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.
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.
Biomass-derived dynamic covalent thermoset has been considered as a promising solution to the high dependence on fossil resources and the difficulty in recyclability after curing of conventional bisphenol A epoxy resins. However, the design and preparation of a dynamic covalent biobased epoxy thermoset with both comparable thermal and mechanical performances to bisphenol A epoxy resins and reprocessibility remains a significant challenge. Herein, based on imine chemistry, a novel Schiff base-containing dynamic covalent epoxy thermoset was facilely fabricated from biobased protocatechualdehyde and synthetic siloxane diamine. Due to the more reactive epoxides in the epoxy monomer than in bisphenol A epoxy oligomer, the thermoset exhibited a high cross-linking density, resulting in high thermal stability and glass transition temperature. The rigid aromatic Schiff base moieties endowed the thermoset with excellent mechanical properties: Thanks to the plasticization of the flexible siloxane, the thermoset displayed high impact strength. Meanwhile, owing to the high segmental mobility, the fast exchange of imine bonds was guaranteed; and the thermoset was able to be recycled through reprocessing. Taking these features, this work provided great potential for designing and preparing sustainable substitutes for bisphenol A epoxy resins in the high-performance applications.
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.
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).
The simplification of localized surface plasmon resonance (LSPR) detection can further promote the development of optical biosensing application in point-of-care testing. In this study, we proposed a simple light emitting diode (LED) based single-wavelength LSPR sensor modulated with bio-electron transfers for the detection of electroactive biomolecules. Indium tin oxide electrode loaded with nanocomposites of polyaniline coated gold nanorod was used as LSPR chip, and the applied electric potential was scanned at the LSPR chip for single-wavelength LSPR biosensing. Under the scanning of applied potentials, biological electron transfer of redox reaction was employed to demonstrate the bioelectronic modulation of single-wavelength LSPR for selective electroactive biomolecule detection. Without any additional recognition material, electroactive biomolecules uric acid and dopamine were detected directly with a sensitivity of 5.05 μmol/L and 7.11 μmol/L at their specific oxidation potentials, respectively. With the simplified optical configuration and selective bioelectronic modulation, the single-wavelength LSPR sensor is promising for the development of simple, low-cost, and high specificity optical biosensor for point-of-care testing of electroactive biomolecules.
Excellent optical properties involving strong visible light response and superior carrier transport endow metal halide perovskites (MHP) with a fascinating prospect in the field of photocatalysis. Nevertheless, the poor stability of MHP nanocrystals (NCs) in water-contained system, especially without the protection of long alkyl chain ligands, severely restricts their photocatalytic performance. In this context, we report an effortless strategy for the generation of ligand-free MHP NCs based photocatalyst with high water tolerance, by coating PbI2 on the surface of ligand-free formamidinium lead bromide (FAPbBr3) NCs via the facile procedure of in-situ conversion with the aid of ZnI2. Under the protection of PbI2 layer, the resultant FAPbBr3/PbI2 composite exhibits significantly ameliorated stability in an artificial photosynthesis system with CO2 and H2O vapor as feedstocks. Moreover, the formation of compact PbI2 layer can accelerate the separation of photogenerated carriers in FAPbBr3 NCs, bringing forth a remarkable improvement of CO2 photoreduction efficiency with an impressive electron consumption yield of 2053 µmol/g in the absence of organic sacrificial agents, which is 7-fold over that of pristine FAPbBr3 NCs.
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