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Hollow-sphere ZnSe is successfully obtained through Ostwald ripening. Carbon nanoparticles are designed and utilized to form a wrapped carbon network as a conductive buffering matrix by subsequent annealing. The ZnSe/C composites, as anode materials for lithium-ion batteries (LIBs), exhibit excellent Li+ storage properties, delivering a high reversible capacity of 573.7 mA h g−1 at 1.0 A g−1 after 800 cycles. Even upon increasing the high current density to 20.0 A g−1, the reversible capacity can achieve 318.8 mA h g−1 after 5000 cycles. The superior rate capability is confirmed through the current density return from 20.0 to 1.0 A g−1, and ZnSe/C composites still recover up to 469 mA h g−1, with a retention of 92%. The enhanced electrochemical performances of ZnSe/C composites are attributed to the unique structure and the introduction of conductive carbon networks, which can improve the Li+ diffusion coefficient in the insertion and extraction process. Furthermore, the interconnected network also alleviates the volume variation during cycling and further enhances the structural stability. [ABSTRACT FROM AUTHOR]

We have developed an ultra-sensitive electrochemical DNA biosensor by assembling probe ssDNA on a glassy carbon electrode modified with a composite made from molybdenum disulfide, graphene, chitosan and gold nanoparticles. A thiol-tagged DNA strand coupled to horseradish peroxidase conjugated to AuNP served as a tracer. The nanocomposite on the surface acts as relatively good electrical conductor for accelerating the electron transfer, while the enzyme tagged gold nanoparticles provide signal amplification. Hybridization with the target DNA was studied by measuring the electrochemical signal response of horseradish peroxidase using differential pulse voltammetry. The calibration plot is linear in the 5.0 × 10 and 5.0 × 10 M concentration range, and the limit of detection is 2.2 × 10 M. The biosensor displays high selectivity and can differentiate between single-base mismatched and three-base mismatched sequences of DNA. The approach is deemed to provide a sensitive and reliable tool for highly specific detection of DNA. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Layered Li1.2V3O8 has been efficiently prepared via a sol–gel method. XRD and particle size analysis indicate that the final product with monoclinic structure consists of homogeneously distributed particles whose sizes are in a very narrow range. There are two different water molecules in the compound according to TGA and DTA. The structural water works as a pillar in the structure and is lost at higher temperature than the combined water. The as-prepared material was also compared with the one synthesized from the conventional solid-state method in terms of their morphology, electrochemistry capacity and electrodynamic characteristics. As a result, the Li1.2V3O8 obtained at 300°C for 10h has excellent electrochemical properties. A high-first discharge capacity of 286.4mAh/g was observed at a current rate of C/5 between 1.7 and 3.8V and the structure of Li1.2V3O8 remains stable in the subsequent cycles. EIS calculation suggests a better diffusion path for lithium ions in as-prepared material than in the solid-state compound. [Copyright &y& Elsevier]

Abstract: Different dimensions of carbon materials with various features have captured numerous interests due to their applications on the tremendous fields. Restricted by the raw materials and devices, the controlling of their morphology is a major challenge. Utilizing the catalytic features of the intermediates from the low‐cost salts and polymerization of 0D carbon quantum dots (CQDs), 0D CQDs are expected to self‐assemble into 1/2/3D carbon structures with the assistance of temperature‐induced intermediates (e.g., ZnO, Ni, and Cu) from the salts (ZnCl2, NiCl2, and CuCl). The formation mechanisms are illustrated as follows: 1) the “orient induction” to evoke “vine style” growth mechanism of ZnO; 2) the “dissolution–precipitation” of Ni; and 3) the “surface adsorption self‐limited” of Cu. Subsequently, the degree of graphitization, interlayer distance, and special surface area are investigated in detail. 1D structure from 700 °C as anode displays a high Na‐storage capacity of 301.2 mAh g−1 at 0.1 A g−1 after 200 cycles and 107 mAh g−1 at 5.0 A g−1 after 5000 cycles. Quantitative kinetics analysis confirms the fundamentals of the enhanced rate capacity and the potential region of Na‐insertion/extraction. This elaborate work opens up an avenue toward the design of carbon with multidimensions and in‐depth understanding of their sodium‐storage features. [ABSTRACT FROM AUTHOR]

A "signal off" electrochemical aptasensor based on metal-organic framework (MOF) - based nanocomposites and RecJf exonuclease-assisted target recycling was constructed for ultrasensitive detection of vanillin (VAN). In this work, benefited from the high catalytic activity of the synthesized gold nanoparticle/iron-based MOF/polyetherimide-reduced graphene oxide (AuNPs/NH 2 -MOF-235(Fe)/PEI-rGO) and the AuNPs/Ce-MOF nanocomposites toward thionine (Thi), the electrochemical signal was amplified. And the target recycling assisted by RecJf exonuclease were triggered with the presence of VAN, which induced the strongly reduced electrochemical signal. On account of dual amplification strategies, the performance of the aptasensor was significantly improved to achieve ultrasensitive detection of VAN. Under optimal conditions, the linear relationship was fitted for VAN with a linear range of 2 pM - 0.2 mM and the detection limit of 1.14 pM (S/N = 3). Furthermore, this assay for VAN has excellent specificity, long-term stability, and satisfactory results of the detection in the real samples. In summary, the aptasensor could be further used for the specific quantitative determination of other targets in foods. [Display omitted] • MOF-based nanocomposites of both AuNPs/NH 2 -MOF-235(Fe)/PEI-rGO and AuNPs/Ce-MOF were used for signal amplification. • RecJf exonuclease was used for target recycling. • Ultrasensitive detection of vanillin with a detection limit of 1.14 pM achieved by the dual signal amplification strategy • This developed aptasensor was successfully applied to detect vanillin in the chocolate, milk, and juice samples. [ABSTRACT FROM AUTHOR]

To facilitate the design and construction of complex functional materials, the field of molecular assembly can learn from the well-established field of catalysis including its branches such as electrocatalysis and photo-electrocatalysis. In this study, we establish a “photo-electro-catassembly” strategy to repeatedly fabricate two-dimensional molecular assemblies on electrode surface by learning from the concept of photo-electrocatalysis. With the rational design of the linear diacetylene building blocks, Au electrode surface itself and the thiol-functionalized electrode both can assist the formation of two-dimensional assemblies and their subsequent covalent stabilization through the polymerization of diacetylene groups. Nevertheless, when using the Au electrode surface as a direct template, the polymerized product would be hardly removed from the electrode due to the strong synergistical interactions through multivalent Au-S bonds. By contrast, when using the thiol-functionalized electrode as an indirect template, the diacetylene building block forms a well-ordered second layer over the thiol monolayer due to the solvent-phobic and solvent-philic effects. After photo-polymerization, the polymerized product can still be removed from the electrode along the electro-induced removal of the thiol monolayer. Driven by electricity and photoirradiation, the thiol-functionalized electrode assists the combined process of assembly and photo-polymerization as a “photo-electrocatassembler”, and it works repeatedly to produce covalently stabilized two-dimensional assemblies. [ABSTRACT FROM AUTHOR]

Room temperature sodium–sulfur batteries have emerged as promising candidate for application in energy storage. However, the electrodes are usually obtained through infusing elemental sulfur into various carbon sources, and the precipitation of insoluble and irreversible sulfide species on the surface of carbon and sodium readily leads to continuous capacity degradation. Here, a novel strategy is demonstrated to prepare a covalent sulfur–carbon complex (SC‐BDSA) with high covalent‐sulfur concentration (40.1%) that relies on SO3H (Benzenedisulfonic acid, BDSA) and SO42− as the sulfur source rather than elemental sulfur. Most of the sulfur is exists in the form of OS/CS bridge‐bonds (short/long‐chain) whose features ensure sufficient interfacial contact and maintain high ionic/electronic conductivities of the sulfur–carbon cathode. Meanwhile, the carbon mesopores resulting from the thermal‐treated salt bath can confine a certain amount of sulfur and localize the diffluent polysulfides. Furthermore, the CSxC bridges can be electrochemically broken at lower potential (<0.6 V vs Na/Na+) and then function as a capacity sponsor. And the R‐SO units can anchor the initially generated Sx2− to form insoluble surface‐bound intermediates. Thus SC‐BDSA exhibits a specific capacity of 696 mAh g−1 at 2500 mA g−1 and excellent cycling stability for 1000 cycles with 0.035% capacity decay per cycle. The covalent sulfur–carbon complex SC‐BDSA (S, 40.1%) with different chain lengths is prepared. The short‐chain bridges can be electrochemically broken at potential <0.6 V (Na/Na+) and then worked together with the long‐chain units as a capacity sponsor. The R‐SO parts anchor Sx2− to form insoluble surface‐bound intermediates, leading to a special capacity of ≈750 mAh g−1 over 200 cycles. [ABSTRACT FROM AUTHOR]

As a result of its high‐energy density, metal–selenides have demanded attention as a potential energy‐storage material. But they suffer from volume expansion, dissolved poly‐selenides and sluggish kinetics. Herein, utilizing' thermal selenization via the Kirkendall effect, microspheres of NiSe2 confined by carbon are successfully obtained from the self‐assembly of Ni‐precursor/PPy. The derived hierarchical hollow architecture increases the active defects for sodium storage, while the existing double N‐doped carbon layers significantly alleviate the volume swelling. As a result, it shows ultrafast rate capability, delivering a stable capacity of 374 mAh g−1, even after 3000 loops at 10.0 A g−1. These remarkable results may be ascribed to the NiOC bonds on the interface of NiSe2 and the carbon film, which leads to the faster transfer of ions, the effective trapping of poly‐selenide, and the highly reversible conversion reaction. The kinetic analysis of cyclic voltammetry (CV) demonstrates that the electrochemical process is mainly dominated by pseudocapacitive behaviors. Supported by the results of electrochemical impedance spectroscopy (EIS), it is confirmed that the solid–electrolyte interface films are reversibly formed/decomposed during cycling. Given this, this elaborate work might open up a potential avenue for the rational design of metal‐sulfur/selenide anodes for advanced battery systems. Hierarchial hollow‐structured NiSe2/N‐C with double carbon films are designed from the self‐assembled clew‐like Ni‐Pr by the Kirkendall effect. And it is found that incorporation of NiOC into the carbon layers enables tailoring of the interfacial traits, inducing the fascinating electrochemical behaviors. This elaborate work might open up a potential avenue for these rational TMDs anodes designs for advanced battery storage systems. [ABSTRACT FROM AUTHOR]