Pt纳米线阵列的氧还原催化性能

采用阳极氧化铝(AAO)模板法电化学沉积制备了Pt纳米线阵列(Pt NWs)氧还原催化剂, 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和电化学测试对Pt纳米线阵列催化剂的形貌和电催化性能进行了表征. 循环伏安法(CV)研究表明Pt纳米线阵列催化剂的电化学活性面积大于其几何面积; 旋转圆盘电极(RDE)测试研究发现, 制备的Pt纳米线阵列催化剂的氧还原反应(ORR)曲线的半波电势相对Pt/C的有正移, 并且Pt纳米线阵列催化剂的极限扩散电流比Pt/C大.     

旋转玻碳电极上二茂铁的电化学阻抗行为及其与DNA的相互作用

应用旋转圆盘电极和电化学阻抗法研究了二茂铁在Tris-NaC l(pH=7.2)缓冲溶液中于旋转玻碳电极上的电化学阻抗行为及其与DNA的相互作用.结果表明,二茂铁于旋转电极的伏安曲线呈现明显的极限电流平阶,而其交流阻抗谱则出现两个电容弧.二茂铁与DNA的作用,若受扩散过程控制则其极限扩散电流随DNA浓度增大而减小,而在电化学控制过程中则表现为电化学反应电阻随DNA浓度增大而增大.根据旋转圆盘电极和电化学阻抗谱测试,表明由这两种方法数据拟合求得的二茂铁条件电位速率常数能够很好地相互吻合,但如存在DNA时,则其条件电位速率常数有一定程度的减小.     

二茂铁及其与DNA复合物的电化学行为

在Tris-NaCl(pH=7.2)缓冲溶液中, 应用循环伏安法、微分脉冲伏安法、旋转圆盘电极实验、电化学阻抗谱等技术研究了二茂铁在旋转碳纳米管(CNT)修饰电极上的电化学行为及其与小牛胸腺DNA的相互作用. 结果表明, 二茂铁及其与双链DNA的电活性产物在静止的CNT修饰电极上均呈现一对基本可逆的氧化还原峰；在旋转电极上呈现出明显的极限扩散电流, 电化学阻抗谱呈现一个压扁的半圆. 二茂铁与DNA的作用在扩散控制过程中表现为峰电流和极限扩散电流随DNA浓度增大而减小；电化学控制过程则表现为电化学反应电阻随DNA浓度增大而增大, 条件电位下的速度常数也有一定程度的减小.     

纳米电极上单个银纳米颗粒氧化电流分辨能力的研究

在单体电化学的研究中,提高信号分辨能力是一项挑战.缩小电极尺寸有利于对体系噪音电流的控制,有望提高电流的分辨能力.本研究制备了直径为480 nm的铂纳米圆盘电极,选用银纳米颗粒碰撞电极产生银电化学氧化行为作为模型,考察了纳米电极相对于微米电极在单体电化学信号分辨能力上的优化作用.研究表明,不同尺寸电极上观察到的银纳米颗粒的碰撞频率符合扩散控制的碰撞规律.说明单个电流信号对应于单个纳米颗粒的电化学氧化过程.同时,当电极尺寸缩小至纳米尺度后,噪音电流下降50%左右,提高了对银纳米颗粒碰撞电极过程中氧化电流的分辨能力.研究结果表明使用纳米电极能进一步提高对单体电化学中微小电流的检测能力.     

硼掺杂的NiO修饰玻碳电极电催化氧化甲醇（英文）

采用计时电流法,线性扫描伏安法和安培曲线来研究B-Ni O的电催化氧化甲醇过程.研究结果表明,该B-Ni O电极具有良好的电催化作用,活性高,稳定性好,在电极上对甲醇的氧化动力学过程为单扩散动力学控制过程.与块状Ni(OH)_2相比,硼掺杂的Ni O纳米花在碱性介质中电催化氧化甲醇的电流密度提高了50倍.由于B-Ni O纳米花出色的电化学性能使其在电氧化甲醇上具有潜在的应用前景.     

微电极的稳态可逆极化曲线

微电极具备一些常规尺寸电极所没有的优点,例如:(1)半径很小的微电极在不对溶液进行搅拌的情况下就具备与高速旋转的圆盘电极类似的性质,即在电位扫描速率较低时,可获得稳态伏安曲线.这一特点使微电极能方便地用于稳态测量.与暂态测量相比,稳态测量精度较高(实验曲线几乎不受充电电流干扰),实验方法较简单,实验结果的数学处理较容易.(2)微电极体系的时间常数(溶液电阻和双层电容的乘积)正比于电极面积的平方根.若在     

磺胺甲恶唑在二硫化钼纳米片修饰电极上的电化学行为

采用了研磨后超声和离心分离方法制备了二硫化钼纳米片,通过原子力显微镜(AFM)和扫描电子显微镜(SEM)对不同离心速度分离的二硫化钼纳米片进行了表征。使用循环伏安法(CV)和差分脉冲伏安法(DPV)在磺胺甲恶唑溶液中对二硫化钼纳米片修饰的玻碳电极进行了电化学行为研究。结果显示,磺胺甲恶唑在二硫化钼修饰电极的循环伏安图上有一对氧化还原峰。其峰电流值与扫描速度的平方根成正比,是扩散控制过程。DPV扫描结果显示,磺胺甲恶唑的峰电流与其浓度之间存在着明显的线性关系。研磨超声方法制备出的二硫化钼纳米片层材料在电极上能够加速电子的转移和传输,从而有效提高峰电流值,为进一步研制准确测定磺胺甲恶唑电化学传感器提供了一种可选择的材料和电化学分析方法。     

多孔电极电池的循环伏安法模拟

锂离子电池的全电池建模模拟对现代新能源领域的发展至关重要。伪二维（P2D）电化学模型是最常使用的全电池模拟模型,但一直被用于输入为电流,输出为电压的模拟中。本文基于P2D模型,通过对内电位、电极电位以及电池端电压的详细讨论,首次采用电压边界条件,利用COMSOL仿真软件完成了实验中常用的两电极体系和三电极体系的循环伏安法建模和模拟。并对比分析了两/三电极体系中扫描速率、颗粒半径、电极锂扩散速率以及最大嵌锂浓度这四个参数对循环伏安曲线形状的影响。结果表明,循环伏安测试时扫描速率越大,循环伏安曲线的峰值电流越大;固相锂扩散速率越大、电活性颗粒半径越小、最大嵌锂浓度越大,峰值电流越大。在相同的测试条件下,三电极体系比两电极体系的循环伏安图对称性更好,电流响应更大,并且颗粒半径、锂扩散速率及最大嵌锂浓度这三个参数对峰值电流的影响也更为明显。     

纳米硫化镉在对氨基苯硫酚自组装单层修饰金电极上的电化学合成

采用电流脉冲法在自组装了对氨基苯硫酚单层的金电极(PATP/Au)上电沉积硫化镉(CdS)纳米薄膜,运用扫描电子显微镜(SEM)和X射线衍射谱(XRD)对其形貌和结构进行了表征,发现得到的是垂直基底生长的CdS纳米棒有序阵列.研究电沉积中电流脉冲参数的影响时发现:随着电流脉冲宽度增大,CdS纳米棒的尺寸增大,有序性降低;脉冲幅度增大,则纳米棒尺寸增大,覆盖度也随之增大.因此通过调节脉冲宽度和脉冲幅度,可对所制备的CdS纳米薄膜的形貌和尺寸进行调控.运用循环伏安法和计时电位法对电沉积机理进行了探究.根据实验结果我们认为Au电极自组装PATP单分子层后,PATP分子中的-NH2与溶液中Cd2+相互作用,使沉积时的电子通过表面的PATP分子链进行传递.并进一步提出纳米CdS在PATP/Au电极上电化学合成的生长机理.     

基于碳纸电极电化学快速合成聚苯胺纳米纤维

利用碳纸电极,采用循环伏安法、恒电流法和恒电位法等电化学聚合法快速合成了高氯酸掺杂聚苯胺纳米纤维.利用电子显微镜、红外光谱和四探针测定仪等对聚苯胺的微观形貌结构、掺杂度和电导率进行了研究.用循环伏安法对聚苯胺的电化学特征进行了分析.研究发现,3种方法合成的聚苯胺均为纳米纤维状结构,长度达3μm,直径为50~150 nm.其中,循环伏安法合成的聚苯胺纳米纤维的均一性和电导率均优于其它2种方法,其电导率高达5.97 S/cm.另外,聚苯胺合成速率顺序为恒电流法>循环伏安法>恒电位法,且恒电流法合成的聚苯胺纳米纤维电极材料的放电比容量最大(578 F/g),电容性能最好.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.