Study on Microcontamination of Silver onto p-Type Crystalline Silicon(111) from an Aqueous Solution Using Cyclic Voltammetry

The microcontamination process of silver onto p-type crystalline silicon(111) in a solution of 0.01 mol L⁻¹ AgNO₃ at room temperature was investigated by studying the anodic stripping behavior using cyclic voltammetry (CV). This paper shows that the rate of Ag deposition is rapid and that deposition is almost fully accomplished within 1 s. Calculating the surface coverage (Γ) for 1 s, 10 min, or 1 h immersion based on the CV curves demonstrated that the silver layer was only a monolayer.     

Microstructure of Nickel Aluminides Formed in Situ in Aluminium Matrix Composites

Nickel aluminides formed in situ in aluminium matrix composites due to the interaction between nickel powder and the matrix were examined. The composite materials were obtained from mixtures of nickel powder and aluminium powder by hot pressing in vacuum in the temperature range of 500–640°C. Depending on hot pressing parameters, the morphology of nickel aluminide particles was layered or homogenous, and their size for the same precursor powder was growing as the pressing temperature increased. XRD, SEM, TEM and EDS characterization methods were used for the microstructure investigation.     

Interface-controlled synthesis of CeO2(111) and CeO2(100) and their structural transition on Pt(111)

Ceria-based catalytic materials are known for their crystal-face-dependent catalytic properties. To obtain a molecular-level understanding of their surface chemistry, controlled synthesis of ceria with well-defined surface structures is required. We have thus studied the growth of CeO_x nanostructures (NSs) and thin films on Pt(111). The strong metal-oxide interaction has often been invoked to explain catalytic processes over the Pt/CeO_x catalysts. However, the Pt-CeO_x interaction has not been understood at the atomic level. We show here that the interfacial interaction between Pt and ceria could indeed affect the surface structures of ceria, which could subsequently determine their catalytic chemistry. While ceria on Pt(111) typically exposes the CeO₂(111) surface, we found that the structures of ceria layers with a thickness of three layers or less are highly dynamic and dependent on the annealing temperatures, owing to the electronic interaction between Pt and CeO_x. A two-step kinetically limited growth procedure was used to prepare the ceria film that fully covers the Pt(111) substrate. For a ceria film of ~3–4 monolayer (ML) thickness on Pt(111), annealing in ultrahigh vacuum (UHV) at 1000 K results in a surface of CeO₂ (100), stabilized by a c-Ce₂O₃(100) buffer layer. Further oxidation at 900 K transforms the surface of the CeO₂(100) thin film into a hexagonal CeO₂(111) surface.     

Pt4(OCOCH3)4(OCOCH=CH2)4的合成及其在n型单晶硅表面的嫁接与组装

利用羧基取代法, 通过化合物Pt4(OCOCH3)8与过量的丙烯酸作用合成了配合物Pt4(OCOCH3)4(OCOCH=CH2)4. 晶体结构研究结果表明, 化合物Pt4(OCOCH3)8中的4个乙羧基能够被烯丙羧基有规律地选择性替换, 从而形成一个含双键的对称铂配合物. 利用Si—H与不饱和键的加成性质将该配合物嫁接到氢化n型单晶硅(111)表面, 发现配合物Pt4(OCOCH3)4(OCOCH=CH2)4除了能嫁接到单晶硅表面外, 还能在n型单晶硅表面进行自组装而形成许多岛状纳米粒子, 这种组装体系具有良好的热稳定性和一定的抗酸性.     

Macroscopic single‐domain graphene sheet on Ni(111)

We observed in situ growth of a single graphene sheet on Ni(111) by low‐energy electron microscopy. The sheet was grown epitaxially beyond the steps on the substrate. The crystalline shapes of graphene islands were clearly seen; the straight edges of the island are crossed at either 60 or 120°, and the linear edges shifted perpendicular to the edge keeping the equilibrium shape. Graphene islands were united to form a single sheet without any grain boundaries and any wrinkles. The Ni substrate of several centimeters in size was covered with a single‐domain graphene sheet. Copyright © 2011 John Wiley & Sons, Ltd.     

Dissociation of N2 on a Si(111)-7x7 Surface at Room Temperature

We demonstrate that the strong N₂ bond can be efficiently dissociated at low pressure and ambient temperature on a Si(111)-7x7 surface. The reaction was experimentally investigated by scanning tunnelling microscopy and X-ray photoemission spectroscopy. Experimental and density functional theory results suggest that relatively low thermal energy collision of N₂ with the surface can facilitate electron transfer from the Si(111)-7x7 surface to the π*-antibonding orbitals of N₂ that significantly weaken the N₂ bond. This activated N₂ triple bond dissociation on the surface leads to the formation of a Si₃N interface.     

Structural Stability of LiCoO2 at 400°C

The relative stability of the lithiated-spinel structure, Li₂[Co₂]O₄, at 400°C to the layered LiCoO₂ structure has been investigated. “Low-temperature” LT-LiCoO₂ samples were synthesized at 400°C by the solid-state reaction of Li₂CO₃ with CoCO₃ (or Co₃O₄) for various times between 10 min and 232 days. Least-squares refinements of X-ray powder diffraction patterns were used to determine the fractions of lithiated-spinel Li₂[Co₂]O₄ and layered LiCoO₂ in the samples. X-ray powder diffraction and transmission electron microscope data show that Li₂[Co₂]O₄ nucleates from an intermediate Li_xCo_1−x[Co₂]O₄ spinel product before transforming very slowly to layered LiCoO₂. The experimental data confirm the theoretical prediction that layered LiCoO₂ is thermodynamically more stable than the lithiated-spinel structure at 400°C and support the arguments that a non-ideal cation distribution in Li₂[Co₂]O₄, non-stoichiometry and kinetic factors restrict the transformation of the lithiated-spinel structure to layered LiCoO₂ at this temperature.     

Cyclic (Alkyl)(Amino)Carbene (CAAC) Gold(I) Complexes as Chemotherapeutic Agents

Cyclic (Alkyl)(Amino)Carbenes (CAACs) have become forceful ligands for gold due to their ability to form very strong ligand-metal bonds. Inspired by the success of Auranofin and other gold complexes as antitumor agents, we have studied the cytotoxicity of bis- and mono-CAAC-gold complexes on different cancer cell lines: HeLa (cervical cancer), A549 (lung cancer), HT1080 (fibrosarcoma) and Caov-3 (ovarian cancer). Further investigations aimed at elucidating their mechanism of action are described. This includes quantification of affinities for TrxR, evaluation of their bioavailability and determination of associated cell death process. Moreover, Transmission Electron Microscopy (TEM) was used to study morphological changes upon exposure. Noticeably, a significant reduction in non-specific binding to serum proteins was observed with CAAC complexes when compared to Auranofin. These results confirm the potential of CAAC-gold complexes in biological environments, which may result in more specific drug-target interactions and decreased side effects.     

Interface of an Al–(Al2O3)p Composite Modified with Nickel

 A composite material with aluminium matrix and alumina particles coated with nickel was investigated. The nickel coating with thickness up to 1 μm formed by a chemical method consisted of a thin film directly on the alumina surface, porous zone of grains 100 nm size and discontinuous zone of grain agglomerates. As a result of the interaction between the alumina particles coated with nickel and the aluminium matrix, dissolution of nickel in aluminium occurred and reactive bonding took place. In the interface characterized by SEM and TEM methods nickel aluminide and locally nickel-iron aluminide were identified. The presence of complex aluminide was a result of local iron impurity in the aluminium powder.     

Conformation Controls Mobility: 2H-Tetranaphthylporphyrins on Cu(111)

The adsorption behavior and the mobility of 2H-Tetranaphthylporphyrin (2HTNP) on Cu(111) was investigated by scanning tunneling microscopy (STM) at room temperature (RT). The molecules adsorb, like the structurally related 2HTPP, in the “inverted” structure with the naphthyl plane restricted to an orientation parallel to the Cu surface. The orientation of the four naphthyl groups yields altogether 16 possible conformations. Due to the existence of rotamer pairs, 10 different appearances are expected on the surface, and all of them are identified by STM at RT. Most interestingly, the orientation of the naphthyl groups significantly influences the diffusion behavior of the molecules on Cu(111). We identify three different groups of conformers, which are either immobile, medium or fast diffusing at RT. The mobility seems to decrease with increasing size of the footprint of the conformers on the surface.     

syn-Diastereoselective glycolate aldol addition reactions of an N(3)-(p-methoxyphenoxy)acetyloxazolidine-2-thione

An N₃-(p-methoxyphenoxy)acetyloxazolidine-2-thione has been synthesized and employed in glycolate asymmetric aldol addition reactions with aromatic and aliphatic aldehydes. It was determined that the titanium tetrachloride medicated aldol reaction afforded diastereoselectivities that ranged from 75:25 to 94:6 when the reaction was conducted at ?78 °C. The absolute stereochemistry of the aldol adducts was determined by ¹H NMR spectroscopy and X-ray crystallography. The ¹H NMR spectra of the aldol adducts contained a signal (the α-proton of the glycolate position of the aldol side chain) that was highly deshielded due to conformational restriction about the N(3)-(p-methoxyphenoxy)acetyl side chain and the oxazolidine-2-thione auxiliary.     

Synthesis and Characterization of [Fe(Htrz)2(trz)](BF4)] Nanocubes

Compounds that exhibit spin-crossover (SCO) type behavior have been extensively investigated due to their ability to act as molecular switches. Depending on the coordinating ligand, in this case 1H-1,2,4-triazole, and the crystallite size of the SCO compound produced, the energy requirement for the spin state transition can vary. Here, SCO [Fe(Htrz)₂(trz)](BF₄)] nanoparticles were synthesized using modified reverse micelle methods. Reaction conditions and reagent ratios are strictly controlled to produce nanocubes of 40–50 nm in size. Decreases in energy requirements are seen in both thermal and magnetic transitions for the smaller sized crystallites, where, compared to bulk materials, a decrease of as much as 20 °C can be seen in low to high spin state transitions.     

含芳酯键的双马来酰亚胺Ia／二苯醚二胺共聚物的合成与液晶行为

本文以苯甲酸对苯二酚酯双马来酰亚胺（Ｉａ）和二苯醚二胺为单体，合成了Ｉａ／二苯醚二胺的共聚物，应用ＦＴＩＲ谱、热分析ＤＴＡ和ＤＳＣ、热台偏光显微镜对共聚物的结构和液晶行为进行了研究。该类共聚物具有较好的热致液晶行为，其液晶相结构可以通过共聚物的化学交联反应而固定在交联网络中，从而形成液晶网络材料。     

The direct observation of 2H‐DPP metalation on Pd(111) and Cu/Pd(111) surface

The metalation behaviors of 5,15‐diphenylporphyrin (2H‐DPP) on Pd(111) and Cu/Pd(111) have been investigated using scanning tunneling microscopy and density functional calculations. We show that 2H‐DPP molecules deposited on Pd(111) surface form Pd‐DPP with a proportion of about 75% already at room temperature (RT). This is in contrast to non‐metalation adsorption of 2H‐DPP on Cu–Pd alloy at RT. Annealing to 323 K facilitates the metalation of 2H‐DPP on Cu–Pd alloy island. The comparison of the results indicates that the metalation of 2H‐DPP calls for both enough surface free energy of approaching N? H bond and enough reactivity of breaking N? H bond. Copyright © 2016 John Wiley & Sons, Ltd.     

Atomic Mechanism of Predictable Phase Transition in Dual‐Phase H2Ti3O7/TiO2 (B) Nanofiber: An In Situ Heating TEM Investigation

The phase transition from H₂Ti₃O₇ to TiO₂ (B) in a 1D single nanocrystal of H₂Ti₃O₇ was observed by in situ heating in a transmission electron microscope experimentally. The results indicate a typical monoclinic‐to‐monoclinic crystallographic orientation relationship between the two phases. Moreover, the fundamental building blocks and invariant deformation element model were both adopted to reveal the atomic mechanism and predict the crystallographic orientation relationship quantitatively for the phase transition. The prediction was precisely consistent with TEM results.     

Identification and hydrogenation of C2 on Pt(111)

Reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) were used to identify the molecular species formed upon the reaction of hydrogen with surface carbon that is deposited by exposing acetylene to a Pt(111) surface held at 750 K. At this temperature, the acetylene is completely dehydrogenated and all hydrogen is desorbed from the surface. Upon subsequent hydrogen exposure at 85 K followed by sequential annealing to higher temperatures, ethylidyne (CCH3), ethynyl (CCH), and methylidyne (CH) are formed. The observation of these species indicates that carbon atoms and C2 molecules exist as stable species on the surface over a wide range of temperatures. Through a combination of RAIRS intensities, hydrogen TPD peak areas, and Auger electron spectroscopy, quantitative estimates of the coverages of the various species were obtained. It was found that 79% of the acetylene-derived carbon was in the form of C2 molecules, with the remainder in the form of carbon atoms. Essentially all of the acetylene-derived carbon could be hydrogenated. In contrast, 85% of an equivalent coverage of carbon deposited by ethylene exposure at 750 K was found to be inert toward hydrogenation.     

The Use of Electron Backscatter Diffraction for the Investigation of Nano Crystalline Materials and the Move Towards Orientation Imaging in the TEM

Electron backscatter diffraction is shown to have a spatial resolution between 5nm and 10nm and is well suited for the investigation of nano crystalline materials. A study of texture and mesotexture in copper Damascene interconnect lines is used as an illustration. Samples were prepared by electro deposition from baths of different compositions and under various power cycles. The resulting grain structures were visually smaller than the 0.3 micron interconnect line width. However, if twin boundaries were considered as substructure rather than true grain boundaries, the effective grain size become larger than the line width. The bath composition affected the 111 texture component from times 5 random to 26 times random whereas different power cycles affected the texture much less. For structures with a grain size smaller than 20nm a new transmission electron microscope technique has been developed. Automated examination of a sequence of dark field images collected from a selected area lead to the reconstruction of a diffraction pattern for each pixel within the area. These patterns are indexed automatically, permitting crystal orientation as a function of spatial positioning to be mapped. The resulting orientation information is equivalent to that obtained using electron backscatter patterns. The practical resolution limit of this technique approaches 1 to 2 nanometers.     

Layered Crystalline and Amorphous Platinum Disulfide (PtS2): Contrasting Electrochemistry

Group 6 transition metal dichalcogenides (TMDs), such as MoS₂ and WS₂ have been extensively studied for various applications while few studies have delved into other TMDs such as platinum dichalcogenides. In this work, layered crystalline and amorphous platinum disulfide (PtS₂) were synthesized, characterised and their fundamental electrochemical properties were investigated. Both materials exhibited inherent oxidation and reduction reactions which would limit their operating potential window for sensing applications. Amorphous phase materials are considered to be promising electrocatalysts due to the porous, and nanostructured morphology with high concentration of unsaturated active sites. The electrocatalytic performances towards oxygen reduction (ORR) and hydrogen evolution reactions (HER) of crystalline and amorphous PtS₂ were analysed. Amorphous PtS₂ was found to exhibit superior electrocatalytic performances towards ORR and HER as compared to crystalline PtS₂. For HER, amorphous and crystalline PtS₂ have overpotential values of 0.30 V and 0.70 V (vs. RHE) at current density of 10 mA cm⁻², respectively. The influence of electrochemical reduction pre-treatment on their catalytic behaviours was also investigated. Electrochemical reduction pre-treatment on both crystalline and amorphous PtS₂ removed the oxidized sulfate groups and increased the proportion of Pt⁰ oxidation state which exposed more catalytic sites. As such, these materials were activated and displayed improved ORR and HER performances. Electrochemically reduced amorphous PtS₂ outperformed the untreated counterparts and exhibited the best HER performance with overpotential of 0.17 V (vs. RHE) at current density of −10 mA cm⁻². These findings provide insights into the electrochemical properties of noble metal PtS₂ in both crystalline and amorphous states which can be activated by electrochemical reduction pre-treatment.