Latest ArticlesWell-defined two-dimensional (2D) cobalt oxalate (CoC2O4·2H2O) nanosheets exhibit more excellent property than common bulk cobalt oxalate due to high specific surface areas and high-efficient transport of ion and electron. However, the delicate control of the 2D morphology of CoC2O4·2H2O during their synthesis remains challenging. Herein, 2D CoC2O4·2H2O nanosheets (M1), grown by straightforward chemical precipitation, can be tuned from three-dimensional (3D) structure during their synthesis with no templates or capping agents. This control is obtained by rationally changing the ratio of reactants with ethylene glycol as solvent. Moreover, Co3O4/CoC2O4 composites (M1-250) have been fabricated through low-temperature thermal treatment of the M1 precursor in air, which possess porous surfaces with the 2D morphology maintained. Benefiting from the porous surfaces, more redox-active sites and better electrical conductivity of Co3O4, the constructed M1-250//AC aqueous device manifest improved kinetics of the electrochemistry process with energy density of 27.9 Wh/kg at 550.7 W/kg and good cycling stability with sustaining 73.0 mAh/g after 5000 cycles.
Micro-nano-level photonic waveguide regulation is essential for future on-chip photonic integrated systems and is still of great challenges. We report a molecular design strategy, changing the position of the methyl substituent makes the arrangement of the three isomer molecules different in their respective crystals. Based on this strategy, three sheet-like crystals with different polygonal morphologies were prepared via solution self-assembly approach. The in-depth optical measurements demonstrated that these three microsheet crystals have different 2D optical waveguide performances related to the shapes. Our work provides a feasible design strategy and material preparation method for realizing precise 2D optical waveguide modulation, which lays the foundation for complex photonic integrated systems in the future.
The thermal decomposition of AgNO3 is known to produce metallic Ag, but single-atomic dispersion is hard to achieve instead of the aggregation state of nanoparticles. Herein, we develop an efficient approach to thermally generate and stabilize single Ag atoms via the coordination effect. Two desired Co-Ag phosphonates [Ag2ⅠCo2Ⅲ(notpH3)2(NO3)]X [X = NO3− (1) or ClO4− (2)] were synthesized by solid-phase grinding method or solution crystallization. Both crystal structures reveal slightly different packing arrangements of various lattice anions and identical one-dimensional (1-D) coordination chains, formed in each case by the coordination of Ag(Ⅰ) to the metalloligand Co(notpH3) and NO3− anion. The number of Ag(Ⅰ) ions connected to each NO3− anion reduces from 5 in bulk AgNO3 to 2 in compounds 1 and 2, leading to the AgNO3 component stepwise decomposition at a lower temperature (< 300 ℃). During the thermal decomposition, the changes of supermolecular structures and Ag oxidation states were monitored by PXRD, IR and XAFS measurements. The most interesting finding is that 1 and 2 can retain chain structures and harvest Ag(0) atoms in the chain by controlling decomposition temperatures (220 ℃ for 1 and 254 ℃ for 2).
Understanding the impact of substituents on the quantum interference effect at single molecule scale is of great importance for the design of molecular devices. In this work, three platinum(Ⅱ) complexes with –H, –NH2 and –NO2 groups on conductive backbones were designed and synthesized. Single-molecule conductance, which was measured using scanning tunnelling microscope break junction (STM-BJ) technique, demonstrated a conductance freeze phenomenon under the variation of substituents. Theoretical study revealed that, despite the electronic effect of the substituents shifting the energy level of molecular orbital, the quantum interference effect vanished the influence of electronic effect on the conductance and eventually leaded to the conductance freeze.
Aggregation-induced emission (AIE) based luminescent materials are generating intensive interest due to their unique fluorescence in the aggregation state. Herein we report a strategy of dynamic covalent chemistry (DCC) controlled AIE luminogens for the regulation of multicolor emission in reversible covalent polymer networks. Tetraphenylethene derived ring-chain tautomers were prepared, and the emission was readily controlled through multimode, such as changing the solvent, adding the base, and dynamic covalent reactions with amines. Moreover, the construction of dynamic covalent cross-linked luminescent hydrogels with tunable fluorescent, self-healing, and mechanical properties, was realized. The combination of AIE and aggregation-caused quenching (ACQ) fluorophores in the polymer network further enabled the realization of a multicolor modulator, including white emission, in both solution and gel states. The strategies and results presented should find utility in dynamic assemblies, polymer networks, chemical sensing, and responsive materials.
The selection and development of cathode of alkaline zinc batteries (AZBs) is still hindered and often leads to poor rate capability and short cycle life. Here, amorphous hollow nickel-cobalt-based sulfides nanocages with nanosheet arrays (AM-NCS) are designed and constructed with ZIF-67 as the self-template to exchange with Ni2+ and S2− by using a two-step ion exchange method. The synthesized AM-NCS possess the high specific capacity (160 mAh/g at 2 A/g), and the assembled battery has excellent rate performance (146 mAh/g reversible capacity at 5 A/g). The assembled device has excellent rate performance (155 mAh/g at 2 A/g) and long cycling stability (7000 cycles, 62.5% of initial capacity). The excellent electrochemical properties of the electrode materials are mainly attributed to the unique structure, in particular, polyhedron structure with hollow structure can improve the cyclic stability, and the amorphous structure can expose more reactive sites on the surfaces of nickel, cobalt and sulfur. This work provides a new strategy for the design and fabrication of high performance cathode materials for AZBs.
Photodynamic therapy (PDT) has been gaining popularity in both scientific research and clinic applications due to its non-invasiveness and spatiotemporal targeting properties. Nevertheless, the local hypoxic microenvironment in tumor tissue impedes PDT universality. To overcome this drawback, a 2-pyridone-bearing BODIPY photosensitizer was synthesized rationally and introduced to polyethyleneglycol-b-poly(aspartic acid) to form a photosensitizer-1O2 generation, storage/release agent dual-loading system (PEG-b-PAsp-BODIPY). The investigation of the PDT effect at different illumination conditions in vitro and in vivo revealed that the system tremendously inhibited tumor proliferation, indicating that this new PEG-b-PAsp-BODIPY could act as a potentially effective photo therapeutic system for cancer therapeutics.
Ammonia borane (NH3BH3, AB) has been considered to be a promising chemical hydrogen storage material. Based on density functional theory, a series of transition metal atoms supported P3C (P3C_O) sheet is systematically investigated to screen out the most promising catalyst for dehydrogenation of AB. The results indicate that the Os/P3C and Os/P3C_O could be an efficient single atom catalyst (SACs) and the stepwise reaction pathway with free energy barrier of 2.07 and 1.54 eV respectively. Remarkably, the rate constant further quantitatively confirmed the real situation of the first step of dehydrogenation of AB on the Os/P3C and Os/P3C_O substrates. We found that kf1 at 400 K is equivalent to kf2 at 800 K, which greatly improves the temperature of the first step of AB dehydrogenation on P3C_O. We hope this work can provide a promising method for the design of catalysts for AB dehydrogenation reactions on the surface of two-dimensional materials (2D).
Dendrite growth in lithium-ion batteries may bring thermal run-away especially at high current densities, which remains the major bottleneck to implement safe and fast charging for portable electronic devices or electronical vehicles. Designing dendrite inhibition separators with proper pore size is considered to be one of the most promising strategies to guarantee the battery safety. However, due to the impossible observation of lithium-ion distribution under separator by experiments, the underlying dendrite inhibition mechanism is still not fully understood. Here, we apply the phase-field model, which takes the separator phase into account to construct the electrochemical system total free energy, to study the ion re-distribution behavior of porous separator and understand the pore size inhibition effect on lithium dendrite. The numerical results indicate that separator with smaller pore size is beneficial to smoother electrodeposition, since the lithium-ion concentration on the electrode surface is more uniform under denser separator pores, when their sizes is larger than the critical nucleus. The proposed model could capture the physicochemical process of electrodeposition under multiphase structures, so it could also be used to explore dendrite growth under composite electrodes and composite solid electrolytes.
Metal-organic framework materials (MOFs), such as zeolitic imidazolate framework (ZIF), have been widely used in energy storage due to their advantages such as high structural stability, large specific surface, more active sites and skeleton structures. Herein, a novel two-dimensional (2D) CoCu-ZIF was synthesized by a facile solvothermal method. The as-prepared CoCu-ZIF nanosheets exhibit an ultrahigh reversible capacity of 2287.4 mAh/g and remains at 1172.1 mAh/g after 300 cycles at a current density of 100 mA/g, far better than that of the single Co-ZIF and Cu-ZIF. Additionally, the specific discharge capacity of CoCu-ZIF nanosheets can maintain at about 590 mAh/g after 1000 cycles at the current density of 2 A/g. Owing to the synergistic effect of two metals, function of nitrogen in the molecular and self-assembly 2D nanosheets, our research can provide strong support for the practical application of CoCu-ZIF materials in lithium ion batteries.
No. 86 Xueyuan South Road, Haidian District, Beijing
010-62662699(Operation and Technical Support)
qkjq@cast.org.cn
Copyright © 2025 China Association for Science and Technology. All rights reserved. For all open access content, the relevant licensing terms apply.
Sponsored by the Office of the Leading Group for Cybersecurity and Informatization of CAST, and supported by Science and Technology Review Publishing House
