Effects of ZrO_2 on the Microstructure of a Mica Glass-ceramic

1 INTRODUCTION Glass-ceramic technology is based on the controlled nucleation and crystallization of glass, and glass-ceramics have several advantages over the conventional powder-processed ceramics. In addition to the easy flexibility of formation in t…     

Nature of the binding of a c(2×2)-CO overlayer on Ag(001) and surface mediated intermolecular coupling

We present a first-principles study of the nature of the binding of a c(2×2)-CO overlayer on Ag(001) and of the origin of CO-CO interactions upon adsorption. Electronic structural changes induced by molecular adsorption provide an interpretation for earlier X-ray photoemission valence band spectra of CO/Ag(001). Our results establish that CO chemisorbs on clean Ag(001) and follows the Blyholder model of donation and back-donation between CO and metal orbitals. We analyze the origin of the dispersion of the C-O stretch mode and attest that it is caused by the metal-CO coupling. Specifically, the coupling of CO to Ag, although the weakest of those between it and transition and other noble metals, greatly enhances the intermolecular force constants. We also find that the response of the charge density around CO is much stronger and of longer range when the molecule stretches than when it rigidly vibrates against the surface. This difference explains why the C-O stretch mode disperses while the Ag-CO stretch mode does not.     

Theoretical study on the reaction mechanism of NH2(-) with O2 (a1Δg)

A detailed theoretical study of the potential energy surface of poorly understood ion-molecule reaction of NH(2)(-) and O(2) (a(1)Δ(g)) is explored at the density functional theory B3LYP/6-311++G(d,p), ab initio of QCISD/6-311++G(d,p) and CCSD(T)/6-311++G(3df, 2pd) (single-point) theoretical levels for the first time. It is shown that there are six total possible products from P(1) to P(6) on the singlet potential energy surface. Among these, the charge-transfer product P(1) (NH(2) + O(2)(-)) is the most favorable product with predominant abundances, whereas P(4) (NO(-) + H(2)O) and P(2) (HNO + OH(-)) may be the second and third feasible products followed by the almost neglectable P(3) (NO(2)(-) + H(2)), while P(5) (c-NO(2)(-) + H(2)) and P(6) (ONO(-) + H(2)) will not be observed due to their either high barriers or being secondary products. The present theoretical study points out that besides P(1) (NH(2) + O(2)(-)) and P(2) (HNO + OH(-)), P(4) (NO(-) + H(2)O) should be also observed, which is different from the previous experiment study by Anthony Midey et al. in 2008. In addition, almost all of the reaction pathways to products are exothermic and the reaction rate should be very fast since the reaction barriers are very low except for P(5) (c-NO(2)(-) + H(2)) which is in agreement with the measured total reaction rate constant k = 9.0 × 10(-10) cm(3)s(-1) at 300 K in the experiment study. It is expected that the present theoretical study may be helpful for the understanding of the reaction mechanism related to NHX(-), NX(2)(-), PHX(-), and PX(2)(-) (X = H, F, and Cl).     

Dynamics of scattering and dissociative adsorption on a surface alloy: H2/W(100)-c(2 × 2)Cu

H(2) scattering and dissociative adsorption on the W(100)-c(2 × 2)Cu surface alloy is studied based on DFT calculations. A strongly site dependent reactivity is observed in line with results obtained for the density of states projected onto the W and Cu atoms of the topmost layer. H(2) dissociation on a defect free terrace of W(100)-c(2 × 2)Cu is found to be a non-activated process like on W(100), despite the reduction of the number of energetically accessible dissociation pathways at low impact energies due to the presence of Cu atoms. A prominence of dynamic trapping and a reduction of the efficacy of trapping to promote dissociation is also verified, leading to a decrease of the initial sticking probability as a function of the molecular impact energy, in qualitative agreement with experimental findings. The heterogeneous reactivity is also evidenced by two different kinds of reflection events at low energies. Its combination gives rise to a broad specular peak superimposed on a cosine-like angular distribution of scattered molecules which is in good agreement with available experimental data.     

Influence of the external electric field distribution on α-Ni(OH)2 electrochemical-synthesis from a NiCl2 solution

Electrolytic systems of a symmetric, an asymmetric and a two-compartment were established in the present work to investigate the effect of the external electric field distribution on α-Ni(OH)₂ electrochemical-synthesis from a NiCl₂ solution. Results demonstrate the sample particle size increased in the order of symmetric, two-compartment and asymmetric systems, with a sharpened diffraction peak of the (1 0 1), (0 1 5) and (1 1 0) plane, and a broadened diffraction peak of (0 0 3) plane. However, the reversibility of the redox reactions and the energy transferred in the redox reactions in the electrodes assembled by the samples from the three electrolytic systems increased based on the contrary order. In terms of the electrolysis process, the energy consumption per unit mass increased in the order of symmetric, two-compartment and asymmetric systems. The catholyte pH for both symmetric and asymmetric systems were more stable than that for the two-compartment system. The external electric filed distribution affected the transportation of Ni²⁺ from the anolyte to the catholyte. At the end of electrolysis, the Ni²⁺ concentration in the anolyte of two-compartment system was obviously higher than that of symmetric and asymmetric systems.     

Development of a N-acetyl-β-D-glucosaminidase (NAG) assay on a centrifugal lab-on-a-compact-disc (Lab-CD) platform

A centrifugal microfluidic platform, which is also known as lab-on-a-compact-disc (Lab-CD), was developed for use as a urinary N-acetyl-β-D-glucosaminidase (NAG) activity assay. In this work, Lab-CD design, centrifugal operations and analytical procedures were established. Automated liquid handling on Lab-CD processes, such as fluid transport, sample metering, mixing, and fluorescence detection are accomplished using a portable Lab-CD system. The linearity of the NAG assay using 4-methylumbelliferyl-N-acetyl-β-D-glucosaminide (4-MU-GlcNAc) was found to be acceptable in the range of 2.5 to 20 U L(-1); the relative standard deviations for the fluorescence intensity of eight samples (7.5 U L(-1)) was 6.4%. Clinical diagnostics is one of the most promising applications for Lab-CD technologies. All the benefits of miniaturization, such as reduced sample requirement, reduced reagent consumption and automation, are realized in this investigation.     

High resolution photoemission and x-ray absorption spectroscopy of a lepidocrocite-like TiO2 nanosheet on Pt(110) (1 × 2)

The electronic structure of TiO(2) nanosheets on the Pt(110)-(1 × 2) surface has been investigated by using high resolution photoemission spectroscopy and x-ray absorption spectroscopy (XAS). The Ti 2p XAS spectra of the deposited TiO(2) films have been theoretically evaluated and, from the comparison with the experimental data, the assignment to a lepidocrocite-like structure is confirmed. Coexistence of TiO(2) islands with PtO(2) stripes for incomplete nanosheets is confirmed by high resolution photoemission data. The location of the valence and conduction band edges of the nanosheet has been experimentally determined allowing us to describe in details subtle electronic effects due to the interface with the substrate. The locations of the valence band maximum and the leading peak in the O 1s XAS spectrum indicate a band gap similar to anatase but with the Fermi level closer to mid-gap than found for bulk, n-type TiO(2).     

Molecular recognition of a self-assembled monolayer of a polydithiocarbamate derivative of β-cyclodextrin on silver

The synthesis and molecular recognition properties of a new sulfur containing β-cyclodextrin (β-CD) derivative chemisorbed on a silver surface are described. Hepta-6-amino-6-deoxy-β-CD was allowed to react with CS₂ in the presence of ammonia to give a mixture of partially substituted dithiocarbamate derivatives with an average degree of substitution of 4.5. A modified silver electrode with this derivative is capable of discriminating between the three positional isomers of nitrobenzoate ion and nitrophenol, as determined by cyclic voltammetry. Only the meta- and para-isomers give a signal corresponding to the reduction of the nitro group. This is attributed to the different orientations of the nitro group with respect to the silver surface after inclusion in the CD cavity. Experiments in the presence of cyclohexanol showed a decrease in signal intensity of the meta- and para-isomers which is associated with the competitive complexation of this guest, suggesting that the electroactive probe is complexed to the cavity.     

Studies on the Crystal Structure and Photoluminescence of a Mercury(Ⅱ)Complex Based on a Novel Pyridine Ligand

<正>A novel mercury(n)complex HgL_2Br_2 was prepared from HgBr_2 and the organic ligand 2-(N-methyl-N-(4-((E)-2-(pyridine-4-yl)vinyl)phenyl)amino)ethanol(L).The ligand was synthesized and then characterized by FT-IR spectroscopy,~1H NMR,mass spectrum and elemental analysis,while the single-crystal diffraction data of the complex were collected on a Siemens Smart CCD diffractometer.The complex crystallizes in triclinic space group P_1~-with a=5.367(5),b= 12.466(5),c=23.945(5)(?),α=90.812(5),β=96.318(4),γ=96.093(5)°,Z=2,D_c=1.817g·cm~(-3),μ=7.395 mm~(-1),S=0.825,and the final R=0.0396.The Hg(Ⅱ)ion in the distorted tetrahedral mercury(Ⅱ)complex C_(32)H_(36)HgBr_2N_4O_2 is coordinated by two N atoms from the two ligands together with two bromide ions.Solid-state emission of the ligand and its complex has been investigated at room temperature.     

Studies on a New System of Lithium Fast Ion Conductors Based on Kaolinite and LiZr_2(PO_4)_3

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The Effect of Temperature on Nucleation of Condensed Water Phase on the Surface of a β-AgI Crystal. 2. Formation Work

In the condensation mechanism of heterogeneous ice formation, water crystallization occurs after a necessary amount of the liquid phase has accumulated on a substrate surface. In this way, the ice-forming activity of the surface is governed by its adsorption ability with respect to water vapor. The Monte Carlo canonical statistical ensemble method has been used to calculate the free energy, entropy, and work of nucleation of a disordered condensed water phase on the surface of crystalline silver iodide and to determine the surface tension. Comparative calculations have been performed at 260 and 320 K for the defect-free surface of a basal face of a crystal. The surface of a β-AgI crystal is completely covered with a monomolecular film even in unsaturated water vapors. The surface tension at the growing nucleus–substrate interface substantially increases due to the formation of the underlying film, and the growth of the nucleus becomes possible only in a supersaturated vapor. As the vapor density increases, the thickness of the condensed water layer grows, and, at negative Celsius temperatures, conditions are created for its crystallization. The underlying film with pronounced hydrophobic properties hinders nucleation, thereby decreasing the ice-forming activity of the surface in the condensation process. Under these conditions, the observed abnormally high ice-forming activity of silver-iodide aerosol particles may be explained by the presence of numerous crystal defects on the particle surface, with these defects representing channels that provide overcoming the hindering action of the film.     

Investigation of the Ti/MgCl2 interface on a Si(111) 7 × 7 substrate

Photoelectron spectroscopy with synchrotron radiation, low energy electron diffraction, and ion-scattering spectroscopy were used in order to study the Ti/MgCl(2) interface grown on an atomically clean Si(111) 7 × 7 substrate. A series of high resolution spectra after deposition of a thick MgCl(2) layer, step by step deposition of Ti and gradual annealing, indicated a very reactive interface even at room temperature. Strong interaction between the incoming Ti atoms and the MgCl(2) layer, leads to the formation of Ti(2+) and Ti(4+) oxidation states. The interfacial interaction continues even at multilayer Ti coverage mainly by the partial disruption of Mg-Cl bonds and the formation of Ti-Cl sites, rendering this interface a very promising UHV-compatible model of a pre-catalyst for olefin polymerization. After the final annealing, the MgCl(2) multilayers desorb while Ti remains on the surface forming a silicide layer on which Cl and Mg atoms are attached.     

Stereoselective synthesis of spirophosphoranes with a phosphorus—carbon bond based on 2-(2-acetylphenoxy)benzo-1,3,2-dioxaphosphole

The reactions of 2-(2-acetylphenoxy)benzo-1,3,2-dioxaphosphole containing the carbonyl group in the δ position with respect to the phosphorus atom with chloral and hexafluoroacetone afford tricyclic spirophosphoranes containing a phosphorus—carbon bond with high regio and stereoselectivity. The structures of the spirophosphoranes were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1528–1532, July, 2008.     

The study on the effect of the substitution of K2CO3 with Ca(OH)2 on kinetics on CO2–lignite coal gasification

Research on Chemical Intermediates - Three kinds of lignite were mixed with K2CO3 and Ca(OH)2 and were gasified with CO2 to investigate the effect that the addition of Ca(OH)2 had on the...     

Construction of a 2D Cd（II） Coordination Polymer Based on a V-shaped Bidentate Ligand

A two-dimensional（2D）coordination polymer{[Cd（bdc）（dpb）]·H2O}n（1）has been prepared by solvothermal reaction of 1,3-dipyridyl benzene（1,3-dpb）with deprotonated1,4-benzenedicarboxylate（H2bdc）,and was characterized by elemental analysis,IR spectroscopy,and X-ray single-crystal diffraction.It crystallizes in the monoclinic system,space group C2/c with a=15.1839（12）,b=20.7585（17）,c=7.2989（6）,β=117.3450（10）°,V=2043.5（3）3,C24H18N2O5Cd,Mr=526.81,Dc=1.712 g/cm3,F（000）=1056.0,μ=1.110 mm-1and Z=4.The neighboring Cd（II）ions link the bdc2-anions and 1,3-dpb to form an infinite 2D sheet,and such two2D sheets are interlocked with each other to form a 2D→2D sheet.Two groups of interlocked sheets are further linked together by intermolecularπ···πinteraction,giving a 3D supramolecular network.In addition,the fluorescence property of 1 was also studied.     

Study on a New Type of All-Solid-StateReference Electrode

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Chemical origin of a graphene moiré overlayer on Ru(0001)

Epitaxial graphene on Ru(0001) was studied by means of large-scale density functional theory (DFT) calculations. The results agree well with scanning tunneling microscopy experiments. In contrast to the current understanding, we show that the measured corrugation originates mainly from a geometric buckling of the graphene sheet, induced by alternating weak and strong chemical interactions with the Ru support. In the strong contact regions, charge transfer is evidenced and the opening of a considerable band gap in the graphene is found.     

Crystal Structure of a New Allotropic Form of trans-Pd(Creat)2Cl2·2H2O

Pd(creat)₂Cl₂·2H₂O crystallizes in space group P&1macr; with a= 7.257(2), b= 8.159(2), c= 14.640(2) Å, f =73.97(2), g =77.0(1), u =72.22(2)°, Z=2, and represents a new allotropic form of this compound. Pd atoms have planar fourfold coordination of N and Cl atoms in trans configuration. Creatinine moieties are coordinated to the Pd atoms via endocyclic N atoms and their essential planarity causes significant delocalization of electron density. The structure is stabilized by a system of weak hydrogen bonds involving interstitial water molecules and creatinine amino-groups.     

Synthesis,Structure and Catalytic Activity of a Manganese(Ⅲ) Complex Based on 2-(2-Hydroxyphenyl)-5,6-dichlorobenzimidazole Ligands

A new ligand, 2-(2-hydroxyphenyl)-5,6-dichlorobenzimidazole, H2pbmCl2(1), and a novel MnIII complex, [MnIII(HpbmCl2)(pbmCl2)(DMF)2](2),(DMF = N,N-dimethylformamide), have been synthesized and characterized. The crystal of compound 1(C13H8Cl2N2O, Mr = 279.12) belongs to the monoclinic system, space group P21 with a = 3.770(5), b = 25.20(3), c = 5.865(7) , = 92.727(17)o, V = 556.6(12) 3, Z = 2, Dc = 1.665 g/cm3, S = 1.137, μ= 0.568 mm-1, F(000) = 284, the final R = 0.0876 and wR = 0.2334 for 1848 independent reflections. The molecule is planar due to the presence of a strong intramolecular hydrogen bond between O–H group of phenol and N atom of imidazole. H2pbmCl2(1) molecules are arranged into a one-dimensional linear chain through intermolecular hydrogen bonds(N–H···O and C–H···Cl). The crystal of complex 2(C32H27Cl4MnN6O4, Mr = 756.34) belongs to the monoclinic system, space group P21/c with a = 19.043(10), b = 10.808(5), c = 18.704(11), = 115.540(6)o, V = 3473(3) 3, Z = 4, Dc = 1.446 g/cm3, S = 1.3, μ = 0.733 mm-1, F(000) = 1544, the final R = 0.1219 and wR = 0.2681 for 7811 independent reflections. The Mn ion adopts a distorted octahedral geometry coordinated by two deprotonated H2pbmCl2 ligands and two DMF molecules. The [MnIII(HpbmCl2)(pbmCl2)(DMF)2] molecules are arranged into a three-dimensional structure through hydrogen bonds(N–H···N, C–H···N and C–H···Cl) and weak π···πinteractions. The activity measurements suggest that complex 2 is able to serve as a catalyst for H2O2 disproportionation reaction to form O2 in neutral water solution.     

Influence of the outer-sphere cation nature on the crystal structures of salts with a cis-[Rh(NH3)2(NO2)4]− anion

Complex rhodium(III) salts of the composition cis-M[Rh(NH₃)₂(NO₂)₄]·nH₂O, where M = K⁺, Cs⁺, Ag⁺, (CH₃)₄N⁺, are synthesized and described. Their molecular and crystal structures are determined by single crystal X-ray diffraction.