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Pseudocapacitance‐dominated MnNb2O6‐C nanofiber anode for Li‐ion batteries
MnNb2O6 anode has attracted much attention owing to its unique properties for holding Li ions. Unluckily, its application as a Li-ion battery anode is restricted by low capacity because of the inferior electronic conductivity and limited electron transfer. Previous studies suggest that structure and component optimization could improve its reversible capacity. This improvement is always companied by capacity increments, however, the reasons have rarely been identified. Herein, MnNb2O6-C nanofibers (NF) with MnNb2O6 nanoparticles (~15 nm) confined in carbon NF, and the counterpart MnNb2O6 NF consisting of larger nanoparticles (40-100 nm) are prepared by electrospinning for clarifying this phenomenon. The electrochemical evaluations indicate that the capacity achieved by the MnNb2O6 NF electrode presents an activation process and a degradation in subsequence. Meanwhile, the MnNb2O6-C NF electrode delivers high reversible capacity and ultra-stable cycling performance. Further analysis based on electrochemical behaviors and microstructure changes reveals that the partial structure rearrangement should be in charge of the capacity increment, mainly including pseudocapacitance increment. This work suggests that diminishing the dimensions of MnNb2O6 nanoparticles and further confining them in a matrix could increase the pseudocapacitance-dominated capacity, providing a novel way to improve the reversible capacity of MnNb2O6 and other intercalation reaction anodes.
Mechanistic Avenues in Chan‐Lam based Etherification Reaction: A Computational Exploration
Ongoing advances in CuII-catalyzed aerobic oxidative coupling reactions between arylboronic esters and diverse heteroatom nucleophiles have strengthened the development of the general Chan-Lam (CL) based reaction protocol, including the C−O bond formation methodologies. In-depth mechanistic understanding of CL etherification with specific emphasize on different reaction routes and its energetics are still lacking, even though the reaction has been experimentally explored. Here, we present a DFT-guided computational study to unravel the mechanistic pathways of the CL-based etherification reaction. The computational findings provide some interesting insights on the fundamental steps of the catalytic cycle, particularly the rate-determining transmetalation event. Aryl boronic ester coordinated, methoxide bridged CuII intermediate acts as resting state, which undergoes transmetalation accompanying an activation barrier of 20.4 kcal/mol. The energy spans of the remaining fundamental steps leading to the methoxylated product are relatively low. The minor product requires an additional 14.2 kcal/mol energy span to surmount in comparison to the favored route. Hammett studies for the substituted aryl boronic esters reveal higher reaction turnover for electron-rich aryl systems. The results agree with the previously reported spectroscopic and kinetic observations. For a series of alcohol substrates, it was observed that except for cyclohexanol, moderate to high etherification turnovers are predicted.
Shock‐Induced Microstructural Evolution, Phase Transformation, Sintering of Al‐Ni Dissimilar Nanoparticles: A Molecular Dynamics Study
Molecular dynamic simulations have been performed to explore contact behavior, microstructure evolution and sintering mechanism of Al-Ni dissimilar nanoparticles under high-velocity impact. We confirmed that the simulated contact stress, contact radius, and contact force under low-velocity impact are in good agreement with the predicted results of the Hertz model. However, with increasing the impact velocity, the simulated results gradually deviate from the predicted results of the Hertz model due to the elastic-plastic transition and atomic discrete structure. The normalized contact radius versus strain exhibits a weak dependence on nanosphere diameter. Below a critical velocity, there are very few HCP atoms in the nanospheres after thermal equilibrium. There are two different sintering mechanisms: under low-velocity impact, the sintering process relies mainly on the dislocation slip of Al nanospheres, while the dislocation slip of Ni nanospheres and the atomic diffusion of Al nanospheres predominate under high-velocity impact.
An efficient catalytic reduction of nitroarenes over metal‐organic framework‐derived magnetic graphitic carbon nitride nanosheet
A nano magnetic MOF-based catalyst containing copper species has been successfully synthesized and characterized. The catalytic performance of magnetic Ox-CN-Cu-MOF evaluated in reduction of nitro-compounds. Moreover, recyclability test of the magnetic Ox-CN-Cu-MOF was performed, and the results proved that this catalyst is simply recovered from the mixture and shows a high and relatively stable catalytic activity during 10 runs with a narrow decrease in product conversion.
Metal–organic frameworks (MOFs) have emerged as highly viable and environmentally friendly alternatives to traditional catalysts within the catalytic family. This project delves into the investigation and subsequent reporting of the remarkable catalytic performance exhibited by magnetic Ox-CN-Cu-MOF in the reduction of nitroarenes. The synthesis of magnetic Ox-CN-Cu-MOF was achieved through a streamlined and intricate process, with its structure meticulously identified via various analytical methods including high-resolution transmision electron microscopy (HRTEM), X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), vibrating-sample magnetometry (VSM) and thermogravimetric (TG) analysis. Of particular significance, the loading of copper (Cu) and its potential leaching were effectively detected through inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis. The catalytic efficacy of magnetic Ox-CN-Cu-MOF was evaluated during the conversion of nitro compounds o related-amines utilizing NaBH4 as the reductant. Remarkably, the unique structure and Lewis acidic properties of copper in the metal nodes contributed to the exceptional catalytic behavior exhibited by the magnetic Ox-CN-Cu-MOF catalyst, surpassing that of previously reported catalysts. Furthermore, magnetic Ox-CN-Cu-MOF demonstrated exceptional recyclability, as validated through repetitive continuous usage.
Non‐classical early lanthanide(II) tris(di‐tert‐butylcyclopentadienyl) complexes
We report the synthesis of a series of temperature-sensitive non-classical early Ln(II) (Ln = lanthanide) complexes, [K(2.2.2-cryptand)][Ln(Cptt)3] (Cptt = C5H3tBu2-1,3; 1-Ln; Ln = La-Nd). Complexes 1-Ln were typically prepared using Schlenk line techniques rather than more common glove box protocols, by the reduction of the parent Ln(III) complexes [Ln(Cptt)3] (2-Ln) with KC8 in THF in the presence of 2.2.2-cryptand at –30 °C. The majority of the 2-Ln series have been reported previously by the salt metathesis reactions of 3 eq. KCptt with parent LnCl3, and these methods were adapted here to afford 2-Pr. Complexes 1-Ln and 2-Pr were characterized by single crystal XRD, elemental analysis, ATR-IR and UV-Vis-NIR spectroscopy; 1-La and 2-Pr were additionally characterized by c.w. EPR spectroscopy, and variable temperature magnetic susceptibility measurements were performed on 2-Pr. During attempts to synthesize 2-Nd and 2-Sm we also obtained small crops of crystals of [Nd(Cptt)2(μ-I)]2 (3) and [Sm(Cptt)2(μ-Cl)]2·C7H8 (4·C7H8), respectively; these complexes were also structurally authenticated. The combination of data obtained indicate that the Ln(II) centers in 1-Ln adopt 4fn5d1 electron configurations, in common with other literature examples of [Ln(CpR)3]– anions (CpR = substituted cyclopentadienyl) for these metals.
The optimal amount of lithium difluorophosphate as an additive for Si‐dominant anodes in an application‐oriented setup
Fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are considered the most effective electrolyte additives for improving the solid electrolyte interphase (SEI) of Si-containing anodes while lithium difluorophosphate (LiDFP) is known to improve the interphases of cathode materials and graphite. Here, we combine VC, FEC, and different amounts of LiDFP in a highly-concentrated electrolyte to investigate the effect on Si-dominant anodes in detail. Cycle life tests, electrochemical impedance spectroscopy and rate tests with anode potential monitoring were conducted in Si/NCM pouch cells. The results reveal that adding LiDFP to the electrolyte improves all performance criteria of the full cells, with a concentration of 1 wt.% being the optimal value for most cases. Post-mortem analyses using scanning electron microscopy and x-ray photoelectron spectroscopy showed that a more beneficial SEI film was formed for higher LiDFP concentrations, which led to less decomposition of electrolyte components and a better-maintained anode microstructure.
Impact of Porous Silica Nanosphere Architectures on the Catalytic Performance of Supported Sulphonic Acid Sites for Fructose Dehydration to 5‐Hydroxymethylfurfural
5-hydroxymethylfurfural represents a key chemical in the drive towards a sustainable circular economy within the chemical industry. The final step in 5-hydroxymethylfurfural production is the acid catalysed dehydration of fructose, for which supported organoacids are excellent potential catalyst candidates. Here we report a range of solid acid catalysis based on sulphonic acid grafted onto different porous silica nanosphere architectures, as confirmed by TEM, N2 porosimetry, XPS and ATR-IR. All four catalysts display enhanced active site normalised activity and productivity, relative to alternative silica supported equivalent systems in the literature, with in-pore diffusion of both substrate and product key to both performance and humin formation pathway. An increase in-pore diffusion coefficient of 5-hydroxymethylfurfural within wormlike and stellate structures results in optimal productivity. In contrast, poor diffusion within a raspberry-like morphology decreases rates of 5-hydroxymethylfurfural production and increases its consumption within humin formation.
Extraction and Characteri zation of Bioactive Compounds from Diverse Marine Microalgae and Their Potential Antioxidant Activities
This study compared free and bound phenolic compounds in various marine microalgae species. It assessed total phenolic content (TPC), total flavonoid content (TFC) and total condensed tannin content (TCT) and their antioxidant capacities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) radical cation-based assay and ferric ion reducing antioxidant power assay. Liquid chromatography-mass spectrometry (LC-MS) was also employed to characterize the phenolic profiling. Results showed that free phenolic compounds ranged from 1.83 – 6.45 mg GAE/g d.w., while bound phenolic compounds ranged from 4.03 – 26.03 mg GAE/g d.w., indicating significant differences. These variations were consistent across assays, highlining unique profiles in different species. A total 10 phenolics were found in these seven microalgae, including 1 phenolic acid, 6 flavonoids, 1 other polyphenol and 2 lignans. 4'-O-methyl-(-)-epigallocatechin 7-O-glucuronide and chrysoeriol 7-O-glucoside in microalgae were firstly reported in microalgal samples. These findings have implications for future applications in industries.
Rational Design, Multistep Synthesis and in Vitro Evaluation of Poly(glycerol) Functionalized Nanodiamond Conjugated with Boron‐10 Cluster and Active Targeting Moiety for Boron Neutron Capture Therapy
Poly(glycerol) functionalized detonation nanodiamonds conjugated with boron-10 cluster and active targeting moiety were designed and synthesized. The nanodrugs were taken up by tumor cells and exhibited boron neutron capture therapy (BNCT) efficacy upon thermal neutron irradiation.
Abstract
Boron neutron capture therapy (BNCT), advanced cancer treatment utilizing nuclear fission of 10B atom in cancer cells, is attracting increasing attention. As 10B delivery agent, sodium borocaptate (10BSH, 10B12H11SH ⋅ 2Na), has been used in clinical studies along with L-boronophenylalanine. Recently, this boron cluster has been conjugated with lipids, polymers or nanoparticles to increase selectivity to and retentivity in tumor. In this work, anticancer nanoformulations for BNCT are designed, consisting of poly(glycerol) functionalized detonation nanodiamonds (DND−PG) as a hydrophilic nanocarrier, the boron cluster moiety (10B12H11 2−) as a dense boron-10 source, and phenylboronic acid or RGD peptide as an active targeting moiety. Some hydroxy groups in PG were oxidized to carboxy groups (DND−PG−COOH) to conjugate the active targeting moiety. Some hydroxy groups in DND−PG−COOH were then transformed to azide to conjugate 10B12H11 2− through click chemistry. The nanodrugs were evaluated in vitro using B16 murine melanoma cells in terms of cell viability, BNCT efficacy and cellular uptake. As a result, the 10B12H11 2− moiety is found to facilitate cellular uptake probably due to its negative charge. Upon thermal neutron irradiation, the nanodrugs with 10B12H11 2− moiety exhibited good anticancer efficacies with slight differences with and without targeting moiety.