Latest ArticlesFe-based phosphates with excellent physical and chemical features are potential electrode materials for supercapacitors. In this work, we successfully synthesized Fe-based phosphates with different dimensions, morphologies, and compositions by one-step hydrothermal method. Influence factors on the chemical composition and morphology of the as-prepared materials were explored and the energy storage performance of the as-prepared samples were tested under the traditional three electrode system. Two-dimensional (2D) iron metaphosphate (Fe(PO3)3) showed the best electrochemical performance. For Fe(PO3)3 electrode materials, the layered structure can provide a larger specific surface area than the bulk structure, which is conducive to the diffusion and transport of electrolyte ions during charging-discharging and further improves the rate performance and cycle stability of supercapacitor. 2D Fe(PO3)3 and activated carbon were used as electrode materials to construct a 2D Fe(PO3)3//AC supercapacitor. The supercapacitor showed high energy density, high power density, and excellent cycling stability, which indicates 2D Fe(PO3)3 is a promising electrode material for supercapacitors.
Lithium polymer batteries (LPBs) rely on a high ion transport to gain improved cell performance. Thermostable and porous gel polymer electrolytes (GPEs) have attracted much attention due to their excellent properties in electrolyte wettability and ionic conductivity. In this work, iron-nickel-cobalt trimetal Prussian blue analogue (PBA) nanocubes are filled into the electrospun polyacrylonitrile (PAN)-based membranes to generate GPE composites with morphological superiority consisting of fine fibers and interconnected pores. The thus obtained PBA@PAN fibrous membrane showcases good thermal stability, high porosity and electrolyte uptake, as well as a peak ionic conductivity of 2.7 mS/cm with the addition of 10% PBA. Consequently, the assembled lithium iron phosphate (LiFePO4) battery using PBA@PAN-10 as the GPE delivers a high capacity of 152.2 mAh/g at 0.2 C and an ultralow capacity decay of 0.09% per cycle in a long-term cycle life of 350 cycles at 1 C, endorsing its promising applications in LPBs.
Reliable technologies for CO2 capture and conversion (C3) are of vital importance for the establishment of a sustainable society. Metal-organic framework (MOF) composites have shown their compelling potentials for C3 due to the plentiful reticular chemistry of MOF structures and the synergistic catalysis between MOFs and the functional guests. This review focuses on the syntheses and catalytic applications towards C3 of MOF composites, which is divided into three sections. The first section gives a brief introduction about synthetic strategies of MOF composites. The second section discusses the recent progress of MOF composites in C3, including CO2 chemical fixation, hydrogenation, photoreduction, electroreduction and photoelectroreduction. The third section summarizes the challenges and future prospects of MOF composites for C3. We hope that this review cannot only provide an inspiration for the rational design of MOF composites for C3, but also stimulate more and more research works in this emerging area.
Metal organic framework (MOF) has been confirmed as the promising precursor to develop the conversion-typed anode materials of sodium-ion batteries (SIBs) because of the tunable structure design and simple functional modification. Here, we prepare the ultrasmall Ni3S2 nanocrystals embedded into N-doped porous carbon nanoparticles using the scalable Ni-MOF as precursor (denoted as Ni3S2@NPC). The ultrasmall size of Ni3S2 can work for accelerated electron/ion transfer to facilitate the electrochemical reaction kinetics. Moreover, the robust conductivity network originated from N-doped porous carbon nanoparticles can not only improve the electron conductivity, but also enhance the electrode integrity and stability of the electrode/electrolyte interface. In addition, the N heteroatoms provide extra Na storage sites. Accordingly, the electrode delivers the obviously competitive capacities and high-power output with respect to the currently reported Ni3S2/C composites. This study provides a scalable and universal strategy to develop the advanced transition metal sulfides for practically feasible SIBs.
Transition-metal chalcogenides with hollow nanostructure, especially cobalt sulfides, are considered as the most promising non-precious metal catalysts for oxygen evolution reaction. However, it is difficult to synthesize oxygen-containing cobalt sulphides with hollow structure due to the different physical/chemical properties between metal sulfides and metal cobalts. Herein, we report a novel oxygen-containing amorphous cobalt sulfide ball-in-ball hollow spheres (Co-S-O BBHS) synthesized by an anion exchange method. Taking advantage of the ball-in-ball hollow structure, the amorphous Co-S-O BBHS shows superior oxygen evolution reaction (OER) electrocatalytic performance with a low overpotential of 285 mV at 10 mA/cm2, small Tafel slope of 49.67 mV/dec, high Faraday efficiency of 96%, and satisfied durability. Experiments and DFT calculations demonstrate that the introduction of oxygen and sulfur modulates the electronic structure of Co-S-O BBHS, thus enhancing the adsorption of *O (adsorbed O species on catalyst surface) intermediate, which greatly boosts the catalytic activity towards OER. This work provides a new strategy for controllable synthesis of complex hollow structures of transition-metal chalcogenides for OER.
We design a ratiometric fluorescent sensing platform for bleomycin (BLM) by using proximity-dependent DNA-templated silver nanoclusters (DNA-AgNCs) probe. This ratiometric sensing system is constructed with DNA-AgNCs as single fluorophore. The proposed strategy is based on the two following facts: (1) a covert DNA can approach and transform the DNA-AgNCs with green emission (G-DNA-AgNCs) into red emission through hybridization reaction. (2) The specific cleavage of the convert DNA by BLM in the presence of Fe(II) inhibits the discoloration of G-DNA-AgNCs. Thus, benefiting from the specific recognition of BLM and unique properties of G-DNA-AgNCs, a highly-sensitive ratiometric sensor for BLM has been successfully developed. The detection limit is as low as 30 pmol/L. This label-free fluorescence probe possesses advantages of convenient synthetic process and low cost. Moreover, this ratiometric method has been applied to the detection of BLM in human serum samples, illustrating a promising tool for analysis of BLM in cancer therapy.
We presented a low-abundance mutation detection method with lambda exonuclease and DNA three-way junction structure. The assistant strand in the DNA three-way junction structure could regulate the reaction system from the kinetics and thermodynamics aspects. The optimization of the assistant strand helps to improve the selectivity of the mutant-type DNA to the wild-type DNA about 35 times. Moreover, the cost of the optimization process could be saved by about 90%. The method was applied to the detection of a human ovarian cancer-related gene mutation BRCA1 (rs1799949, c.2082C>T). The limit of detection to the mutation abundance in the DNA three-way junction structure system (0.2%) was one order lower compared with that in the double-stranded DNA structure system (2%). The mutation abundance in different standard samples was quantitively measured, and the results were consistent with the initial abundance in the standard samples.
Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent (TADF) emitters (namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via CN coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core. It is found that, compared with the commonly-used tert-butyl groups, the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers, producing stronger TADF effect together with faster reverse intersystem crossing process. Solution-processed TADF organic light-emitting diodes (OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%, respectively, which are ~1.6 and ~2.0 times that of the tert-butyl-encapsulated counterparts. These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.
Ion diffusion kinetics, depending on the size, tortuosity, connectivity of the channels, greatly affects the rate performance of the electrodes. Two-dimensional materials (2DMs) has emerged as promising electrode materials in the past decades. However, the applications of 2DMs electrodes are limited by the strong restacking problem, which leads to a poor rate capability. In this work, we for the first time mediated the morphology of molybdenum disulfide (MoS2) nanosheets via a facile coagulation method; abundant sheet crumples were induced, which greatly enhance their surface accessibility and thus benefit the ion diffusion kinetics. Consequently, the crumpled-MoS2 electrodes follow a capacitive Na-ion charge-storage mechanism to a large extent. Importantly, we demonstrate the special role of organic cations in the inter-sheet assembly configuration, in sharp contrast with that of alkali/alkaline-earth ones. We propose that organic cations cause edge/face contact of the sheets, instead of the face/face contact, thus affording a house-of-cards structure.
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