微电极上单核沉积的现场电化学原子力显微镜研究

用现场电化学原子力显微镜（ＥＣＡＦＭ）观察玻碳微电极上银单核电化学成核与生长的不同阶段的行为,结果表明银单核在玻碳边缘生成以（１００）面择优的晶粒,证实了成核过程强烈地信赖于玻碳棋底的状态,有成核历史的基底沉积多核,经特殊方法“清洗”的基底沉积单核,本工作首次把ＥＣＡＦＭ应用于微电极系统的研究,对微是极上的单核生长进行实时观察;同非现场测量进行比较,演示一种轩单晶微电极的可行方法。     

微电流法直接检测非电话性气体二氧化碳

基于非电活性气体ＣＯ２在‘二甲亚砜／铂微电极’体系中定量的电还原反应，提出微电流法常温直接检测二氧化碳，在常规气敏微有和硅一体化薄膜微电极器件上获得了满意的气敏响应特性：好的线性响应关系、娄敏度和响应速度。     

C60微电极伏安法研究

自从1990年用电弧法成功地制备出宏观量的C60和C70以来，富勒烯的电化学研究有了迅速的发展．理论研究指出，在一个C60簇化合物中，有六个吡喃环烯单元，可分别得到一个电子使五元环芳香化，从而形成C（n＝1～6）阴离子．Haufler首先报导了C60可逆的两步单电子还原，之后一些作者陆续得到了三步、四步和五步单电子电还原过程．直到达1992年，在使用混合溶剂并控制低温-10℃至5℃和-88℃至60℃条件下，才得到了C60的六步电还原伏安图．富勒烯的微电极伏安法的研究极少见报导．杨汉西等用铂微电极得到了C60三步电还原的稳态伏安图．本文在…     

纳米Al_2O_3颗粒对镍电结晶过程的影响

借助循环伏安(CV)和计时安培(CA)研究了在不同电位下,纳米Al2O3微粒对镍由硫酸盐混合溶液在铜基底上电结晶沉积的影响.结果表明,Ni-Al2O3镀液体系电沉积的起始电位约为-740 mV.随着阶跃电位负移,Ni-Al2O3镀液体系电沉积成核时间tm逐渐缩短.与纯Ni镀液体系电沉积的tm相比,在-740~-830mV较低阶跃电位下,Ni-Al2O3镀液体系电沉积的成核时间tm明显缩短,表明Al2O3微粒有助于镍的电结晶成核.在-890 mV阶跃电位下,Ni-Al2O3镀液体系电沉积初始阶段的成核过程满足Scharifker-Hills三维瞬时成核模型.     

n型半导体硅电极表面Au的电化学成核机理

在成功实现半导体硅表面电沉积致密金膜的柠檬酸盐镀金实际应用体系中,运用循环伏安和电位阶跃法研究了Au在n型Si(111)电极表面的电沉积过程和成核机理.结果表明,在该体系中, Au在Si表面呈现不可逆电极过程,成核过电位达到250 mV;根据Cottrell方程求得扩散系数D = (1.81 ± 0.14) × 10^-4 cm₂·s^-1;运用Scharifker-Hills (SH)理论模型对比分析拟合实验结果,表明Au在n型Si表面遵循扩散控制下的三维连续成核机理;通过扫描电子显微镜观察Au初期成核、生长形貌,进一步证实了Au的三维连续成核机制,并讨论了阶跃电位和阶跃时间对Au核形貌和密度的影响.     

Microelectrode Studies on the Pitting Corrosion Process of Stainless Steel

应用微电极法研究不锈钢点腐蚀发生发展过程，首次获得不锈钢夹杂物缺陷在阳极活化电位的活性溶解信息和点腐蚀发展过程蚀点生长和消止两个相互竞争、不断发展的动态行为，深化对夹杂物缺陷诱导点腐蚀的发生及点腐蚀发展过程机理的认识。实验表明，应用微电极技术研究点腐蚀过程可具有若干明显特点：ａ．由于界面双层电容和背景电流的大幅度降低，有利于检测点腐蚀发生和发展过程快速、信号微弱；ｂ．可考察夹杂物缺陷的电化学活性及其诱导点腐蚀成核的重要作用；ｃ．可研究单孔点腐蚀发展的动态行为及影响因素。     

碳化钨在对硝基苯酚电还原过程中的电催化行为

以碳化钨(WC)粉末为电催化材料制成了碳化钨粉末微电极(WC-PME). 采用循环伏安和线性扫描等方法研究了酸性溶液中对硝基苯酚(PNP)在WC-PME上的电还原行为. 研究表明, 在相同测试条件下, PNP在WC-PME上电还原的电位比Cu-Hg微电极正得多；WC-PME对氢具有较强的吸附能力, 有利于有机物的电还原反应. PNP在WC-PME上和Pt微电极上的还原电位相近, 但在WC-PME上的峰电流比在Pt微电极上高5倍多, 这主要与WC粉末的结构形貌有关.     

微电流法直接检测非电活性气体二氧化碳

基于非电活性气体CO_2在‘二甲亚砜/铂微电极’体系中定量的电还原反应,提出微电流法常温直接检测二氧化碳.在常规气敏微电极和硅一体化薄膜微电极器件上获得了满意的气敏响应特性:好的线性响应关系、灵敏度和响应速度.用硅微机械加工技术批量构制的薄膜微电极器件,既保持了微电极的全部优点,又实现了微电流器件结构的一体化,电流响应异常稳定和重现.     

Electrochemical Behavior of Copper in CuCI2 Silica Sol and Aqueous Solutions

采用循环伏安法和计时安培法研究了CuCl2硅溶胶和水溶液中铜在玻碳电极上的电沉积和电结晶行为．结果表明在两种CuCl2电解质中，铜的电沉积分两个步骤完成，Cu^2＋还原为Cu^＋在硅溶胶中较水溶液中容易；采用吸附一成核模型解析电流一时间暂态曲线，并确定铜的电结晶机理为扩散控制下的连续成核三维生长（3DP），Cu^2＋在水溶液中的扩散系数较硅溶胶中的大，但相同电位下在硅溶胶中的饱和成核数密度高于水溶液中．     

圆盘微电极的卷积和交流伏安行为

研究了可逆氧化还原对(以二茂铁为例)在圆盘微铂电极上的卷积法,包括一阶导数卷积(e),二阶导数卷积(e′),三阶导数卷积(e″)的行为.结果表明,在微电极上的 e-E曲线类似于常规电极的循环伏安曲线。e、e′和e″曲线的峰高与扫速幂次的关系与悬汞电极上的规律相符,但其值分别为0.5、1.5、2.5.还研究了微电极的交流伏安行为,得到铁氰化钾的特征电位值。     

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.     

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.     

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.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.