Numerical simulation and structure optimization of a liquid–vapor separation plate condenser

Journal of Thermal Analysis and Calorimetry - Based on innovative design, a liquid–vapor separation plate condenser with excellent heat transfer performance is invented. It takes less time to...     

Interfacial Engineering FeOOH/CoO Nanoneedle Array for Efficient Overall Water Splitting Driven by Solar Energy

Interface engineering has been applied as an effective strategy to boost the electrocatalytic performance because of the strong coupling and synergistic effects between individual components. Here, we engineered vertically aligned FeOOH/CoO nanoneedle array with a synergistic interface between FeOOH and CoO on Ni foam (NF) by a simple impregnation method. The synthesized FeOOH/CoO exhibits outstanding electrocatalytic activity and stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. For the overall water splitting, the bifunctional FeOOH/CoO nanoneedle catalyst requires only a cell voltage of 1.58 V to achieve a current density of 10 mA cm⁻², which is much lower than that required for IrO₂//Pt/C (1.68 V). The FeOOH/CoO catalyst has been successfully applied for solar cell-driven water electrolysis, revealing its great potential for commercial hydrogen production and solar energy storage.     

Stimuli-Responsive Fluorescent Nanoswitches: Solvent-Induced Emission Enhancement of Copper Nanoclusters

Copper nanoclusters (CuNCs) as a new class of fluorescent materials have attracted a great deal of interest due to their outstanding fluorescence properties. In this work, a variety of organic solvents were used to induce self-assembly of glutathione-capped CuNCs (GSH-CuNCs) to form ordered assemblies with enhanced fluorescence properties. Assemblies with multicolor fluorescence emission were constructed on the basis of the aggregation-induced emission (AIE) of GSH-CuNCs and the solvent effect. The fluorescence emission from these GSH-CuNCs assemblies can also be tuned from yellow to purple by changing the organic solvent. A possible mechanism based on the size of the assemblies and electron transfer was explored to explain the solvent effects on GSH-CuNCs. Stimuli-responsive nanoswitches with excellent reversibility can be controlled by changing the type of organic solvent and the ratio of the organic solvent to the aqueous solution of GSH-CuNCs. As the CuNCs assemblies exhibit strong, stable, and color-tunable fluorescence, they were employed as color-conversion materials for recognizing different organic solvents.     

In Situ Structural Determination of a Homogeneous Ruthenium Racemization Catalyst and Its Activated Intermediates Using X-Ray Absorption Spectroscopy

The activation process of a known Ru-catalyst, dicarbonyl(pentaphenylcyclopentadienyl)ruthenium chloride, has been studied in detail using time resolved in situ X-ray absorption spectroscopy. The data provide bond lengths of the species involved in the process as well as information about bond formation and bond breaking. On addition of potassium tert-butoxide, the catalyst is activated and an alkoxide complex is formed. The catalyst activation proceeds via a key acyl intermediate, which gives rise to a complete structural change in the coordination environment around the Ru atom. The rate of activation for the different catalysts was found to be highly dependent on the electronic properties of the cyclopentadienyl ligand. During catalytic racemization of 1-phenylethanol a fast-dynamic equilibrium was observed.     

Engineering Lithium Ions Embedded in NiFe Layered Double Hydroxide Lattices To Activate Laminated Ni2+ Sites as High-Efficiency Oxygen Evolution Reaction Catalysts

NiFe layered double hydroxides (LDHs) have been denoted as benchmark non-noble-metal electrocatalysts for the oxygen evolution reaction (OER). However, for laminates of NiFe LDHs, the edge sites are active, but the basal plane is inert, leading to underutilization as catalysts for the OER. Herein, for the first time, light and electron-deficient Li ions are intercalated into the basal plane of NiFe LDHs. The results of theoretical calculations and experiments both showed that electrons would be transferred from near Ni²⁺ to the surroundings of Li⁺, resulting in electron-deficient properties of the Ni sites, which would function as “electron-hungry” sites, to enhance surface adsorption of electron-rich oxygen-containing groups, which would enhance the effective activity for the OER. As demonstrated by the catalytic performance, the Li−NiFe LDH electrodes showed an ultralow overpotential of only 298 mV at 50 mA cm⁻², which was lower than that of 347 mV for initial NiFe LDHs and lower than that of 373 mV for RuO₂. Reasonable intercalation adjustment effectively activates laminated Ni²⁺ sites and constructs the electron-deficient structure to enhance its electrocatalytic activity, which sheds light on the functional treatment of catalytic materials.     

Aggregation-Induced Synergism by Hydrophobic-Driven Self-Assembly of Amphiphilic Oligonucleotides

The evident contradiction between high local-concentration-based substrate reactivity and free-diffusion-based high reaction efficiency remains one of the important challenges in chemistry. Herein, we propose an efficient aggregation-induced synergism through the hydrophobic-driven self-assembly of amphiphilic oligonucleotides to generate high local concentration whereas retaining high reaction efficiency through hydrophobic-based aggregation, which is important for constructing efficient DNA nanomachines for ultrasensitive applications. MicroRNA-155, used as a model, triggered strand displacement amplification of the DNA monomers on the periphery of the 3D DNA nanomachine and generated an amplified fluorescent response for its sensitive assay. The local concentration of substrates was increased by a factor of at least 9.0×10⁵ through hydrophobic-interaction-based self-assembly in comparison with the traditional homogeneous reaction system, achieving high local-concentration-based reactivity and free-diffusion-based enhanced reaction efficiency. As expected, the aggregation-induced synergism by hydrophobic-driven self-assembly of amphiphilic oligonucleotides created excellent properties to generate a 3D DNA nanomachine with potential as an assay for microRNA-155 in cells. Most importantly, this approach can be easily expanded for the bioassay of various biomarkers, such as nucleotides, proteins, and cells, offering a new avenue for simple and efficient applications in bioanalysis and clinical diagnosis.     

Visible-Light-Mediated Click Chemistry for Highly Regioselective Azide–Alkyne Cycloaddition by a Photoredox Electron-Transfer Strategy

Click chemistry focuses on the development of highly selective reactions using simple precursors for the exquisite synthesis of molecules. Undisputedly, the Cu^I-catalyzed azide–alkyne cycloaddition (CuAAC) is one of the most valuable examples of click chemistry, but it suffers from some limitations as it requires additional reducing agents and ligands as well as cytotoxic copper. Here, we demonstrate a novel strategy for the azide–alkyne cycloaddition reaction that involves a photoredox electron-transfer radical mechanism instead of the traditional metal-catalyzed coordination process. This newly developed photocatalyzed azide–alkyne cycloaddition reaction can be performed under mild conditions at room temperature in the presence of air and visible light and shows good functional group tolerance, excellent atom economy, high yields of up to 99 %, and absolute regioselectivity, affording a variety of 1,4-disubstituted 1,2,3-triazole derivatives, including bioactive molecules and pharmaceuticals. The use of a recyclable photocatalyst, solar energy, and water as solvent makes this photocatalytic system sustainable and environmentally friendly. Moreover, the azide–alkyne cycloaddition reaction could be photocatalyzed in the presence of a metal-free catalyst with excellent regioselectivity, which represents an important development for click chemistry and should find versatile applications in organic synthesis, chemical biology, and materials science.