Latest ArticlesAprotic lithium-air batteries (LABs) have been known as the holy grail of energy storage systems due to their extremely high energy density. However, their real-world application is still hindered by the great challenges from the Li anode side, like dendrite growth and corrosion reactions, thus a pure oxygen atmosphere is usually adopted to prolong the lifetime of LABs, which is a major obstacle to fully liberate the energy density advantages of LABs. Here, a gel polymer electrolyte has been designed through in-situ polymerization of 1,3-dioxolane (DOL) by utilizing the unique semi-open nature of LABs to protect the Li anode to conquer its shortcomings, enabling the high-performance running of LABs in the ambient air. Unlike common liquid electrolytes, the in-situ formed gel polymer electrolyte could facilitate constructing a gradient SEI film with the gradual decrease of organic components from top to bottom, preventing the Li anode from dendrite growth and air-induced corrosion reactions and thus realizing durable Li repeated plating/stripping (2000 h). Benefiting from the anode protection effects of the gradient SEI film, the LABs display a long lifetime of 170 cycles, paving an avenue for practical, long-term, and high-efficiency operation of LABs.
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.
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.
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.
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.
Büchner reaction, as a unique type of expansive dearomatization, has become a practical strategy for the straightforward assembly of valuable functionalized cycloheptatrienes from ubiquitous aromatic precursors. Although the asymmetric version has been investigated since the early 1990s, enantioselective Büchner reaction is still limited by the catalyst type and substrate scope. This review aims to propose the limitation and possible development direction of this field by summarizing the evolution of catalytic asymmetric Büchner reaction, which is organized on the basis of intra- and intermolecular reactions. Considering the different metal carbene precursors, the reactions are further classified by carbene sources.
Reactive oxygen species (ROS) are essential for biological processes like cell signaling and chemical processes like organic oxidation. Moreover, the sufficient generation of ROS plays a significant role in targeted tumor treatments or oxidation of organics. Herein, a hydrazone-linked porphyrin covalent organic framework (Por-DETH-COF) is developed for red light-induced generation of ROS like singlet oxygen (1O2) or superoxide (O2•−) to undertake different but targeted oxidations. First, 1O2 is adopted in photodynamic therapy (PDT) for the oxidation of glioma cells. The PDT efficiency of Por-DETH-COF on the apoptosis of glioma cells is explored through flow cytometry and western blot assay. The apoptosis rate of glioma cells significantly increases over Por-DETH-COF under 660 nm red light illumination, suggestive of the potency of 1O2. Second, O2•− is employed for the targeted oxidation of thiols. A series of thiols could be efficiently oxidized to corresponding disulfides over Por-DETH-COF under 660 nm red light illumination, indicative of the significance of O2•−. This work highlights the potential of covalent organic frameworks in generating ROS for precise medical applications of complex chemical environments.
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.
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.
The mitigation of under-coordinated Pb2+ (halide vacancy) defect remains an imperative challenge in the perovskite solar cells, especially printable mesoscopic perovskite solar cells (FP-PSCs). Here we report a commercial-available polyazin anticancer drug Sapanisertib as coordination passivator of halide vacancies in FP-PSCs, thereby achieving the photoelectric conversion efficiency (PCE) to 18.46%, along with a record certified PCE of 18.27%. In polazin Sapanisertib (Sap), there exists two kinds of nitrogen atoms: in-aromatic ring (in purine and oxazole rings, IAR-Ns) and out-aromatic ring (substituted amino groups, OAR-Ns). Through multiple characterizations, and DFT calculations show that substituted amino groups OAR-Ns hardly get interaction with the halide vacancy due to the distribution of charge density in Sapanisertib. Our work suggests that the selective coordination is of great significance for the design of high-performance passivators for printable mesoscopic perovskite solar cells.
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