Metallurgy in a beaker: nanoparticle toolkit for the rapid low-temperature solution synthesis of functional multimetallic solid-state materials

Intermetallic compounds and alloys are traditionally synthesized by heating mixtures of metal powders to high temperatures for long periods of time. A low-temperature solution-based alternative has been developed, and this strategy exploits the enhanced reactivity of nanoparticles and the nanometer diffusion distances afforded by binary nanocomposite precursors. Prereduced metal nanoparticles are combined in known ratios, and they form nanomodulated composites that rapidly transform into intermetallics and alloys upon heating at low temperatures. The approach is general in terms of accessible compositions, structures, and morphologies. Multiple compounds in the same binary system can be readily accessed; e.g., AuCu, AuCu3, Au3Cu, and the AuCu-II superlattice are all accessible in the Au-Cu system. This concept can be extended to other binary systems, including the intermetallics FePt3, CoPt, CuPt, and Cu3Pt and the alloys Ag-Pt, Au-Pd, and Ni-Pt. The ternary intermetallic Ag2Pd3S can also be rapidly synthesized at low temperatures from a nanocomposite precursor comprised of Ag2S and Pd nanoparticles. Using this low-temperature solution-based approach, a variety of morphologically diverse nanomaterials are accessible: surface-confined thin films (planar and nonplanar supports), free-standing monoliths, nanomesh materials, inverse opals, and dense gram-scale nanocrystalline powders of intermetallic AuCu. Importantly, the multimetallic materials synthesized using this approach are functional, yielding a room-temperature Fe-Pt ferromagnet, a superconducting sample of Ag2Pd3S (Tc = 1.10 K), and a AuPd4 alloy that selectively catalyzes the formation of H2O2 from H2 and O2. Such flexibility in the synthesis and processing of functional intermetallic and alloy materials is unprecedented.     

Dischroïsme circulaire des alcaloïdes du groupe de l'hétéroyohimbane

Circular Dischroism of Heteroyohimbane-Type Alkaloids Circular dichroism cannot be used directly to determine the C (3)-configuration of heteroyohimbines. A preliminary chemical transformation is necessary.     

原子尺寸差异与非晶形成能力

采用分子动力学模拟技术，研究了纯Au及AuCu合金的熔化、非晶化和晶化过程.模拟结果表明,在冷却速率为5×1011 K•s－1至4×1012 K•s－1的范围内，液态Au总是形成晶体，且冷速越快，结晶温度越低；而AuCu合金则形成非晶，且冷速越快，非晶转变温度越高.验证了原子尺寸的不匹配有利于非晶形成这一规律.     

Synthesis of atomically ordered AuCu and AuCu(3) nanocrystals from bimetallic nanoparticle precursors

A new multistep approach was developed to synthesize atomically ordered intermetallic nanocrystals, using AuCu and AuCu(3) as model systems. Bimetallic nanoparticle aggregates are used as precursors to atomically ordered nanocrystals, both to precisely define the stoichiometry of the final product and to ensure that atomic-scale diffusion distances lower the reaction temperatures to prevent sintering. In a typical synthesis, PVP-stabilized Au-Cu nanoparticle aggregates synthesized by borohydride reduction are collected by centrifugation and annealed in powder form. At temperatures below 175 degrees C, diffusion of Cu into Au occurs, and the atomically disordered solid solution Cu(x)Au(1)(-)(x) exists. For AuCu, nucleation occurs by 200 degrees C, and atomically ordered AuCu exists between 200 and 400 degrees C. For AuCu(3), an AuCu intermediate nucleates at 200 degrees C, and further diffusion of Cu into the AuCu intermediate at 300 degrees C nucleates AuCu(3). Atomically ordered AuCu and AuCu(3) nanocrystals can be redispersed as discrete colloids in solution after annealing between 200 and 300 degrees C.     

Cathodic corrosion as a facile and effective method to prepare clean metal alloy nanoparticles

The cathodic corrosion method described here is a simple, clean, and fast way of synthesizing nanoalloys with high catalytic performance. Using a series of Pt-Rh alloys as an example, we show that this one-step method can convert a bulk alloy electrode into an aqueous suspension of nanoparticles, retaining the composition and crystal lattice structure of the starting alloy. Compared to pure metals, these alloy nanocatalysts are more active toward CO and methanol oxidation and nitrate reduction reactions. Nanoparticles made of PtRu, PtIr, PtNi, AuCo, AuCu, and FeCo bulk alloys demonstrate the universality of this synthesis method.     

Influence des propriétés intrinsèques de ligands calixaréniques sur des réactions de transformation catalytique de l'éthylène

Influence of the intrinsic properties of calixarene ligands on catalytic reactions involving ethylene. This review shows how the particular structural and chemical properties of calix[4]arene-derived ligands can be exploited in the catalytic transformation of ethylene into dimers, oligomers, and polymers.     

Electrocatalytic Oxidation and Determination of Hydrazine at an AuCu Nanoparticles – Graphene – Ionic Liquid Composite Film Coated Glassy Carbon Electrode

Gold‐copper alloy nanoparticles (AuCu NPs) were electrodeposited on a graphene – ionic liquid composite film (EGN‐IL). The AuCu NPs showed high electrocatalysis to the oxidation of hydrazine with a catalytic reaction rate constant of about 5.0×10⁴ mol/Ls. In phosphate buffer solutions (pH 6.8) the oxidation current of hydrazine at 0.15 V (vs. SCE) at the resulting electrode (AuCu? EGN‐IL/GCE) was linear to its concentration in the range of 0.2–110 µM with a sensitivity of 56.7 µA/mM, and the detection limit was 0.1 µM (S/N=3). The electrode was successfully applied to the determination of waste water.     

Furannes et pyrroles disubstitues en 2,3. XVII. Structure des composés formés par eyanuration des halogénométhyl-2 méthoxycarbonyl-3 et −5 furannes

Treatment of methyl 2-bromomethylfuran-3-carboxylate with potassium cyanide yielded methyl 2-cyanomethylfuran-3-carboxylate, methyl 2-methyl-5-cyanofuran-3-carboxylate and two unusual products which appeared by nucleophilic substitution of the activated methylene group of the preceding furylacetonilrile. Products from the cyanide displacement reaction of methyl 5-chloromethylfuran-2-carboxylate are formed in the same way and their previously described formulas are corrected. On the other hand, it was pointed out that phosphorus oxychloride-pentachloride transformation of 2-cyanomethylfuran-3-carboxylic acid leads to 4,6-disubstituted furo[3,2-c]pyridines.     

熔体快速冷凝过程的微观结构演化

采用分子动力学模拟技术研究了金属间化合物AuCu3熔体的双体分布函数、键对、多面体、配位数等在快速凝固条件下随温度的变化情况，详细考察了AuCu3中微观组团随温度的演化特点.结果表明，AuCu3熔体降温至700 K时双体分布函数的第二峰已发生劈裂，液态金属中已经产生了非晶态；同时液体中的键对数及多面体数与温度的关系都表明，在上述向非晶转变的过程中，AuCu3熔体的确发生了微观结构组态的变化，其中以液体中的缺陷多面体随温度变化最为剧烈.     

AuCu/ZnAl-LDO复合光催化剂的制备及其光催化性能

采用浸渍还原法成功将金铜纳米颗粒负载到锌铝水滑石表面(AuCu/ZnAl-LDHs),焙烧制得复合金属氧化物(AuCu/ZnAlLDO)。通过X射线粉末衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis DRS)技术对材料的晶型、形貌、元素组成以及光吸收性能进行分析。以邻苯二酚为降解物,研究AuCu/ZnAl-LDO在可见光下的光催化性能。实验结果显示:相比于纯锌铝复合金属氧化物(ZnAl-LDO),AuCu/ZnAl-LDO具有更强的可见光吸收能力。Au、Cu负载比例为5∶1,焙烧温度为400℃的催化剂在5 h内对邻苯二酚的降解率为94.5%,其降解的反应速率常数为ZnAl-LDO的13.4倍。此外,借助理论计算推测了AuCu/ZnAl-LDO电子转移的路径,并以此提出可能的光催化降解机理。     

Synthesis of silica supported AuCu nanoparticle catalysts and the effects of pretreatment conditions for the CO oxidation reaction

Supported gold nanoparticles have generated an immense interest in the field of catalysis due to their extremely high reactivity and selectivity. Recently, alloy nanoparticles of gold have received a lot of attention due to their enhanced catalytic properties. Here we report the synthesis of silica supported AuCu nanoparticles through the conversion of supported Au nanoparticles in a solution of Cu(C(2)H(3)O(2))(2) at 300 °C. The AuCu alloy structure was confirmed through powder XRD (which indicated a weakly ordered alloy phase), XANES, and EXAFS. It was also shown that heating the AuCu/SiO(2) in an O(2) atmosphere segregated the catalyst into a Au-CuO(x) heterostructure between 150 °C to 240 °C. Heating the catalyst in H(2) at 300 °C reduced the CuO(x) back to Cu(0) to reform the AuCu alloy phase. It was found that the AuCu/SiO(2) catalysts were inactive for CO oxidation. However, various pretreatment conditions were required to form a highly active and stable Au-CuO(x)/SiO(2) catalyst to achieve 100% CO conversion below room-temperature. This is explained by the in situ FTIR result, which shows that CO molecules can be chemisorbed and activated only on the Au-CuO(x)/SiO(2) catalyst but not on the AuCu/SiO(2) catalyst.     

Mecanismes de durcissement structural des alliages plomb-cadmium (etain,argent) pour grilles de batterie I- alliages plomb-cadmium

The reequilibration of supersatured Pb-Cd alloys was studied by different experimental methods: hardness measurements, optical and electron microscopy, electron microprobe. Two structural states were considered: as-cast alloys, rehomogenised alloys. The Cd contents were 1, 1.5, 2 and 3.2 weight%. The explored temperatures were 20 and 80 °C. This last temperature corresponds to the curing temperature of battery's grids and to the highest operating temperature. The evolution of the quenched structure towards the equilibrium state was studied for the time range one minute to one year. The corresponding aging is characterized by a continuous precipitation and a discontinuous transformation. The hardening process is followed by an overaging which consists of a discontinuous transformation with a reprecipitation of the Cd from the fine hardening precipitates of the same phase.     

AuCu3熔体快速冷却过程中的键对与多面体

Based on the FS(Finnis-Sinclair) many-body potential model, the rapid cooling process of a system, which consists of 375 Cu atoms and 125 Au atoms, controlled by period boundary condition was simulated. The dependence of pair distribution function of melten compound AuCu3 on the temperature under these conditions was researched. It can be concluded that the noncrystal exists under 700 K, and the liquid-glass transition temperature is approximately 680 K according to the Abraham′s method. Furthermore, the feature of version of cluster in melten AuCu3 was investigated by Honeycutt pair analysis technique. It is demonstrated that the structural configuration in melten AuCu3 has remarkable variation during the formation of noncrystal according to the relationship between the bonded pairs and polyhedron and temperatures. The defective polyhedra in liquid AuCu3 have greatest changes accompanying the changing temperatures.     

Influence de la Température et de la Présence des Ions Etrangers sur la Cinétique et le Mécanisme de Formation de la Goethite en Milieu Aqueux

Effect of Temperature and Presence of Foreign Ions on the Kinetics and Mechanism of the Goethite Formation in Liquid Phase We studied the influence of temperature and addition of some foreign ions on the kinetics of transformation of the goethite in sulfate medium by slow air bubbling. The temperature up to 70°C does not influence the kinetics of oxidation; this proves that the transfer of oxygen taken place through the liquid phase. Manganese and colbalt cations impede the formation and the growth of αFeOOH crystallites. Citrate and phosphate anions both hinder this transformation.     

含50-100at%Pd的Ce-Pd系相图

本文通过X射线衍射实验证实了CePd5化合物的结构, 进一步研究了含50-100at%Pd的Ce-Pd系相图, 在750℃以上含50-100at%Pd的Ce-Pd系相图中共有5个中间化合物:CePd5, CePd3, Ce2Pd3, Ce3Pd4和CePd。     

Caractérisation des polymègres réaticuléas sous tension

This paper is devoted to the determination of the number of intermolecular bonds in a polymer crosslinked according to the following process: (1) crosslinking in the usual isotropic state, (2) additional crosslinking of the strained primary network. The Flory equation for swelling in solvents has been modified in order to take into account the oriented state of the initial network at the time of secondary crosslinking. The combination of this equation with those relating the modulus of elasticity and the dimensions of the relaxed sample to the deformation of the primary network at the time of secondary crosslinking leads to different possible evaluations of the number of intermolecular bonds. Their significance is discussed. The equations thus established are tested with natural rubber samples vulcanized according to the above-mentioned process. The validity of the number of crosslinks thus calculated is discussed; a partial degradation of the primary network occurs during the second crosslinking. Its influence is taken into account by using the approximated equations proposed by Flory. The efficiency of the vulcanizing agent (TMTD) is consequently shown to be practically independent of the deformation of the primary network at the time of secondary crosslinking.     

Théorie quantique du pouvoir rotatoire magnétique des molécules diamagnétiques. II. Applications

The general formalism of the variational theory of the Faraday effect established in the first part of this paper is now applied to the actual computation of the Verdet constant of the hydrogen molecule, of water and of some saturated hydrocarbons. The numerical results have a correct order of magnitude and even, for hydrogen, are rather close to the experimental value.     

IsoméRisation avant la perte d'eau des ions aldéhydes et cétones protonés en spectrométrie de masse

Isomerization of Protonated Aldehyde and Ketone Ions in the Mass-Spectrography Before the Loss of Water In mass spectrometry, protonated aldehyde and ketone ions isomerize before the loss of a molecule of water. In order to specify this process, the spectra of deuterium labelled protonated aldehydes and ketones have been compared to the spectra of the corresponding isomer ions.     

Etude RMN 13C d'un Dérivé Uniformément Enrichi en 13C. Signe des Valeurs des Constantes de Couplage Observées

The ¹³C NMR parameters of 3-O-acetyl-1,2:5,6-di-O-isopropylidène-α-D-[U-¹³C] glucofuranose, used as a sample for analysis in double labelling biosynthetic experiments, have been measured. Homonuclear double resonance experiments ¹³C? {¹³C} at 62.8 MHz have permitted the determination of all the ¹³C? ¹³C coupling constants. By theoretical computation of spectra, in connection with the second order effects existing at 25.2 MHz and 15.08 MHz, the sign of the coupling constants has been determined. The theoretical computation of spectra took into account all the isotopomers and was calculated with the help of a program (adapted from the LAOCOON program) allowing for the weighted addition of the spectra.     

Compositional dependence of the stability of AuCu alloy nanoparticles

The oxidation of AuCu nanoparticles was studied as a function of composition and temperature. Oxidation rates at 110 °C were higher for NPs with higher Cu content, showing that Au stabilized the Cu. Electrochemistry measurements show that AuCu could be a promising catalyst for lowering the over potential of CO(2) reduction.