X-ray diffraction and Raman spectra of merrillite at high pressures

ABSTRACT

The compressibility and effect of pressure on the vibrations of merrillite, Ca₉NaMg(PO₄)₇, were studied by using diamond anvil cell at room temperature combined with in-situ synchrotron X-ray diffraction and Raman spectroscopy up to about 18 and 15?GPa, respectively. The pressure-volume data was fitted by a third-order Birch–Murnaghan equation of state to determine the isothermal bulk modulus as K₀ ?=?87.2(32) GPa with pressure derivative K₀′?=?3.2(4). If K₀′?=?4, the isothermal bulk modulus was obtained as 81.6(10) GPa. The axial compressibility was estimated and an axial elastic anisotropy exists since a-axis is less compressible than the c-axis. The Raman frequencies of all observed modes for merrillite continuously increase with pressure, and the pressure dependences of stretching modes (v ₃ and v ₁) are larger than those of the bending modes (v ₄ and v ₂) and external modes. The isothermal mode Grüneisen parameters and intrinsic anharmonicity of merrillite were also calculated.     

间二甲苯分子在不同外电场下结构和解离特性研究

间二甲苯是挥发性有机物(VOCs, Volatile Organic Compounds)的关键活性成分,研究其在外电场下的性质十分重要.采用密度泛函理论(DFT),在B3LYP/6-311G++基组水平上对间二甲苯分子进行优化,从分子结构研究了不同外电场(-0.025 a.u.～0.025 a.u.)作用下,间二甲苯分子的总能量,键长,电偶极矩,前线轨道,红外光谱和解离势能面.计算结果表明,沿两甲基中C原子连线方向的电场(-0.025 a.u.～0.025 a.u.)增加时,分子总能量和能隙先增大后减小,电偶极矩先减小后增加.通过计算发现外电场对间二甲苯分子不同键长和不同振动模式的红外光谱的影响均有所不同.间二甲苯分子的解离特性表现为:沿两甲基中C原子连线方向施加强度超过0.047 a. u.的电场时,位于电场增加方向的甲基与苯环之间起连接作用的C-C键断裂.以上计算结果可为利用电场降解间二甲苯提供重要理论参考.     

Surface antimicrobial modification of polyamide by poly(hexamethylene guanidine) hydrochloride

Antimicrobial polyamide (PA) received much attention for the demand of packaging and biomedical fields. In this paper, an antimicrobial PA6 membrane was prepared via a surface chemical reaction. A highly effective antibacterial component (PHMG‐E) with terminal epoxy group was firstly synthesized via a reaction between polyhexamethylene guanidine hydrochloride (PHMG) and ethylene glycol diglycidyl ether (EGDE). Then, PHMG‐E was bonded on the surface of PA6 membrane with secondary amine reduced by borane‐tetrahydrofuran (BH₃‐THF). The antimicrobial rates of surface‐modified PA6 membrane (PA6‐PHMG) against Escherichia coli and Staphylococcus aureus were both higher than 99.99%, and the PHMG was non‐leaching due to the chemical bonding. The hydrophilicity of antibacterial PA6 membrane was also significantly improved and the mechanical performance became better.     

A microfluidics-dispensing-printing strategy for Janus photonic crystal microspheres towards smart patterned displays

From the implementation point of view, the printable magnetic Janus colloidal photonic crystals (CPCs) microspheres are highly desirable. Herein, we developed a dispensing-printing strategy for magnetic Janus CPCs display via a microfluidics-automatic printing system. Monodisperse core/shell colloidal particles and magnetic Fe₃O₄ nanoparticles precursor serve as inks. Based on the equilibrium of three-phase interfacial tensions, Janus structure is successfully formed, followed by UV irradiation and self-assembly of colloid particle to generate magnetic Janus CPCs microspheres. Notably, this method shows distinct superiority with highly uniform Janus CPCs structure, where the TMPTA/Fe₃O₄ hemisphere is in the bottom side while CPCs hemisphere is in the top side. Thus, by using Janus CPCs microspheres with two different structural colors as pixel points, a pattern with red flower and green leaf is achieved. Moreover, 1D linear Janus CPCs pattern encapsulated by hydrogel is also fabricated. Both the color and the shape can be changed under the traction of magnets, showing great potentials in flexible smart displays. We believe this work not only offers a new feasible pathway to construct magnetic Janus CPCs patterns by a dispensing-printable fashion, but also provides new opportunities for flexible and smart displays.     

Highly Stable Univalent Copper of a Cu@Al/SBA-15 Nanocomposite Catalyzes the Synthesis of Fluorescent Aminobenzotriazoles Derivatives

With the development of green chemistry, it is still a challenge to maintain the unstable valence state of the metal in heterogeneous catalysts and realize new catalytic synthesis methods. In this paper, it is reported that an univalent copper nanocomposite (Cu@Al/SBA-15) can efficiently catalyze the formation of novel amino-containing benzotriazoles with great fluorescence properties in a new synthetic strategy. Subsequently, its application is further verified by an acylation reaction to produce a series of novel benzotriazoles derivatives with high yield. It is worth noting that the Cu@Al/SBA-15 nanocomposites not only enable the reaction completed with high yield in a short time, but can also be recycled many times without a significant reduction in activity, and the leaching of copper and aluminum species in reaction system is negligible. Finally, the detailed and feasible reaction mechanism is also provided.     

Stable Heterometallic Cluster‐Based Organic Framework Catalysts for Artificial Photosynthesis

A series of stable heterometallic Fe₂M cluster‐based MOFs ( NNU‐31‐M , M=Co, Ni, Zn) photocatalysts are presented. They can achieve the overall conversion of CO₂ and H₂O into HCOOH and O₂ without the assistance of additional sacrificial agent and photosensitizer. The heterometallic cluster units and photosensitive ligands excited by visible light generate separated electrons and holes. Then, low‐valent metal M accepts electrons to reduce CO₂, and high‐valent Fe uses holes to oxidize H₂O. This is the first MOF photocatalyst system to finish artificial photosynthetic full reaction. It is noted that NNU‐31‐Zn exhibits the highest HCOOH yield of 26.3 μmol g^?1 h^?1 (selectivity of ca. 100 %). Furthermore, the DFT calculations based on crystal structures demonstrate the photocatalytic reaction mechanism. This work proposes a new strategy for how to design crystalline photocatalyst to realize artificial photosynthetic overall reaction.     

Visible‐Light‐Driven Halogen Bond Donor Based Molecular Switches: From Reversible Unwinding to Handedness Inversion in Self‐Organized Soft Helical Superstructures

Visible‐light‐driven molecular switches endowing reversible modulation of the functionalities of self‐organized soft materials are currently highly sought after for fundamental scientific studies and technological applications. Reported herein are the design and synthesis of two novel halogen bond donor based chiral molecular switches that exhibit reversible photoisomerization upon exposure to visible light of different wavelengths. These chiral molecular switches induce photoresponsive helical superstructures, that is, cholesteric liquid crystals, when doped into the commercially available room‐temperature achiral liquid crystal host 5CB, which also acts as a halogen‐bond acceptor. The induced helical superstructure containing the molecular switch with terminal iodo atoms exhibits visible‐light‐driven reversible unwinding, that is, a cholesteric–nematic phase transition. Interestingly, the molecular switch with terminal bromo atoms confers reversible handedness inversion to the helical superstructure upon irradiation with visible light of different wavelengths. This visible‐light‐driven, reversible handedness inversion, enabled by a halogen bond donor molecular switch, is unprecedented.     

中国聚变工程实验堆水冷包层钢构件流道成形控制研究

针对CFETR水冷包层流道钢构件热等静压制备时易变形压塌问题，利用单轴扩散焊设备开展了焊接工艺参数优化试验。在此基础上，重新设计了流道焊接界面位置和尺寸，用两步热等静压扩散焊法制备出了流道变形可控的平板型第一壁钢构件模块。优化试验表明，低活化钢试样的固相扩散焊温度需高于950℃，焊后经过760℃/60min回火热处理试样力学性能可以得到有效回复。     

Organocatalytic Enantioselective Synthesis of Atropisomeric Aryl‐p‐Quinones: Platform Molecules for Diversity‐Oriented Synthesis of Biaryldiols

Presented here is a class of novel axially chiral aryl‐p‐quinones as platform molecules for the preparation of non‐C₂ symmetric biaryldiols. Two sets of aryl‐p‐quinone frameworks were synthesized with remarkable enantiocontrol by means of chiral phosphoric acid catalyzed enantioselective arylation of p‐quinones by central‐to‐axial chirality conversion. These aryl‐p‐quinones were then used to access a wide spectrum of highly functionalized non‐C₂ symmetric biaryldiols with excellent retention of the enantiopurity.