丁二烯在烯土配位催化剂下的活性聚合

本文用动力学方法处理了丁二烯在NdCl₃·3i-PrOH-AlEt₃催化体系中,-70℃下聚合结果:发现聚合体系中不存在可检测出的使活性中心失活的不可逆的链终止反应和限制产物分子量的链转移反应,产物的分子量分布较窄并具有特高顺1,4-微观结构,平均活性链寿命相当长。     

不同样品前处理技术对同时测定土壤中铊和锑的影响

为了比较不同前处理方法对土壤中重金属铊和锑的同时提取能力,采用3种加热方法和8种消解体系的不同组合对4种标准土壤样品进行处理。实验探究了不同前处理方法并结合电感耦合等离子体质谱(ICP-MS)进行检测,通过精密度和准确度的分析,优化了同时检测铊和锑两种重金属元素的最合适的样品前处理方法。研究结果表明,电热板加热HNO_3-HF体系和微波消解HNO_3-HF-HCl-HClO_4体系,结合ICP-MS能够更加准确的同时测定重金属铊和锑。将最适合的两种前处理方法分别用于4个实际样品的处理,结果表明上述两种不同的消解体系对土壤中铊和锑的提取能力基本一致。本研究方法可以同时准确的测定土壤样品中的铊和锑。     

丁二烯在稀土配位催化剂下的“活性”聚合

本文用动力学方法处理了丁二烯在NdCl_3·3i-PrOH-AIEt_3催化体系中,-70,-30和0℃下聚合结果,得出在-700℃下聚合时,聚合体系中不存在可检测出的使活性中心失活的不可逆的链终止和限制产物分子量的链转移反应。发现产物的分子量分布窄,具有特高顺-1,4结构和平均活性链寿命趋于无限大。成功地合成了丁二烯-异戊二烯嵌段共聚物,并用GPC,IR和~(13)C NMR对产物进行了表征。结果表明在此条件下,丁二烯在本催化体系聚合是接近于理想的活性聚合。     

陶瓷微细镀覆新技术的研究

建立微机处理体系(包括线路、图形设计,光照点选择及活化处理等)与化学镀铜相结合的微细镀覆新技术.该技术可在Al2O3基底上获得性能良好的Cu镀层,其布线速率达 50mm/s,线分辨率 35μm,工艺简便,条件温和,为陶瓷微细镀覆开辟了新途径.     

新型PEG双子温控离子液体中的缩醛反应

制备了具备温控功能的新型PEG双子离子液体(IL200, IL400, IL1000), 考察了该离子液体和甲苯形成“高温均相, 低温两相”体系, 对芳香醛与乙二醇缩合反应的影响, 当离子液体3 mL, 甲苯5 mL, 对甲苯磺酸6 mmol, 苯甲醛5 mmol, 乙二醇15 mmol, 反应时间4 h, 温度80 ℃时, 产率达到92%. 该体系对芳香醛与乙二醇缩合反应有广泛的适用性, 且不经任何处理可多次循环使用.     

Sb2O3与HZSM-5的相互作用

研究了氮气气氛下于500℃处理2h后的Sb₂O₃/HZSM-5体系中Sb₂O₃在分子筛表面上的分散行为.发现处理后的体系中Sb₂O₃晶相消失,HZSM-5晶相减少,非晶相增加.经XRD相定量、氮气吸附、正己烷吸附及NH₃-TPD实验可知,高温下酸性Sb₂O₃破坏了分子筛的部分骨架,生成无定形硅铝胶,同时Sb₂O₃高分散在其中.含Sb₂O₃的无定形硅铝胶修饰了分子筛表面,减小了孔口,提高了分子筛在甲苯烷基化反应中的择形性能,对二甲苯的选择性可高达89.     

农、兽药及工业化学物残留量分析中样品前处理微量化学法技术研究

建立了一种用于残留物分析样品处理的微量化学法(MICCM)体系,提出了该体系的基本概念、原理、单元操作,选择了一套基本系列设备和器具,并将这一体系用于检测不同样品中的农药、兽药、工业化学物残留量及食品添加剂。实例中,各方法检测限、回收率、变异系数的实验数据均达到了国际上对残留量分析方法的技术要求。该体系与经典常量化学法(MaCCM)样品处理体系相比,具有快速、简便、工效高,节省人力、试剂材料、能源以及占用场地小等多种优点。残留物分析可广泛用该体系取代经典法样品处理体系。     

Tl^3^+─H2O2─Fe^2^+体系的反应动力学研究

本文用Tl(I)离子选择性电极测定了Tl^3^+-H2O2-Fe^2^+体系的反应参数, 据此计算了该体系的反应级数, 得到了反应速率方程式, 对该反应体系的反应机理进行了探讨, 并用稳态处理法对所提出机理进行验证, 其结论与实验所得速率方程完全符合。     

Tl^3^+─H2O2─Fe^2^+体系的反应动力学研究

本文用Tl(I)离子选择性电极测定了Tl^3^+-H2O2-Fe^2^+体系的反应参数, 据此计算了该体系的反应级数, 得到了反应速率方程式, 对该反应体系的反应机理进行了探讨, 并用稳态处理法对所提出机理进行验证, 其结论与实验所得速率方程完全符合。     

基于二肽的相选择胶凝剂对水中油污和有毒染料的清污性能

设计合成了一系列相选择胶凝剂(3a-3e),并通过¹H和¹³C核磁共振波谱和质谱对其结构进行了表征。 在有机溶剂和水的混合体系中对目标化合物进行相选择凝胶性能试验,结果表明化合物3c在粉末状态下表现出出色的相选择胶凝能力,在室温下可通过摇晃从油水两相体系中快速除去苯、甲苯、二甲苯和汽油。 另外,实验证明以3d-苄醇凝胶作为吸附剂可以实现有毒染料溶液的有效吸附,而且通过紫外-可见光谱实验可以对其清除效果进行量化。 操作简单和高效除污等优点表明这些二肽胶凝剂在污水纯化处理中具有广阔的应用前景。     

脉冲电势调制型电化学气体传感器

根据暂态电化学原理 ,使用微电极并融合计算机控制的快速电势调制技术和数据采集、处理功能 ,提出并建立了一类全新的集信号提取、处理与结果显示等功能于一体的“脉冲电势调制型气体传感器” .在优化传感器性能及其新的功能开发和集成方面取得了重要进展 ,是一类为常规电化学气体传感器无法比拟而有发展前景的暂态电化学多组份气体传感器 .     

基于电化学噪声研究模拟海洋大气环境下304不锈钢的点蚀行为

基于电化学噪声技术建立了不锈钢海洋大气点蚀监测系统,利用该系统对处于干湿循环环境下不锈钢的点蚀行为进行监测. 使用时域谱图、时域统计、频域谱图和散粒噪声理论等分析方法对采集到的电化学噪声数据进行处理分析,并结合动电位极化法,形貌分析法共同研究不锈钢的点蚀行为. 研究结果表明,304不锈钢在模拟海洋大气环境下的点蚀行为分为钝化、亚稳态点蚀和稳态点蚀三个阶段. 在钝化阶段,电位电流噪声信号出现少量的同步异向波动,腐蚀事件发生频率高,平均电量低;在亚稳态点蚀阶段,电位电流噪声信号出现大量的同步同向波动,腐蚀事件发生频率降低,平均电量上升,通过扫描电镜观察蚀点;在稳态点蚀阶段,电位电流噪声信号不仅存在大量的同步同向波动,还出现了同步异向波动,腐蚀事件发生频率较低,平均电量大幅度上升,通过扫描电镜观察到电极表面出现小而浅的蚀点. 而动电位极化法可以证实304不锈钢点蚀的发生. 两种分析方法所得结果具有较好的一致性,证明该监测系统很好地实现了对模拟海洋大气环境下304不锈钢点蚀行为的连续监测,并能判断点蚀的发生.     

单个Nafion@Ru和Au-Nafion@Ru纳米粒子的电化学和电化学发光碰撞行为研究

通过静电作用在Nafion和Au-Nafion纳米粒子(NPs)上负载钌联吡啶(Ru(bpy)₃²⁺)分别制得Nafion@Ru和Au-Nafion@Ru NPs.分析并比较了Au-Nafion@Ru和Nafion@Ru NPs在金超微电极(Au UME)上随机碰撞产生电流响应峰的平均峰大小、峰电量和单峰持续时间,建立了以Au-Nafion@Ru NPs为主体的电化学碰撞体系.研究结果表明,制备的Au-Nafion@Ru NPs因其特殊结构,Nafion和AuNPs的共同参与增加了NPs与Au UME的有效接触或碰撞面积,产生了更强的电化学碰撞响应信号.在Au-Nafion@Ru NPs-三正丙胺(TPrA)体系中,同时使用电流-时间曲线和电化学发光(ECL)-时间曲线监测Au-Nafion@Ru NPs碰撞Au UME产生的电化学和ECL瞬变信号,建立了单个Au-Nafion@Ru NPs-TPrA在Au UME上瞬变电化学信号与ECL信号之间的相关性.该策略为研究其他分子电化学碰撞体系提供了思路.     

Pulse radiolysis based on a femtosecond electron beam and a femtosecond laser light with double-pulse injection technique

A new pulse radiolysis system based on a femtosecond electron beam and a femtosecond laser light with oblique double-pulse injection was developed for studying ultrafast chemical kinetics and primary processes of radiation chemistry. The time resolution of 5.2 ps was obtained by measuring transient absorption kinetics of hydrated electrons in water. The optical density of hydrated electrons was measured as a function of the electron charge. The data indicate that the double-laser-pulse injection technique was a powerful tool for observing the transient absorptions with a good signal to noise ratio in pulse radiolysis.     

A pH-controllable electrochemical molecule switch employing a new electrochemical measurement system as switching transducer

A new design concept of electrochemical pH-controllable molecular switch is presented by utilizing a new electrochemical measurement system as switching transducer. A pH sensor is connected in series between the terminal points of the working and counters electrodes of a potentisostat, and immersed in the solution together with a reference electrode, establishing a novel electrochemical measurement system. In this system, the variation of pH-controllable interface potential at the pH-sensing film/solution interface can be converted to current response when amperometry technique is employed. Based on this unique current–potential relationship, a pH-controllable switch is designed to monitor the protonation and deprotonation reaction of pH-sensing molecule. The current direction interchanges between positive and negative via pH control, illustrating a reversible conformation transition between protonated state and deprotionated state of molecule. The magnitude of current value represents the degree of protonation and deprotonation reaction of molecule. The strategy is successfully demonstrated with a remarkably reversible polyaniline-based pH-controllable switch, which confirms the feasibility of the novel electrochemical measurement system as switching transducer for designing electrochemical pH-controllable switches. This study may open up a potential avenue to construct the electrochemical pH-controllable switches.     

Tip current/positioning close-loop mode of scanning electrochemical microscopy for electrochemical micromachining

Scanning electrochemical microscopy (SECM) has been approved as a prospective electrochemical micromachining (ECMM) technique soon after its birth. However, it still remains challenge for SECM to fabricate arbitrary three-dimensional (3D) microstructures because of the limitation of positioning system. To solve this problem, we proposed a tip current signal/positioning close-loop mode in which the tip current signal is fed back to the positioning system in order to program the motion trial of SECM tip. Both the triedge-cone and sinusoidal microstructures were obtained by the close-loop positioning mode. The static-state etching process was demonstrated not to be disturbed by the slow motion rate of SECM tip. The unique positioning mode would be significant for both ECMM and electrochemical imaging.     

电化学噪音数据小波分析法研究

电化学动力系统演化过程中 ,其状态参量 (如电极电位、电解池电流等 )的随机波动现象被称为“电化学噪音”(ECN) .小波变换是近年来数学与信号处理领域获得突破性进展的一种数据处理方法 .本文首次用连续小波变换的方法对混凝土中钢筋腐蚀产生的“电化学噪音”信号进行初步研究 ,通过将原始的时域信号变换至时_频相平面来观察其结构特征 ,并揭示出电化学腐蚀过程的混沌动力学行为 .     

Performance of a general-purpose electrochemical instrument aided by a stand-alone microcomputer system in trace analysis

The features of a microprocessor-based data acquisition and control unit, dedicated to electrochemical experiments, are described. The menu-selectable software allows smoothing, baseline drawing and subtraction as well as differentiation, even with signal amplitudes of some tenths of nA at signal/noise ratios lower than one, without forcing the data to follow theoretical models. Concentrations of cadmium ion as low as 2 × 10^?7, 5 × 10^?8 and 5 × 10^?9 M can be measured, within 10% accuracy and precision, by using sampled d.c. polarography, staircase voltammetry and fast-sweep differential pulse voltammetry, respectively; this is a consistent improvement on literature data. Depending on the electrochemical technique used, the most significant signal parameters, including derivatives, are measured automatically, listed and used in the decision-making process for chemical characterization.     

Nanosecond time-resolved EPR spectroscopy: time profiles via integration of free induction decays

Tune dependence of transient magnetization can be sampled by using a single microwave pulse and observing the intensity of free induction decay (FID). The FID method is illustrated and compared to the two-pulse electron spin echo (ESE) technique. The time pronies of the hydrogen atoms created by electron beam pulse radiolysis or acidic water are used to illustrate the advantages of the FID method. Superior signal to noise and better effective response time of the F ID method makes it an ideal tool for the study of fast reacting radicals in liquids.     

A new direct current method for resistance measurements of ionic membranes and its application to composite membranes

The present paper deals with a D.C. method for measuring membrane electrical resistance making use of a constant current pulse, automated measuring equipment and taking into account polarization phenomena. The potential transient, subsequent to application of current, is analyzed, and membrane electrical resistance is determined by extrapolation to zero time of the potential differences measured after the current step. Experimental results obtained with commercial ion-exchange membranes were in good agreement with those computed from the diffusion equation. The method developed gives values with a standard deviation lower than traditional techniques. As an application example, the current pulse technique allows measurement of electrical resistance of composite silicafouled membranes in the electrodialysis process in both current directions. In this case the different response of the system, after the current pulse, gives useful information about membrane structure and ion distribution on the double layers surrounding the membrane.