The Superstructure of Lead Tetragonal Tungsten Bronze

Electron-optical studies of the superstructure of lead tetragonal tungsten bronze (lead-TTB) are presented. Samples were synthesized for a range of lead compositions and synthesis conditions. For lead-TTB synthesized for very short reaction times, compositional analysis combined with electron diffraction revealed these specimens to also contain significant levels of an intergrowth tungsten bronze (ITB) phase. It was proposed that ITB was formed during the reaction as an intermediate between the tungsten oxide reagent and lead-TTB. Electron-diffraction investigations of lead-TTB over a range of specimen compositions determined that the large majority of crystallites examined exhibited a well-ordered 2√2a_TTB×√2b_TTB×2c_TTB supercell periodicity, although evidence of a larger a-axis repeat was also observed. No evidence for a variation in the supercell with lead composition was observed. A model for the supercell was generated from consideration of stacking sequences of correlated ordered arrays of lead and tilted octahedra and it was demonstrated that larger superstructures could be generated using alternative stacking sequences.     

Highly Crystalline and Semiconducting Imine-Based Two-Dimensional Polymers Enabled by Interfacial Synthesis

Single-layer and multi-layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long-range transport properties. Here we employ a surfactant-monolayer-assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine-based 2D polymer (PI-2DP) films with square and hexagonal lattices, respectively. The synthetic PI-2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100–150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI-2DP are investigated by time-resolved terahertz spectroscopy. Typically, the porphyrin-based PI-2DP 1 film exhibits a p-type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm² V⁻¹ s⁻¹, superior to the previously reported polyimine based materials.     

Na0.33WO3溶胶及薄膜的制备与光致变色性质研究

无机光致变色材料在图像显示、光记录、信息存储和光转换方面有着巨大的潜在应用前景,引起了材料工作者的广泛重视[1￣3]。氧化钨是一种重要的无机光致变色材料,目前对氧化钨的研究多以无定     

An X-Ray and Electron Diffraction Study of the Tetragonal Lead Tungsten Bronze Pb0.26WO3

The average structure of the tetragonal lead tungsten bronze, Pb_0.26WO₃, has been determined by single-crystal X-ray diffraction (P4/mbmspace group,a_av=12.217(1)Å ,c_av=3.7828(7)Å andZ=10). The structure refinement based on 370 observed unique reflections (2539 totally measured reflections) withF_o>4σ(F_o) converged toR=0.035 (R_w=0.031). All but one of the oxygen atoms exhibit a twofold disorder. The lead atoms are distributed over three, symmetrically independent, positions inside the pentagonal tunnels. Electron diffraction observations recognize the X-ray average structure. Furthermore, satellite spots appear on the ED patterns revealing a modulated structure, which may be described in terms of a periodic repetition of antiphase boundary planes inside a superstructure related to the average structure by andc_s=2c_av. The repetition distance isd=5/2a_sand the displacement vector is R= 1/2 a_av.     

Observing Defect Passivation of the Grain Boundary with 2-Aminoterephthalic Acid for Efficient and Stable Perovskite Solar Cells

Metal halide perovskite solar cells (PSCs), with their exceptional properties, show promise as photoelectric converters. However, defects in the perovskite layer, particularly at the grain boundaries (GBs), seriously restrict the performance and stability of PSCs. Now, a simple post-treatment procedure involves applying 2-aminoterephthalic acid to the perovskite to produce efficient and stable PSCs. By optimizing the post-treatment conditions, we created a device that achieved a remarkable power conversion efficiency (PCE) of 21.09 % and demonstrated improved stability. This improvement was attributed to the fact that the 2-aminoterephthalic acid acted as a cross-linking agent that inhibited the migration of ions and passivated the trap states at GBs. These findings provide a potential strategy for designing efficient and stable PSCs regarding the aspects of defect passivation and crystal growth.     

氧化钨介孔材料的制备与表征

以介孔二氧化硅(KIT-6)为硬模板, 硅钨酸为钨源, 用硬模板法制备WO3-SiO2复合材料, 再利用HF除去二氧化硅, 得到了介孔三氧化钨材料. 用X射线衍射(XRD)、能量扩散X射线(EDX)、高分辨透射电镜(HRTEM)、N2吸附-脱附等表征手段, 对制备复合材料的物料比、煅烧温度以及不同分散剂等条件进行了考察. 结果表明, 硅钨酸与硅介孔的物料比(m(WO3)/m(SiO2))在3:1到4:1之间, 在600-750 ℃下煅烧, 能制备结构较好的介孔氧化钨. 乙醇和蒸馏水为分散剂时, 用乙醇为分散剂所得的介孔WO3材料具有更高的比表面积和孔体积.     

Intrinsically Low Thermal Conductivity and High Carrier Mobility in Dual Topological Quantum Material,n-Type BiTe

A challenge in thermoelectrics is to achieve intrinsically low thermal conductivity in crystalline solids while maintaining a high carrier mobility (μ). Topological quantum materials, such as the topological insulator (TI) or topological crystalline insulator (TCI) can exhibit high μ. Weak topological insulators (WTI) are of interest because of their layered hetero-structural nature which has a low lattice thermal conductivity (κ_lat). BiTe, a unique member of the (Bi₂)_m(Bi₂Te₃)_n homologous series (m:n=1:2), has both the quantum states, TCI and WTI, which is distinct from the conventional strong TI, Bi₂Te₃ (where m:n=0:1). Herein, we report intrinsically low κ_lat of 0.47–0.8 W m⁻¹ K⁻¹ in the 300–650 K range in BiTe resulting from low energy optical phonon branches which originate primarily from the localized vibrations of Bi bilayer. It has high μ≈516 cm² V⁻¹ s⁻¹ and 707 cm² V⁻¹ s⁻¹ along parallel and perpendicular to the spark plasma sintering (SPS) directions, respectively, at room temperature.     

混合价钨氧化物的制备及其性质研究

Precursors were synthesized with hydrazine oxalic acid and tungstic acid in different ratios and a series of tungsten oxides， O/W ratios from 2.90 to 2.30，were obtained by thermal decomposition from the precursors under nitrogen atmosphere at 640～760℃. This kind of tungsten oxides were found to belong to mixed valence compounds which have some special electrical properties. The experimental result indicated that the electrical conductivity of this tungsten oxide has a close relation with its O/W ratio and reach the maximum at WO_2.50. Seclecting WO_2.50 as an example， its conductivity was measured at different temperatures from -197 ℃ to -2.5 ℃ and it was found that the mixed valence tungsten oxide as conductor belongs to the class of metal ones. Owing to their relatively high electrical conductivity and stability in air， mixed valence tungsten oxide shows some potential use in polymer products as additives.     

Synthesis of Organic-Inorganic Hybrid Materials by Incorporation of Molybdenum and Tungsten Hydrated Oxides in Polymers

In order to obtain new organic-inorganic hybrid materials the method exploiting the phenomenon of polymer crazing was investigated. Polypropylene and polyethyleneterephtalate films were subjected to crazing to achieve high porosity. Incorporation of hydrated oxides of Mo and W in porous polymer matrix was performed by hydrolysis of alkoxides in pores using counterflow diffusion technique. It was shown that peculiarities of the hydrolysis of the initial compounds affect significantly the distribution of substances inside porous polymer matrix and the possibility of accumulation of inorganic component inside the film. Mo matter in contrast to W is easily incorporated in the polymer matrix to form a well-defined layer. These samples demonstrated high photosensitivity.     

电化学还原制备铂-氢钨青铜阳极

用电化学还原法在炭布上电沉积铂-氢钨青铜复合催化剂作为质子交换膜燃料电池(PEMFC)阳极。 利用X射线衍射、扫描电子显微镜、单电池极化性能测试以及电化学阻抗谱(EIS)法研究了催化剂的组成、分散性及其对氢氧化的电催化性能。 实验结果表明,阴极还原顺序对催化剂的形貌及分散有较大的影响。 采用分步还原法制备的HxWO3/Pt电极(先沉积铂,后沉积氢钨青铜)对氢氧化具有较高的催化活性,氢钨青铜与铂形成协同催化效应,提高了铂对氢氧化的催化活性。 而共沉积制备的Pt-HxWO3催化剂的电催化活性较差,这是因为共沉积过程中,由于受到2种电解液共存的影响,电极催化层中没有或较少得到氢钨青铜,且铂催化剂出现明显的团聚现象。     

Reversible Thermochromism and Strong Ferromagnetism in Two-Dimensional Hybrid Perovskites

Two-dimensional (2D) hybrid perovskites have shown many attractive properties associated with their soft lattices and multiple quantum well structure. Herein, we report the synthesis and characterization of two new multifunctional 2D hybrid perovskites, (PED)CuCl₄ and (BED)₂CuCl₆, which show reversible thermochromic behavior, dramatic temperature-dependent conductivity change, and strong ferromagnetism. Upon temperature change, the (PED)CuCl₄ and (BED)₂CuCl₆ crystals exhibit a reversible color change between yellow and red-brown. The associated structural changes were monitored by in situ temperature-dependent powder X-ray diffraction (PXRD). The (BED)₂CuCl₆ exhibits superior thermal stability, with a thermochromic working temperature up to 443 K. The conductivity of (BED)₂CuCl₆ changes over six orders of magnitude upon temperature change. The 2D perovskites exhibit ferromagnetic properties with Curie temperatures around 13 K.     

Nature of Proton-Containing Groups of Solid Electrolytes: Polyantimonic Acids of Tetragonal and Cubic Structure

We have used proton magnetic resonance to study the molecular structure of proton-containing groups of two crystalline modifications of polyantimonic acids (PAA): tetragonal and cubic. The difference observed in the proton conductivity of these solid electrolytes is explained from the standpoint of the molecular structure of these compounds. The presence on the surface of tetragonal polyantimonic acid of proton dihydrates, the formation of which involves protons of Brönsted acid centers and water molecules, is the reason for its higher proton conductivity compared with the cubic modification.     

Synthesis of Tertiary Bisphosphine Oxides from Methylacetylene and Secondary Phosphine Oxides

Russian Journal of Organic Chemistry -     

四方相钛酸钡纳米枝晶阵列的水热合成

采用水热法,在表面活性剂十六烷基三甲基溴化铵(CTAB)和合适的矿化剂NaOH的作用下,得到具有新颖结构的钛酸钡纳米枝晶阵列。X射线衍射(XRD)和拉曼光谱(Raman)结果分析显示该枝晶为四方相,随着时间的延长其结晶性增强、四方相更加明显。利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)和电子衍射(ED)研究了该枝晶的生长特点和生长机理,结果表明该枝晶其各枝均沿着[111]方向生长,并且同级枝相互平行形成阵列;在枝晶阵列的外侧部分会有2级子枝长出,中间部位由于空间阻碍没有子枝形成。同时探讨了CTAB和NaOH在枝晶形成过程中的作用机理,以及枝晶产品的介电性能。     

Synthesis of Novel Organosilicon Compounds Possessing Fully Substituted Imidazole Nucleus Sonocatalyzed by Fe-Cu/ZSM-5 Bimetallic Oxides

An efficient four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles is described by one-step condensation of an aldehyde, benzil, ammonium acetate, and primary aromatic amine with nanostructure Fe-Cu/ZSM-5 bimetallic oxides in water under ultrasonic irradiation. The short reaction time, good yields, environmental friendly procedure, mild reaction conditions, and convenient operation are important advantage of this protocol. The products generated during the study have been utilized as substrates for synthesis of organosilicon-containing imidazoles. Synthesis of tris(triorganosilyl)methylimidazole derivatives were carried out using organolithium reagent (Me₃Si)₃CLi, prepared via metalation of (Me₃Si)₃CH with methyllithium in tetrahydrofuran, in excellent yields.     

Phase Transition of a Structure II Cubic Clathrate Hydrate to a Tetragonal Form

The crystal structure and phase transition of cubic structure II (sII) binary clathrate hydrates of methane (CH₄) and propanol are reported from powder X‐ray diffraction measurements. The deformation of host water cages at the cubic–tetragonal phase transition of 2‐propanol+CH₄ hydrate, but not 1‐propanol+CH₄ hydrate, was observed below about 110 K. It is shown that the deformation of the host water cages of 2‐propanol+CH₄ hydrate can be explained by the restriction of the motion of 2‐propanol within the 5¹²6⁴ host water cages. This result provides a low‐temperature structure due to a temperature‐induced symmetry‐lowering transition of clathrate hydrate. This is the first example of a cubic structure of the common clathrate hydrate families at a fixed composition.     

氧化钨对 Pt-RuOxHy 电催化剂甲醇氧化性能的促进作用

 在多壁碳纳米管负载的 Pt-RuOxHy 样品中引入氧化钨 (WOm), 能有效抑制样品中水合氧化钌 (RuOxHy) 在酸性电解质溶液中的溶解. 在扩展电势 (–0.20~0.96 V vs SCE) 的电化学预处理过程中, RuOxHy 的溶解程度从 Pt-RuOxHy 中的 70% 降至 Pt-RuOxHy-WOm 中的 15%. 计时电流曲线测试结果表明, 与窄电势区间 (–0.20~0.46 V vs SCE) 预处理的钌物种没有流失的样品相比, 经扩展电势区间预处理的 Pt-RuOxHy-WOm 样品上甲醇电氧化反应的活性没有下降, 而 Pt-RuOxHy 样品的活性则下降 50%.     

Synthesis of Glycosylphosphine Oxides and Related Compounds

The benzyl-protected glycosyl acetates 1 , 6 , 11 , and 15 react with MeOPPh₂ under catalysis by TMSOTf to yield diastereoselectively the glycosylphosphine oxides 2 , 3 , 8 , 12 , 13 , and 16 , with a strong preference for the 1,2-cis-configurated anomers. Hydrogenolysis of the major products gave the crystalline, unprotected phosphine oxides 4 , 9 , 14 , and 17 , of which 4 was transformed in to the acetate 5 , and 9 into the benzoate 10 . The benzylated phosphine oxides 4 , 8 , 12 , and 16 were reduced with Cl₃SiH in the presence of a tertiary amine to form the phosphines 18 , 21 , 24 , and 26 , which were transformed into the phosphine sulfides 19 , 22 , 25 , and 27 . Moreover, 18 and 21 , were characterized as the borane adducts 20 , and 23 . The structure of the (arabinofuranosyl)phosphine oxide 12 , the corresponding sulfide 25 , and of the borane complex 20 were established by X-ray analysis. According to NMR spectroscopy, the equatorial pyranosylphosphine oxide 8 , the sulfide 22 , and the borane complex 23 adopt a ⁴C₁ conformation. The axial phosphine oxide 2 is a flattened ⁴C₁, the sulfide 19 exists as a B_2,5, and the borane complex 20 is a flattened ⁴C₁ in the solid sate and a B_2,5 in solution. Thus, the conformational behavior of these α-D -glucopyranose derivatives reflects the steric requirement of the P-substituents.     

球状、立方状及空心立方状PbS纳米晶的控制合成及其形成机理

以醋酸铅为铅源,硫代乙酰胺为硫源,在表面活性剂十二烷基硫酸钠(SDS)和十六烷基三甲基溴化铵(CTAB)共同作用下,通过简单地调节水热反应的反应温度控制合成出球状、立方状和空心立方状PbS纳米晶。利用XRD、TEM对合成产物的结构和形貌进行了表征,发现合成的球状、立方状和空心立方状PbS纳米晶尺寸均一,直径为100 nm左右。对球状、立方状和空心立方状PbS纳米晶的形成机理进行了初探,结果表明反应温度较低时,水热反应初始阶段形成的PbS小颗粒呈球形,在表面活性剂SDS的烷基链模板和CTAB微胶束软模板共同作用下生成球状PbS纳米晶;反应温度较高时,水热反应初始阶段形成的PbS小颗粒由于自身的立方相岩盐晶体结构的影响有呈立方状趋势,在SDS和CTAB共同作用下产物堆积成空心立方体状或立方状。