A novel terbium composite nanoparticles: Preparation and selective fluorescence determination of chromium(VI)

A highly efficient ultrasonic-assisted method was successfully applied to prepare the strong fluorescence Tb/acetyl acetone (acac)/poly (2-Acrylamidoglycolic acid monohydrate) (PAAM) composite nanoparticles. Based on the fluorescence quenching of Tb/acac/PAAM by Cr(VI), an assay for the selective determination of Cr(VI), without separation of Cr(III), was developed. It is characteristic of very few interferences, stable fluorescence signals (at least 2 h), simple instrument (common spectrofluorometer) and simple step. Under optimal experimental conditions, the fluorescence intensity of the system is linearly proportional to the concentration of Cr(VI) in concentration range of 5-800 ng mL⁻¹ with a correlation coefficient of 0.9983. The limit of detection was found to be 0.5 ng mL⁻¹.The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples with satisfactory results.     

激光辐照下转动柱壳平均温度与破坏时间的工程估算

 推导了激光辐照下转动壳体平均温度沿壳体母线方向分布的解析公式。由于对高斯功率密度分布光束无法得到工程上实用的结果,对公式进行了解析拟合,仅由一个具有实际物理意义的拟合系数——分布因子确定了解析拟合公式的形式,明确了温度估算公式中各项的物理意义。解析拟合公式计算结果与数值模拟结果较为一致。作为温升估算方法的一个应用实例,推导了转动充压柱壳在激光辐照下破坏时间的解析公式,与数值计算结果吻合得较好。     

A study of energy dissipation and critical speed of granular flow in a rotating cylinder

Tuned vibration absorbers may improve the safety of flexible structures which are prone to excessive oscillation magnitudes under dynamic loads. A novel absorber design proposes sloshing of granular material in a rotating cylinder where the granular material is the energy dissipating agent. As the conventional dissipative elements require maintenance due to the nature of their function, the new design may represent a virtually maintenance free alternative.     

斜切蓝宝石衬底MOCVD生长GaN薄膜的透射电镜研究

利用MOCVD技术在斜切角度为0.3°的c面蓝宝石衬底上生长了非故意掺杂 GaN 薄膜, 并采用透射电子显微镜对材料的质量和材料内部缺陷进行了分析. 研究发现斜切蓝宝石衬底上外延的GaN材料中,位错在距离衬底0.8 μm附近大量湮灭, 同时位错扎堆出现.基于上述现象, 提出了斜切衬底上GaN材料中位错的湮灭机制, 解释了斜切衬底能够提高GaN晶体质量的原因.     

基于晶体旋光效应的近场光学空间滤波

 在激光传输与放大系统中,激光束的空间滤波是光束质量控制的重要环节。利用各向同性晶体的旋光性,采用偏振光检偏法选择不同空间频率光束的通过与阻挡,实现激光光束的近场空间滤波。用多个滤波器串接构成滤波器组,可提高光束空间窄带滤波性能。该方法有利于克服激光工程中采用4f滤波带来的空间滤波器体积庞大与抽空耗能的缺点。     

Experimental and numerical examination of eddy (Foucault) currents in rotating micro-coils: Generation of heat and its impact on sample temperature

The application of nuclear magnetic resonance (NMR) to systems of limited quantity has stimulated the use of micro-coils (diameter <1 mm). One method recently proposed for the union of micro-coils with Magic Angle sample Spinning (MAS), involves the integration of a tuned micro-coil circuit within standard MAS rotors inductively coupled to the MAS probe coil, termed “magic-angle coil spinning” (MACS). The spinning of conductive materials results in the creation of circulating Foucault (eddy) currents, which generate heat. We report the first data acquired with a 4 mm MACS system and spinning up to 10 kHz. The need to spin faster necessitates improved methods to control heating. We propose an approximate solution to calculate the power losses (heat) from the eddy currents for a solenoidal coil, in order to provide insight into the functional dependencies of Foucault currents. Experimental tests of the dependencies reveal conditions which result in reduced sample heating and negligible temperature distributions over the sample volume.     

Photocatalytic reduction of chromium(VI) in aqueous solution using dye-sensitized nanoscale ZnO under visible light irradiation

Photocatalytic removal of Cr⁶⁺ from aqueous solution using dye-sensitized nanoscale ZnO under visible light irradiation was studied in this work. First, nanoscale ZnO was prepared by the co-precipitation method. Then, sensitization of nanoscale ZnO by Alizarin Red S dye followed. Further, nanoscale ZnO and dye-sensitized nanoscale ZnO (designated nanoZnO and nanoZnO*, respectively) were both characterized by various photospectrometry methods, such as scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), EDS-mapping, transmission electron microscopy (TEM), and X-ray diffractometry (XRD). It was found that both types of prepared particles are spherical in shape with a size range of 20 to 50 nm. XRD patterns showed that both nanoZnO and nanoZnO* had the same crystalline structure of zincite. In the photocatalytic reduction aspect, effects of different light sources and dosage of nanoZnO* on Cr⁶⁺ reduction ([Cr⁶⁺]_initial = 20 mg/L) were evaluated in this work. Treatment of chromium(VI)-bearing wastewater under the conditions of using 1.0 g/L of nanoZnO*, neutral pH, irradiation of household fluorescence lamps for 6 h and 17 h would yield Cr⁶⁺ removal efficiencies of about 68% and 90%, respectively. When the household fluorescence lamps were replaced by visible-light lamps of 400–500 nm in wavelength, the corresponding removal efficiencies dropped to about 50% and 75%, respectively. When nanoZnO* was irradiated by sunlight under almost the same experimental conditions, the Cr⁶⁺ reduction efficiency increased up to 90%. In summary, sensitizing nanoscale ZnO with Alizarin Red S dye for photocatalytic applications using visible light is feasible. The relevant reaction mechanism and pathways were also proposed in this work.     

A theoretical and numerical consideration of the longitudinal and transverse relaxations in the rotating frame

We previously derived a simple equation for solving time-dependent Bloch equations by a matrix operation. The purpose of this study was to present a theoretical and numerical consideration of the longitudinal (R_1ρ = 1/T_1ρ) and transverse relaxation rates in the rotating frame (R_2ρ = 1/T_2ρ), based on this method. First, we derived an equation describing the time evolution of the magnetization vector (M(t)) by expanding the matrix exponential into the eigenvalues and the corresponding eigenvectors using diagonalization. Second, we obtained the longitudinal magnetization vector in the rotating frame (M_1ρ(t)) by taking the inner product of M(t) and the eigenvector with the smallest eigenvalue in modulus, and then we obtained the transverse magnetization vector in the rotating frame (M_2ρ(t)) by subtracting M_1ρ(t) from M(t). For comparison, we also computed the spin-locked magnetization vector. We derived the exact solutions for R_1ρ and R_2ρ from the eigenvalues, and compared them with those obtained numerically from M_1ρ(t) and M_2ρ(t), respectively. There was excellent agreement between them. From the exact solutions for R_1ρ and R_2ρ, R_2ρ was found to be given by R_2ρ = (2R₂ + R₁)/2 − R_1ρ/2, where R₁ and R₂ denote the conventional longitudinal and transverse relaxation rates, respectively. We also derived M_1ρ(t) and M_2ρ(t) for bulk water protons, in which the effect of chemical exchange was taken into account using a 2-pool chemical exchange model, and we compared the R_1ρ and R_2ρ values obtained from the eigenvalues and those obtained numerically from M_1ρ(t) and M_2ρ(t). There was also excellent agreement between them. In conclusion, this study will be useful for better understanding of the longitudinal and transverse relaxations in the rotating frame and for analyzing the contrast mechanisms in T_1ρ- and T_2ρ-weighted MRI.     

Theoretical study of core ionized Cr(CO)6

The satellite structure of the C1s and O1s photoelectron spectra of chromium hexacarbonyl Cr(CO)₆ has been calculated by the INDO/CI method and compared with available high resolution core level photoelectron spectra. A reassignment of some of the lines is made. It is found that the satellite structure in both cases is dominated by excitations from metal-ligand bonding to metal-ligand antibonding Me(3d)-π^* orbitals, and that these shake-up excitations involve a significant charge transfer to the core ionized ligand from the rest of the molecule.     

Bias voltage effect on the structure and property of chromium copper-diamond-like carbon multilayer films fabricated by cathodic arc plasma

Chromium copper-diamond-like carbon (Cr:Cu)-DLC films were deposited onto silicon and by cathodic arc evaporation process using chromium (Cr) and copper (Cu) target arc sources to provide Cr and Cu in the Me-DLC. Acetylene reactive gases were the carbon source and activated at 180 °C at 13 mTorr, and a substrate bias voltage was varied from −50 V to −200 V to provide the (Cr:Cu)-DLC structure. The structure, interface, and chemical bonding state of the produced film were analyzed by transmission electron microscope (TEM), IR Fourier transform (FTIR) spectra, and X-ray photoelectron spectroscopy (XPS). The results showed that the Cr-containing a-C:H/Cu coatings exhibited an amorphous layer of DLC:Cr layer and a crystalline layer of Cu multilayer structure. The profiles of sp³/sp² (XPS) ratios corresponded to the change of microhardness profile by varying the pressure of the negative DC bias voltage. These (Cr:Cu)-DLC coatings are promising materials for soft substrate protective coatings.     

Influence of Mixing Technique on Microstructure and Impact Properties of Isotactic Polypropylene/ Poly(Cis-Butadiene) Rubber Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR vol%: 80/20) blends were prepared by melt mixing with various mixing rotation speeds. The effect of mixing technique on microstructure and impact property of blends was studied. Phase structure of the blends was analyzed by scanning electron microscopy (SEM). All of the blends had a heterogeneous morphology. The spherical particles attributed to the PcBR-rich phase were uniformly dispersed in the continuous iPP matrix. With increase of the mixing rotation speed, the dispersed phase particle's diameter distribution became broader and the average diameter of the separated particles increased. The spherulitic morphology of the blends was observed by small angle light scattering (SALS). Higher mixing rotation speed led to a more imperfect spherulitic morphology and smaller spherulites. Crystalline structure of the blends was measured by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). The introduction of 20 vol% PcBR induced the formation of iPPβ crystals. Higher rotation speed led to a decrease in microcrystal dimensions. However, the addition of PcBR and the increase of mixing rotation speed did not affect the interplanar distance. The long period values were the same within experimental error as PcBR was added or the mixing rotation speed quickened. The normalized relative degree of crystallinity of the blends slightly increased under lower rotation speeds (30 and 45 rpm) and decreased under higher rotation speeds. The notched Izod impact strength of the blends was enhanced as a result of the increase of mixing rotation speed.     

长链脂肪酸稀土络合体系的光致发光现象研究

本文合成了两烯长链脂肪酸和铕的二元配合物，进而以邻菲罗淋作为第二配体制得三元配合物，是很好的光致发光物质，元素分析及FTIR光谱初步确定了结构，分别为Eu(L1)32H2O,Eu(L1)3phen,Eu(L2)32H2O,Eu(L2)3phen(L1=月桂酸根、L2=硬脂酸根），长链脂肪酸通过羧酸双齿螯合配位，运用紫外吸收光谱和荧光光谱进一步讨论其发光机理。通过TEM电镜研究了配合物掺杂在高分子中的形貌与颗粒大小等分布情况。     

Influence of Cu electroplating solutions on boron carbon nitride (BCN) film

Cu electroplating is required for the fabrication of Cu/low-k interconnections. The permeation of a plating solution into low-k films during Cu electroplating is a serious challenge for 45-nm nodes and more complex devices. We investigated the influence of Cu electroplating solutions on boron carbon nitride (BCN) as a low-k film. After dipping it into a Cu electroplating solution that contained additives, the BCN film's hydrophilic surface changed to a hydrophobic surface, and the incorporation of water into the BCN film was suppressed by surfactant adsorption. Sulfuric residue was detected on the BCN sample by thermal desorption spectroscopy after treatment in the Cu electroplating solution with additives; however, it was found through electrical measurements that this solution did not affect the leakage current or the dielectric constant of the BCN film. We successfully fabricated an electroplating Cu layer on a BCN film with good adhesion, and we believe that this BCN film is a sufficiently useful material for Cu/BCN integration in LSI.     

Theoretical study of the electronic structure of a tetragonal chromium(III) complex

The low-temperature single-crystal polarized absorption and the luminescence spectra of Cs₂[CrCl₂(H₂O)₄]Cl₃ are theoretically analyzed in order to determine the electronic structure of the trans-[CrCl₂(H₂O)₄]⁺ complex. This study, based on the Racah theory, leads to a good agreement between the theoretical and experimental energy levels. The electronic-exited state ⁴T_2g(O_h) is split into ⁴E_g and ⁴B_2g components due to the lowering of the symmetry from O_h to D_4h. The polarized absorption spectrum and the theoretical energies show that the ⁴E_g(D_4h) state is lower in energy than the ⁴B_2g(D_4h) state. The resolved vibronic structure in the luminescence spectrum reveals a progression in a non-totally symmetric b_1g mode, a manifestation of a Jahn-Teller effect in the emitting state ⁴T_2g(O_h). Both Jahn-Teller and spin-orbit coupling in the orbitally degenerated ⁴E_g(D_4h) state are necessary to account for the spectroscopic observations.     

Hb-SDS-Ag水凝胶聚合物超细微粒的制备及表征(Ⅰ)

本文报道Hb SDS Ag聚合物超细微粒的制备 (取一定量的Hb ,SDS于烧杯中 ,加入Ag(NH3) 2 NO3溶液及 pH～ 12的tris OH缓冲液 ,庚烷和异戊醇 ;在另一烧杯中 ,加入甲醛、庚烷和异戊醇。分别乳化 ,将二者混合 ,于 6 0± 0 5℃下恒温 1 5h ,然后水浴减压回流 1 5h ,冷却、分离、洗涤、干燥得样品 )及性质表征。用X 射线衍射 (XRD) ,TEM ,EDS ,IR光谱考察这种聚合物超细微粒的表面结构 ,微粒粒径 12 0nm。研究表明 :Ag+ 离子先与Hb产生化学键合 ,再还原为Ag粒 ,进而聚合成网状结构的聚合物。     

A study of fermions coupled to gauge and gravitational fields on a cylinder

Fermions on a cylinder coupled to background gravitation and gauge fields are examined by studying the geometric action associated with the symmetries of such a system. We are able to show that the gauge coupling constant is constrained to a value of 1/N where N is an integer. Furthermore, in direct analogy with a Yang-Mills theory a new gravitational theory is introduced which couples to the fermions by promoting the coadjoint vector of the diffeomorphism sector to a dynamical variable. The classical dynamics of this theory are examined by displaying its symplectic structure and showing that it is equivalent to a one-dimensional system.     

A combined experimental and theoretical investigation on the oxygenation of organic sulfides by oxo(salen)chromium(V) ion

The mechanism of oxygenation of organic sulfide by oxo(salen)chromium(V) complexes has been studied experimentally and by the density functional theory (DFT) method. Spectral studies show DMSO ligands bind with the Cr center of oxidant and the adduct formed was responsible for the oxygenation reaction. The reaction was first order with respect to oxidant and substrate. Hammett plot shows the formation of positive charge over sulfur atom and the development of negative charge over the oxidant in the transition state (TS). For the substrate ρ values are in the range from ?1.5 to ?1.8. The geometry has been correctly predicted by the B3LYP function, and it gives better results for spin states, harmonic frequencies, and thermodynamic energies for the system. DFT results indicate the existence of oxo(salen)chromium(V) and Cr(III)–salen at doublet and quartet as ground state, respectively. Binding of donor ligand weakens the Cr? O bond. TS structures show an increase in the negative charge and spin density over Cr atom indicating the involvement of spin inversion and radical character. The low activation energy and high free energy change are responsible for the enhancement of the reaction rate and product yield in the presence of DMSO donor ligand, while the rebound mechanism and the direction of substrate approach perpendicular to the salen plane are responsible for their higher selectivity. From this combined study, a mechanism involving consecutive two‐electron transfer from the oxo(salen)chromium(V) ion to the electron‐rich sulfur atom is proposed. Copyright © 2008 John Wiley & Sons, Ltd.     

Growth of fcc(111) on bcc(110): Influence of growth and annealing temperature on epitaxy and surface morphology for Pd on Cr

The effects of growth versus annealing temperature on epitaxial relationship and surface morphology were studied for Pd(111) films on Cr(110) surfaces. While the epitaxial orientation of the Pd films depends on film thickness as well as on growth temperature, subsequent annealing has no effect on the epitaxial orientation. Instead, additional annealing of room temperature grown films takes the surface morphology from an island to a terrace shape, which was not observed for samples directly grown at elevated temperatures. These different effects that growth and annealing temperature have, help understanding the resulting structure and morphology of the heteroepitaxial system.     

Effects of chromium on structure and mechanical properties of vanadium:A first-principles study

Stability and diffusion of chromium （Cr） in vanadium （V）, the interaction of Cr with vacancies, and the ideal me- chanical properties of V are investigated by first-principles calculations. A single Cr atom is energetically favored in the substitution site. Vacancy plays a key role in the trapping of Cr in V. A very strong binding exists between a single Cr atom and the vacancy with a binding energy of 5.03 eV. The first-principles computational tensile test （FPCTT） shows that the ideal tensile strength is 19.1 GPa at the strain of 18% along the [100] direction for the ideal V single crystal, while it decreases to 16.4 GPa at a strain of 12% when one impurity Cr atom is introduced in a 128-atom V supercell. For shear deformation along the most preferable { 110} （111） slip system in V, we found that one substitutional Cr atom can decrease the cleavage energy （7cl） and simultaneously increase the unstable stacking fault energy （]＇us） in comparison with the ideal V case. The reduced ratio of ]＇cl/]＇us in comparison with pure V suggests that the presence of Cr can decrease the ductility of V.     

Morphology and crystallographic properties of rubrene thin films grown on muscovite(0 0 1)

Thin films of the organic semiconductor rubrene were deposited on muscovite (0 0 1) substrates by hot wall epitaxy. The morphology of rubrene thin films in combination with their crystallographic properties was characterized by transmission electron microscopy. The initial growth proceeds in a partially wetting regime where amorphous droplets are formed. Through diffusive interactions the droplets merge together in partially crystalline open networks. At a more advanced growth stage, spherulites are formed and a variety of crystalline morphologies appears. Platelet- and needle-like morphologies can be assigned to the orthorhombic phase of rubrene with the [3 0 1] and [1 1 0] zone axes, respectively.