An investigation of the chemiluminescence reaction in the sodium hypochlorite–folic acid–emicarbazide hydrochloride system

A chemiluminescence method for the determination of folic acid by the sodium hypochlorite–folic acid–semicarbazide hydrochloride system with a new flow injection technique has been established. The new method can perform simple, sensitive and rapid determinations of folic acid. The response to the concentration of folic acid, in the range of 1.0×10⁻⁷5.0×10⁻⁵ g/ml, is linear. The relative standard deviation of the method is 2.3% (C_s=4.0×10⁻⁶ g/ml, n=11). The detection limit is 2.7×10⁻⁸ g/ml. This method is suitable for automatic and continuous analysis, and has been successfully tested for the determination of folic acid in a folic acid tablet.     

Growth and characterization of Mn- and Co-doped ZnO nanowires

A flow injection chemiluminescence method is proposed for the determination of cobalt, based on the strong catalytic effect of Cobalt(II) (1,10-phenanthroline)₃ complex on the lucigenin-periodate reaction in alkaline medium. Under the optimum experimental conditions, the chemiluminescence signal responded linearly to the concentration of cobalt(II) in the 1.0 × 10⁻⁹–3.0 × 10⁻⁷ g mL⁻¹ range with a detection limit of 4.4 × 10⁻¹⁰ g mL⁻¹ cobalt(II). The relative standard deviation for the determination of 5.0 × 10⁻⁸ g mL⁻¹ of cobalt was 2.3% in eleven replicated measurements. The method was successfully applied to the determination of cobalt(II) in pharmaceutical preparations.     

Electrogenerated Chemiluminescence (ECL) Determination of Ephedrine with a Self-Assembly Multilayer Ni(II)-Polyluminol Modified Electrode

By combining the layer-by-layer (LBL) self-assembly technique with the electrochemical polymerization method, multilayer Ni(II)-polyluminol films were modified on the surface of a vaseline-impregnated graphite electrode. It was found that, compared with an electrode modified by direct electrochemical polymerization, this modified electrode offered a suitable ECL reaction micro-environment created by the special multilayer films, which was beneficial to the ephedrine hydrochloride enhancing effect for luminol ECL intensity. The ECL enhancing effect of ephedrine hydrochloride on the electro-oxidation luminol was improved on this modified electrode. Based on this finding, a new sensitive ECL method was developed for ephedrine hydrochloride determination under the optimal conditions. At the same time, a new idea is proposed for improving the analytical performance of the luminol ECL system by modifying the ECL reaction micro-environment with the layer-by-layer self- assembly method. Under the optimum experimental conditions, the ephedrine hydrochloride concentration in the range of 2.0 × 10⁻⁸–7.0 × 10⁻⁶ mol L⁻¹ was proportional to the enhanced ECL signal, and it offered an 8.0 × 10⁻⁹ mol L⁻¹ detection limit for ephedrine hydrochloride.     

Speciation of chromium by in-capillary reaction and capillary electrophoresis with chemiluminescence detection

A sensitive method for the simultaneous determination of chromium(III) (Cr3+) and chromium(VI) (CrO4(2-)) using in-capillary reaction, capillary electrophoresis (CE) separation and chemiluminescence (CL) detection was developed. The chemiluminescence reaction was based on luminol oxidation by hydrogen peroxide in basic aqueous solution catalyzed by Cr3+ ion followed by capillary electrophoresis separation. Based on in-capillary reduction, chromium(VI) can be reduced by acidic sodium hydrogensulfite to form chromium(III) while the sample is running through the capillary. Before the electrophoresis procedure, the sample (Cr3+ and CrO4(2-)), buffer and acidic sodium hydrogensulfite solution segments were injected in that order into the capillary, followed by application of an appropriate running voltage between both ends. As both chromium species have opposite charges, Cr3+ ions migrate to the cathode, while CrO4(2-) ions, moving in the opposite direction toward the anode, react with acidic sodium hydrogensulfite which results in the formation of Cr3+ ions. Because of the migration time difference of both Cr3+ ions, Cr(III) and Cr(VI) could be separated. The running buffer was composed of 0.02 mol l(-1) acetate buffer (pH 4.7) with 1 x 10(-3) mol l(-1) EDTA. Parameters affecting CE-CL separation and detection, such as reductant (sodium hydrogensulfite) concentration, mixing mode of the analytes with CL reagent, CL reaction reagent pH and concentration, were optimized. The limits of detection (LODs) of Cr(III) and Cr(VI) were 6 x 10(-13) and 8 x 10(-12) mol l(-1) (S/N=3), respectively. The mass LODs for Cr(III) and Cr(VI) were 1.2 x 10(-20) mol (12 zmol) and 3.8 x 10(-19) mol (380 zmol), respectively.     

Reductions of (1R,3R,4R)-3-([1,2,4]triazolo[4,3-x]azin-3-yl)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones and their analogues

Reductions of (1R,3R,4R)-3-([1,2,4]triazolo[4,3-x]azin-3-yl)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones and their lactone analogues, prepared from (1R)-(+)-camphor, were studied. Catalytic hydrogenation selectively led to partial saturation of the [1,2,4]triazolo[4,3-x]azine residue, while in reactions with borane–methylsulfide coordination of borane to the 1-position of [1,2,4]triazolo[4,3-x]azine system took place. On the other hand, activation of the carbonyl group in (1R,3R,4R)-3-([1,2,4]triazolo[4,3-x]azin-3-yl)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones with boron trifluoride etherate followed by reaction with borane–methylsulfide furnished the corresponding isoborneols, stereoselectively. The structures of all representative compounds were confirmed by X-ray diffraction.     

Transient photopotentials at the cobalt-doped zinc oxide/electrolyte interface

The time evolution of the pulsed-laser-induced photopotentials of pure and cobalt-sensitized ZnO electrodes is analyzed after 365 and 640 nm excitations. This analysis, as a function of various parameters, enables a determination of the influence of Co²⁺ ions and excitation wavelength on the kinetics of electron-hole recombination and electron transfer at the interface to be made.     

背包客身份认同对主观幸福感的影响

已有研究表明,在“日常生活世界”形成的群体身份认同能提升人们的主观幸福感。作为对当前社会快速变化的一种回应,背包旅行能提供展露自我的“自由空间”,建构独特的背包客身份认同。为探明背包客在“旅游世界”建构的身份认同是否显著提升其主观幸福感这一问题,基于社会认同理论和自我决定理论,将自尊作为中介变量,检验了背包客身份认同与主观幸福感之间的关系。通过问卷调查（n=400）收集数据,运用结构方程模型偏最小二乘法（PLS-SEM）进行统计分析。发现：（1）背包客身份认同的自我归类维度、群体自我价值维度对主观幸福感有显著正向影响;（2）群体自我评价维度、群体自我价值维度对自尊具有显著正向影响;（3）自尊对主观幸福感也有显著正向影响,且自尊在群体自我价值影响主观幸福感的过程中起部分中介作用。所得结果丰富了旅游者幸福感与背包客身份认同的理论研究。     

陕甘宁革命老区生态系统服务价值时空分异及影响因素研究

陕甘宁革命老区是黄土高原和黄河中上游的重点生态治理区,作为重要的生态屏障区,其生态治理意义重大。以陕甘宁革命老区为研究区域,基于改进的生态系统服务价值（ecosystem service value,ESV）当量因子法,利用地理探测器及地理加权回归（geographically weighted regression,GWR）模型,分析1995—2018年各县ESV时空变化特征、影响因素及各主导因素作用强度的空间分异特征。结果表明：（1） 1995—2018年,陕甘宁革命老区ESV呈先下降后上升的特征,整体呈上升趋势,草地与林地对该区域ESV的贡献较大;（2） ESV空间等级转化呈现较显著的两极变化趋势,其中低级、高级ESV区域面积显著扩张,较高级ESV区域面积明显缩减;（3）地被覆盖度、人口密度、垦殖系数是ESV空间分异的主导因素,平均空间解释力超过0.378 0,自然、社会、经济因素间的交互协同增强了其对陕甘宁革命老区ESV的影响程度;（4）各主导因素对ESV的影响程度表现出空间异质性,其中地被覆盖度及垦殖系数的影响程度由东向西递减,人均GDP和人口密度的影响程度则由西向东递减。     

On the stability of thin epitaxial NiSi2 layers on Si (111)

By repeated deposition of several Å of Ni below 100 °C and subsequent annealing to typically 350 °C, thin continuous NiSi₂-layers have been grown epitaxially on Si (111). Thicknesses exceeding ∼- 70 Å require a different procedure due to the increasing importance of lateral growth, spoiling the layer quality. We show that MBE at substrate temperatures above 500 °C is not a viable technique to increase the thickness of the ultrathin layers. The reason is found to lie in the insufficient stability of the NiSi₂ templates, disintegrating into islands at temperatures above 500 °C. Perfectly smooth layers up to 1000 Å have, however, been grown by a new method in which alternate layers of Ni and Si (typically 1 Å and 4 Å respectively) are deposited onto the initial template at substrate temperatures between 350 °C and 380 °C.     

Phonons,defects and optical damage in crystalline acetanilide

Intense picosecond pulses cause accumulated optical damage in acetanilide crystals at low temperature. Catastrophic damage to the irradiated volume occurs after an incubation period where defects accumulate. The optical damage is monitored with subanosecond time resolution. The generation of defects is studied with damage-detected picosecond spectroscopy. The accumulation of defects is studied by time-resolved coherent Raman scattering, which is used to measure optical phonon scattering from the accumulating defects.