl₄ undergoes a ferroelectric phase transition from Pca2₁ to Pbcm at a significantly high Curie temperature of 413 K, accompanied by a color change from yellow to red that is due to the remarkable deformation of [CuCl₄]^2? tetrahedron, where the ferroelectric and paraelectric phases correspond to yellow and red, respectively. Combined with multiple bistable physical properties, [DMe‐DABCO]CuCl₄ would be a promising candidate for next‐generation smart devices, and should inspire further exploration of multifunctional molecular ferroelectrics.     

反相高效液相色谱-增敏化学发光同时测定VB1和VC

本文基于维生素B1(VB1)、维生素C(VC)对鲁米诺(Luminol)和铁氰化钾(K3[Fe(CN)6])化学发光反应的增敏作用原理,建立了反相高效液相色谱(RP-HPLC)分离、柱后化学发光检测VB1与VC的新方法。当在鲁米诺中加入KBr时可以大大增敏该反应。本法已成功运用于蜂蜜和复合维生素片中VB1与VC的测定。