Syntheses,Crystal Structures and Non‐linear Optical Properties of Cluster Compounds [MoAu2S4(PPh2Py)2] and [WAu2S4(PPh2Py)2]

The cluster compounds, [MoAu₂S₄(PPh₂Py)₂] ( 1 ) and [WAu₂S₄(PPh₂Py)₂] ( 2 ), were synthesized by the reaction of (NH₄)₂MS₄ (M = Mo, W), H[AuCl₄]·4H₂O and diphenyl‐2‐pyridyl‐phosphine (PPh₂Py) in CH₂Cl₂ solution. [MoAu₂S₄(PPh₂Py)₂] crystallizes in the monoclinic space group P2₁/c with a = 18.385(2), b =12.304(1), c = 16.904(2) Å, β =110.722(2)°, and Z = 4. [WAu₂S₄(PPh₂Py)₂] crystallizes in the triclinic space group P‐1 with a = 9.333 (3), b = 10.628(3), c = 19.566(6) Å, α = 89.26(1), β = 80.87(1), γ = 68.85(1)°, and Z = 2. Single crystal X‐ray analysis showed that these two compounds are isostructural, but belong to different space groups. The Mo (W) atom has a slightly distorted tetrahedral coordination, and the two Au atoms are distorted from trigonal planar, the P—Au—M—Au—P chain is nearly linear. Measurement of the nonlinear optical (NLO) properties using the Z‐scan technique with an 8‐ns pulsed laser at 532 nm showed that 1 and 2 possess NLO absorption and effective self‐focusing effect. The effective α₂ and n₂ values of cluster 1 are 5.89 × 10^—12 m · W^—1 and 6.45 × 10^—18 m² · W^—1; the effective α₂ and n₂ values of compound 2 are 4.35 × 10^—11 m · W^—1 and 3.73 × 10^—17 m² · W^—1.     

Double Elimination Voltammetry of Short Oligonucleotides

In connection with adsorptive stripping (AdS) technique, elimination voltammetry with linear scan (EVLS) in double mode was successfully employed in the analysis of homo‐ODNs: 5′‐AAA AAA AAA‐3′ (dA₉) and 5′‐CCC CCC CCC‐3′ (dC₉), and hetero‐ODNs: 5′‐CCC AAA CCC‐3′ (H3), 5′‐CAC CAC CAC‐3′ (H4), and 5′‐ACC CAC CCA‐3′ (H9) on hanging mercury drop electrode (HMDE). Analogously to single EVLS function E4 (conserving the diffusion current I_d and eliminating kinetic and charging currents I_k, I_c) for the electroactive substance adsorbed, the double EVLS function E4 yields well readable peak‐counterpeaks of reducible nucleic acid bases (adenine A and cytosine C). In comparison with single EVLS these peak‐counterpeaks are higher by more than one order of magnitude (twenty times for dA₉, fourteen times for dC₉, from eight to sixteen times for hetero‐ODNs). The increase of reduction signals with higher resolution was also observed using other two EVLS functions in double mode, the functions E5 eliminating I_c and I_d, but conserving I_k and E6 eliminating I_d and I_k, but conserving I_c. The amplifications of double /single EVLS signals of A and C range from 3.4 to 8.4, and from 3.1 to 8.3 for E5 and E6, respectively. It was proved that AdS double EVLS offers a new, fast, simple and inexpensive electroanalytical tool, which can be considered as a device not only for very good resolution of A and C in ODNs, but also for sensitive detection of changes in the primary structure of nucleic acid bases in ODN chains, depending on experimental conditions, such as pH, temperature, and time and potential of accumulation.     

直接甲醇燃料电池阳极催化剂的新体系: 纳米TiO2-CNT-PtNi复合纳米催化剂

采用电合成前驱体Ti(OEt)4直接水解法和电化学扫描电沉积法制备纳米TiO2-CNT-PtNi复合纳米催化剂.透射电镜(TEM)和X射线衍射(XRD)测试结果表明,纳米PtNi合金粒子(平均粒径8 nm)均匀地分散在纳米TiO2-CNT复合膜的三维网络结构中.通过暂态电化学方法研究表明,复合纳米催化剂的电化学活性比表面积为90 m2/g,对甲醇氧化具有很高的电催化活性和稳定性,常温常压下甲醇氧化峰电位为0.67和0.44 V,当温度为60℃时,氧化峰电位负移至0.64和0.30V,氧化峰电流密度高达1.38Mcm2.复合纳米催化剂对甲醇电氧化的高催化活性和稳定性可归因于多元复合纳米组分的协同催化作用,这种作用导致CO在复合纳米催化剂上的弱吸附,从而避免了催化剂的中毒.     

Electrochemical and kinetic behavior of the MnO<Subscript><Emphasis Type="Italic">X</Emphasis></Subscript>/C–β-PbO<Subscript>2</Subscript> electrode

The MnO_X/C–-PbO₂ electrode was obtained by admixture of -PbO₂ to MnO_X/C. Slow scan voltammetry shows a double reduction peak which is discussed. Galvanostatic intermittent titration technique curves are also used and the value of the proton diffusion coefficient, D(H⁺), is determined. All studies are made in 2 M KOH.Presented at the 3rd International Meeting on Advanced Batteries and Accumulators, 16–20 June 2002, Brno, Czech Republic     

Linear scan stripping voltammetry of copper(II) at the chemically modified carbon paste electrode

A new chemically modified electrode (CME), -benzoinoxime (CUPRON) modified carbon paste electrode, for determining copper(II) is reported because of its excellent selectivity and sensitivity. The electrode is made by mixing a quantity of CUPRON (25%, w/w) with graphite powder (50%, w/w) and paraffin oil (25%, w/w). The CME preferentially deposits copper from the pH 8.5 NH₃-NH₄Cl buffer solution containing copper(II) under an open circuit and most of metal ions do not interfere with the measurements. The detection limit (S/N of three) for determining Cu(II) is 3 × 10^–10 g/ml after 10 min accumulation in fast linear scan stripping voltammetric measurement. Linear calibration curves are obtained for Cu(II) concentration ranged from 1 × 10^–8 M to 1 × 10^–6 M. The response can be maintained with relative standard deviation of 6.0% in a 5 × 10^–6 M Cu(II) solution after eight accumulation/measurement/ regeneration cycles at the same electrode surface. The effect resulted from carbon paste preparation, reduction potential, electrode renewal, electrolyte and solution pH, preconcentration time, concentration dependence, possible interference and other variables has been evaluated. As for application, the CME demonstrates its high sensitivity and copper-selectivity in complex composition samples, such as anodic mud and polluted water.     

茶叶香味扫描和挥发性化学成分分析

为区分不同茶叶的香味，利用电子扫描仪对铁观音、兰贵人、玉针、碧螺春和云雾茶等5种茶叶进行了香味扫描，确定了电子鼻在茶叶香味辨别中的作用。采用固相微萃取．气相色谱／质谱联用法对这5种茶叶样品中的挥发性化学成分进行了定性和定量分析，分别鉴定出40、40、35、16和13种化合物。在鉴定出的化学成分中，乙酸、大茴香醚、十六烷、咖啡因、十六酸和双酚A是5种茶叶样品中所共有的化学成分，每种茶叶样品中又都含有一些特有的化学成分。最后对香味扫描结果和挥发性化学成分分析结果进行了分析，研究了挥发性化学成分组成和含量上的差别，对茶叶样品数据点在香味分析三维图中位置的影响。     

石墨烯/氧化铜纳米粒子/铜修饰电极对亚叶酸钙的电催化氧化及其分析应用

采用阳极极化的方法在铜电极表面形成氧化铜纳米粒子,然后采用循环伏安法将羧基化石墨烯电沉积到上述电极表面,成功制备了石墨烯/氧化铜纳米粒子/铜电极,用于碱性溶液中亚叶酸钙的检测.采用循环伏安法对亚叶酸钙在修饰电极上的催化氧化行为进行了研究,阳极扫描极化反向催化伏安法应用于亚叶酸钙的检测.在2.0×10^-7~2.0×10^-5 mol/L范围内,该电极显示出良好的线性关系,灵敏度为22.0 μA·μL/（μmol/cm²）,检测限达到7.6×10^-8 mol/L（S/N=3）,成功应用于实际样品的检测.     

离散小波变换耦合静电场理论的图像快速伪造检测算法

为了解决当前图像伪造检测算法主要是在图像空域中定位伪造区域,难以降低图像维数,使其复杂度大;且不能有效检测几何变换篡改形式的伪造区域,导致其鲁棒性不佳的不足,本文提出了离散小波变换耦合静电场理论的图像伪造检测算法。首先,引入离散小波变换,提取伪造图像的低频子带,降低图像空间;再基于静电场理论,将提取子带映射到虚拟电场中,提取鲁棒性较强的特征,利用Radix排序算法对特征完成重组,形成特征矩阵;最后,定义相同仿射变换,并用其处理排序矩阵,完成伪造区域检测。实验测试结果显示：与当前的移动复制伪造检测技术相比,本文算法具有更高的定位效率与检测精度;同时拥有较强的鲁棒性,有效抗击几何变换篡改。     

Vibrational spectra and ab initio molecular orbital calculations of the novel anti-cancer drug combretastatin A-4 prodrug

The NIR-FT Raman and FT-IR spectral studies of the novel antineoplastic and antiangiogenesis substance comprestatin A-4 prodrug (CA4P) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of CA4P have been investigated with the help of B3LYP density functional theory (DFT) method. The most preferred cis-configuration for its bioactivity has been demonstrated on the basis of torsional potential energy surface (PES) scan studies. Stability of the molecule arising from hyperconjugative interactions leading to its bioactivity, charge delocalization and mesomeric effects have been analyzed using natural bond orbital (NBO) analysis. Detailed assignments of the vibrational spectra have been made with the aid of theoretically predicted vibrational frequencies. The optimized geometry shows near-planarity of phenyl rings and perpendicular conformation of meta substituted methoxy group. The vibrational analysis confirms the differently acting ring modes, steric repulsion, pi conjugation and back-donation.