Hydrothermal Syntheses of CuO,CuO/Cu2O,Cu2O,Cu2O/Cu and Cu Microcrystals Using Ionic Liquids

In this paper, CuO, CuO/Cu₂O, Cu₂O, Cu₂O/Cu and Cu microcrystals were synthesized via a hydrothermal method by mixing Cu(NO₃)₂·3H₂O and NaOH together in the presence of an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM]BF₄) or 1-butyl-3-methylimidazolium chloride([BMIM]Cl). The structures and the morphologies of the obtained products were characterized by means of X-ray diffractometer(XRD), field-emission scanning electron microscopy/energy-dispersive spectroscopy(FESEM/EDS), transmission electron microscopy/selected area electron diffraction(TEM/SAED) and Raman spectroscopy. The result of XRD indicates that Cu₂O and Cu microcrystals are cubic phase and the Raman spectra confirm the presence of carbon. The results of FESEM and TEM images show Cu₂O microcrystals as rule cubes of 2 μm in length and Cu particles of 5 μm in diameter. According to the difference between crystal structures, bi-component and single component products were synthesized by adjusting the reaction conditions. A possible formation mechanism of Cu₂O and Cu was proposed in[BMIM]BF₄.     

Radiothermoluminescence of polycrystalline high-temperature superconducting YBa2Cu3O6.94, EuBa2Cu3O6.9, and SmBa2Cu3O6.9 samples

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1934, August, 1991.     

纳米Cu_2O材料的合成及其修饰电极安培法测定多巴胺

本文采用简单的一步化学还原方法合成了粒径均一的纳米Cu2O材料并采用扫描电子显微镜对其形貌进行了表征。研究发现,在p H 7.0的磷酸盐缓冲溶液中,采用纳米Cu2O和Nafion(全氟磺酸离子交换树脂)膜制备的复合修饰电极对多巴胺(DA)呈现出较强的电化学催化作用。优化实验条件后,建立了计时电流法直接测定多巴胺的痕量分析体系。在0.5~270μmol·L-1浓度范围内,多巴胺的阳极峰电流与浓度呈良好的线性关系(r=0.9980),检测限为0.17μmol·L-1,灵敏度为20.44μA m M-1且响应时间不超过3 s。该电极可有效屏蔽抗坏血酸(AA)的干扰,在20倍AA共存下仍能准确地测定DA。对含50μmol·L-1DA的溶液平行测定11次,相对标准偏差为3.3%,表明修饰电极的重现性和稳定性好。将该修饰电极用于模拟样品中DA的测定,结果令人满意。     

High-pressure phase transitions of Cu2O

In the present study, we extensively explored the crystal structures of Cu₂O on increasing the pressure from 0 GPa to 24 GPa using the first-principles density functional calculations. A series of pressure-induced structure phase transitions of Cu₂O are examined. The calculated results show that the phase transitions (Pn-3m phase → R-3m phase → P-3m1 phase) occur at 5 GPa and 12 GPa, respectively. The P-3m1 phase is found to be the metallic phase via band-gap closure under high pressure.     

微波热解法制备Cu/Cu2O纳米材料

在二乙二醇溶剂体系中利用微波介电加热分解醋酸铜前体,进一步还原得到Cu2O和Cu纳米粒子以及Cu/Cu2O核壳结构。 采用X射线衍射、透射电子显微镜、扫描电子显微镜和紫外吸收光谱测试技术对产物的形貌、结构和组成进行了研究,结果表明,得到的Cu/Cu2O核壳结构直径为500 nm左右。 对比实验研究了不同聚合度乙二醇系列溶剂、反应时间以及表面活性剂或配位剂对产物形貌、组成的影响,表明低聚合度乙二醇和长的反应时间有利于醋酸铜还原形成铜。     

构建稳定的CuO/La2Sn2O7催化剂用于碳烟颗粒燃烧:CuO在La2Sn2O7烧绿石复合氧化物载体上的单层分散行为

柴油车尾气排放的碳烟颗粒造成了日益严重的环境污染.目前催化燃烧是消除碳烟颗粒污染的有效技术.针对金属氧化物负载体系,20世纪70年代末谢有畅教授等人提出了单层分散理论,是指导设计高效负载催化剂的一个重要思想,已被科研工作者们普遍接受.当负载催化剂体系用于某个特定反应时,通常会表现出单层分散阈值效应,即负载的活性组分含量...     

Sonochemical Preparation of Micro-and Nanometer Cu2O

Cu2O particles with different morphologies and scales were prepared sonochemically on the solid-liquid interface of CuCl and water, by adjusting the reaction factors. The products were characterized by powder X-ray diffraction(XRD) and scanning electron microscopy(SEM). The formation and morphology of Cu2O crystals were influenced by high-intensity ultrasound,reaction temperature,and addition of CuCl.The results indicate that micrometer Cu2O was crystallized in cubic and octahedral shapes, whereas, nanometer Cu2O was not produced in well-shaped crystals.     

Selective electrodeposition of ZnO onto Cu2O

The co-deposition of cuprous oxide (Cu₂O) and zinc oxide (ZnO) on indium tin oxide (ITO) substrate was executed by two different electrochemical methods and the formation mechanism of ZnO onto Cu₂O was investigated by ex-situ SEM, XRD, and XPS. The single galvanostatic electrodeposition step in a mixed nitrate electrolyte offered a useful method in preparing ZnO onto triangular Cu₂O islands formed. On the other hand, hexagonal shaped ZnO phase was electrodeposited on ITO substrate as well as on Cu₂O islands when two steps of the galvanostatic and potentiostatic process were applied.     

Order-disorder in YBa2Cu3O7

We summarize here results of a fairly detailed study by high-resolution electron microscopy and electron diffraction of the high-temperature superconductor YBa₂Cu₃O_7−δ. Data from the perfect structure for (100), (110), and (001) zones indicate that the material has an oxygen-deficient perovskite structure as previously reported from X-ray and neutron diffraction studies. In some cases planar defects along (001) directions were observed. A more important observation is the existence of a phase with disorder of the Y and Ba ion positions and of an additional amorphous phase. The perfectly ordered (defect-free) phase grows from the disordered material, and the planar defects are probably due to mechanical deformation during preparation of the material. These defects probably are not related to the superconducting properties, as recently suggested. The conclusions are consistent with the commonly encountered problems in the preparation of superconductors in high yields.     

Molybdenum phosphate glasses modified by Cu2O

Glasses in the system Cu₂O-P₂O₅-MoO₃ were prepared. The transformation temperature of glasses,T _g, ranges from 122 to 436°C and depends strongly on their composition.T _g values are mainly controlled by the oxygen-packing density. The structure of glasses was studied by infrared spectroscopy. The presence of various phosphate and molybdate units, from discrete monomeric to those with three-dimensional networks, has been observed. The electrical conductivity of prepared glasses depends mainly on Cu₂O content and varies from 10^–14–1cm^–1, for the glass free of Cu₂O, to 10^–6–1cm^–1, for glasses with compositions near of the binary Cu₂O-MoO₃ composition.This work was supported by grant No 1/731/94 of the Slovak Grant Agency for Science. The paper was presented on TERMANAL'94, XIII. International Conference on Thermal Analysis, October 1994, High Tatras, Slovakia.     

Ferromagnetism in malonato-bridged copper(II) complexes. Synthesis,crystal structures,and magnetic properties of [[Cu(H2O)3][Cu(mal)2(H2O)]]n and [[Cu(H2O)4]2[Cu(mal)2(H2O)]][Cu(mal)2(H2O)2][[Cu(H2O)4][Cu(mal)2(H2O)2][(H2mal = malonic acid)

Three malonato-bridged copper(II) complexes of the formulas [[Cu(H2O)3][Cu(C3H2O4)2(H2O)]]n (1), [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]] [Cu(C3H2O4)2(H2O)2][[Cu(H2O)4][Cu(C3H2O4)2(H2O)2]] (2), and [Cu(H2O)4][Cu(C3H2O4)2(H2O)2] (3) (C3H2O4 = malonate dianion) have been prepared, and the structures of the two former have been solved by X-ray diffraction methods. The structure of compound 3 was already known. Complex 1 crystallizes in the orthorhombic space group Pcab, Z = 8, with unit cell parameters of a = 10.339(1) A, b = 13.222(2) A, and c = 17.394(4) A. Complex 2 crystallizes in the monoclinic space group P2/c, Z = 4, with unit cell parameters of a = 21.100(4) A, b = 21.088(4) A, c = 14.007(2) A, and beta = 115.93(2) degrees. Complex 1 is a chain compound with a regular alternation of aquabis(malonato)copper(II) and triaquacopper(II) units developing along the z axis. The aquabis(malonato)copper(II) unit acts as a bridging ligand through two slightly different trans-carboxylato groups exhibiting an anti-syn coordination mode. The four carboxylate oxygens, in the basal plane, and the one water molecule, in the apical position, describe a distorted square pyramid around Cu1, whereas the same metal surroundings are observed around Cu2 but with three water molecules and one carboxylate oxygen building the equatorial plane and a carboxylate oxygen from another malonato filling the apical site. Complex 2 is made up of discrete mono-, di-, and trinuclear copper(II) complexes of the formulas [Cu(C3H2O4)2(H2O)2]2-, [[Cu(H2O)4] [Cu(C3H2O4)2(H2O)2]], and [[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]]2+, respectively, which coexist in a single crystal. The copper environment in the mononuclear unit is that of an elongated octahedron with four carboxylate oxygens building the equatorial plane and two water molecules assuming the axial positions. The neutral dinuclear unit contains two types of copper atoms, one that is six-coordinated, as in the mononuclear entity, and another that is distorted square pyramidal with four water molecules building the basal plane and a carboxylate oxygen in the apical position. The overall structure of this dinuclear entity is nearly identical to that of compound 3. Finally, the cationic trimer consists of an aquabis(malonato)copper(II) complex that acts as a bismonodentate ligand through two cis-carboxylato groups (anti-syn coordination mode) toward two tetraaqua-copper(II) terminal units. The environment of the copper atoms is distorted square pyramidal with four carboxylate oxygens (four water molecules) building the basal plane of the central (terminal) copper atom and a water molecule (a carboxylate oxygen) filling the axial position. The magnetic properties of 1-3 have been investigated in the temperature range 1.9-290 K. Overall, ferromagnetic behavior is observed in the three cases: two weak, alternating intrachain ferromagnetic interactions (J = 3.0 cm-1 and alpha J = 1.9 cm-1 with H = -J sigma i[S2i.S2i-1 + alpha S2i.S2i+1]) occur in 1, whereas the magnetic behavior of 2 is the sum of a magnetically isolated spin doublet and ferromagnetically coupled di- (J3 = 1.8 cm-1 from the magnetic study of the model complex 3) and trinuclear (J = 1.2 cm-1 with H = -J (S1.S2 + S1.S3) copper(II) units. The exchange pathway that accounts for the ferromagnetic coupling, through an anti-syn carboxylato bridge, is discussed in the light of the available magneto-structural data.     

偏压控制Cu2O和Cu在TiO2表面的生长及其光电化学性质

基于TiO2/Ti电极在含Cu2+溶液中的循环伏安图,调节电沉积的沉积电压,我们在TiO2平整表面制备出Cu2O和/或Cu颗粒.通过扫描电镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)表征,发现Cu2O和Cu有不同的生长机制:Cu2O颗粒在TiO2表面分散结晶,而Cu颗粒是在已生长的颗粒上成核,从而形成堆积颗粒结构.这是由于在Cu2O/TiO2界面和Cu/TiO2界面形成不同的能带结构,使得电子的转移方式不同.与纯TiO2光阳极比较,可以观察到Cu2O/TiO2和Cu/TiO2异质结构的光电流均有显著增强.特别地,存在一个电压区间使得Cu2O和Cu同时生长在TiO2表面,此时对应的光电流比较稳定并且能达到最大.紫外-可见(UV-Vis)漫反射光谱、电化学阻抗谱(EIS)和光电流-电压特性曲线均显示,Cu2O和Cu明显有助于光的可见光吸收,同时Cu/TiO2在光电转换过程中显示更宽波段的可见光利用率.此外,开路电压的增加、有效的电荷分离和电极/电解质界面上载流子的快速迁移也增强了材料的光电化学性质.     

偏压控制Cu2O和Cu在TiO2表面的生长及其光电化学性质

基于TiO2/Ti电极在含Cu2+溶液中的循环伏安图,调节电沉积的沉积电压,我们在TiO2平整表面制备出Cu2O和/或Cu颗粒.通过扫描电镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)表征,发现Cu2O和Cu有不同的生长机制:Cu2O颗粒在TiO2表面分散结晶,而Cu颗粒是在已生长的颗粒上成核,从而形成堆积颗粒结构.这是由于在Cu2O/TiO2界面和Cu/TiO2界面形成不同的能带结构,使得电子的转移方式不同.与纯TiO2光阳极比较,可以观察到Cu2O/TiO2和Cu/TiO2异质结构的光电流均有显著增强.特别地,存在一个电压区间使得Cu2O和Cu同时生长在TiO2表面,此时对应的光电流比较稳定并且能达到最大.紫外-可见(UV-Vis)漫反射光谱、电化学阻抗谱(EIS)和光电流—电压特性曲线均显示,Cu2O和Cu明显有助于光的可见光吸收,同时Cu/TiO2在光电转换过程中显示更宽波段的可见光利用率.此外,开路电压的增加、有效的电荷分离和电极/电解质界面上载流子的快速迁移也增强了材料的光电化学性质.     

Neue Oxocuprate (I). Über Cs3Cu5O4, Rb2KCu5O4, RbK2Cu5O4 und K3Cu5O4

New Oxocuprates(I). On Cs₃Cu₅O₄, Rb₂KCu₅O₄, RbK₂Cu₅O₄ and K₃Cu₅O₄ Cs₃Cu₅O₄ light yellow, powder as well as single crystals [a = 10.313(9), b = 7.630(1), c = 14.750(4) Å, β = 106.48(6)°], Rb₂KCu₅O₄ [a = 9.724(2), b = 7.443(0), c = 14.246(2) Å, β = 106.78(8)°], RbK₂Cu₅O₄ [a = 9.561(1), b = 7.411(0), c = 14.111(1) Å, β = 106.76(7)°] and K₃Cu₅O₄ [a = 9.422(1), b = 7.364(1), c = 13.995(2) Å, β = 107.00(2)°] are new prepared. The colour of the powders becomes lighter according to the sequence showed above. K₃Cu₅O₄ shows pale yellow. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Additive-Free,Robust H2 Production from H2O and DMF by Dehydrogenation Catalyzed by Cu/Cu2O Formed In Situ

Hydrogen production from organic/inorganic hydrides is a promising strategy for the development of novel clean energy resources to replace fossil fuels and satisfy ever-increasing energy demands. Most current processes involve small flammable chemicals and are catalyzed by noble metals in basic media with the release of the greenhouse gas CO₂. Herein, we describe an alternative pathway for highly efficient and robust H₂ production through a dehydrogenation reaction between water and N,N-dimethylformamide catalyzed by Cu/Cu₂O catalysts formed in situ. The catalysts exhibit high and robust activity for H₂ production. Importantly, the formation of H₂ as the sole gas and the valuable by-product N,N-dimethylaminoformic acid make this process clean and valuable with 100 % atom economy.     

The composition analysis of YBa2Cu3O7-δ or PrBa2Cu3O7-δ thin films and (YBa2Cu3O7-δ/PrBa2Cu3O7-δ)n heterostructures prepared by CVD

Some YBa₂Cu₃O_7-δ films and heterostructures prepared by Chemical Vapor Deposition (CVD) were analyzed in our laboratories by EPMA-EDX or WDX, RBS, SNMS and AES. It was found that in some cases the results of composition analysis can significantly deviate from each other. At least two main reasons for these deviations exist: the different lateral resolution and the application of different reference samples for the calibration. Received: 3 June 1996 / Revised: 14 October 1996 / Accepted: 16 October 1996