One-step synthesis of Ag<Subscript>2</Subscript>S/Ag@MoS<Subscript>2</Subscript> nanocomposites for SERS and photocatalytic applications

This paper reported a one-step synthesis of Ag₂S/Ag@MoS₂ nanocomposites and its applications in the surface-enhanced Raman scattering (SERS) detection and photocatalytic degradation of organic pollutants. The nanocomposites were well characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammograms (CV), the Brunauer-Emmett-Teller (BET), and Fourier transforms infrared spectra (FTIR). The AgNPs were uniformly dispersed on the MoS₂ nanosheets and the particle size of the AgNPs was about 10–30 nm. These Ag₂S/Ag@MoS₂ nanocomposites offered sensitive SERS signals for the detection of R6G with the limit of detections as low as 10^?10 M. The photocatalytic activity of the composite catalyst was studied by the degradation of methylene blue (MB) dye under light illumination. The apparent rate constant of MB degradation for the obtained catalyst could reach 6.6?×?10^?2 min^?1, indicating that the novel Ag₂S/Ag@MoS₂ nanocomposites can be explored for organic pollutant’s detection and degradation.

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Graphical abstract One-step synthesis of Ag₂S/Ag@MoS₂ nanocomposites for SERS and photocatalytic applications

     

The technique of high-pressure powder pressing with polyester film covering for XRF of geochemical samples

The method of determination of major (Si, Al, Fe, Mg, Ca, Na, K, Mn, P, Ti) and trace elements (As, Ba, Br, Ce, Cl, Co, Cr, Cu, F, Ga, Nb, Sr, La, Ni, Pb, Rb, S, U, Th, V, Y, Zn, Zr) in geochemical samples by wavelength dispersive X-ray fluorescence spectrometer with a new sample preparation technique-high pressure pressed pellet and covered with a 3.6 μm polyester film is proposed. The pellet was pressed at 2,000 kN, which was particularly meaningful for the sample with high silicon content and ideal pellet was formed without binder. Coating with a polyester film prevented the variation of chlorine content after multiple analyses of the same pellet, which was caused by the vacuum and long-time irradiation. And 62 rock, soil and sediment reference materials were applied to create calibration curves. The accuracy of the method was evaluated with another eight certified reference materials that were not used in the regression curve. In most cases, the relative error between the certified value and the calculated value was <10% for major elements and <25% for trace elements, except for those approaching the limit of detection. The limit of detection obtained using this pellet preparation technology is suitable for geochemical analyses.     

Total Synthesis of Spiroalkaloids Lycibarbarines A–C

The concise and efficient synthesis of tetrahydroquinoline alkaloids lycibarbarines A−C has been accomplished in four steps from a common intermediate derived from commercially available 2-deoxy-D-ribose and 8-hydroxyquinoline. For the synthesis of the unique tetracyclic spiro-heterocycle skeleton we employed a synthetic strategy that features two key transformations: iodomethyllithium-based homologation of lactone / N-alkylation to access tetracyclic spiro-heterocycle skeleton in one step and one-pot acetonide deprotection, hemiacetal formation, and spirocyclization cascade process.     

A confined micro-reactor with a movable Fe3O4 core and a mesoporous TiO2 shell for a photocatalytic Fenton-like degradation of bisphenol A

Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants. However, the practical applications ...     

Hydrothermal synthesis of hollow silica spheres under acidic conditions

It is well-known that silica can be etched in alkaline media or in a unique hydrofluoric acid (HF) solution, which is widely used to prepare various kinds of hollow nanostructures (including silica hollow structures) via silica-templating methods. In our experiments, we found that sto?ber silica spheres could be etched in generic acidic media in a well-controlled way under hydrothermal conditions, forming well-defined hollow/rattle-type silica spheres. Furthermore, some salts such as NaCl and Na(2)SO(4) were found to be favorable for the formation of hollow/rattle-type silica spheres.     

2D Covalent Organic Framework for Water Harvesting with Fast Kinetics and Low Regeneration Temperature

Atmospheric water harvesting represents a promising technique to address water stress. Advanced adsorbents have been rationally designed to achieve high water uptake, yet their water sorption kinetics and regeneration temperature greatly limit water production efficiency. Herein, we demonstrated that 2D covalent organic frameworks (COFs), featuring hydrophobic skeleton, proper hydrophilic site density, and 1D open channels significantly lowered the water diffusion and desorption energy barrier. DHTA-Pa COF showed a high water uptake of 0.48 g/g at 30 % R.H. with a remarkable adsorption rate of 0.72 L/Kg/h (298 K) and a desorption rate of 2.58 L/Kg/h (333 K). Moreover, more than 90 % adsorbed water could be released within 20 min at 313 K. This kinetic performance surpassed the reported porous materials and boosted the efficiency for multiple water extraction cycles. It may shed light on the material design strategy to achieve high daily water production with low-energy input.     

Hydroxyl Radical-Mediated Efficient Photoelectrocatalytic NO Oxidation with Simultaneous Nitrate Storage Using A Flow Photoanode Reactor

The selective conversion of dilute NO pollutant into low-toxic product and simultaneous storage of metabolic nitrogen for crop plants remains a great challenge from the perspective of waste management and sustainable chemistry. This study demonstrates that this bottleneck can be well tackled by refining the reactive oxygen species (ROS) on Ni-modified NH₂-UiO-66(Zr) (Ni@NU) using nickel foam (NF) as a three-dimensional (3D) substrate through a flow photoanode reactor via the gas-phase photoelectrocatalysis. By rationally refining the ROS to ⋅OH, Ni@NU/NF can rapidly eliminate 82 % of NO without releasing remarkable NO₂ under a low bias voltage (0.3 V) and visible light irradiation. The abundant mesoporous pores on Ni@NU/NF are conducive to the diffusion and storage of the formed nitrate, which enables the progressive conversion NO into nitrate with selectivity over 99 % for long-term use. Through calculation, 90 % of NO could be recovered as the nitrate species, indicating that this state-of-the-art strategy can capture, enrich and recycle the pollutant N source from the atmosphere. This study offers a new perspective of NO pollutant treatment and sustainable nitrogen exploitation, which may possess great potential to the development of highly efficient air purification systems for industrial and indoor NO_x control.     

Modulating Electronic Structures of Iron Clusters through Orbital Rehybridization by Adjacent Single Copper Sites for Efficient Oxygen Reduction

The atom-cluster interaction has recently been exploited as an effective way to increase the performance of metal-nitrogen-carbon catalysts for oxygen reduction reaction (ORR). However, the rational design of such catalysts and understanding their structure-property correlations remain a great challenge. Herein, we demonstrate that the introduction of adjacent metal (M)−N₄ single atoms (SAs) could significantly improve the ORR performance of a well-screened Fe atomic cluster (AC) catalyst by combining density functional theory (DFT) calculations and experimental analysis. The DFT studies suggest that the Cu−N₄ SAs act as a modulator to assist the O₂ adsorption and cleavage of O−O bond on the Fe AC active center, as well as optimize the release of OH* intermediates to accelerate the whole ORR kinetic. The depositing of Fe AC with Cu−N₄ SAs on nitrogen doped mesoporous carbon nanosheet are then constructed through a universal interfacial monomicelles assembly strategy. Consistent with theoretical predictions, the resultant catalyst exhibits an outstanding ORR performance with a half-wave potential of 0.92 eV in alkali and 0.80 eV in acid, as well as a high power density of 214.8 mW cm⁻² in zinc air battery. This work provides a novel strategy for precisely tuning the atomically dispersed poly-metallic centers for electrocatalysis.     

Ultrathin Ca‐PO4‐CO3 Solid‐Solution Nanowires: A Controllable Synthesis and Full‐Color Emission by Rare‐Earth Doping

It was found that calcium carbonate (CaCO₃) and hydroxyapatite (Ca₁₀(OH)₂(PO₄)₆), which are two crucial constituents of the most abundant minerals in nature and very important bioinorganic components in the tissues of mineralizing organisms, can form solid solutions in a wide range of PO₄^3?/CO₃^2? (P/C) ratios at low temperature when prepared as ultrathin nanowire structures. This is due to the special reactivity of ultrasmall nanocrystals, which can effectively lower the synthetic temperature and promote the formation of solid solutions. The as‐prepared ultrathin nanowires with suitable P/C ratios presented strong blue luminescence due to the existence of abundant defects strengthened by CO₃^2?. If used as the matrix, the as‐prepared ultrathin nanowires demonstrated bright green or red luminescent properties when doped with Tb³⁺ or Eu³⁺ ions, and simultaneously retained their original morphologies. These three kinds of fluorescent nanowires could reproduce a full range of luminescence colors based on additive color mixtures of the three primary colors (red, green, and blue). In addition, under the same reaction system, ultrafine rare‐earth‐doped (Ce³⁺, Tb³⁺, Eu³⁺) nanowires (about 1 nm in diameter) were synthesized by using a one‐step hydrothermal process, which further pushed the size of the Ca‐PO₄‐CO₃ nanobuilding blocks to one unit cell region. These ultrafine nanowires displayed excellent film‐forming properties and the ability to absorb UV radiation.     

无皂乳液聚合法制备Fe3O4@P(St-GMA)复合微球

用化学共沉淀法制备了磁性四氧化三铁纳米粒子. 在油酸和氨水的作用下, 使之分散在水中, 得到了水分散的磁流体. 在水基磁流体的存在下, 进行苯乙烯和甲基丙烯酸缩水甘油酯(GMA)的无皂乳液共聚合, 得到了Fe₃O₄@P(St-GMA)复合微球. 综合考察了反应温度、磁流体和单体的用量、引发剂的用量对聚合转化率的影响, 并用TEM, TGA和VSM对磁性复合微球进行了表征.