Latest ArticlesA cooperative Pd/Cu-catalyzed three-component cross-coupling reaction of alkynes, B2Pin2 and alkene-tethered aryl halides is reported. This reaction proceeds under mild conditions and shows broad substrate scope, providing a variety of heterocycles containing tetrasubstituted alkenylboronate moieties in synthetically useful yields with excellent chemoselectivity and regioselectivity. This transformation features the catalytic generation of β-borylalkenylcopper intermediates and their use in Pd-catalyzed Heck cyclization/cross-couplings. An enantioselective cascade cyclization/cross-coupling process has also been developed for the synthesis of enantiomerically enriched oxindole bearing a tetrasubstituted alkenylboronate moiety.
Single-atomic catalysts (SACs) caught considerable attention due to their unique structural properties, complete exposed active site, and 100% atom utilization efficiency with remarkable catalytic activity. Mesoporous single-atomic cobalt catalyst with Co-N4 active sites was synthesized by using nitrogen-doped graphene derived from acrylonitrile. Single-atomic cobalt was observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) in Co@Nx-C-800. Notably, the density functional theory (DFT) calculation and the extended X-ray absorption fine structures (EXAFS) fitting results indicate that the coordination structure of Co-N is four-coordinated. In this work, the practical hydrogenation of nitroarenes to anilines enabled by Co@Nx-C-800 was established with excellent yields and selectivity, which proved its advantages and potential applications.
Herein, we describe the selective formation of a barrel-shaped or a ball-shaped fluorescent metallacage by controlling the shape and stoichiometry of the building blocks. Specifically, the tetraphenylethylene-based donor and two acceptors with different numbers of Pt(Ⅱ) centers were combined via coordination-driven self-assembly. Owing to the differences in the shapes of the assemblies, the resultant ball-shaped metallacage displayed stronger and blue-shifted fluorescence compared to the barrel-shaped one in dilute solutions, while a reversal of fluorescence intensities was observed in the aggregation process. Overall, this work demonstrates that the photophysical properties of supramolecular coordination complexes can be affected by subtle geometrical factors, which can be controlled precisely at the molecular level.
Generally, the metal sulfide itself has poor conductivity, and the volume expansion occurs when it is converted with sodium, which will destroy the integrity of the electrode structure, resulting in poor cycle performance and rate performance. To solve the problems of low initial coulombic efficiency (ICE) and volume expansion of metal compounds used as anodes in sodium-ion batteries (SIBs). Inspired by nature, the CoSO4/hard carbon/graphene (CHG) fractal structure electrode was designed. Self-fractal structures with electron/ion transport channels and high strain tolerance proved to be an effective strategy to overcome these challenges. The fractal dimension (D) is measured by synchronous Small Angle X-ray scattering, and the D remains stable during charging and discharging. The fractal CHG also showed excellent electrochemical performance, especially 97.4% ICE. Theoretical calculation shows that self-fractal CHG can promote the formation of a thin solid electrolyte interface (SEI). Synchrotron radiation absorption spectrum proved the reaction mechanism of CHG. This study not only proves that cobalt sulfate is a feasible strategy for developing high-performance SIBs anodes but also provides an advanced method for measuring the fractal dimension of energy storage electrode materials.
Transition metal and nitrogen co-doped carbons (M-N-C) have proven to be promising catalysts for CO2 electroreduction into CO because of the high activity and selectivity. Effective enrichment of the active transition metal coordinated nitrogen sites is desirable but is challenging for a practical volumetric productivity. Herein, we report four kinds of model electrocatalysts to unveil this issue, which include the NC structures with surface N-functionalities, Ni-N-C_I with one layer of surface Ni-N3C sites, NC@Ni-N-C_I with surface N-functionalities and underneath Ni-N3C sites as well as Ni-N-C_II with doubled surface Ni-N3C sites. The X-ray absorption spectroscopy indicates the coordination configuration of Ni-N3C. For NC catalysts, when N-doping level increased from 3.5 at% to 8.4 at%, the CO partial current density increased from below 0.1 mA/cm2 to 3 mA/cm2. Introducing one layer of Ni-N3C onto the NC structures leads to a 54 times higher CO partial current density than that of NC, in the meantime the FECO is 66 times higher. Furthermore, doubling the density of surface Ni-N3C sites by a layer-by-layer method doubles the CO partial current density (jCO), indicating its potential to achieve a high density of active coordinated sites and current densities.
A novel solid–liquid-core fiber-optic biosensor was fabricated for highly sensitive and selective detection of 4-chlorophenol in water. The sensor comprised horseradish peroxidase (HRP)-coated U-shaped liquid-core optical fiber (LCOF) and 4-chlorophenol permselective polymer membrane. The U-shaped LCOF was filled with ethanol suspension of SiO2 particles and the polymer membrane was composed of molecularly imprinted polymer, sulfonated polyethersulfone, and polysulfone. The morphology, composition, and surface luminous properties of the sensing region were examined. The effects of the diameter and content of SiO2 particles and temperature of 4-chlorophenol solutions on the sensitivity of the biosensors were investigated. Further, the sensitivity, selectivity, response time, and limit of detection (LOD) of the biosensors was investigated. In addition, the effects of fiber core materials on the light transmission in sensing region were investigated and a biosensor sensing model was established. The proposed sensor exhibited high selectivity for 4-chlorophenol with satisfactory sensitivity, LOD, and response time: -1.18 (µg/L)−1, 30 µg/L, and 400 s, respectively. The results are expected to aid in the development of methods for enhancing sensitivity of fiber-optic sensors and surface luminous intensity of optical fibers.
P2-type layered oxides are receiving significant interest due to their superior structure and intrinsic performances. There are strenuous attempts to balance the structure stability, phase transition as well as desirable electrochemical performances by inducing anion/cation ions, changing morphology, adjusting valence, etc. In this work, several same-period elements of Sc, Ti, V, Cr, Fe, Cu and Zn are doped into Na0.50Li0.08Mn0.60Co0.16Ni0.16O2 cathodes, which are manipulated by ions radii and valence state, further studied by operando X-ray powder diffraction patterns (XRD). As a result, the Cu2+ doped cathode performed higher rate capacities (as high as 86 mAh/g even at 10 C) and more stable structures (capacity retention of ~89.4% for 100 cycles), which owing to the synergistic effect among the tightened TMO2 layer, enlarged d-spacing, reduce OO electrostatic repulsion, ameliorate lattice distortion as well as mitigate ordering of Na+/vacancy.
DNA-based supramolecular hydrogels are important and promising biomaterials for various applications due to their inherent biocompatibility and tunable physicochemical properties. The three-dimensional supramolecular matrix of DNA formed by non-covalently dynamic cross-linking provides exceptional adaptability, self-healing, injectable and responsive properties for hydrogels. In addition, DNA hydrogels are also ideal bio-scaffold materials owing to their tissue-like mechanics and intrinsic biological functions. Technically, DNA can assemble into supramolecular networks by pure complementary base pairing; it can also be combined with other building blocks to construct hybrid hydrogels. This review focuses on the development and construction strategies of DNA hydrogels. Assembly and synthesis methods, diverse responsiveness and biomedical applications are summarized. Finally, the challenges and prospects of DNA-based supramolecular hydrogels are discussed.
Graphene and its derivatives have sparked intense research interest in wearable temperature sensing due to their excellent electric properties, mechanical flexibility, and good biocompatibility. Despite these advantages, the weak temperature dependence of charge transport makes them difficult to achieve a highly sensitive temperature response, which is one of the remaining bottlenecks in the progress towards practical applications. Unfortunately, detailed knowledge about the key factors of the charge transport temperature dependence in this material that determines the critical performance of electrical sensors is very limited up to now. Here, we reveal that oxygen absorption on the ultrathin reduced graphene oxide (RGO) films (~3 nm) can significantly increase their conductance activation energy over 200% and thus greatly improve the temperature dependence of thermal-activated charge transport. Further investigations suggest that oxygen introduces the deep acceptor states, distributed at an energy level ~0.175 eV from the valence-band maximum, which allows a highly temperature-dependent impurity ionization process and the resulting vast holes release in a wide temperature range. Remarkably, our temperature sensors based on oxygen-doped ultrathin RGO films show a high sensitivity with temperature conductive coefficient of 14.58% K−1, which is one order of magnitude higher than the reported CNT or graphene-based devices. Moreover, the ultrathin thickness and high thermal conductivity of RGO film allow an ultrafast response time of ~86 ms, which represents the best level of temperature sensors based on soft materials. Profiting from these advantages, our sensors show good capacity to identify the slight temperature difference of human body, monitor respiratory rate, and detect the environmental temperature. This work not only represents substantial performance advances in temperature sensing, but also provides a new approach to modulate the charge transport temperature dependence, which could be benefited to both device design and fundamental research.
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