Latest ArticlesThe detrimental "shuttle effect" of lithium polysulfides (LiPSs) together with sluggish multi-order reaction kinetics are the main drawbacks hindering lithium-sulfur (Li-S) batteries from commercial success. Here, we first propose the implementability of layered rare-earth hydroxides (LREHs) in Li-S batteries to optimize electrochemical performance. In this work, a two-dimensional (2D) rare-earth-based composite constructed by the layered gadolinium hydroxy chloride [Gd2(OH)5(H2O)]Cl nanoplates (LGdH NPs) and graphene oxide (GO) was designed as a sulfur immobilizer for Li-S batteries. Combining the experimental results and density functional theory (DFT) calculations, it is revealed that the LGdH@GO composite not only provides a strong anchoring of the intermediates during cycling, but also acts as an effective catalyst to accelerate the liquid-solid conversion of polysulfides. The Li-S batteries assembled by LGdH@GO modified separators delivered a superior rate performance with a specific capacity of 605.34 mAh/g at 5 C, as well as excellent cycle stability with a decay rate of 0.087% over 500 cycles at 2 C. This study provided a deep understanding of the mechanism to suppress the "shuttle effect" by the LREHs, and a guide to design effective functional interlayers for high-performance Li-S batteries with excellent electrocatalytic activity.
Multifunctional drug delivery systems (DDSs) have shown great prospects in overcoming the heterogeneous barrier of delivery drugs to the complex tumor microenvironment (TME). In this study, multifunctional AS/Ge-pNAB microgels with dual-active targeting, triple environment responsiveness, and fluorescence imaging capability were prepared through a straightforward procedure. This was aimed to improve the antitumor therapeutic application of gambogic acid (GA) based on the biological characteristics of TME. The microgels have a uniform double-layer structure with aptamer in the outer layer which helps in recognizing receptors on the tumor cells. The GA loaded nano-herb exhibited environment-responsive drug release profiles under acidic pH, reductant and high temperature. The nano-herb significantly improved the accumulation of GA in tumor sites through the synergistic combination of the enhanced permeability and retention effect and dual-ligand mediated internalization. Then, it accelerated intracellular drug release and killed tumor cells. Therefore, the nano-herb had specific therapeutic effects on the tumor in vitro and in vivo as they remarkably inhibited tumor growth while depicting optimal biosafety and lower levels of off-target toxicity. Overall, these findings demonstrate the great potential of the multifunctional AS/Ge-pNAB microgels for precisely targeted GA delivery and open a new avenue for the facile preparation of multifunctional DDSs.
Metal–organic framework (MOF) is a periodic sexual network structure with large surface area and high porosity, which is assembled by inorganic nodes and organic ligands through coordinate covalent bond. MOFs have the advantages of controllable pore size and shape, large specific surface area, easy modification and more active sites. In addition, MOF based nanoenzymes display excellent enzyme catalytic activity due to their special structure and multiple exposed metal active sites, controlling the production of reactive oxygen species (ROS) in cells or the body, and thus regulating the polarization of macrophage. This article reviews the mechanism of MOF material regulating macrophage polarization and the function of macrophages with different phenotypes. By utilizing the excellent properties of MOFs and the advantages of combining them with bioactive materials, we have discovered their excellent applications in the treatment of inflammatory diseases. Finally, we discussed the current challenges and prospects faced by MOF based composite materials. We expect that the research in this developing field will play a more important role in combating inflammatory diseases in the field of nanomedicine.
Single crystallization is an important strategy to resolve intergranular cracks and unnecessary side reactions with electrolytes in layered transition metal oxide cathodes LiNi0.8Mn0.1Co0.1O2 (NMC811). Due to the limitations of high-temperature sintering and multi-step calcination, single crystal NMC811 generally shows irregular particles with a size of 2–3 µm. However, the prolonged Li-ion diffusion pathway and the stress generated by the uneven de-/intercalation sluggish Li-ion diffusion kinetics, what is more, cause structural damage such as intragranular cracks. A slow Li extraction rate or particle size reduction will ameliorate the structural damage and improve the cycling stability. As the most promising cathodes for next-generation power batteries, NMC811 required fast charge performance and cycle stability. Particle size reduction appears to be the displacement option. Nanonization is an effective strategy to mitigate intragranular cracks of single crystal NMC811. However, the serious aggregation and increased specific surface area become new challenges. In this article, we synthesized monodisperse nanoscale single crystal NMC811 by molten salt method and modified the surface by LiNbO3 coating. The electrochemical performance shows that nanoscale single crystal NMC811 has faster kinetic and higher capacity retention, so the strategy of combining nanonization and surface coating is an alternative way to prepare high specific capacity and cycle stable single crystal NMC811.
Saccharides are a sort of ubiquitous and vital molecules within the whole life. However, the application of saccharides analysis with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is restricted by their low ionization efficiency and the instability of the sialic acid fraction. Derivatization strategy based on nonreductive amination provides a good solution, however, this is often time consuming and may result in sample loss due to removal of excessive derivatization reagents. Herein, hydralazine (HZN) was utilized as a reactive matrix for labeling reducing saccharides directly on MALDI target which eliminated tedious sample preparation and avoided sample loss. After optimization, effective and reproducible on-MALDI-target derivatization of neutral and acidic saccharides was achieved in both positive and negative modes. Compared with 2,5-dihydroxybenzoic acid (DHB) and 9-aminoacridine (9-AA), HZN improved the detection sensitivity of reducing saccharides and provided more abundant fragment ions in MS/MS analysis. Moreover, 26 kinds of neutral glycans and 5 kinds of sialic glycans were identified from ovalbumin (OVA) and bovine fetuin, respectively. Combined with the statistical models, this strategy could be used to distinguish and predict samples of 6 brands of beer, and discriminate 2 kinds of beer fermentation modes. In addition, HZN was applied for quantitative analysis of glucose in urine samples, and the obtained urine glucose concentrations of diabetic patients were consistent with the clinical test results, showing the potential of qualitative and quantitative analysis of reducing saccharides in complex samples.
Grain boundary (GB), as a kind of lattice defect, widely exists in two-dimensional transition metal dichalcogenides (2D TMDs), which has complex and diverse influences on the physical/chemical properties of 2D TMDs. GBs are universally considered to be a double-edged sword, although some electrical and mechanical properties of 2D TMDs would be adversely affected leading to the reduced overall quality, certain structure-oriented applications could be realized based on its unique properties. In this review, we first detailed the atomic structure characteristics of GBs and the corresponding techniques, then we systematically summarized the methods of introducing GBs into 2D TMDs. Next, we expounded unique electrical, mechanical, and chemical properties of the GBs in 2D TMDs and clarified its internal relationship with the atomic structure. Moreover, the application of GB structure in hydrogen evolution reaction (HER) is also discussed. In the end, we make a conclusion and put forward outlooks, hoping to further promote the basic research of GB and boost the wide application of 2D TMDs.
Porphyrins and their derivatives are excellent photosensitizers in photodynamic therapy (PDT). The modification of porphyrin molecules into metal-organic cages (MOCs) is a viable strategy to improve their bioavailability. In this work, MOC C66 based on porphyrin was synthesised by a one-pot self-assembly method. The three-dimensional structure of the metal-organic cage ameliorated the aggregation and self-quenching of porphyrins and increased the molar absorption coefficient in the visible light region, which enhanced the reactive oxygen species (ROS) yield of porphyrins and effectively improved the efficiency of photodynamic therapy. ROS generation ability tests in solution confirmed the improved reactive oxygen capacity of the cage, which showed greater phototoxicity to HeLa and MCF-7 cells in vitro, suggesting a new strategy for future modifications of the simple synthesis of porphyrins as photosensitizers.
The fascinating chemical structure and broad application prospect of Keggin-type polyoxometalates (POMs) have attracted many chemists to explore and discover continuously. Unlike the traditional Keggin, larger metal atomic radius, higher metal coordinated numbers, lower metal valence states and other features allow the group IVB metal-based Keggin (IVB-Keggin) more space and unknown in terms of structure and performance. Herein, density functional theory (DFT) calculations were performed to explore the influences including cores, shells, caps, and terminal ligands, et al. on IVB-Keggin, and analyze the possibility of novel structure synthesis. From the perspective of multi-layer onion-like clusters, molecular energy level, host-guest interaction energy, surface charge and covalent bond polarity can be further adjusted to achieve the oriented design of functional IVB-Keggin. These insights are expected to provide theoretical support for experimental synthesis, opening a new perspective to understand the growth of Keggin.
Increasing use of silver in various fields has caused Ag+ pollution in water environment, taking great threats to people's health. As a consequence, establishing rapid and reliable methods for sensitive determination of Ag+ is of great significance. Fluorescent (FL) sensors based on carbon dots (CDs), an excellent carbonaceous nanomaterial with strong and stable fluorescence, have absorbed extensive attentions in analysis of pollutants due to its advantages of carbon sources being readily available, low cost, easy operation and fast response. Moreover, ion-imprinting is a better way to increase the selectivity of the proposed method. Present work described an effective method for the sensitive measurement of silver ion in water samples in combination with magnetic ion-imprinted solid phase extraction and CDs based fluorescent sensor, which took full advantages of easy separation and high enrichment of magnetic solid phase extraction, high selectivity of ion-imprinting technology, and sensitivity and rapid response of fluorescent sensor from CDs. Sulfur-doped CDs derived from dithizone and magnetic ion-imprinted nanomaterial were prepared, and characterized with Fourier transform infrared spectroscopy and transmission electron microscope, etc. Magnetic Ag+ imprinted nanomaterial based solid phase extraction was employed for separating and enriching Ag+ from water samples. The significant parameters were optimized in detail. Under the optimal conditions, the proposed method provided good linearity in the range of 0.01–0.4 µmol/L and low detection limit of 3 nmol/L. The reliability of the proposed method was validated with real water samples, and the results demonstrated that the proposed method was simple, robust, selective and sensitive detection tool for Ag+ in real water samples.
Rhodium(Ⅲ)-catalyzed CH couplings of arenes with alkenes are among the most powerful methods for CC bond formation. For these transformations, subtle manipulation of ancillary ligands can lead to dramatic changes in reactivity and selectivity. However, detailed mechanistic studies concerning the ligand effects are rare. In this study, we investigated the origin of ligand-controlled product-selectivity in rhodium(Ⅲ)-catalyzed CH couplings of arenes with alkenes, using a series of well-defined [CpXRhⅢ] complexes that feature electronically or sterically distinct CpX (Cp (η5-C5H5), CpCF3 (η5-C5Me4CF3) and Cp* (η5-C5Me5)) ligands. A combination of experimental and theoretical investigations showed that (i) rhodium hydride species containing the electron rich Cp* ligand can undergo reinsertion of the alkene, thereby allowing rhodium-walking, (ii) rhodium hydride species involving the electron-deficient Cp or CpCF3 ligands prefer reductive elimination rather than alkene insertion. These findings offer valuable insights on future rational catalyst design for selective arene–alkene cross coupling reactions.
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