Self-Catalyzed Growth of Co4N and N-Doped Carbon Nanotubes toward Bifunctional Cathode for Highly Safe and Flexible Li-Air Batteries.

The practical application of high-energy density lithium-oxygen (Li-O2) batteries is severely impeded by the notorious cycling stability and safety, which mainly comes from slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at cathodes, causing inferior redox overpotentials and reactive lithium metal in flammable liquid electrolyte. Herein, a bifunctional electrode, a safe gel polymer electrolyte (GPE), and a robust lithium anode are proposed to alleviate above problems. The bifunctional electrode is composed of N-doped carbon nanotubes (N-CNTs) and Co4N by in situ chemical vapor deposition self-catalyzed growth on carbon cloth (N-CNTs@Co4N@CC). The self-supporting, binder-free N-CNTs@Co4N@CC electrode has a strong and stable three-dimensional (3D) interconnected conductive structure, which provides interconnectivity between the active sites and the electrode to promote the transfer of electrons. Furthermore, the N-CNT-intertwined Co4N ensures efficient catalytic activity. Hence, the electrode demonstrates improved electrochemical properties even under a large current density (2000 mA g-1) and long cycling operation (250 cycles). Moreover, a highly safe and flexible rechargeable cell using the 3D N-CNTs@Co4N@CC electrode, GPE, and robust lithium anode design has been explored. The open circuit voltage is stable at ∼3.0 V even after 9800 cycles, which proves the mechanical durability of the integrated GPE cell. The stable cable-type Li-air battery was demonstrated to stably drive the light-emitting diodes (LEDs), highlighting the reliability for practical use.

Recent Advances in Aerobic Oxidative of C-H Bond by Molecular Oxygen Focus on Heterocycles.

Aerobic oxidative cross-coupling represents one of the most straightforward and atom-economic methods for construction of C-C and C-X (X=N, O, S, or P) bonds using air as a sustainable external oxidant. The oxidative coupling of C-H bonds in heterocyclic compounds can effectively increase their molecular complexity by introducing new functional groups through C-H bond activation, or by formation of new heterocyclic structures through cascade construction of two or more sequential chemical bonds. This is very useful as it can increase the potential applications of these structures in natural products, pharmaceuticals, agricultural chemicals, and functional materials. This is a representative overview of recent progress since 2010 on green oxidative coupling reactions of C-H bond using O2 or air as internal oxidant focus on Heterocycles. It aims to provide a platform for expanding the scope and utility of air as green oxidant, together with a brief discussion on research into the mechanisms behind it.

Synthetic Electrochemistry Enabled Esterification via Oxidative Mesolytic Cleavage of Alkoxyamines.

Stable benzylic carbocations were generated via mesolytic cleavage of TEMPO-derived alkoxyamines, which was realized by electrochemical oxidation. This strategy provided an efficient and unique approach to access stabilized carbocations under mild conditions. Esterification of benzylic carbocations using carboxylic acid produced a variety of benzylic esters with a broad substrate scope and excellent functional group compatibility.

Canonical and non-canonical functions of STAT in germline stem cell maintenance.

BACKGROUND: Maintenance of the Drosophila male germline stem cells (GSCs) requires activation of the Janus kinase/signal transducer and activators of transcription (JAK/STAT) pathway by niche signals. The precise role of JAK/STAT signaling in GSC maintenance, however, remains incompletely understood. RESULTS: Here, we show that, GSC maintenance requires both canonical and non-canonical JAK/STAT signaling, in which unphosphorylated STAT (uSTAT) maintains heterochromatin stability by binding to heterochromatin protein 1 (HP1). We found that GSC-specific overexpressing STAT, or even the transcriptionally inactive mutant STAT, increases GSC number and partially rescues the GSC-loss mutant phenotype due to reduced JAK activity. Furthermore, we found that both HP1 and STAT are transcriptional targets of the canonical JAK/STAT pathway in GSCs, and that GSCs exhibit higher heterochromatin content. CONCLUSIONS: These results suggest that persistent JAK/STAT activation by niche signals leads to the accumulation of HP1 and uSTAT in GSCs, which promote heterochromatin formation important for maintaining GSC identity. Thus, the maintenance of Drosophila GSCs requires both canonical and non-canonical STAT functions within GSCs for heterochromatin regulation.

A Gradient Doping Strategy toward Superior Electrochemical Performance for Li-Rich Mn-Based Cathode Materials.

Lithium-rich layered oxides (LLOs) are concerned as promising cathode materials for next-generation lithium-ion batteries due to their high reversible capacities (larger than 250 mA h g-1 ). However, LLOs suffer from critical drawbacks, such as irreversible oxygen release, structural degradation, and poor reaction kinetics, which hinder their commercialization. Herein, the local electronic structure is tuned to improve the capacity energy density retention and rate performance of LLOs via gradient Ta5+ doping. As a result, the capacity retention elevates from 73% to above 93%, and the energy density rises from 65% to above 87% for LLO with modification at 1 C after 200 cycles. Besides, the discharge capacity for the Ta5+ doped LLO at 5 C is 155 mA h g-1 , while it is only 122 mA h g-1 for bare LLO. Theoretical calculations reveal that Ta5+ doping can effectively increase oxygen vacancy formation energy, thus guaranteeing the structure stability during the electrochemical process, and the density of states results indicate that the electronic conductivity of the LLOs can be boosted significantly at the same time. This strategy of gradient doping provides a new avenue to improve the electrochemical performance of the LLOs by modulating the local structure at the surface.

Efficient Aerobic Oxidative Coupling of Methyl Heteroarenes with Indoles.

Direct oxidative coupling of inert C(sp3 )-H bond has been a great challenge. Herein, an environmentally friendly aerobic oxidative coupling of α-methyl substituted N-heteroarenes with indoles is reported. A variety of diheteroaryl ketones were prepared in good yields (up to 72 %). This protocol features simple operation and broad substrates scope (26 examples). Significantly, a plausible mechanism about catalytic cycle was proposed, and two key intermediates were confirmed by high resolution mass spectrometry.

De novo asymmetric Achmatowicz approach to oligosaccharide natural products.

The development and application of the asymmetric synthesis of oligosaccharides from achiral starting materials is reviewed. This de novo asymmetric approach centers around the use of asymmetric catalysis for the synthesis of optically pure furan alcohols in conjunction with Achmatowicz oxidative rearrangement for the synthesis of various pyranones. In addition, the use of a diastereoselective palladium-catalyzed glycosylation and subsequent diastereoselective post-glycosylation transformation was used for the synthesis of oligosaccharides. The application of this approach to oligosaccharide synthesis is discussed.

TinO2n-1/MXene Hierarchical Bifunctional Catalyst Anchored on Graphene Aerogel toward Flexible and High-Energy Li-S Batteries.

The development of lithium-sulfur (Li-S) batteries with high-energy density, flexibility, and safety is very appealing for emerging implantable devices, biomonitoring, and roll-up displays. Nevertheless, the poor cycling stability and flexibility of the existing sulfur cathodes, flammable liquid electrolytes, and extremely reactive lithium anodes raise serious battery performance degradation and safety issues. Herein, a metallic 1T MoS2 and rich oxygen vacancies TinO2n-1/MXene hierarchical bifunctional catalyst (Mo-Ti/Mx) anchored on a reduced graphene oxide-cellulose nanofiber (GN) host (Mo-Ti/Mx-GN) was proposed to address the above challenges. By applying a directional freezing process, the hierarchical architecture of a flexible GN scaffold composed of waved multiarch morphology with long-range alignment is achieved. The synergetic effects of 1T MoS2 and TinO2n-1/MXene are beneficial to suppress the shuttling behavior of lithium polysulfides (LiPSs), expedite the redox kinetics of sulfur species, and promote the electrocatalytic reduction of LiPSs to Li2S. The electrode demonstrates improved electrochemical properties with high sulfur-mass loading (8.4 mgs cm-2) and lean electrolyte (7.6 µL mgs-1) operation. We also explored the feasibility of producing pouch cells with such flexible electrodes, gel polymer electrolytes, and a robust lithium anode, which exhibited reversible energy storage and output, wide temperature adaptability, and good safety against rigorous strikes, implying the potential for practical applications.

In Situ Growth of CoP Nanosheet Arrays on Carbon Cloth as Binder-Free Electrode for High-Performance Flexible Lithium-Ion Batteries.

Cobalt phosphide (CoP) is considered as one of the most promising candidates for anode in lithium-ion batteries (LIBs) owing to its low-cost, abundant availability, and high theoretical capacity. However, problems of low conductivity, heavy aggregation, and volume change of CoP, hinder its practical applicability. In this study, a binder-free electrode is successfully prepared by growing CoP nanosheets arrays directly on a carbon cloth (CC) via a facile one-step electrodeposition followed by an in situ phosphorization strategy. The CoP@CC anode exhibits good interfacial bonding between the CoP and CC, which can improve the conductivity of the integrated electrode. More importantly, the 3D network structure composed of CoP nanosheets and CC provides sufficient space to alleviate the volume expansion of CoP and shorten the electron/ion transport paths. Moreover, the support of CC effectively prevents the agglomeration of CoP. Based on these advantages, when CoP@CC is paired with the NCM523 cathode, the full cell delivers a high discharge capacity 919.6 mAh g-1 (2.1 mAh cm-2 ) after 200 cycles at 0.5 A g-1 . The feasibility and safety of producing pouch cells are also explored, which show good flexibility and safety despite rigorous strikes (mechanical damage and severe deformations), implying a great potential for practical applications.

The C(sp3)-H bond functionalization of thioethers with styrenes with insight into the mechanism.

A metal-free inactive C(sp3)-H bond functionalization of thioethers with styrenes using TBHP as an initiator and DBU as a base has been developed. This transformation has broken through the low activity of thioethers and realized moderate yields. Herein extended experiments were conducted to confirm the radical relay process, reaction energy and intermediate transformations.

Copper-Catalyzed Aldehyde Exchanged Amidation.

The synthesis of bioactive amides has been the pursuit of chemists. Herein secondary amides incorporated with an aldehyde group were first generated using aldehydes and secondary amines. Various (hetero)aryl aldehydes and even aliphatic aldehydes (>40 examples) were converted into the desired products in moderate to excellent yields (up to 89%). A plausible mechanism involving a Cu(I/II/III) catalytic cycle combined with radical rearrangement was proposed and confirmed with four key intermediates detected by high-resolution mass spectrometry.

Graphene-Based Materials for Flexible Lithium-Sulfur Batteries.

The increasing demand for wearable electronic devices necessitates flexible batteries with high stability and desirable energy density. Flexible lithium-sulfur batteries (FLSBs) have been increasingly studied due to their high theoretical energy density through the multielectron chemistry of low-cost sulfur. However, the implementation of FLSBs is challenged by several obstacles, including their low practical energy density, short life, and poor flexibility. Various graphene-based materials have been applied to address these issues. Graphene, with good conductivity and flexibility, exhibits synergistic effects with other active/catalytic/flexible materials to form multifunctional graphene-based materials, which play a pivotal role in FLSBs. This review summarizes the recent progress of graphene-based materials that have been used as various FLSB components, including cathodes, interlayers, and anodes. Particular attention is focused on the precise nanostructures, graphene efficacy, interfacial effects, and battery layout for realizing FLSBs with good flexibility, energy density, and cycling stability.

Recyclable Catalysts for Alkyne Functionalization.

In this review, we present an assessment of recent advances in alkyne functionalization reactions, classified according to different classes of recyclable catalysts. In this work, we have incorporated and reviewed the activity and selectivity of recyclable catalytic systems such as polysiloxane-encapsulated novel metal nanoparticle-based catalysts, silica-copper-supported nanocatalysts, graphitic carbon-supported nanocatalysts, metal organic framework (MOF) catalysts, porous organic framework (POP) catalysts, bio-material-supported catalysts, and metal/solvent free recyclable catalysts. In addition, several alkyne functionalization reactions have been elucidated to demonstrate the success and efficiency of recyclable catalysts. In addition, this review also provides the fundamental knowledge required for utilization of green catalysts, which can combine the advantageous features of both homogeneous (catalyst modulation) and heterogeneous (catalyst recycling) catalysis.

A Flexible Li-Air Battery Workable under Harsh Conditions Based on an Integrated Structure: A Composite Lithium Anode Encased in a Gel Electrolyte.

Flexible lithium-air batteries (FLABs) with ultrahigh theoretical energy density are considered as the most promising energy storage devices for next-generation flexible and wearable electronics. However, their practical application is seriously hindered by various obstacles, including bulky and rigid electrodes, instability/low conductivity of electrolytes, and especially, the inherent semi-open structure. When operated in ambient air, moisture penetrated from an air cathode inevitably corrodes a Li metal anode, and most of the reported FLABs can only work under a pure oxygen or specific air (relative humidity: <40%) atmosphere, which cannot be regarded as a real "lithium-air battery". Herein, the author designed an innovative battery configuration by the synergy of a 3D open-structured Co3O4@MnO2 cathode and an integrated structure: a composite lithium anode encased in a gel electrolyte. A composite lithium anode fabricated through a simple, low-cost, and effective rolling method significantly relieves the fatigue fracture of the lithium electrode. Subsequently, an in situ-formed gel electrolyte encloses the composite lithium electrode, which not only reduces the electrode/electrolyte interfacial resistance but also acts as a protective layer, effectively preventing the lithium anode from corrosion. Consequentially, the battery can achieve more than 100 stable cycles in ambient air with a high relative humidity of 50%. To our surprise, the FLAB remains operational under extreme conditions, such as bending, twisting, clipping, and even soaking in water, demonstrating widespread applications in flexible electronics.

Benzylic Hydroperoxidation via Visible-Light-Induced Csp3-H Activation.

A highly efficient benzylic hydroperoxidation has been realized through a visible-light-induced Csp3-H activation. We believe that this reaction undergoes a direct HAT mechanism catalyzed by eosin Y. This approach features the use of a metal-free catalyst (eosin Y), an energy-economical light source (blue LED), and a sustainable oxidant (molecular oxygen). Primary, secondary, and tertiary hydroperoxides as well as silyl, benzyl, and acyl peroxides were successfully prepared with good yields and excellent functional group compatibility.

Lychee-like TiO2@TiN dual-function composite material for lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are promising candidates for next generation rechargeable batteries because of their high energy density of 2600 W h kg-1. However, the insulating nature of sulfur and Li2S, the "shuttle effect" of lithium polysulfides (LiPSs), and the volumetric change of sulfur electrodes limit the practical application of Li-S batteries. Here, lychee-like TiO2@TiN hollow spheres (LTTHS) have been developed that combine the advantages of high adsorption TiO2 and high conductivity TiN to achieve smooth adsorption/spread/conversion of LiPSs and use them as a sulfur host material in Li-S batteries for the first time. The cathode exhibits an initial specific capacity of 1254 mA h g-1 and a reversible capacity of 533 mA h g-1 after 500 cycles at 0.2C, which corresponds to an average coulombic efficiency up to 99%. The cell with the LTTHS@S cathode achieved an extended lifespan of over 1000 cycles. Such good performance can be assigned to the good adsorption and catalysis of the dual-function TiO2@TiN composite. This work proved that the TiO2@TiN composite can be an attractive matrix for sulfur cathodes.

ZnO quantum dot-modified rGO with enhanced electrochemical performance for lithium-sulfur batteries.

Lithium-sulfur batteries are considered the most promising next-generation energy storage devices. However, problems like sluggish reaction kinetics and severe shuttle effect need to be solved before the commercialization of Li-S batteries. Here, we successfully prepared ZnO quantum dot-modified reduced graphene oxide (rGO@ZnO QDs), and first introduced it into Li-S cathodes (rGO@ZnO QDs/S). Due to its merits of a catalysis effect and enhancing the reaction kinetics, low surface impedance, and efficient adsorption of polysulfide, rGO@ZnO QDs/S presented excellent rate capacity with clear discharge plateaus even at a high rate of 4C, and superb cycle performance. An initial discharge capacity of 998.8 mA h g-1 was delivered, of which 73.3% was retained after 400 cycles at a high rate of 1C. This work provides a new concept to introduce quantum dots into lithium-sulfur cathodes to realize better electrochemical performance.

Rare-Earth Y(OTf)3 Catalyzed Coupling Reaction of Ethers with Azaarenes.

Rare-earth catalysis has become a hot topic in the field of catalytic organic reaction. Chain ethers mostly have lower reactivity and lower boiling points which limited their reaction scope. Herein, we found a rare-earth Y(OTf)3 can catalyze the coupling reaction of ethers especially chain ethers and thioethers with azaarenes. This protocol features simple operations, a broad substrate scope (31 examples), moderate to good yields (up to 85%), and atom economy.

Highly Efficient Recyclable Sol Gel Polymer Catalyzed One Pot Difunctionalization of Alkynes.

Amino-bridged gel polymer P1 was discovered to catalyze alkyne halo-functionalization in excellent yields, regioselectivity, functional group compatibility, and recyclability. We have observed that both aromatic and aliphatic alkynes can be converted to α,α-dihalogenated ketones in the presence of polymer P1 under metal-free conditions at room temperature within a short reaction time.

Advances in Decarboxylative Oxidative Coupling Reaction.

Since carboxylic acid derivatives are commercially available, nontoxic, cheap, and normally stable to air and moisture, carboxylic acid derivatives are ideal reactants for synthetic strategy. In recent years, decarboxylative oxidative coupling reactions, which normally involve direct C-H bond activation, have attracted more and more interest from the synthetic community. Compared with conventional methods, this strategy is more environmentally friendly and step-economic. This review mainly focuses on recent advances of the decarboxylative oxidative coupling reaction.