Pressure-induced isostructural phase transition and correlation of FeAs coordination with the superconducting properties of 111-type Na(1-x)FeAs

The effect of pressure on the crystalline structure and superconducting transition temperature (T(c)) of the 111-type Na(1-x)FeAs system using in situ high-pressure synchrotron X-ray powder diffraction and diamond anvil cell techniques is studied. A pressure-induced tetragonal to tetragonal isostructural phase transition was found. The systematic evolution of the FeAs(4) tetrahedron as a function of pressure based on Rietveld refinements on the powder X-ray diffraction patterns was obtained. The nonmonotonic T(c)(P) behavior of Na(1-x)FeAs is found to correlate with the anomalies of the distance between the anion (As) and the iron layer as well as the bond angle of As-Fe-As for the two tetragonal phases. This behavior provides the key structural information in understanding the origin of the pressure dependence of T(c) for 111-type iron pnictide superconductors. A pressure-induced structural phase transition is also observed at 20 GPa.     

g-C3N4表面改性及其光催化制H2与CO2还原研究进展

Solar energy is the largest renewable energy source in the world and the primary energy source of wind energy, tidal energy, biomass energy, and fossil fuel. Photocatalysis technology is a sunlight-driven chemical reaction process on the surface of photocatalysts that can generate H₂ from water, decompose organic contaminants, and reduce CO₂ into organic fuels. As a metal-free polymeric material, graphite-like carbon nitride (g-C₃N₄) has attracted significant attention because of its special band structure, easy fabrication, and low costs. However, some bottlenecks still limit its photocatalytic performance. To date, numerous strategies have been employed to optimize the photoelectric properties of g-C₃N₄, such as element doping, functional group modification, and construction of heterojunctions. Remarkably, these modification strategies are strongly associated with the surface behavior of g-C₃N₄, which plays a key role in efficient photocatalytic performance. In this review, we endeavor to provide a comprehensive summary of g-C₃N₄-based photocatalysts prepared through typical surface modification strategies (surface functionalization and construction of heterojunctions) and elaborate their special light-excitation and response mechanism, photo-generated carrier transfer route, and surface catalytic reaction in detail under visible-light irradiation. Moreover, the potential applications of the surface-modified g-C₃N₄-based photocatalysts for photocatalytic H₂ generation and reduction of CO₂ into fuels are summarized. Finally, based on the current research, the key challenges that should be further studied and overcome are highlighted. The following are the objectives that future studies need to focus on: (1) Although considerable effort has been made to develop a surface modification strategy for g-C₃N₄, its photocatalytic efficiency is still too low to meet industrial application standards. The currently obtained solar-to‑hydrogen (STH) conversion efficiency of g-C₃N₄ for H₂ generation is approximately 2%, which is considerably lower than the commercial standards of 10%. Thus, the regulation of the surface/textural properties and electronic band structure of g-C₃N₄ should be further elucidated to improve its photocatalytic performance. (2) Significant challenges remain in the design and construction of g-C₃N₄-based S-scheme heterojunction photocatalysts by facile, low-cost, and reliable methods. To overcome the limitations of conventional heterojunctions thoroughly, a promising S-scheme heterojunction photocatalytic system was recently reported. The study further clarifies the charge transfer route and mechanism during the catalytic process. Thus, the rational design and synthesis of g-C₃N₄-based S-scheme heterojunctions will attract extensive scientific interest in the next few years in this field. (3) First-principle calculation is an effective strategy to study the optical, electrical, magnetic, and other physicochemical properties of surface strategy modified g-C₃N₄, providing important information to reveal the charge transfer path and intrinsic catalytic mechanism. As a result, density functional theory (DFT) computation will be paid increasing attention and widely applied in surface-modified g-C₃N₄-based photocatalysts.     

商用聚丙烯酸类高吸水树脂粒子尺寸及分布与其凝胶浓度的关系

研究了6种商用聚丙烯酸类高吸水树脂(SAP)粒子尺寸大小及分布对其形成凝胶的临界浓度的影响,通过傅里叶变换红外光谱、X射线光电子能谱对样品的成分进行了分析,使用光学显微镜和ImageJ软件统计了样品未吸水时粒子的尺寸及分布,通过测定样品吸水后的膨胀比,估算得到了样品吸水后的粒子的尺寸及分布,用流变学方法和倒置实验法测定了高吸水树脂形成凝胶的临界浓度(凝胶点)。 结果表明,这6种商用聚丙烯酸类高吸水树脂吸水后的粒子的尺寸大小对其形成凝胶的临界浓度的影响不符合理论预测,这是由于粒子尺寸分布宽度不均一造成的。 在选择粒子大小分布占优的均一范围内,样品的凝胶浓度随着粒子尺寸的增大而降低。     

Synergistic effect between phosphorus tailings and aluminum hypophosphite in flame‐retardant thermoplastic polyurethane composites

The massive accumulation of phosphorus tailings (PT) not only occupies land resources and also causes great threat to ecological environment and human security. It is of great significance to explore the resource utilization of PT in some fields. Herein, aluminum hypophosphite (AHP) and PT are blended together to enhance the flame retardancy of thermoplastic polyurethane (TPU) composites, and the synergistic effects between AHP and PT are investigated systematically. Cone calorimeter test (CCT) results indicate that the peak heat release rate (PHRR) and total heat release (THR) of the samples containing 25 wt% AHP are decreased by 89% and 68%, respectively, and the total smoke release (TSR) show a reduction of 58.8%, in comparison with those of neat TPU. For the sample TPU/22.5AHP/2.5PT, the PHRR, THR, and TSR are decreased by 91.2%, 70%, and 63%, respectively. Scanning electron microscopy (SEM) analysis results demonstrate that the addition of PT can facilitate the generation of dense and compact char layers, preventing the release of heat and smoke effectively. All the abovementioned results indicate that the synergistic effects are existed between AHP and PT for enhancing the fire safety of TPU composites, which can provide a new way for the utilization of PT.     

N-取代苄基-3,5-双苄叉基-哌啶-4-酮的合成及其抗癌活性的测定

以取代苄胺或伯胺为原料,依次经过Michael加成、Dieckmann缩合、水解脱羧和羟醛缩合反应,合成了10种新化合物(8a～8j),目标化合物的结构经1H NMR、IR、MS和元素分析确证。 初步的MTT法生物活性测试表明,目标化合物在100 mg/L浓度下能有效抑制白血病K562细胞、乳腺癌HO8910PM细胞和卵巢癌MDR-MB-231细胞的增殖,具有潜在的抗癌活性。     

Thiol–Anhydride Dynamic Reversible Networks

The reaction of thiols and anhydrides to form ring opened thioester/acids is shown to be highly reversible and it is accordingly employed in the fabrication of covalent adaptable networks (CANs) that possess tunable dynamic covalent chemistry. Maleic, succinic, and phthalic anhydride derivatives were used as bifunctional reactants in systems with varied stoichiometries, catalyst, and loadings. Dynamic characteristics such as temperature-dependent stress relaxation, direct reprocessing and recycling abilities of a range of thiol–anhydride elastomers, glasses, composites and photopolymers are discussed. Depending on the catalyst strength, 100 % of externally imposed stresses were relaxed in the order of minutes to 2 hours at mild temperatures (80–120 °C). Pristine properties of the original materials were recovered following up to five cycles of a hot-press reprocessing technique (1 h/100 °C).     

The use of chiral BINAM NHC-Rh(III) complexes in enantioselective hydrosilylation of 3-oxo-3-arylpropionic acid methyl or ethyl esters

Axially chiral BINAM N-heterocyclic carbene (NHC)-Rh(III) complexes were applied in the enantioselective hydrosilylation of 3-oxo-3-arylpropionic acid methyl or ethyl esters. The reduction products 3-hydroxy-3-arylpropionic acid methyl or ethyl esters could be obtained in good yields with good to excellent enantioselectivities under mild conditions.     

生附子中C19型二萜生物碱的高速逆流色谱分离及其结构鉴定

应用高速逆流色谱法分离制备了生附子中的3个C19型二萜生物碱类化合物。以正己烷-乙酸乙酯-甲醇-水(3:5:4:5, v/v/v/v)为两相溶剂系统,上相为固定相,下相为流动相,在主机转速850 r/min、流动相流速2.0 mL/min、检测波长235 nm条件下进行分离制备;一次性从90 mg附子总碱粗提物中分离制备得到15.3 mg北草乌碱,35.1 mg中乌头碱和22.7 mg次乌头碱,经高效液相色谱分析,测得它们的纯度分别为97.9%、96.2%和99.2%。并应用波谱(电喷雾离子质谱、核磁共振氢谱和核磁共振13C谱)解析法确定了它们的结构。利用该方法可以对生附子中的二萜类生物碱成分进行快速的分离和纯化     

活性炭吸附饮用水中三卤甲烷的实验研究

采用活性炭吸附方法控制饮用水中的三卤甲烷(THMs)。对筛选的活性炭进行动态和静态吸附实验。在ACL₁,ACL₂,ACY,ACM 4种活性炭中,椰壳活性炭ACL₁对THMs的平衡吸附量最高;吸附行为更符合Freundlich经验模型。静态吸附实验结果表明,前1 h ACL₁对THMs的吸附效率较高,4 h内达到吸附平衡,当温度为27～36℃时,温度变化对活性炭吸附THMs的影响较小;当THMs的初始浓度为200μg·L^-1时,ACL₁对THMs的去除率大于90%;ACL₁对THMs的吸附效率依次为CHBr₃>CHClBr₂>CHCl₂Br>CHCl₃。动态吸附实验结果表明,当进水的THMs浓度为200μg·L^-1时,出水THMs达到《生活饮用水卫生标准》(GB5749—2006)所需的最大吸附时长分别为：CH...