Beetles (Coleoptera) are the most diverse and species-rich group of insects, and a robust, time-calibrated phylogeny is fundamental to understanding macroevolutionary processes that underlie their ...diversity. Here we infer the phylogeny and divergence times of all major lineages of Coleoptera by analyzing 95 protein-coding genes in 373 beetle species, including ~67% of the currently recognized families. The subordinal relationships are strongly supported as Polyphaga (Adephaga (Archostemata, Myxophaga)). The series and superfamilies of Polyphaga are mostly monophyletic. The species-poor Nosodendridae is robustly recovered in a novel position sister to Staphyliniformia, Bostrichiformia, and Cucujiformia. Our divergence time analyses suggest that the crown group of extant beetles occurred ~297 million years ago (Mya) and that ~64% of families originated in the Cretaceous. Most of the herbivorous families experienced a significant increase in diversification rate during the Cretaceous, thus suggesting that the rise of angiosperms in the Cretaceous may have been an 'evolutionary impetus' driving the hyperdiversity of herbivorous beetles.
Hydrogen generation from the direct splitting of water by photocatalysis is regarded as a promising and renewable solution for the energy crisis. The key to realize this reaction is to find an ...efficient and robust photocatalyst that ideally makes use of the energy from sunlight. Recently, due to the attractive properties such as appropriate band structure, ultrahigh specific surface area, and more exposed active sites, two-dimensional (2D) photocatalysts have attracted significant attention for photocatalytic water splitting. This Review attempts to summarize recent progress in the fabrication and applications of 2D photocatalysts including graphene-based photocatalysts, 2D oxides, 2D chalcogenides, 2D carbon nitride, and some other emerging 2D materials for water splitting. The construction strategies and characterization techniques for 2D/2D photocatalysts are summarized. Particular attention has been paid to the role of 2D/2D interfaces in these 2D photocatalysts as the interfaces and heterojunctions are critical for facilitating charge separation and improving photocatalysis efficiency. We also critically discuss their stability as photocatalysts for water splitting. Finally, we highlight the ongoing challenges and opportunities for the future development of 2D photocatalysts in this exciting and still emerging area of research.
Conspectus The functionalization of unactivated carbon–hydrogen bonds is a transformative strategy for the rapid construction of molecular complexity given the ubiquitous presence of C–H bonds in ...organic molecules. It represents a powerful tool for accelerating the synthesis of natural products and bioactive compounds while reducing the environmental and economic costs of synthesis. At the same time, the ubiquity and strength of C–H bonds also present major challenges toward the realization of transformations that are both highly selective and efficient. The development of practical C–H functionalization reactions has thus remained a compelling yet elusive goal in organic chemistry for over a century. Specifically, the capability to form useful new C–C, C–N, C–O, and C–X bonds via direct C–H functionalization would have wide-ranging impacts in organic synthesis. Palladium is especially attractive as a catalyst for such C–H functionalizations because of the diverse reactivity of intermediate palladium–carbon bonds. Early efforts using cyclopalladation with Pd(OAc)2 and related salts led to the development of many Pd-catalyzed C–H functionalization reactions. However, Pd(OAc)2 and other simple Pd salts perform only racemic transformations, which prompted a long search for effective chiral catalysts dating back to the 1970s. Pd salts also have low reactivity with synthetically useful substrates. To address these issues, effective and reliable ligands capable of accelerating and improving the selectivity of Pd-catalyzed C–H functionalizations are needed. In this Account, we highlight the discovery and development of bifunctional mono-N-protected amino acid (MPAA) ligands, which make great strides toward addressing these two challenges. MPAAs enable numerous Pd(II)-catalyzed C(sp2)–H and C(sp3)–H functionalization reactions of synthetically relevant substrates under operationally practical conditions with excellent stereoselectivity when applicable. Mechanistic studies indicate that MPAAs operate as unique bifunctional ligands for C–H activation in which both the carboxylate and amide are coordinated to Pd. The N-acyl group plays an active role in the C–H cleavage step, greatly accelerating C–H activation. The rigid MPAA chelation also results in a predictable transfer of chiral information from a single chiral center on the ligand to the substrate and permits the development of a rational stereomodel to predict the stereochemical outcome of enantioselective reactions. We also describe the application of MPAA-enabled C–H functionalization in total synthesis and provide an outlook for future development in this area. We anticipate that MPAAs and related next-generation ligands will continue to stimulate development in the field of Pd-catalyzed C–H functionalization.
Electronically matched nucleophilic 1,6‐conjugate addition has been well studied and widely applied in synthetic areas. In contrast, nucleophilic 1,5‐conjugate addition represents an electronically ...forbidden process and is considered unfeasible. Here, we describe modular protocols for 1,5‐conjugate addition reactions via palladium hydride catalysis. Both palladium and synergistic Pd/organocatalyst systems are developed to catalyze 1,5‐conjugate reaction, followed by inter‐ or intramolecular 3+2 cyclization. A migratory 1,5‐addition protocol is established to corroborate the feasibility of this umpolung concept. The 1,5‐addition products are conveniently transformed into a series of privileged enantioenriched motifs, including polysubstituted tetrahydrofuran, dihydrofuran, cyclopropane, cyclobutane, azetidine, oxetane, thietane, spirocycle and bridged rings. Preliminary mechanistic studies corroborate the involvement of palladium hydride catalysis.
An unconventional umpolung protocol was demonstrated for novel 1,5‐conjugate additions via palladium hydride catalyst. Three catalytic reaction modes including 1,5‐addition cascade with inter‐ and intramolecular 3+2 cyclization and migratory 1,5‐addition were established via palladium or palladium/organo‐cocatalysis.
The century‐old zinc–air (Zn–air) battery concept has been revived in the last decade due to its high theoretical energy density, environmental‐friendliness, affordability, and safety. Particularly, ...electrically rechargeable Zn–air battery technologies are of great importance for bulk applications like electric vehicles, grid management, and portable electronic devices. Nevertheless, Zn–air batteries are still not competitive enough to realize widespread practical adoption because of issues in efficiency, durability, and cycle life. Here, following an introduction to the fundamentals and performance testing techniques, the latest research progress related to electrically rechargeable Zn–air batteries is compiled, particularly new key findings in the last five years (2013–2018). The strategies concerning the development of Zn and air electrodes are in focus. The design of other battery components, namely electrolytes and separators are also discussed. Poor performance of O2 electrocatalysts and the lack of the long‐term stability of Zn electrodes and electrolytes remain major challenges. Finally, recommendations regarding the testing routines and materials design are provided. It is hoped that this up‐to‐date account will help to shape the future research activities toward the development of practical electrically rechargeable Zn–air batteries with extended lifetime and superior performance.
The latest research progress related to electrically rechargeable Zn–air batteries is reviewed. It includes the strategies concerning the development of Zn and air electrodes, and the design of other battery components, namely electrolytes and separators. The poor performance of O2 electrocatalysts and the lack of long‐term stability of Zn electrodes and electrolytes remain major challenges.
Titania (TiO2) nanoparticles were added to polydimethylsiloxane (PDMS) matrix to form nanocomposite coating via spin coating method on the AA 2024 (one of the aluminum alloys) to improve the ...anticorrosion ability of metal. The microstructures of the PDMS/TiO2 composite coating were detected by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrometry to verify the structure of composite coating. The corrosion properties of PDMS/TiO2 composite coating was evaluated by the electrochemical tests. The results showed that the anticorrosion ability of the composite coating has been significantly affected by the TiO2 content. For example, the impedance modulus value reached 106 Ωcm2 of the composite coating with 8 wt % nano-TiO2 fillers. Meanwhile, the corrosion current density (Icorr) of the coating was smaller than that of bare aluminum. The long term immersion experiments of coating were performed and the results demonstrated that the coating still had a protective effect on aluminum after 40 days of immersion.
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•Nano titania improved the anticorrosion performance of the polymer coating.•The titania content influenced the corrosion resistance.•Long-term anti-corrosion was demonstrated with PDMS nanocomposite coating.
Magnetite (Fe3O4)/carbon (C) composite flowers with an average size of 4–6 μm were prepared through a facile route including a solvothermal approach and a carbon reduction process. The resultant ...Fe3O4/C composites are porous and exhibit a three-dimensional (3D) flower-like morphology with the core–shell Fe3O4@C nanoparticles hybridized by amorphous carbon sheets. The epoxy resin composites containing 50 wt % 3D porous Fe3O4/C composite flowers display an optimal reflection loss (RL) value of −54.6 dB at 5.7 GHz at a thin thickness of 4.27 mm and the effective bandwidth with RL < −10 dB reaches 6.0 GHz at a thickness of 2.1 mm. These enhanced EM wave absorption performances are attributed to the synergistic effects of Fe3O4 and carbon as well as the structural advantages, e.g., three-dimensional structure with large surface area, porous and core–shell structures of Fe3O4/C flowers. These results suggest the 3D porous Fe3O4/C composite flowers designed here can serve as ideal candidates for high-performance EM wave absorption.
Computer simulations are an important implementation to experimental methods working on polymer nanocomposites (PNCs), which have advanced properties because of their unique hierarchy ...microstructures. In this paper, different computer simulation methods applied to investigate the structures and properties of PNCs and the simulation predicted physical properties of PNCs are reviewed. The fundamentals of applying molecular dynamics simulation method to calculate different physical properties of PNCs are explained accompanied with detailed examples. The results can help to understand the progress on PNC field using simulation methods especially different-sized molecular dynamics simulation methods.
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•Diverse kinds of computer simulation methods were reviewed and compared.•Simulation results of multiple physical properties were explored.•The fundamentals of calculating different physical properties using simulation methods were explained.
The self-healing abilities inside polymeric materials are desirable functions in materials science. Host–guest chemistry, combined with excellent properties of graphene, was used for the construction ...of multistimuli-responsive intrinsic self-healing epoxy materials. By ultraviolet (UV) curing, the unsaturated epoxy resin was connected with β-cyclodextrin/graphene complex through free radical copolymerization. The introduced complex, acting as macro-cross-linker and photothermal agent, can reconnect the damage-induced broken bonds through dynamic host–guest interaction. In this work, the epoxy composites exhibited a high healing efficiency of up to 79.2% and tensile strength of up to 20.8 MPa under heating or near-infrared stimulation, which represent relatively excellent values among all the reported intrinsic self-healing epoxy resin and host–guest self-healing systems.
Trimethyltin chloride (TMT) is an organotin heat stabilizer that is widely used in the production of plastics, and has strong toxicity. Here, the effect of trimethyltin chloride on mouse kidneys and ...its related mechanism were studied by taking TMT mouse with drinking water as a model. Histological examination and TUNEL results showed that the trimethyltin chloride group had typical apoptosis and necroptosis characteristics. Therefore, the level of oxidative stress was detected,and the expression of related genes was verified by real-time quantitative polymerase chain reaction (qRT-PCR) and Western blot methods. The results showed that oxidative stress was activated (MDA,SOD,CAT,T-AOC), released ROS, activated NF-κB pathway,activated inflammasome (NLRP3,Caspase-1,ASC), and inflammasome-secreted inflammatory factors (IL-1β). The expression of apoptosis (BCL-2, BAX, Caspase-3, Caspase-9) and necroptosis (RIPK1, RIPK33, MLKL, Caspase-8) increased.In addition, HEK293T human embryonic kidney cells were treated with trimethyltin chloride, and the results were similar to the tissue. In conclusion, TMT can induce oxidative stress, activate NF-κB pathway, and induce apoptosis and necroptosis through inflammasomes.
•The kidney is the target organ of trimethyltin chloride toxicity.•The trimethyltin chloride activates oxidative stress/NF-κB/NLRP3 pathway.•The renal cell was induced necroptosis via accumulation of trimethyltin chloride.
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