Latest ArticlesReasonable construction of sulfur host with high conductivity, large sulfur storage gap, strong chemical adsorption, and fast oxidation–reduction kinetics of polysulfide is very significant for its practical use in lithium-sulfur batteries (LSBs). In this paper, the surface modification of MIL-88A(Fe) is carried out by Dawson-type polyoxometalate (POM), and a hollow capsule shell material with P2W18, Fe3O4, and C components is synthesized by the subsequent carbonization process. When applied as the sulfur host, the hollow capsule shell material can efficiently improve the conductivity of sulfur electrode and restrain the volumetric change of active sulfur while charging and discharging. On this foundation, electrochemical analysis and density functional theory (DFT) calculation show that the P2W18 on the outer layer of the capsule shell have effective electrocatalytic activity and potent chemical bond on the lithium polysulfides (LiPSs), which is helpful to block the shuttle effect. Therefore, the as-assembled LSBs display the outstanding specific capacity and prominent cycle stability. Specifically, it delivers an excellent reversible capacity of 1063 mAh/g after 100 cycles of charge–discharge at a rate of 0.5 C, accounting for a preservation by 96% in comparison to that of the initial cycle. Moreover, even after 2000 cycles at 1 C, the reversible specific capacity of 585 mAh/g can still be maintained with an average decay rate of only 0.021%.
In this study, an ambient mass spectrometry (AMS) based method was developed for rapid detection of organophosphorus pesticides in strawberry. This method combines an electric arc and a microsyringe tip to realize tip-assisted ambient electric arc ionization (TAAEAI). A high-voltage electric arc can be applied to the microsyringe tip to generate an electric field, which results in corona discharge at the microsyringe tip. The juiced strawberry sample loaded on the tip could be directly ionized with TAAEAI and then analyzed by a mass spectrometer. TAAEAI-MS was successfully applied to analyze 6 organophosphorus pesticides in three strawberry samples. Malathion and profenofos were detected from the investigated strawberry samples. This method could quantitatively determine the contents of organophosphorus pesticides in strawberry with high reproducibility, high precision, and high sensitivity. Sample matrices did not interfere with the pesticide analysis. The recoveries of organophosphorus pesticides spiked in strawberry samples varied between 82.6% and 116% with relative standard deviations (RSDs) less than 9.2%. The limits of detection (LODs) varied between 0.0124 µg/g and 0.0245 µg/g, while the limits of quantification (LOQs) varied between 0.0413 µg/g and 0.0817 µg/g. The coefficients of determination (R2) of the method were determined to be > 0.995. The method established here may have potential application in the detection of organophosphorus pesticides in vegetables and fruits.
Although the construction of specific functional crystalline materials is still challenging, the multi-component molecular assembly has become a key solution for the design of functional materials. Here, we report a hydrogen-bonded organic framework (HOF) material FJU-360 constructed from disodium 6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonate (SSY) and terephthalimidamide. The charge-assisted hydrogen bonding between amidinium and sulfonate makes FJU-360 produce much stronger fluorescence than SSY, and can be used as a luminescence sensor to rapidly quench aniline through luminescence quenching. FJU-360 is sensitive and highly selective for the detection of aniline, and the detection limit reached 3.2 nmol/L, which is the lowest value reported currently. The mechanism of aniline response was analyzed through the aniline@FJU-360 single crystal structure, and the luminescence mechanism was clarified through density function theory calculations. This work is an important step towards the rational synthesis and assembly of sensing materials.
Phosphorylated di-, tri- and tetra-saccharides of β-1, 2-mannan antigen derived from Candida albicans (C. albicans) cell wall were synthesized and covalently conjugated with keyhole limpet hemocyanin (KLH) and human serum albumin (HSA) via a bifunctional linker under mild conditions. The semi-synthetic β-1, 2-mannoside–KLH conjugates were evaluated for the immunization of BALB/c mice. The ELISA results revealed that all three conjugates could elicit high levels of specific IgG antibodies and the acquired antisera could effectively identify the β-1, 2-mannan epitope. Furthermore, the immunofluorescence and flow cytometry assays also uncovered that the induced antibodies, especially that obtained from immunization with β-1, 2-mannotriose–KLH conjugate (1b), could bind well to fungi cell. Eventually, the structure–immunogenicity relationship analysis of β-mannan showed that the length of oligo-β-mannoses had a big impact on their immunogenicity and β-1, 2-mannotriose showed the strongest immunogenicity. The results suggested the great potential of β-1, 2-mannotriose–KLH conjugate as an antifungal vaccine candidate.
Hybrid quantum mechanics/molecular mechanics calculations were performed to elucidate how [MnIIIporphyrin]+X−-based metal-organic frameworks (MOFs) catalyze the [2 + 1] cycloisomerization of enynes and why zwitterionic MOFs exhibit strong activity in Lewis acid catalysis. The calculations showed that zwitterionic MOFs have a "pure cationic active center" leading to a concerted nucleophilic attack pathway with lower barriers. In contrast, metals with coordinating anions have reduced electrophilicity, resulting in a stepwise radical-type pathway with much higher barriers. Further calculations showed the nature of catalysis was strongly depended on the charge on the anion ligand. A good linear relationship between the NPA charge and barrier was found, and verified by 73 anions with small derivations, which presents a universal adaptive character for various coordinated anions.
A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem-difluoroalkenes in mild conditions was described. The combination of lithium organoborate and ZnBr2 generated in situ lithium aryl zincates, which facilitates the transmetalation step of the nickel-catalyzed cross coupling reaction.
The emergence of disseminated metastasis is the leading cause of mortality in patients with malignant tumor. The pre-metastatic microenvironment, including the primary tumor-derived components, pre-metastatic niche (PMN), circulating tumor cells (CTCs), micro-metastases, and tumor immune microenvironment (TIM), are the crucial factors to initiate metastasis and form macro-metastases. It may be a more promising strategy for directly targeting pre-metastatic microenvironment-interrelated factors and cells before they have the chance to form secondary tumors to prevent metastasis. During recent years, a variety of nanosystems, with specific microstructures and functional properties, have been devised to selectively target pre-metastatic cells components and interrelated molecular, and exhibited strong potential on anti-metastatic therapy by absorbing and neutralizing primary tumor-derived components, preventing establishment of the PMN, eliminating the CTCs, eradicating the micro-metastases and modulating the TIM. In this review, we comprehensively review the emerging nanosystems based on the pre-metastatic microenvironments. Hopefully, this review can cast new lights for early preventing and attenuating metastatic progression.
Carbon dioxide electrochemical reduction (CO2RR) has been recognized as an efficient way to mitigate CO2 emissions and alleviate the pressure on global warming and associated environmental consequences. Gold (Au) is reported as stable and active electrocatalysts to convert CO2 to CO at low overpotential due to its moderate adsorption strength of *COOH and *CO. The request for improved catalytic performance, however, is motivated by current unsatisfied catalytic selectivity because of the side hydrogen evolution reaction. In this context, the design of Au based binary catalysts that can boost CO selectivity is of great interest. In the present work, we report that Au nanoparticles can be feasibly dispersed and anchored on silicon nanowires to form Au-Si binary nanomaterials. The Au-Si may stably drive CO2RR with a CO Faraday efficiency of 95.6% at −0.6 V vs. RHE in 0.5 mol/L KHCO3 solution. Such selectivity outperforms Au particles by up to 61%. Controlled experiments illustrate that such catalytic enhancement can chiefly be ascribed to electronic effects of binary catalysts. Theoretical calculations reveal that spontaneously produced silicon oxide may not only inhibit hydrogen evolution reaction, but also stabilize the key intermediate *COOH in CO formation.
Fluorescent dyes play a crucial role in fluorescence imaging and sensing technology. However, there is a dilemma that they are usually intrinsically hydrophobic which lacks of emission in water and modification with ionic groups to access water solubility may result in poor membrane permeability. Fluorescent dyes with strong fluorescence emission in both nonpolar and polar solvents are highly desirable. In this manuscript, we reported a strategy to develop fluorescent BODIPY dyes via installation of amide moiety at meso position of 1, 3, 5, 7-tetramethyl-BODIPY and discovered that N, N'-dialkylsubstituted BODIPY amides possessed highly fluorescent emission with favorable environment-insensitive properties.
Available online The abnormal carboxylesterase (CES) expression is closely related to many diseases such as hyperlipidemia, atherosclerosis, obesity, liver cancer, type 2 diabetes mellitus and gastrointestinal stromal tumors. The detection of a single enzyme in practical samples is often constrained by the structural diversity of CESs. Thus, the development of broad-carboxylesterase responsive fluorescent probe, which can detect the presence of wide variety of CESs, may provide overall or category information from another point of view, supplementing the deficiency of single detection for CES subspecies. Organelle lysosome is involved in various cell processes, such as cell signaling, apoptosis, secretion, and energy metabolism. Up to date, lysosome-targeted fluorescent probes, especially those with red emission (over 550 nm, with relatively low biological harmfulness), for CES detection are still rare. A lysosomes-targeted red fluorescent probe CES-Lyso was designed to monitor intracellular a variety of carboxylesterases alteration with wonderful selectivity and sensitivity, which was further applied to distinguish different derived breast cancer cells and monitor carboxylesterase activity in the anticancer drug treatment.
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