醋酸铀酰负离子气相分解反应的密度泛函理论研究

采用密度泛函理论(DFT), 选择杂化密度泛函TPSSh和TZVP基组, 对一个UO₂(CO₃)₃^4-负离子的结构进行优化, 理论计算所得结果(键长等参数)与实验数据一致. 应用TPSSh/TZVP(ECP)方法对醋酸铀酰负离子UO₂(CH₃COO)₃^-的气相分解反应进行了理论计算, 成功地解释了含+5价铀的气相自由基负离子的稳定性, 并对2个负离子(CH₃COO)UO₂CH₃^-和CH₃UO₂OH^-分别与水的复分解反应进行了理论计算, 所得数据与质谱的实验结果较好地吻合.     

H3+O和H3+O(H2O)n(n=1,2,3)阳离子振动力场和光谱频率的理论计算

本文利用多原子分子振动力场的模型势函法对H₃⁺O和H₃⁺O(H₂O)_n(n=1～3)阳离子的振动力场作了理论计算,并对其光谱频率进行了预测.H₃⁺O和H₉⁺O₄的振动频率的结果优于从头算梯度法的结果.本文首次给出了H₅⁺O₂、H₇⁺O₃伸缩振动频率的理论预测值.     

V2H分子的分子结构与势能函数

用密度泛函理论(DFT), 在BP86/6-311＋＋g(d,p)水平上对V₂, VH和V₂H进行了理论研究. 得到该系列分子的基态电子态分别为: V₂( ), VH( ) , V₂H ( ), V₂H分子的基态稳定构型具有C_2v对称性. 用Murrell-Sorbie势能函数对V₂和VH分子的扫描势能点进行了拟合, 其扫描点都与四参数Murrell-Sorbie函数拟合曲线符合很好, 在此基础上推导出了它们的光谱数据和力常数. 用多体项展开理论导出了V₂H分子的解析势能函数, 在固定键角∠VHV＝58.7^o时, RH-V＝0.1790 nm处存在一个势阱, 深度为7.26 eV, 表示在该处容易形成稳定的V₂H分子.     

双笼羰基化合物C120CO的理论研究

用INDO系列方法对双笼化合物C₁₂₀CO进行了理论研究,结果表明,C₁₂₀CO中O具有较大的电负性,在此位置可形成氢键.分子内电荷转移较大,非线性光学系数可能较大.C₁₂₀CO的电子光谱与C₁₂₀CH₂和C₁₂₀O的相似.     

金属硫化物富勒烯Sc2S@C90的结构与性质

Sc₂S@C₉₀存在的信号已经被质谱检测到,但其结构还没有得到表征. 为了研究Sc₂S@C₉₀的结构和性质,通过密度泛函理论计算方法对Sc₂S@C₉₀的异构体进行了系统的筛选. 计算结果表明,能量最低的两个异构体分别为Sc₂S@C₉₀：99913和Sc₂S@C₉₀：99915. 对Sc₂S@C₉₀在0到4000 K温度下的相对浓度进行了评估,结果显示,Sc₂S@C₉₀：99913和Sc₂S@C₉₀：99915可以在高温下共存. 分析研究了Sc₂S@C₉₀的内嵌团簇与碳笼间的键连关系和相互作用特性. 这些研究可为Sc₂S@C₉₀的结构确定提供指导.     

氟磺酸氯分子振动光谱的从头算研究

采用从头算HF方法以6-31G^*基组研究了对ClOSO₂F分子的几何结构、振动谐性力场和红外光谱.理论力场由Pulay的标度量子力学方法进行标度,算得的振动频率与实验值比较,平均偏差为6.0cm^-1.根据振动频率的势能分布和从头算红外光谱强度值对此分子的振动基频进行了理论归属.     

NCS自由基与NO反应动力学的理论研究

用量子化学密度泛函理论B3LYP/6-31+G^*和高级电子相关校正的偶合簇[CCSD(T)/6-311+G^*]方法,对NCS自由基与NO反应的机理和动力学进行了理论研究,得到了体系的势能面信息和可能的反应机理.计算了反应的热力学参数及反应能垒.采用传统过渡态理论计算了各反应通道的速率常数.研究结果表明,NCS自由基与NO反应中存在4个反应通道,产物分别为OCS+N₂,CS+N₂O,ONS+CN和ONCNS.从能量变化和反应速率两方面考虑,NCS+NOOCS+N₂应为主反应通道.     

C59(C6H4OCH3)N的结构、光谱和二阶非线性光学性质的理论研究

用INDO系列方法对由(C₅₉N)₂和苯甲醚合成的衍生物C₅₉(C₆H₄OCH₃)N进行了理论研究,得到了分子的稳定构型.结果表明,C₅₉(C₆H₄OCH₃)N具有C_s对称性.以优化构型为基础讨论了分子的UV-Vis光谱、NMR谱线数,结果与实验符合得很好.本文还计算了C₅₉(C₆H₄OCH₃)N的二阶非线性光学系数β_μ,结果表明这种物质具有较大的二阶非线性光学系数.     

ClC(O)NCS分子振动光谱的理论研究

采用密度泛函理论DFT(B3LYP)方法,以6-31G^*为基组对ClC(O)NCS的反式和顺式两种构型的几何结构、振动谐性力场和红外光谱进行了研究.B3LYP/6-31G^*的理论力场由适用于B3LYP/6-31G^*计算水平和大多数有机分子的一套固定标度因子进行标度.根据标度后的理论力场进行简正坐标分析得到的势能分布(PED)和红外光谱强度值对ClC(O)NCS分子的顺式和反式两种构型的振动基频进行了理论归属.     

噻吩光解反应机理的理论研究

使用密度泛函理论(DFT)中的B3LYP方法, 采用6-31G**和6-31＋＋G**基组, 对噻吩的光解反应进行了理论研究. 对照实验结果, 我们研究了五个光解通道, 包括生成C₄H₄＋S, C₂H₂＋C₂H₂S和CS＋C₃H₄的三个闭壳层分子解离通道与生成HCS＋C₃H₃和HS＋C₄H₃的自由基解离通道. 各个可能的反应通道的产物碎片的具体形式得到了确认. 研究发现在基态生成C₂H₂＋C₂H₂S和在最低三态生成C₄H₄＋S的反应从能量上考虑最为有利, 而实验上观测到的主要产物C₂H₂＋C₂H₂S主要是在基态上产生的. 通过对比实验结果与计算结果, 我们认为噻吩光解反应机理与所用激发光波长有关.     

Faradaic electrochemistry at microcylinder,band, and tubular band electrodes

Current-time relationships of faradaic processes at microcylinder, band, and tubular band electrodes have been evaluated. Microcylinder electrodes were fabricated from platinum wires (5 μm radius) sealed in glass capillaries. Band and tubular electrodes were constructed with platinum sheets (～ 20 μm width) or thin pieces of graphite (～ 5 μm width) sealed between insulating mateials. The temporal response of the current at a microcylinder electrode for the reduction of ferricyanide in aqueous potassium chloride solutions is in excellent agreement with that predicted by equations derived for heat flux to a cylinder. An estimation of the magnitude and temporal properties of the measured current at a band electrode can be obtained when a hemicylinder geometry is assumed. The current respone is identical at band and tubular band electrodes even for the smallest tubular radius investigated, 0.54 mm. Cyclic voltammograms at electrodes of all three geometries show significant contributions from radial diffusion at slow scan rates (< 20 mV s^?1). The current at a graphite tubular band electrode was found to be independent of flow of solution through the electrode at flow rates up to 3 ml min^?1.     

New Techniques in Electrometric Titrations

Five new techniques in electrometric titration are described: 1.Oscillopolarographic titration without incision at 1 micro and 1 macro Pt electrodes.2.Oscillopolarographic titration without in -cision at 3 electrodes.3.Oscillo potentiometric titration at 3 electrodes.4.Zero current oscillo bipotentiometric titration.5.Alternating current oscillo bipotentiometric at 2 similar electrodes.Among them methods 1,4,5 are very useful.     

The electrochemistry of gold–platinum alloys

The electrochemical properties of gold, platinum and gold–platinum alloy electrodes under different heat treatment conditions have been studied in 0.5 M H₂SO₄ and 0.5 M NaOH. The electro-oxidation of 0.1 M ethylene glycol in 0.5 M NaOH at these electrodes has also been studied. It was found that all the gold–platinum electrodes are more active for ethylene glycol electro-oxidation than both pure gold and platinum, and that the gold–platinum electrodes in the solid solution condition are more active than the two-phase electrodes. Poisoning of all the electrodes occurs during electrolysis of ethylene glycol at a fixed potential. Potential pulsing is successful in removing the poisoning species formed at the pure gold and pure platinum electrodes. High apparent current densities are found during the first few cycles at the Au–Pt alloy electrodes. These high current densities are also associated with more severe poisoning – than at both pure gold and platinum – and longer cleaning cycles are needed to remove the poisons at these electrodes.     

Microwave enhanced electroanalysis of formulations: processes in micellar media at glassy carbon and at platinum electrodes

The direct electroanalysis of complex formulations containing alpha-tocopherol (vitamin E) is possible in micellar solution and employing microwave-enhanced voltammetry. In the presence of microwave radiation substantial heating and current enhancement effects have been observed at 330 microm diameter glassy carbon electrodes placed into a micellar aqueous solution and both hydrophilic and highly hydrophobic redox systems are detected. For the water soluble Fe(CN)(6)(3-/4-) redox system in micellar aqueous solutions of 0.1 M NaCl and 0.1 M sodium dodecylsulfate (SDS) at low to intermediate microwave power, thermal effects and convection effects are observed. At higher microwave power, thermal cavitation is induced and dominates the mass transport at the electrode surface. For the micelle-soluble redox systems tert-butylferrocene and 2,5-di-tert-butyl-1,4-benzoquinone, strong and concentration dependent current responses are observed only in the presence of microwave radiation. For the oxidation of micelle-soluble alpha-tocopherol current responses at glassy carbon electrodes are affected by adsorption and desorption processes whereas at platinum electrodes, analytical limiting currents are obtained over a wide range of alpha-tocopherol concentrations. However, for the determination of alpha-tocopherol in a commercial formulation interference from proteins is observed at platinum electrodes and direct measurements are possible only over a limited concentration range and at glassy carbon electrodes.     

Changes in zeta potential caused by a dc electric current for thin double layers

An asymptotic solution was obtained to describe one-dimensional, steady-state transport of a symmetric binary electrolyte normal to two large parallel electrodes, in the limit in which the Debye length is infinitesimal compared to the distance separating the two electrodes. Despite the nonzero ion flux, Boltzmann's equation continues to describe the relationship between either ion concentration and the electrostatic potential inside the diffuse part of the double layer, while local electroneutrality applies outside, even for current densities approaching the limiting value. In the absence of ion adsorption or dissociation reactions at the electrodes, the magnitude of any charge or zeta potential arising on the electrodes at zero current is determined by the equilibrium constant for the redox reactions which would exchange ionic charge carriers for electric charge carriers at the electrode surface. Nonzero current causes the ionic strength of the bulk to vary with position. This perturbs the Debye length of the diffuse cloud on either electrode: it is the local ionic strength just outside the cloud which determines the Debye length for that cloud. Nonzero current also changes the zeta potential. The dimensionless rate of change dζ/dJ was as large as 30.     

高性能Sm0.5Sr0.5CoO3阴极的制备与表征

用固相合成法合成了Sm0.5Sr0.5CoO3 (SSC)中温固体氧化物燃料电池阴极材料.以La0.9Sr0.1Ga0.8Mg0.2O3为电解质,利用多种技术考察了不同温度(1173～1373 K)焙烧的SSC阴极,以及1173 K 焙烧、掺杂La0.8Sr0.2Ga0.8Mg0.15Co0.05O3(LSGMC5)或La0.8Sr0.2Ga0.8Mg0.09Co0.11O3 (LSGMC11)高氧离子电导材料的复合SSC阴极.SEM的结果显示,随着电极焙烧温度的增加,电极的颗粒度增大,孔隙度减小；LSGMC5、LSGMC11的掺杂对电极微观结构影响不大.交流阻抗和极化实验的结果表明,SSC电极的活性随电极焙烧温度的增加而减小,电极的最佳焙烧温度在1173 K左右；掺杂了LSGMC5或LSGMC11的复合SSC电极的活性以及稳定性显著高于SSC电极.     

线状铜电极在磷酸溶液中电流混沌振荡的同步行为

研究了恒电位下两个铜线电极在磷酸溶液中的电流混沌振荡行为,通过恒定不同的电位数值,改变单个电极的电流振荡混沌行为,研究了不同混沌间的相互作用.调整线电极间的距离,研究了电极间距对电流振荡行为的影响.实验中两电极的振荡间呈现了复杂的耦合作用,耦合后的频率与耦合前电极原有的频率不同.两电极的混沌电流振荡中呈现出同步、准周期同步和反相同步等现象.电极距离一定时,振荡波形差别很大的两电极的电流容易呈现反相同步和准周期同步,波形差别不大时容易产生同步.强的耦合导致电极间电流振荡的同步,电极距离的加大,电极间电流振荡难以产生同步.对耦合作用机制也进行了探讨.     

Electrochemical Detection of TNT at Cobalt Phthalocyanine Mediated Screen‐Printed Electrodes and Application to Detection of Airborne Vapours

We describe the use of cobalt phthalocyanine as a mediator to improve the sensitivity for the electrochemical detection of TNT. Commercial screen‐printed electrodes containing cobalt phthalocyanine were employed for determination of TNT. Improved sensitivities compared to screen‐printed carbon electrodes without phthalocyanine were observed, current response for cyclic voltammetric measurements at modified electrodes being at least double that of unmodified electrodes. A synergistic effect between oxygen and TNT reduction was also observed. Correlation between TNT concentrations and sensor output was observed between 0–200 µM TNT. Initial proof‐of‐concept experiments combining electrochemical determinations, with the use of an air‐sampling cyclone, are also reported.     

Electrochemical Detection of Protons Produced in an Electrode Reaction Using Interdigitated Microarray Electrodes

This work describes the use of interdigitated array electrodes (IDAE) for proton detection. Methanol electrooxidation in sulfuric acid solution was exemplified. Reduction currents originating in the reaction product generated by methanol electrooxidation on a Pt generator electrode were observed at the Pt collector electrode, the potential of which was fixed in the hydrogen evolution region. In order to reduce the background current of hydrogen evolution, an Hg‐plated Pt collector electrode was fabricated. Compared to the Pt collector electrode, the reduction current observed at the Hg collector electrode was extremely small. The product detected was found to be a proton from the current responses observed at Pt and Hg collector electrodes.     

锌-铟合金电极在浓KOH溶液中的电化学行为

应用动电位扫描,恒流放电等电化学方法研究含铟锌电极的电化学行为.用SEM和EDS观察放电后的Zn-In合金电极表面形貌,初步探讨了不同In含量的锌-铟合金电极在浓KOH溶液中电化学行为及其影响因素.结果表明,与纯锌电极相比,Zn-In合金的电极致钝电流增大,达到钝化的时间缩短,从而明显地提高了该电极的电化学活性.