Solving a superstructure from two-wavelength x-ray powder diffraction data － a simulation

Two different kinds of phase ambiguities are intrinsic in two-wavelength x-ray powder diffraction from acentric crystal structures having pseudo-translation symmetry. In a test calculation we have solved the problem for the first time by two different phasing procedures developed originally in single-crystal structure analysis. They are the direct method of breaking enantiomorphous phase ambiguity in protein crystallography and that of breaking translational phase ambiguity for superstructures. An artificial structure was used in the test, which is based on atomic coordinates of the known structure, SHAS (C_5H_6O_5N_3K), with the atom K replaced by Rb. The arrangement of Rb atoms possesses a subperiodicity of t=(a+b+c)/2. Two-wavelength synchrotron x-ray powder diffraction data were simulated with λ_1=0.0816nm and λ_2=0.1319nm. Overlapped reflections were uniformly decomposed at the beginning and redecomposed afterward when the partial-structure information became available. The enantiomorphous phase ambiguity was resolved only for reflections with h+k+l even. Phases of reflections with h+k+l odd were derived by the direct method of solving superstructures. A fragment was then obtained, which led to the complete structure in five cycles of Fourier iteration.     

Ab-initio determination of the incommensurate modulated structure of Bi-2212 from x-ray powder diffraction data －a simulation

A set of x-ray powder diffraction data of the high-T_c superconductor Bi_2Sr_2Ca_1Cu_2O_y (Bi-2212) was simulated based on the experimental single-crystal diffraction data by merging together reflections with diffraction angles (2θ) closer to each other than 0.04 degrees. There are three types of overlapping in the powder diffraction data, i.e. (i) overlapping of main reflections; (ii) overlapping of satellite reflections and (iii) overlapping of main and satellite reflections. The third type of overlapping was first separated into main and satellite components according to the ratio between the average intensity of that of types (i) and (ii). Then the overlapped reflections of main reflections and those of the satellites were uniformly partitioned. Heavy-atom sites in the basic/average structure were found using the uniformly decomposed main reflections by the conventional direct method. Phases of the satellites were derived by the multidimensional direct method. The resultant four-dimensional Fourier maps revealed correctly the essential feature of the modulation. No assumption on either the basic structure or the modulation is needed.     

Two Manganese Halide Hybrids Based on 1-Butyl-2,3-dimethylimidazolium: Synthesis,Crystal Structure and Photoluminescence

Two new inorganic-organic hybrid manganese(II) halide crystals,namely[BMMIm]_2[MnCl_4](1,BMMIm=1-butyl-2,3-dimethylimidazolium) and[BMMIm]_2[MnBr_4](2),have been obtained simply by heating/stirring with nearly 100%yield.Single-crystal X-ray diffraction (SCXRD) study reveals that 1 crystallizes in triclinic space group of P1 with a=10.0176(7),b=14.9603(11),c=12.9086(8)?,a=91.060(4)°,β=110.204(5)°,g=92.361(4)°,V=1235.19(12)?~3,Z=2,D_c=1.353 g·cm~(-3),F(000)=526,μ=0.978 mm~(-1),R=0.0410 and w R=0.0690 (I2σ(I)) and M_r=503.23;2 belongs to orthorhombic space group of P2_12_12_1 with a=10.0176(7),b=14.9603(11),c=17.4450(14)?,V=2614.4(3)?~3,Z=4,D_c=1.730 g·cm~(-3),F(000)=1340,μ=6.629 mm~(-1),R=0.0440 and w R=0.0520 (I2σ(I)) and M_r=681.07.The ionic compounds 1 and 2 are composed of mononuclear tetrahedral[Mn X_4]~(2-)anion and two ionic liquid cations of[BMMIm]~+.The photoluminescence (PL)of 1 and 2 was characterized and the influence of halogen atom types on PL was investigated.     

A self-powered and drug-free diabetic wound healing patch breaking hyperglycemia and low H2O2 limitations and precisely sterilizing driven by electricity

Accelerating diabetes-related chronic wound healing is a long-sought-after goal in diabetes management. However, therapeutic strategies based on antibiotics or catalysts still face great challenges to break the limitations of antimicrobial resistance, low H₂O₂ and the blocking effect of bacterial biofilms on antibiotic/catalyst penetration. Herein, we reported a glucose biofuel cell-powered and drug-free antibacterial patch, which consisted of an MAF-7 protected glucose oxidase/horseradish peroxidase anode and a horseradish peroxidase cathode, for treating diabetic wounds. This self-powered patch could take high blood glucose as fuel to generate electricity and abundant reactive oxygen species (ROS) in situ, synergistically regulating local hyperglycemia and breaking the limitations of insufficient ROS caused by low H₂O₂ levels. In particular, the electric field created by the GBFC could drive the negatively charged bacteria to adhere firmly to the electrode surface. As a result, the ROS produced in situ on the electrodes was localized to the bacteria, realizing precise sterilization. In vivo experiments confirmed that this self-powered patch enabled the wounds on diabetic mice to take a mere 10 days to eliminate inflammation and form mature skin with new hair follicles, demonstrating its great potential in treating bacteria-infected diabetic wounds.

A GBFC-powered antibacterial patch which can break low H₂O₂ limitations and precisely sterilize driven by electricity was created to treat bacteria-infected diabetic wounds without depending on any exogenous drugs.     

Nanomaterials Facilitating Conversion Efficiency Strategies for Microbial CO2 Reduction

Microbial electro- and photoelectrochemical CO₂ reduction represents an opportunity to tackle the environmental demand for sustainable fuel production. Nanomaterials critically impact the electricity- and solar-driven microbial CO₂ reduction processes. This minireview comprehensively summarizes the recent developments in the configuration and design of nanomaterials for enhancement of the bacterial adhesion and extracellular electron transfer (EET) processes, based on the modification technologies of improving chemical stability, electrochemical conductivity, biocompatibility, and surface area. Furthermore, the investigation of incorporating non-photosynthetic microorganisms using advanced light-harvesting nanostructured photoelectrodes for solar-to-chemical conversion, as well as the current understanding of EET mechanisms occurring at photosynthetic semiconductor nanomaterials-bacteria biohybrid interface is detailed. The crucial factors influencing the performance of microbial CO₂ reduction systems and future perspectives are discussed to provide guidance for the realization of their large-scale application.     

Synthesis, Crystal Structure, and Properties of Inorganic-organic Hybrid M(Ⅱ)-Nb(Ⅴ)(M = Co, Cu)Oxyfluorides

T Two isostructural inorganic-organic hybrid M(Ⅱ)-Nb(Ⅴ)oxyfluorides, namely,M(H<,2>O)<,2>(pyz)NbOF<,5>(M = Co 1, Cu 2; pyz = pyrazine)have been hydrothermally synthesized and structurally characterized. Both compounds possess two-dimensional layer structure constructed by neutral M(H<,2>0)<,2>NbOF<,5> chains inter-connected via bridging pyrazine ligands. The structure is further extended into three-dimensional supramolecular architecture through inter-layer H-bonding interactions between the coordinated water molecules and fluorine ions. The luminescent properties and thermal stability of both compounds have been investigated.     

铝基矿物在钙基固硫过程中的固相反应机理分析

在高温电阻炉中对高硫煤掺入钙铝基添加剂后进行燃烧试验,分析了不同条件下煤中加入添加剂后固硫效率、固硫灰渣的矿物组成及微观形貌的变化特性;综合采用TG-FTIR-XRD研究了化学纯矿物CaO-A12O3-CaSO4体系中硫酸钙的高温热分解过程及产物组成.结果表明,A12O3的加入通过固相反应来影响钙基固硫效率,A12O3对固硫效率的影响并非呈单一性;低温下生成Ca-Al酸盐矿物削弱了固硫反应,而高温下CaSO4与灰中生成的含Ca、Al类矿物反应形成高温固硫物相硫铝酸钙并抑制其分解则提高了钙基固硫效率.     

机械合金化La0.7Ca0.3MnO3的晶化动力学及磁电阻研究

通过机械合金化方法制备了单相La_0.7Ca_0.3MnO₃化合物.球磨形成的非晶态结构在920K退火时转变为钙钛矿型相结构.根据质量作用定律,讨论了非晶晶化动力学行为,其晶化转变激活能约为265kJ/mol.同时研究了化合物的电阻特性,发现低温下样品的电阻ρ与温度T的关系为ρ∝T²,随退火温度的升高,ρ-T²曲线斜率下降.在远离居里温度处的低温磁电阻可用Δρ/ρ₀=p₁-p₂T^3/2-p₃T描述. 关键词：     

熔体快淬Pr(Fe1-xCox)2合金的结构和磁性

通过熔体快淬方法获得Pr(Fe_1-xCo_x)₂合金条带,经过X射线衍射、差示扫描量热计和磁性测量对其结构、磁性和热稳定性进行了研究.发现当Co的含量x大于0.2时才可能获得Pr(Fe,Co)₂立方Laves相化合物.对Pr(Fe_0.6Co_0.4)₂合金,在快淬速度为30m/s时,条带由Pr₂(Fe,Co)₁₇,Pr(Fe,Co)₂和富稀土相组成;在速度为40m/s时,获得了几乎单相的Pr(Fe_0.6Co_0.4)₂化合物,其居里温度为305℃;在速度为45m/s时,除了Pr(Fe_0.6Co_0.4)₂化合物外,还存在少量的非晶相.Pr(Fe_0.6Co_0.4)₂化合物在770℃以上发生分解.用40m/s快淬纳米晶粉胶粘磁体有大的磁致伸缩系数（λ_∥-λ_⊥=140×10^-6)和高的硬磁性能（_iH_c=398kA/m). 关键词：     

Amine-containing tertiary phosphine-substituted diiron ethanedithioate (edt) complexes Fe2(μ-edt)(CO)6-nLn (n= 1, 2): Synthesis,protonation, and electrochemical properties

As diiron subsite models of [FeFe]-hydrogenases for catalytic proton reduction to hydrogen (H₂), a new series of the phosphine-substituted diiron ethanedithiolate complexes Fe₂(μ-edt)(CO)_6-nL_n (n = 1, 2) were prepared from the variable substitutions of all-CO precursor Fe₂(μ-edt)(CO)₆ ( A ) and tertiary phosphines (L1-L4) under different reaction conditions. While the Me₃NO-assisted substitutions of A and one equiv. ligands L1-L4 [L = Ph₂P(CH₂NHBu^t), Ph₂P(CH₂CH₂NH₂), Ph₂P(NHBu^t), and Ph₂P(C₆H₄Me-p)] produced the monosubstituted complexes Fe₂(μ-edt)(CO)₅L ( 1 – 4 ) in good yields, the refluxing xylene solution of A and two equiv. ligand L1 prepared complex Fe₂(μ-edt)(CO)₅{κ¹-Ph₂P(CH₂NHBu^t)} ( 1 ) in low yield. Meanwhile, the UV-irradiated toluene solution of A and two equiv. ligand L3 resulted in the rare formation of the disubstituted complex Fe₂(μ-edt)(CO)₄{κ¹, κ¹-(Ph₂PNHBu^t)₂} ( 5 ) in low yield, whereas the Me₃NO-assisted substitution of A and two equiv. ligand L4 afforded the disubstituted complex Fe₂(μ-edt)(CO)₄{κ¹, κ¹-(Ph₂PC₆H₄Me-p)₂} ( 6 ) in good yield. All the model complexes 1 – 6 have been characterized by elemental analysis, FT-IR, NMR spectroscopy, and particularly for 1 , 3 , 5 by X-ray crystallography. Further, the protonations of complexes 1 – 4 are studied and compared with excess acetic acid (HOAc) and trifluoroacetic acid (TFA) by using FT-IR and NMR techniques. Additionally, the electrochemical and electrocatalytic properties of model complexes 1 – 6 are investigated and compared by cyclic voltammetry (CV), suggesting that they are electrocatalytically active for proton reduction to H₂ in the presence of HOAc.