Latest ArticlesSilyl cobalt species are putative intermediates in cobalt-catalyzed transformations of hydrosilanes. However, their reactivity has remained poorly understood. Reported here is the investigation on four-coordinate disilyl Co(Ⅱ) complexes with N-hetereocyclic carbene ligation. The reactions of [(ICy)2Co(vtms)] (ICy = 1, 3-dicyclohexylimidazol-2-ylidene, vtms = vinyltrimethylsilane) with primary and secondary hydrosilanes (3 equiv.) furnish the four-coordinate disilyl complexes [trans-(ICy)2Co(SiHRRʹ)2] (SiHRRʹ = SiH2Mes, 1; SiH2Ph, 2; SiH2Cy, 3; SiHPh2, 4; SiHEt2, 5) in moderate to good yields. The structures of 1, 2 and 4 were established by single-crystal X-ray diffraction. Solution magnetic susceptibility measurement and EPR spectroscopy indicate their low-spin nature (S = 1/2). Reactivity studies on 4 led to the establishment of the conversions of 4 to the disilyl dihydride Co(Ⅲ) complex [K(THF)][(ICy)2Co(H)2(SiHPh2)2]n (6) and the fluorosilyl Co(Ⅱ) complex [(ICy)2Co(THF)(SiFPh2)][BF4] (7) when 4 was treated with excess amount of K and AgBF4, respectively, in THF. These conversions hint at the high activity of low-valent and high-valent disilyl cobalt species [trans-(ICy)2Co(SiHPh2)2]1− and [trans-(ICy)2Co(SiHPh2)2]2+. Complex 4 is reactive toward terminal alkynes, but inert toward alkenes and internal alkynes. The reactions of 4 with terminal alkynes CyCCH and Me3SiCCH (3 equiv.) yield the Co(Ⅱ) complexes [(ICy)2Co(CCCy)2] (8) and [(ICy)2Co(CCSiMe3)((SiMe3)CCH2)] (9), respectively, along with H2SiPh2 and alkynylsilanes RCCSiHPh2 (R = Cy, SiMe3), whereas the reaction with 4-CF3C6H4CCH (3 equiv.) produce [(ICy)2Co(CCAr)((Ar)CCH(SiHPh2)CCHAr)] (Ar = 4-CF3C6H4) (10) and H2SiPh2. These reactions are proposed to involve σ-bond metathesis reactions between alkyne C(sp)-H bonds and Co-Si bonds in 4. Complexes 6–10 have been characterized by NMR spectroscopy, X-ray diffraction study, and elemental analysis.
Electrochemical oxidation is an effective method to degrade persistent organic pollutants. However, due to the limited catalytic activity of traditional thin film electrodes, the anodic oxidation process is slow and usually requires high energy consumption. Herein, Ti/SnO2-Sb electrode with regulated surface structure was reported to enhance the performance for electrochemical oxidation of persistent organic pollutants. The electrode deposited with SnO2-Sb nanoneedles (Ti/N-SnO2-Sb) showed higher oxidation activity. Its kinetic constant for perfluorooctanoic acid (PFOA) oxidation was 2.0 h−1 and the total organic carbon removal rate was 81.7% (4 h) at a relatively low current density of 6 mA/cm2. Compared with Ti/SnO2-Sb thin film and nanoparticles, Ti/N-SnO2-Sb significantly improved the electrochemical active area and •OH yield, and simultaneously reduced the electron transfer resistance, which enabled it to oxidize PFOA more rapidly even at a lower potential. This work provides a new strategy for promoting the electrochemical oxidation performance.
Manganese oxides (MnOx), as low-toxicity and high-abundance catalysts, have been demonstrated to hold great promise for application in advanced oxidation processes (AOPs). However, further application of this material is restricted due to its unsatisfactory oxidant activation efficiency. Fortunately, recently remarkable research on deep activation mechanisms and modification of MnOx have been undertaken to improve its reactivity. Herein, modification enhancement mechanisms of MnOx to efficiently degrade various organic contaminants were discussed and highlighted, including metal doping, coupling with other metal oxides, composite with carbonaceous material, and compounding with other support. The activation mechanisms of different MnOx and derivative-modified material (such as doped MnOx, metal oxide-MnOx hybrids, and MnOx-carbonaceous material hybrids) were summarized in great details, which was specifically categorized into both radical and non-radical pathways. The effects of pH, inorganic ions, and natural organic matter on degradation reactions are also discussed. Finally, future research directions and perspectives are presented to provide a clear interpretation on the MnOx initiated AOPs.
Nitrogen oxide (NOx) is one of the most critical contaminants in the air, and the control of NOx emission from diesel vehicles is very important. Cu-based small-pore zeolites have already been applied for NOx abatement on diesel vehicles. Among the small-pore zeolites, Cu-SSZ-50 catalysts with good NH3-SCR catalytic activity were believed to have potential for application. In this study, a one-pot synthesis method for Cu-SSZ-50 catalysts was developed for the first time, using the co-templates of Cu-TEPA and 2,6-dimethyl-N-methylpyridinium hydroxide. In this synthesis method, Cu-SSZ-50 with various Cu contents can be obtained by adjusting the amount of Cu-TEPA without the need for a further after-treatment process. The addition of Cu-TEPA affected the framework atoms and Cu species, and a lower Si/Al ratio and more SCR active Cu species were obtained. The synthesized catalyst with a Cu/Al ratio of 0.40 exhibited over 90% NOx conversion between 200 ℃ and 450 ℃ for the selective catalytic reduction of NOx with NH3 (NH3-SCR). Meanwhile, over 80% NOx conversion could be obtained from 250 ℃ to 450 ℃ after hydrothermal aging at 750 ℃ for 16 h. In addition, both L-H and E-R mechanisms were proven to exist for the one-pot-synthesized Cu-SSZ-50 by in situ DRIFTS experiments. The simple synthesis procedure, excellent catalytic activity and hydrothermal stability brighten the prospects for the application of Cu-SSZ-50.
The innovation in polymer design to rival conventional polyethylene glycol (PEG) is an important approach to achieving a more sustainable society. Here, cyclic PEG-like polycarbonates having high molecular weight (4.4–49.5 kg/mol) were enabled through zwitterionic ring-opening polymerization (ZROP) of macrocyclic carbonates (MCs) mediated by N-heterocyclic carbene (NHC). The thermodynamic behavior of polymerization depends on the ring size of monomers. During this process, the ZROP of 11-membered MC was driven by the change of enthalpy (ΔHp) which differed from the ZROP of 14-membered MC driven by the entropic change (ΔSp). Cyclic polycarbonates depicted improved thermostability (Td5% ≥ 204 ℃) and higher glass transition temperatures (Tg > ‒40 ℃) in comparison to their linear analogues (Td5% ≤ 185 ℃, Tg ~‒50 ℃). In addition, the mechanism of ZROP of MC was addressed through computational study. A distinct mechanism of polymerization distinguishable from the well-known NHC-mediated ZROP of cyclic esters was revealed, where the zwitterion from nucleophilic addition to MC, i.e. tetrahedral intermediate, cannot be ring-opened probably due to the delocalization of negative charge on the carbonate group, but serves as an active center for the polymerization. In comparison to PEG, the attained polymer demonstrated comparable hydrophilic and biocompatible properties, as revealed by the results of contact angle and in vitro cytotoxicity studies, suggesting that cyclic polycarbonate hold the promise as the alternative of PEG.
Thrombosis remains a major global health concern mainly characterized by high rates of morbidity and mortality. Animal models serve as an indispensable tool to understand the underlying pathogenesis of thrombosis and assess the efficacy of novel antithrombotic drugs. Currently, zebrafish has emerged as a valuable model organism for thrombosis research. However, the traditional method of studying zebrafish thrombosis requires a laborious and time-consuming procedure, including anesthesia and manual immobilization of zebrafish. In this study, based on hydrodynamic force, a lateral-immobilization zebrafish microfluidic chip (LIZMC) was designed to evaluate the cardiovascular system of multiple larvae within a single microscope field of view. Specifically, coupling with microscope imaging, real-time monitoring of the peripheral blood circulation in the tail of phenylhydrazine (PHZ)-induced zebrafish thrombosis was enabled. Furthermore, the reliability of LIZMC for in vivo evaluation of antithrombotic agents in zebrafish was verified using aspirin. Collectively, this novel LIZMC-based system can be used for in vivo zebrafish thrombosis studies and rapid screening of antithrombotic agents.
Remodeling tumor microenvironment (TME) is a very promising and effective strategy to enhance the effects of chemotherapy, photodynamic therapy, and immunotherapy. Normalization of tumor vasculature as well as depletion of glutathione (GSH) can improve the TME. Here, we developed a novel therapeutic nanoparticle functional enzyme ultra QDAU5 nanoparticles (FEUQ Nps) based on a fluorescence-on and releasable strategy by combining a vascular normalization inducer, a GSH depleting agent, and an activated fluorophore. In which the cleavage of disulfide bonds releases active molecules that induce vascular normalization and improve the hypoxic microenvironment. In addition, it may deplete GSH in cancer cells, thus inducing the production of reactive oxygen species (ROS) and lipid peroxide (LPO) and promoting iron toxicity. It may also lead to endoplasmic stress and release of calmodulin, which activates the immune system. Meanwhile, quenched fluorophores are turned on in the presence of galactosidase (GLU) for tumor-specific labeling. In summary, we developed novel therapeutic agent nanoparticles with the function of vascular normalization inducers to achieve specific labeling of hepatocellular carcinoma while exerting efficient antitumor effects in vivo.
A charge transfer complex (CTC)-enabled photoreduction of ether phosphonium salts for the generation of oxyalkyl radicals was described. The photoreduction provides a convenient method to achieve selective oxyalkylation of enamides with broad substrate scope. The method features operational simplicity, mild and inherent green conditions.
Si-based materials have shown great potential as lithium-ion batteries (LIBs) anodes due to their natural reserves and high theoretical capacity. However, the large volume changes during cycles and poor conductivity of Si lead to rapid capacity decay and poor cycling stability, ultimately limiting their commercial applications. Herein, we have skillfully utilized the microporous MCM-22 zeolite as the unique silicon source to produce porous Si (pSi) sheets by a simple magnesiothermic reduction, followed by a carbon coating and further Ti3C2Tx MXene assembly, obtaining the ternary pSi@NC@TNSs composite. In the design, porous Si sheets provide more active sites and shorten Li-ion transport paths for electrochemical reactions. The N-doped carbon (NC) layer serves as a bonding layer to couple pSi and Ti3C2Tx. The conductive network formed by 2D Ti3C2Tx and medium NC layer effectively enhances the overall charge transport of the electrode material, and helps to stabilize the electrode structure. Therefore, the as-made pSi@NC@TNSs anode delivers an improved lithium storage performance, exhibiting a high reversible capacity of 925 mAh/g at 0.5 A/g after 100 cycles. This present strategy provides an effective way towards high-performance Si-based anodes for LIBs.
The compatibility of the gate dielectrics with semiconductors is vital for constructing efficient conducting channel for high charge transport. However, it is still a highly challenging mission to clearly clarify the relationship between the dielectric layers and the chemical structure of semiconductors, especially vacuum-deposited small molecules. Here, interfacial molecular screening of polyimide (Kapton) dielectric in organic field-effect transistors (OFETs) is comprehensively studied. It is found that the semiconducting small molecules with alkyl side chains prefer to form a high-quality charge transport layer on polyimide (PI) dielectrics compared with the molecules without alkyl side chains. On this basis, the fabricated transistors could reach the mobility of 1.2 cm2 V−1 s−1 the molecule with alkyl side chains on bare PI dielectric. What is more, the compatible semiconductor and dielectric would further produce a low activation energy (EA) of 3.01 meV towards efficient charge transport even at low temperature (e.g., 100 K, 0.9 cm2 V−1 s−1). Our research provides a guiding scheme for the construction of high-performance thin-film field-effect transistors based on PI dielectric layer at room and low temperatures.
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