Sulfur-Bridged Asymmetric CuNi Bimetallic Atom Sites for CO2 Reduction with High Efficiency.

Double-atom catalysts (DACs) with asymmetric coordination are crucial for enhancing the benefits of electrochemical carbon dioxide reduction and advancing sustainable development, however, the rational design of DACs is still challenging. Herein, this work synthesizes atomically dispersed catalysts with novel sulfur-bridged Cu-S-Ni sites (named Cu-S-Ni/SNC), utilizing biomass wool keratin as precursor. The plentiful disulfide bonds in wool keratin overcome the limitations of traditional gas-phase S ligand etching process and enable the one-step formation of S-bridged sites. X-ray absorption spectroscopy (XAS) confirms the existence of bimetallic sites with N2Cu-S-NiN2 moiety. In H-cell, Cu-S-Ni/SNC shows high CO Faraday efficiency of 98.1% at -0.65 V versus RHE. Benefiting from the charge tuning effect between the metal site and bridged sulfur atoms, a large current density of 550 mA cm-2 can be achieved at -1.00 V in flow cell. Additionally, in situ XAS, attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and density functional theory (DFT) calculations show Cu as the main adsorption site is dual-regulated by Ni and S atoms, which enhances CO2 activation and accelerates the formation of *COOH intermediates. This kind of asymmetric bimetallic atom catalysts may open new pathways for precision preparation and performance regulation of atomic materials toward energy applications.

Platinum single atom on CsPbBr3 nanocrystals as electrocatalyst boosts electrochemical sensing of ascorbic acid.

Monitoring ascorbic acid (AA) levels in human body can provide valuable clues for disease diagnosis. Anchoring noble metal single atoms on perovskite substrate is a promising strategy to design electrocatalysts with outstanding electrocatalytic performance. Herein, we design an electrochemical method for detecting AA by utilizing Pt single atoms-doped CsPbBr3 nanocrystals (Pt SA/CsPbBr3 NCs) fixed on a glassy carbon electrode as an electrochemical catalyst. The uncharged 3,5,3',5'-tetramethylbenzidine (TMB) undergoes oxidation to form the positively charged oxidized TMB (oxTMB) owing to the exceptional electrochemical catalytic performance of Pt SA/CsPbBr3 NCs. Subsequently, the target AA reduces oxTMB to TMB, which is then electrocatalytically oxidized to oxTMB, producing significant oxidation current. In this way, such characteristic provides a sensitive electrochemical strategy for AA detection, achieving a concentration range of 50-fold with the detection limit of 0.0369 µM. The developed electrochemical method also successfully generates accurate detection response of AA in complex sample media (urine). Overall, this approach is expected to offer a novel way for early disease diagnosis.

Preparation and Magnetic Manipulation of Fe3O4/Acrylic Resin Core-Shell Microspheres.

Core-shell microspheres refer to duo-layer or multilayer microspheres, which are widely used in drug delivery, microreactors, etc. Accurate manipulation of microspheres is a research hot spot, while traditional manipulation methods including ultrasonic manipulation and laser manipulation still face some limitations. In this study, magnetic core-shell microspheres were adopted to realize the accurate manipulation of microspheres. Combined with microfluidic technology, polystyrene sulfonic acid (PSSA)/Fe3O4 magnetic fluid was utilized as the core material and photosensitive acrylic resin became the shell material. After UV curing, a magnetic core-shell microsphere with an average size of 55 µm could be achieved, and the diameter was uniform and controllable. By adjusting the flow rate of the dispersed phase, the dual-core microspheres with different core particle sizes that ranged from 9.3 to 28.4 µm could be prepared. Experimental results showed that the prepared Fe3O4/acrylic resin core-shell microspheres can be used as functionalized microspheres that have good magnetic response properties and self-assembly ability. In addition, the magnetic manipulation and self-assembly of the prepared core-shell microspheres were presented with different external magnetic fields. The magnetic core-shell microspheres have shown great potential in the fields of biomedical engineering and targeted delivery of drugs.

Nickel cobalt sulfide coated iron nickel selenide hierarchical nanosheet arrays toward high-performance supercapacitors.

Tailoring the electronic structure of nanomaterials by constructing core-shell heterostruture is a compelling strategy to design novel electrode materials with modified physiochemical properties for supercapacitors with improved performance. Herein, for the first time, we in situ fabricate iron nickel selenide (FeNiSe2)@nickel cobalt sulfide (Ni4.5Co4.5S8) core-shell nanosheet arrays on carbon cloth by an electrodeposition approach and a selenization treatment. This three-dimensional hierarchcial porous framework formed by plentiful interconnected nanosheets can expose numerous redox active sites with varied oxidation states and provide a conductive and porous skeleton for rapid ion/electrolyte ions transport. Benefiting from its modulated electronic structure and synergetic effect of metal-like FeNiSe2 and Ni4.5Co4.5S8, the as-synthesized FeNiSe2@Ni4.5Co4.5S8 electrode displays a large specific capacity of 236.9 mAh g-1 at 1 A g-1, remarkable rate capability with 80.6% capacity retention at 20 A g-1, and stable cyclic performance, which are superior to those of pure FeNiSe2 and Ni4.5Co4.5S8 electrodes. Besides, the assembled FeNiSe2@Ni4.5Co4.5S8//porous carbon hybrid supercapacitor device offers an energy density of 69.0 Wh kg-1 at 799.2 W kg-1, and exceptional cycling stability with 91.2% capacity retention after 10,000 cycles. This work offers a synthetic strategy to explore core-shell electrode materials with tunable architecture and morphology for high-performance energy storage devices.

Significant Decrease in Heavy Metals in Surface Sediment after Ten-Year Sustainable Development in Huaxi Reservoir Located in Guiyang, Southwestern China.

In the Karst area of southwestern China, the heavy metals in the sediment of a reservoir are determined by both human activities and the high background values. Thus, this study explores the change of heavy metals in surface sediment after ten-year sustainable development in the upstream areas of a reservoir, Huaxi Reservoir, located in Guiyang of southwestern China, then evaluates the risk of these heavy metals to water environment systematically and finally identifies the sources in both 2019 and 2009. The results reveal that all of the measured heavy metals decrease dramatically and their spatial distributions change from the increase-decrease pattern to decrease-increase pattern, implying different locations of main source input. The risk indices based on the total or average content and relative or reference values have decreased to the lowest level. However, those indices calculated from the absolute content of each metalloid still show a low or a moderate risk because of the high background value, such as As and Cr. Moreover, although only one main source of heavy metals is identified in both 2019 and 2009, the risk from human activities still cannot be neglected because agricultural production and infrastructure construction would promote the weathering of soil and then these heavy metals from the soil will be brought into the reservoir with the rainfall-runoff process. The high background value of specific heavy metals, e.g., As and Cr would still exert some challenges to the water environment protections because the non-point source input of heavy metal cannot be controlled easily by promulgating a series of bans. These results provide important reference for creating the policies of water environment protection, especially in some Karst area of southwestern China that exhibits high background value of heavy metals.

Self-Assembled Hexagonal Superparamagnetic Cone Structures for Fabrication of Cell Cluster Arrays.

In this study, we demonstrated that arrays of cell clusters can be fabricated by self-assembled hexagonal superparamagnetic cone structures. When a strong out-of-plane magnetic field was applied to the ferrofluid on a glass substrate, it will induce the magnetic poles on the upper/lower surfaces of the continuous ferrofluid to increase the magnetostatic energy. The ferrofluid will then experience hydrodynamic instability and be split into small droplets with cone structures because of the compromising surface tension energy and magnetostatic energy to minimize the system's total energy. Furthermore, the ferrofluid cones were orderly self-assembled into hexagonal arrays to reach the lowest energy state. After dehydration of these liquid cones to form solid cones, polydimethylsiloxane was cast to fix the arrangement of hexagonal superparamagnetic cone structures and prevent the leakage of magnetic nanoparticles. The U-343 human neuronal glioblastoma cells were labeled with magnetic nanoparticles through endocytosis in co-culture with a ferrofluid. The number of magnetic nanoparticles internalized was (4.2 ± 0.84) × 106 per cell by the cell magnetophoresis analysis. These magnetically labeled cells were attracted and captured by hexagonal superparamagnetic cone structures to form cell cluster arrays. As a function of the solid cone size, the number of cells captured by each hexagonal superparamagnetic cone structure was increased from 48 to 126 under a 2000 G out-of-plane magnetic field. The local magnetic field gradient of the hexagonal superparamagnetic cone was 117.0-140.9 G/mm from the cell magnetophoresis. When an external magnetic field was applied, we observed that the number of protrusions of the cell edge decreased from the fluorescence images. It showed that the local magnetic field gradient caused by the hexagonal superparamagnetic cones restricted the cell growth and migration.

GaAs-Based Superluminescent Light-Emitting Diodes with 290-nm Emission Bandwidth by Using Hybrid Quantum Well/Quantum Dot Structures.

A high-performance superluminescent light-emitting diode (SLD) based upon a hybrid quantum well (QW)/quantum dot (QD) active element is reported and is assessed with regard to the resolution obtainable in an optical coherence tomography system. We report on the appearance of strong emission from higher order optical transition from the QW in a hybrid QW/QD structure. This additional emission broadening method contributes significantly to obtaining a 3-dB linewidth of 290 nm centered at 1200 nm, with 2.4 mW at room temperature.