Synthesis of Carboxylic Acids Containing α-All-Carbon Quaternary Centers from Diazo Compounds and Trialkylboranes.

The construction of C-C bonds to form all-carbon quaternary centers remains a significant challenge in synthetic chemistry. Herein, we report a tandem process involving a 1,2-migration of a tetra-coordinated boron intermediate followed by a Claisen rearrangement of the boron enolate, achieved through a reaction between allyl diazoacetates and trialkylboranes. The transformation forms two C-C bonds at the carbenic position of diazo substrate in a single-step operation under neutral conditions.

Enhanced removal of 1,2-dichloroethane by nanoscale calcium peroxide activation with Fe(III) coupled with different iron sulfides.

Fe(II) is of great importance in iron-based advanced oxidation processes. However, traditional methods to maintain Fe(II) concentration, such as the addition of chelating agents or reducing agents, may lead to an increase in chemical oxygen demand of secondary pollution. Therefore, in this study, iron sulfides, namely ferrous sulfide (FeS), pyrite (FeS), and sulfidated nanoscale zero-valent iron (S-nZVI), were applied for not only the regeneration of Fe(II) but also the direct dissolution of Fe(II).

Self-Powered Circularly Polarized Light Detection Enabled by Chiral Two-Dimensional Perovskites with Mixed Chiral-Achiral Organic Cations.

Direct detection of circularly polarized light (CPL) holds great promise for the development of various optical technologies. Chiral 2D organic-inorganic halide perovskites make it possible to fabricate CPL-sensitive photodetectors. However, selectively detecting left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light remains a significant challenge.

Adaptive Ion Channels Formed in Ultrathin and Semicrystalline Polymer Interphases for Stable Aqueous Batteries.

Aqueous Zn batteries have recently emerged as promising candidates for large-scale energy storage, driven by the need for a safe and cost-effective technology with sufficient energy density and readily accessible electrode materials. However, the energy density and cycle life of Zn batteries have been limited by inherent chemical, morphological, and mechanical instabilities at the electrode-electrolyte interface where uncontrolled reactions occur. To suppress the uncontrolled reactions, we designed a crystalline polymer interphase for both electrodes, which simultaneously promotes electrode reversibility via fast and selective Zn transport through the adaptive formation of ion channels.

Small to Large Polaron Behavior Induced by Controlled Interactions in Perovskite Quantum Dot Solids.

The polaron is an essential photoexcitation that governs the unique optoelectronic properties of organic-inorganic hybrid halide perovskites, and it has been subject to extensive spectroscopic and theoretical investigation over the past decade. A crucial but underexplored question is how the nature of the photogenerated polarons is impacted by the microscopic perovskite structure and what functional properties this affects. To tackle this question, we chemically tuned the interactions between perovskite quantum dots (QDs) to rationally manipulate the polaron properties.

Coumarin Dimer Is an Effective Photomechanochemical AND Gate for Small-Molecule Release.

Stimulus-responsive gating of chemical reactions is of considerable practical and conceptual interest. For example, photocleavable protective groups and gating mechanophores allow the kinetics of purely thermally activated reactions to be controlled optically or by mechanical load by inducing the release of small-molecule reactants. Such release only in response to a sequential application of both stimuli (photomechanochemical gating) has not been demonstrated despite its unique expected benefits.

Mechanochemically assisted morphing of shape shifting polymers.

Morphing in creatures has inspired various synthetic polymer materials that are capable of shape shifting. The morphing of polymers generally relies on stimuli-active (typically heat and light active) units that fix the shape after a mechanical load-based shape programming. Herein, we report a strategy that uses a mechanochemically active 2,2'-bis(2-phenylindan-1,3-dione) (BPID) mechanophore as a switching unit for mechanochemical morphing.

Exploration of s new biomarker in osteosarcoma and association with clinical outcomes: cancer associated fibroblasts.

Background: Osteosarcoma (OS) is the leading malignant primary bone tumor in young adults and children and has a high mortality rate. Cancer-associated fibroblasts (CAFs) are major components of the tumor microenvironment, influencing cancer progression and metastasis. However, there is no systematic study on the role of CAF in OS.

Combined treatment with glucosamine and chondroitin sulfate improves rheumatoid arthritis in rats by regulating the gut microbiota.

Background: To investigate the ameliorative effects of glucosamine (GS), chondroitin sulphate (CS) and glucosamine plus chondroitin sulphate (GC) on rheumatoid arthritis (RA) in rats, and to explore the mechanism of GS, CS and GC in improving RA based on the gut microbiota.

Methods: RA rat models were effectively developed 14 days after CFA injection, and then garaged with GS, CS and GC. Body weight and paw volume of rats were monitored at multiple time points at the beginning of CFA injection.

The Influence of COVID-19 Pandemic on Management Earnings Forecasts.

As the biggest black swan event of 2020, the COVID-19 pandemic has significantly weakened the ability of corporate stakeholders to monitor companies on site. In this context, exploring whether the on-site supervision restrictions triggered by the COVID-19 pandemic affect management earnings forecast disclosure is crucial to protect investors' interests and promote the stable development of the capital market. Based on quarterly data of Chinese A-share listed companies' earnings forecasts, this paper finds that: First, when the company's registry region is more severely affected by the COVID-19 pandemic, the company has less willingness to disclose its management earnings forecast.

Adiabatically focusing X-rays to the nanometer scale by one dimensional long kinoform lenses: comparison between an ideal Cartesian oval refocusing lens and a parabolic lens.

The nano-focusing performance of adiabatically designed Cartesian oval refocusing lenses is compared with other well known compound refractive lenses with parabolic profiles (both simple concave and kinoform types). Using beam propagation method (BPM) simulation, it is shown that our design based on oval lenses does significantly improve the focusing properties compared to other parabolic lens based designs, e.g.

Concise Synthesis of Chromene/Chromane-Type Aryne Precursors and Their Applications.

The gram-scale synthesis of 5,6-, 6,7-, and 7,8-chromene/chromane-type aryne precursors and their applications in regioselective transformation to other functional derivatives is reported. Chromene/chromane-type arynes are generated under mild conditions, which can further undergo [2 + 2], [3 + 2], and [4 + 2] cycloaddition reactions, nucleophilic addition reactions, and σ-insertion reactions to produce structurally novel substituted chromenes and chromanes. The excellent regioselectivity of the reaction is facilitated by the oxygen-containing guiding groups at the -position of the triple bond, which can be removed or switched to other functional groups including alkenyl, aryl, heteroaryl, and arylamino groups.

Processing-Structure-Performance Relationships of Microporous Metal-Organic Polymers for Size-Selective Separations.

Small-molecule impurities, such as -nitrosodimethylamine (NDMA), have infiltrated the generic drug industry, leading to recalls in commonly prescribed blood pressure and stomach drugs in over 43 countries since 2018 and directly affecting tens of millions of patients. One promising strategy to remove small-molecule impurities like NDMA from drug molecules is by size exclusion, in which the contaminant is removed by selective adsorption onto a (micro)porous material due to its smaller size. However, current solution-phase size-exclusion separations are primarily limited by the throughput-selectivity trade-off.

A Polymer with Mechanochemically Active Hidden Length.

Incorporating hidden length into polymer chains can improve their mechanical properties, because release of the hidden length under mechanical loads enables localized strain relief without chain fracture. To date, the design of hidden length has focused primarily on the choice of the sacrificial bonds holding the hidden length together. Here we demonstrate the advantages of adding mechanochemical reactivity to hidden length itself, using a new mechanophore that integrates ()-2,3-diphenylcyclobutene-1,4-dicarboxylate, with hitherto unknown mechanochemistry, into macrocyclic cinnamate dimers.

Mechanistic Insights into Superlattice Transformation at a Single Nanocrystal Level Using Nanobeam Electron Diffraction.

Understanding the mechanism and ultimately directing nanocrystal (NC) superlattice assembly and attachment have important implications on future advances in this emerging field. Here, we use 4D-STEM to investigate a monolayer of PbS NCs at various stages of the transformation from a hexatic assembly to a nonconnected square-like superlattice over large fields of view. Maps of nanobeam electron diffraction patterns acquired with an electron microscope pixel array detector (EMPAD) offer unprecedented detail into the 3D crystallographic alignment of the polyhedral NCs.

Fabrication of CdS Nanorods on Si Pyramid Surface for Photosensitive Application.

It is the first time that cadmium sulfide (CdS) nanorods have been fabricated on silicon (Si) pyramid surface by the hydrothermal reaction method. In our work, the Si pyramid morphology is able to increase the adhesion between the CdS seed layer and Si wafer. Hence, it is critical for CdS nanorods to grow successfully.

Mechanochromism and optical remodeling of multi-network elastomers containing anthracene dimers.

Multi-network elastomers are both stiff and tough by virtue of containing a pre-stretched stiff network that can rupture and dissipate energy under load. However, the rupture of this sacrificial network in all described covalent multi-network elastomers is irreversible. Herein, we describe the first example of multi-network elastomers with a reformable sacrificial network containing mechanochemically sensitive anthracene-dimer cross-links.

Multi-modal mechanophores based on cinnamate dimers.

Mechanochemistry offers exciting opportunities for molecular-level engineering of stress-responsive properties of polymers. Reactive sites, sometimes called mechanophores, have been reported to increase the material toughness, to make the material mechanochromic or optically healable. Here we show that macrocyclic cinnamate dimers combine these productive stress-responsive modes.

Mechanochromism and Mechanical-Force-Triggered Cross-Linking from a Single Reactive Moiety Incorporated into Polymer Chains.

Incorporation of small reactive moieties, the reactivity of which depends on externally imposed load (so-called mechanophores) into polymer chains offers access to a broad range of stress-responsive materials. Here, we report that polymers incorporating spirothiopyran (STP) manifest both green mechanochromism and load-induced addition reactions in solution and solid. Stretching a macromolecule containing colorless STP converts it into green thiomerocyanine (TMC), the mechanically activated thiolate moiety of which undergoes rapid thiol-ene click reactions with certain reactive C=C bonds to form a graft or a cross-link.

Mechanochemistry of Topological Complex Polymer Systems.

Although existing since the concept of macromolecules, polymer mechanochemistry is a burgeoning field which attracts great scientific interest in its ability to bias conventional reaction pathways and its potential to fabricate mechanoresponsive materials. We review here the effect of topology on the mechanical degradation of polymer chains and the activation of mechanophores in polymer backbones. The chapter focuses on both experimental and theoretical work carried out in the past 70 years.

Mechanical Activation of Mechanophore Enhanced by Strong Hydrogen Bonding Interactions.

A mechanically active spiropyran (SP) mechanophore is incorporated into the backbone of prepolymer which is further end-capped with ureidopyrimidinone (UPy) or urethane. Strong mechanochromic reaction of SP arises in the bulk films of UPy containing materials whereas much weaker activation occurs in urethane containing counterparts, coincident with their stress-strain responses. The difference in the magnitudes of supramolecular interactions leads to different degrees of chain orientation and strain induced crystallization (SIC) in the bulk and consequently distinct capabilities to transfer the load to the mechanophores.

Using metal-ligand interactions to access biomimetic supramolecular polymers with adaptive and superb mechanical properties.

The development of polymer materials that exhibit excellent mechanical properties and can respond to environmental stimuli is of great scientific and commercial interest. In this work, we report a series of biomimetic supramolecular polymers using a ligand macromolecule carrying multiple tridentate ligand 2,6-bis(1,2,3-triazol-4-yl)pyridine (BTP) units synthesized via CuAAC in the polymer backbone together with transition and/or lanthanide metal salts. The metal-ligand complexes phase separate from soft linker segments, acting as physical crosslinking points in the materials.

Mechanoresponsive PS-PnBA-PS Triblock Copolymers via Covalently Embedding Mechanophore.

A mechanically active spiropyran (SP) mechanophore is incorporated into the center of poly(-butyl acrylate) (PnBA) block to construct a series of mechanoresponsive polystyrene (PS)-PnBA-SP-PnBA-PS triblock copolymers. Similar mechanical activations of SP occur in all of the copolymers in solution, whereas a unique PS fraction-dependent mechanochromism is observed in the bulk. Effective mechanical activation occurs in the copolymer with a medium PS block length, whereas a very weak color change is observed in the samples bearing low PS fractions and activation appears only in the vicinity of the fracture point in the copolymer bearing long PS blocks.

Liquid-to-solid transition of concentrated suspensions under complex transient shear histories.

Suspensions containing noncolloidal aluminum particles in a Newtonian carrier liquid and the effects of shear history on the rheological properties of suspensions are investigated showing a critical concentration phi(c), which is close to the "freezing" packing fraction of spherical particle suspensions. An apparent liquid-to-solid transition was clearly found for suspensions below phi(c) via transient step shear after long shear history as well as via the large amplitude oscillatory shear flow with controlled shear stress. The microstructures or the local flow characteristics of suspensions with phiphi(c) are still different according to the Fourier Transform Rheological analysis.