One-pot controlled synthesis of hexagonal-prismatic Cu1.94S-ZnS, Cu1.94S-ZnS-Cu1.94S, and Cu1.94S-ZnS-Cu1.94S-ZnS-Cu1.94S heteronanostructures

Playing six-a-side: Complex hexagonal prism Cu(1.94)S-ZnS heteronanostructures were synthesized by a colloidal route. Cu(1.94)S-ZnS, Cu(1.94)S-ZnS-Cu(1.94)S, and Cu(1.94)S-ZnS-Cu(1.94)S-ZnS-Cu(1.94)S structures are formed with screw-, dumbbell-, and sandwich-like shapes by using CuI and [Zn(S(2)CNEt(2))(2)] as precursors in oleylamine.     

A facile approach to synthesize high-quality Zn(x)Cu(y)InS(1.5+x+0.5y) nanocrystal emitters

A facile approach to synthesize Zn(x)Cu(y)InS(1.5+x+0.5y) nanocrystal emitters was presented. The compositions of these nanocrystals were precisely controlled, and the relative PL quantum yields were up to 40%, with tunable emissions in 450-640 nm.     

Shape evolution of Cu2O nanostructures via kinetic and thermodynamic controlled growth

We report the shape evolution process of Cu(2)O nanocrystals upon slow oxidation of Cu under ambient conditions, yielding novel hexagonal and triangular platelike morphologies. The shape of the obtained nanocrystals evolves from hexagonal to triangular to octahedral; the growth patterns are governed by kinetically and thermodynamically controlled growth. Preferential adsorption of I(-) on {111} planes of Cu(2)O nanoparticles induced the selective crystal growth of metastable platelike structures with {111} faces as the basal planes. On aging, the growth process appeared to shift into the thermodynamic regime and the thermodynamically stable octahedral shape is obtained. The possible growth mechanisms were investigated by varying the synthetic conditions. The band gap of Cu(2)O nanooctahedrons was determined by the classical Tauc approach to be 2.24 eV, which is blue shifted with respect to the bulk Cu(2)O value (2.17 eV). Results suggest that the slow oxidation process and use of crystallographic selective surfactants are essential for the appearance of anisotropic metastable shapes. In general, surface energy control by surfactant molecules might provide a convenient channel for tailoring nanocrystal shapes of metal oxides.     

Plasma-assisted oxidation of Cu(100) and Cu(111)

Oxidized copper surfaces have attracted significant attention in recent years due to their unique catalytic properties, including their enhanced hydrocarbon selectivity during the electrochemical reduction of CO₂. Although oxygen plasma has been used to create highly active copper oxide electrodes for CO₂RR, how such treatment alters the copper surface is still poorly understood. Here, we study the oxidation of Cu(100) and Cu(111) surfaces by sequential exposure to a low-pressure oxygen plasma at room temperature. We used scanning tunnelling microscopy (STM), low energy electron microscopy (LEEM), X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and low energy electron diffraction (LEED) for the comprehensive characterization of the resulting oxide films. O₂-plasma exposure initially induces the growth of 3-dimensional oxide islands surrounded by an O-covered Cu surface. With ongoing plasma exposure, the islands coalesce and form a closed oxide film. Utilizing spectroscopy, we traced the evolution of metallic Cu, Cu₂O and CuO species upon oxygen plasma exposure and found a dependence of the surface structure and chemical state on the substrate''s orientation. On Cu(100) the oxide islands grow with a lower rate than on the (111) surface. Furthermore, while on Cu(100) only Cu₂O is formed during the initial growth phase, both Cu₂O and CuO species are simultaneously generated on Cu(111). Finally, prolonged oxygen plasma exposure results in a sandwiched film structure with CuO at the surface and Cu₂O at the interface to the metallic support. A stable CuO(111) surface orientation is identified in both cases, aligned to the Cu(111) support, but with two coexisting rotational domains on Cu(100). These findings illustrate the possibility of tailoring the oxidation state, structure and morphology of metallic surfaces for a wide range of applications through oxygen plasma treatments.

A low-pressure oxygen plasma oxidized Cu(100) and Cu(111) surfaces at room temperature. The time-dependent evolution of surface structure and chemical composition is reported in detail for a range of exposure times up to 30 min.     

Self-assembly and hierarchical organization of Ga2O3/In2O3 nanostructures

We report on the realization of novel 3-D hierarchical heterostructures with 6-and 4-fold symmetries by a transport and condensation technique. It was found that the major core nanowires or nanobelts are single-crystalline In2O3, and the secondary nanorods are single-crystalline monoclinic beta-Ga2O3 and grow either perpendicular on or slanted to all the facets of the core In2O3 nanobelts. Depending on the diameter of the core In2O3 nanostructures, the secondary Ga2O3 nanorods grow either as a single row or multiple rows. The one-step growth of the unique Ga2O3/In2O3 heteronanostructures is a spontaneous and self-organized process. The simultaneous control of nanocrystal size and shape together with the possibility of growing heterostructures on certain nanocrystal facets opens up novel routes to the synthesis of more sophisticated heterostructures as building blocks for opto- and nanoelectronics.     

氧化锌有序结构在Au(111)和Cu(111)上的生长

利用NO₂或O₂作为氧化剂,研究了氧化锌在Au(111)和Cu(111)上的生长和结构。NO₂表现了更好的氧化性能,有利于有序氧化锌纳米结构或薄膜的生长。在Au(111)和Cu(111)这两个表面上,化学计量比氧化锌都形成非极性的平面化ZnO(0001)的表面结构。在Au(111)上,NO₂气氛下室温沉积锌倾向于形成双层氧化锌纳米结构;而在更高的沉积温度下,在NO₂气氛中沉积锌则可同时观测到单层和双层氧化锌纳米结构。O₂作为氧化剂时可导致形成亚化学计量比的ZnO_x结构。由于铜和锌之间的强相互作用会促进锌的体相扩散,并且铜表面可以被氧化形成表面氧化物,整层氧化锌在Cu(111)上的生长相当困难。我们通过使用NO₂作为氧化剂解决了这个问题,生长出了覆盖Cu(111)表面的满层有序氧化锌薄膜。这些有序氧化锌薄膜表面显示出莫尔条纹,表明存在一个ZnO和Cu(111)之间的莫尔超晶格。实验上观察到的超晶格结构与最近理论计算提出的Cu(111)上的氧化锌薄膜结构相符,具有最小应力。我们的研究表明,氧化锌薄膜的表界面结构可能会随氧化程度或氧化剂的不同而变化,而Cu(111)的表面氧化也可能影响氧化锌的生长。当Cu(111)表面被预氧化成铜表面氧化物时,ZnO_x的生长模式会发生变化,锌原子会受到铜氧化物晶格的限域形成单位点锌。我们的研究表明了氧化锌的生长需要抑制锌向金属基底的扩散,并阻止亚化学计量比ZnO_x的形成。因此,使用原子氧源有利于在Au(111)和Cu(111)表面上生长有序氧化锌薄膜。     

Electrochemical detection of Cu(I) and Cu(II) in styrene media

A method is described to detect Cu(II) and Cu(I) added as bromide simultaneously in styrene solution containing tetrahexylammoniumperchloraat (THAP) as supporting electrolyte. It was found that Cu(II) and Cu(I) behave similarly in styrene and in aqueous solution. Reduction of Cu(II) and Cu(I) to metallic copper, as well as oxidation of Cu(I) to Cu(II) and the dissolution of a deposited metallic copper layer are observed. Ohmic drop problems were circumvented by adding THAP to the styrene solution and using ultramicro electrodes. The simultaneous detection of Cu(II) and Cu(I) is based on recording a cyclic voltammetric curve in a mixture of these compounds and calculating their concentration from the cathodic limiting current obtained at −0.80 V vs. RE and the anodic stripping peak corresponding to the dissolution of metallic copper. A detection limit of 2.0×10⁻⁴ mol l⁻¹ was obtained for both Cu(II) and Cu(I) and reproducible results were obtained concerning sensitivity and stability of the calibration curves.     

Seed‐Mediated and Iodide‐Assisted Synthesis of Gold Nanocrystals with Systematic Shape Evolution from Rhombic Dodecahedral to Octahedral Structures

We report the development of a seed‐mediated and iodide‐assisted method for the synthesis of monodisperse gold nanocrystals with systematic shape evolution from rhombic dodecahedral to octahedral structures. Particle growth is complete in 15 min at room temperature, so the process is fast and energy‐efficient. By progressively increasing the volume of KI used in a growth solution while keeping the amount of ascorbic acid added constant, nanocrystals with morphologies that vary from rhombic dodecahedral to rhombicuboctahedral, edge‐ and corner‐truncated octahedral, corner‐truncated octahedral, and octahedral structures were synthesized. The nanocrystals are monodisperse in size and readily form self‐assembled structures on substrates. By simply adjusting the volume of gold seed solution added to a growth solution, particle sizes of the octahedral gold nanocrystals can be tuned with average opposite corner‐to‐corner distances of 42, 48, 54, 60, 68, 93, 107, and 125 nm. In the presence of HAuCl₄, iodide may act as a reducing agent. Variation of its volume in the solution may slightly modulate the reduction rate and affect the final crystal morphology. Intermediate structures collected during crystal growth reveal the presence of many twisted structures that surround a developing nanocrystal core. This nanocrystal growth mechanism and the less important role of surfactant in directing the polyhedral nanocrystal morphology is discussed.     

Structural snapshots of a flexible Cu2P2 core that accommodates the oxidation states Cu(I)Cu(I), Cu1.5Cu1.5, and Cu(II)Cu(II)

The phosphido-bridged dicopper(I) complex {(PPP)Cu}2 has been synthesized and structurally characterized ([PPP]- = bis(2-di-iso-propylphosphinophenyl)phosphide). Cyclic voltammetry of {(PPP)Cu}2 in THF shows fully reversible oxidations at -1.02 V (Cu1.5Cu1.5/CuICuI) and -0.423 V (CuIICuII/Cu1.5Cu1.5). Chemical oxidation of {(PPP)Cu}2 by one electron yields the class III mixed-valence species [{(PPP)Cu}2]+ (EPR, UV-vis). Structural data establish an unexpectedly large change (0.538 A) in the Cu...Cu distance upon oxidation state. Oxidation of {(PPP)Cu}2 by two electrons yields the dication [{(PPP)Cu}2]2+, an antiferromagnetically coupled dicopper(II) complex. Maintenance of a pseudotetrahedral geometry that is midway between a square plane and an ideal tetrahedron at the copper centers, along with a high degree of flexibility at the phosphide hinges, allows for efficient access to CuICuI, Cu1.5Cu1.5, and CuIICuII redox states without the need for ligand exchange, substitution, or redistribution processes.     

Synthesis and shape-tailoring of copper sulfide/indium sulfide-based nanocrystals

Heterostructured Cu2S-In2S3 nanocrystals with various shapes and compositions were synthesized by a high-temperature precursor-injection method using the semiconductor nanocrystal Cu1.94S as a catalyst. The intrinsic cationic deficiencies formed at high temperature by Cu ions made the Cu1.94S nanocrystal a good candidate for catalyzing the nucleation and subsequent growth of In 2S3 nanocrystals, eventually leading to the formation of heterostructured Cu2S-In2S3 nanocrystals. Gelification of the reaction systems, which were composed of different types of nanocrystal precursors and solvent, was found to be a very effective measure for controlling the growth kinetics of the heterostructured particles. Consequently, matchsticklike Cu2S3-In2S3 heterostructured nanorods, teardroplike quasi-core/shell Cu2S@In2S3 nanocrystals, and pencil-like In2S3 nanorods were successfully obtained by manipulating the gelification of the reaction system; this formed a solid experimental basis for further discussion of the growth mechanisms for differently shaped and structured nanocrystals. By reaction with 1,10-phenanthroline, a reagent that strongly and selectively binds to Cu(+), a compositional transformation from binary matchsticklike Cu2S-In2S3 nanorods to pure In2S3 nanorods was successfully achieved.     

Diffusion Dynamics of Cux Cluster on Cu(111) Surface

The diffusion dynamics of small two-dimensional atomic clusters Cux (1·x·8) on Cu(111) surface were studied using the molecular dynamics simulations and a modified analytic embedded-atom method in the temperature range from 200 K to 800 K. The cluster size and temperature dependence of the diffusion coefficients and migration energies are presented. Our simulations show that the diffusion migration energy of the Cu7 cluster is the highest and the prefactor for the Cu7 cluster is almost three orders of magnitude larger than that for single atom diffusion. This conclusion is consistent with the experimental results for similar metals. In addition, the dependence of cluster diffusion on film growth is also discussed.     

Cu2ZnGeSe4 nanocrystals: synthesis and thermoelectric properties

A synthetic route for producing Cu(2)ZnGeSe(4) nanocrystals with narrow size distributions and controlled composition is presented. These nanocrystals were used to produce densely packed nanomaterials by hot-pressing. From the characterization of the thermoelectric properties of these nanomaterials, Cu(2)ZnGeSe(4) is demonstrated to show excellent thermoelectric properties. A very preliminary adjustment of the nanocrystal composition has already resulted in a figure of merit of up to 0.55 at 450 °C.     

Cu(I)-mediated reductive amination of boronic acids with nitroso aromatics

[reaction: see text] A mild method for the reductive amination of aryl boronic acids with nitroso aromatic compounds is reported. This C-N bond formation is mediated by a stoichiometric amount of CuCl as both a catalyst and a reducing agent. Alternatively, 10% Cu(I)-3-methylsalicylate (CuMeSal) catalyzes the same reaction in the presence of either ascorbic acid or hydroquinone as the terminal reducing agent. Diarylamines bearing a variety of functional groups can be obtained in good yields.     

Unusual physical and chemical properties of Cu in Ce(1-x)Cu(x)O(2) oxides

The structural and electronic properties of Ce(1-x)Cu(x)O(2) nano systems prepared by a reverse microemulsion method were characterized with synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy, and density functional calculations. The Cu atoms embedded in ceria had an oxidation state higher than those of the cations in Cu(2)O or CuO. The lattice of the Ce(1)(-x)Cu(x)O(2) systems still adopted a fluorite-type structure, but it was highly distorted with multiple cation-oxygen distances with respect to the single cation-oxygen bond distance seen in pure ceria. The doping of CeO(2) with copper introduced a large strain into the oxide lattice and favored the formation of O vacancies, leading to a Ce(1-x)Cu(x)O(2-y) stoichiometry for our materials. Cu approached the planar geometry characteristic of Cu(II) oxides, but with a strongly perturbed local order. The chemical activities of the Ce(1-x)Cu(x)O(2) nanoparticles were tested using the reactions with H(2) and O(2) as probes. During the reduction in hydrogen, an induction time was observed and became shorter after raising the reaction temperature. The fraction of copper that could be reduced in the Ce(1-x)Cu(x)O(2) oxides also depended strongly on the reaction temperature. A comparison with data for the reduction of pure copper oxides indicated that the copper embedded in ceria was much more difficult to reduce. The reduction of the Ce(1-x)Cu(x)O(2) nanoparticles was rather reversible, without the generation of a significant amount of CuO or Cu(2)O phases during reoxidation. This reversible process demonstrates the unusual structural and chemical properties of the Cu-doped ceria materials.     

Facile in situ copper(II) mediated C-S bond activation transforming dithiocarbimate to carbamate and thiocarbamate generating Cu(II) and Cu(I) complexes

Facile in situ Cu(II) mediated transformation of p-tolylsulfonyldithiocarbimate in conjunction with polypyridyl or phosphine ligands into corresponding carbamate and thiocarbamate led to the formation of new copper complexes with varying nuclearities and geometries, via C-S bond activation of the ligand within identical reaction systems.     

The disproportionation of Cu(I)X mediated by ligand and solvent into Cu(0) and Cu(II)X2 and its implications for SET‐LRP

Disproportionation of Cu(I)X is the major step in Single‐Electron Transfer Living Radical Polymerization (SET‐LRP). The disproportionation of Cu(I)X mediated by Me₆‐TREN in various solvents was studied through UV–vis spectroscopy and Dynamic Light Scattering (DLS). UV–vis experiments reveal that disproportionation is dependent on both solvent composition and concentration of Me₆‐TREN, consistent with a revised equilibrium expression and corroborated by mathematical models. Electrochemistry data do not accurately predict the extent of disproportionation in the presence of Me₆‐TREN. Exemplified by DMSO, a favored solvent for SET‐LRP, UV–vis spectroscopy shows that under certain conditions disproportionation is four‐orders of magnitude greater than the value reported from electrochemistry experiments. Through UV–vis and DLS analysis, it was demonstrated that DMSO, DMF, DMAC, and NMP, stabilize colloidal Cu(0), while acetone, EtOH, EC, MeOH, PC, and H₂O facilitate agglomeration of Cu(0) particles. Additionally, for colloidal Cu(0) stabilizing solvents, the amount of ligand and solvent composition decide the particle size distribution. Therefore, the kinetics of SET‐LRP are cooperatively and synergistically determined by the complex interplay of solvent polarity, the extent of disproportionation in the solvent/ligand mixture, and the ability of that mixture to stabilize colloidal Cu(0) or control particle size distribution. The implications of these results for SET‐LRP are discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5606–5628, 2009     

微波辅助合成发光可调ZnS∶Cu纳米晶

以巯基丙酸(MPA)为稳定剂, 利用微波辐射加热方法制备了水溶性的Cu掺杂的ZnS纳米晶. 通过改变微波条件, 可以在460～572 nm之间实现对ZnS∶Cu纳米晶发射峰位的连续调控. 通过XRD、 UV-Vis、荧光及荧光衰减对ZnS∶Cu纳米晶的结构和发光性质进行了详细探索, 并利用时间分辨荧光光谱对其发光机理进行了初步研究.     

Ab initio calculations of the reaction pathways for methane decomposition over the Cu (111) surface

Growth of large-area, few-layer graphene has been reported recently through the catalytic decomposition of methane (CH(4)) over a Cu surface at high temperature. In this study, we used ab initio calculations to investigate the minimum energy pathways of successive dehydrogenation reactions of CH(4) over the Cu (111) surface. The geometries and energies of all the reaction intermediates and transition states were identified using the climbing image nudged elastic band method. The activation barriers for CH(4) decomposition over this Cu surface are much lower than those in the gas phase; furthermore, analysis of electron density differences revealed significant degrees of charge transfer between the adsorbates and the Cu atoms along the reaction path; these features reveal the role of Cu as the catalytic material for graphene growth. All the dehydrogenation reactions are endothermic, except for carbon dimer (C(2)) formation, which is, therefore, the most critical step for subsequent graphene growth, in particular, on Cu (111) surface.     

Synthesis of Ethanol via Syngas on Cu/SiO(2) Catalysts with Balanced Cu(0)-Cu(+) Sites

This paper describes an emerging synthetic route for the production of ethanol (with a yield of ～83%) via syngas using Cu/SiO(2) catalysts. The remarkable stability and efficiency of the catalysts are ascribed to the unique lamellar structure and the cooperative effect between surface Cu(0) and Cu(+) obtained by an ammonia evaporation hydrothermal method. Characterization results indicated that the Cu(0) and Cu(+) were formed during the reduction process, originating from well-dispersed CuO and copper phyllosilicate, respectively. A correlation between the catalytic activity and the Cu(0) and Cu(+) site densities suggested that Cu(0) could be the sole active site and primarily responsible for the activity of the catalyst. Moreover, we have shown that the selectivity for ethanol or ethylene glycol can be tuned simply by regulating the reaction temperature.     

Doping Cu in semiconductor nanocrystals: some old and some new physical insights

Cu-doped inorganic semiconductors with concomitant optical properties have garnered enormous research interest in the last two decades. However, uncertainties over the origin of Cu emission, its oxidation state, resemblance with trap state emission, position of Cu d-state, emission spectral width, and moreover understanding of the doping mechanism restricted the wide development of the synthetic methodology for high-quality Cu-doped nanocrystals. It has been shown recently that the emission from Cu-doped semiconductor nanocrystals can span over a wide spectral window and could be a potential color tunable dispersed nanocrystal emitter. Herein, we report the size and composition of variable Cu-doped ZnS/Zn(1?x)Cd(x)S zinc-blende (ZB) surface alloyed nanocrystals with intense, stable, and tunable emission covering the blue to red end of the visible spectrum. Further, the Cu dopant emission is distinguished from trap state emission, and the composition variable spectral broadening has been justified on the account of a different environment around the Cu ions in the host lattice. Whereas some findings are in agreement with past reports, several new physical insights presented here would help the community for an in-depth mechanistic study on Cu doping. Moreover, these doped nanocrystal emitters can be a promising candidate for application ranging from optoelectronics to bio-labeling.