碳纳米管修饰电极对多巴胺和肾上腺素的电分离及同时测定

研究了多巴胺 (DA)和肾上腺素 (EP)在多壁碳纳米管 (MWNT)修饰电极上的电化学性质 ,发现该修饰电极对神经递质DA和EP有显著的增敏和电分离作用。还原峰电位差达ΔEp=390mV ,可同时测定DA和EP。DA和EP的还原峰电流与其浓度分别在 2 .0× 10 -6～ 1.0× 10 -3 mol/L和 1.0× 10 -6～ 1.0× 10 -3 mol/L浓度范围内呈良好的线性关系 ;方法的检出限分别为 1× 10 -6mol/L和 5× 10 -7mol/L。由于抗坏血酸 (AA)在MWNT修饰电极上的氧化是不可逆的 ,因此利用还原峰进行测定 ,消除了AA对DA和EP的干扰     

玻碳电极的阳极化预处理及其分析应用

本文研究了玻碳电极(GCE)循环伏安扫描预处理及其应用。阳极化预处理的电极对多巴胺(DA)具有良好的电催化活性,显著增强DA的电流响应。与裸GCE相比,此电极上DA的氧化峰电位负移了350mV、还原峰电位正移了300mV。在最佳条件下,DA浓度在4.1×10-7～1.0×10-5mol/L之间呈良好的线性关系,相关系数为0.9989,检出限为1.0×10-7mol/L。该电极制作简便,稳定性好。     

羧基化碳纳米管嵌入石墨修饰电极对多巴胺和抗坏血酸的电催化

采用涂层和嵌入修饰法 ,将羧基化多层碳纳米管制成两种修饰电极。以多巴胺 (DA)和抗坏血酸(AA)为模型化合物 ,研究了两种修饰电极对DA和AA共存时的电催化作用。结果表明 :嵌入的方式比涂层的方式显示了更多的优点。嵌入修饰电极不仅使峰电流增加 ,并且使两者共存时的氧化峰位分离达 16 0mV ,同时 ,该电极对DA的响应灵敏于AA ,这有利于在大量的AA存在下实现对DA的测定。在 1× 10 - 3 mol/L的AA的存在下 ,还原电流的一阶导数与DA浓度在 5× 10 - 7～ 1× 10 - 4 mol/L范围内呈良好的线性关系 ;检测下限达 1× 10 - 7mol L。     

聚L-谷氨酸/石墨充蜡修饰电极测定多巴胺

用充蜡石墨电极 (WGE)在L 谷氨酸 (GA)无水乙醇溶液中恒电位于 1.6V(vs.SCE)氧化制备了一种聚GA修饰电极 (GA/WGE) ,该电极可用于肾上腺素 (EP)和抗坏血酸 (AA)共存下对多巴胺 (DA)的测定。该电极的灵敏度和选择性主要取决于阳极极化电位与极化时间、富集电位和溶液的pH。DA在该电极上呈现一对循环伏安峰 ,Em=0 .14 5V ,为 1电子 / 1质子的准可逆氧化还原过程。AA和EP也能够在电极上富集和催化氧化 ,伏安峰分别在 0 .30V和 0 .17V。当AA浓度小于 0 .1mmol/L时 ,电极对AA基本不响应 ,可以用DA的氧化峰电流做定量分析。线性范围为 2 .0× 10 -4～ 5 .0× 10 -7mol/L ;检出限为 2 .5× 10 -7mol/L。当AA的浓度较大或在AA、EP共存下 ,可利用DA氧化的再还原峰电流做定量分析。线性范围为 1.0× 10 -4～ 2 .5× 10 -6mol/L ;检出限为 7.5× 10 -7mol/L。该电极制作简便 ,重现性良好 ,定量结果也令人满意     

聚对硝基苯偶氮间苯二酚修饰电极伏安法测定多巴胺

采用循环伏安法研究了多巴胺(DA)在聚对硝基苯偶氮间苯二酚(p-nitrobenzenazo resorcinol,简称NBAR)膜修饰电极上的电化学行为,用差示脉冲伏安法对多巴胺的含量进行测定.结果表明,聚NBAR膜修饰电极对DA有明显的电催化作用.在pH4.0的磷酸盐缓冲液中,氧化峰电流与DA浓度在5.0×10-6~8.0×10-4mol/L范围内呈良好的线性关系,检测限为6.0×10-7mol/L.修饰电极可有效消除针剂中其它组分对DA测定的干扰,已用于实际样品DA含量的测定,结果令人满意.     

2-巯基乙醇自组装膜电极对多巴胺电催化氧化及其分析应用

在裸金电极上制备了 2 巯基乙醇自组装膜电极 (ME AuSAMs) ,研究了多巴胺 (DA)在ME AuSAMs上的电化学行为 ,发现该膜电极对DA的氧化具有良好的电催化作用 ,氧化过电位降低了 3 94mV ,测得DA的扩散系数D为 9.1 4 5× 1 0 - 7cm2 s,初步探讨了电催化机理。采用水平衰减全反射 傅里叶变换红外光谱 (ATR FTIR)技术对ME AuSAMs进行了表征 ;方波伏安法 (squarewavevoltammetry ,SWV)测定DA ,其氧化峰电流与DA浓度在 2 .0 0× 1 0 - 6 ～ 1 .0 0× 1 0 - 4 mol L范围内呈线性关系 ;相关系数为 0 .9998,检出限为 4 .0 0× 1 0 - 7mol L。该电极用于DA药物针剂的测定 ,结果满意     

多巴胺在聚硫堇和Nafion双层修饰玻碳电极上的电化学行为

用电化学聚合法在玻碳电极上制备聚硫堇,然后涂渍一层Nafion膜,采用循环伏安法研究其制备和电化学性质。该电极峰电流与多巴胺(DA)在2.00×10-7~1.43×10-3mol/L浓度范围内呈良好的线性关系,检出限为6.67×10-8mol/L,相关系数为0.995。该修饰电极有效排除了抗坏血酸(AA)的干扰。并且具有良好的灵敏度、重现性、稳定性,可用于实际样品中DA的测定。     

多巴胺在聚钙羧酸膜修饰碳糊电极上的电催化及与尿酸的同时测定

采用循环伏安法(CV)制备了聚钙羧酸(PCCA)膜修饰的碳糊电极(CPE)。考察了电极对多巴胺(DA)、尿酸(UA)的电氧化催化性能。结果显示,聚钙羧酸膜修饰碳糊电极(PCCA/CPE)对DA有良好的电催化效果,DA呈现出一对准可逆的氧化还原峰,氧化峰电流与DA浓度在3.0×10-7～1.0×10-4mol/L范围内呈线性关系,检出限为1×10-7mol/L(S/N=3)。使用微分脉冲伏安法(DPV),DA和UA在PCCA/CPE上的氧化峰能完全分离(ΔEp=192 mV),且峰电流与浓度均呈现良好的线性关系,可实现对DA和UA的同时测定。实验还进行了实际样品测定。     

新型核酸电化学探针及动力学研究

通过电化学法研究了fsDNA影响下芹菜素在金电极上的电极行为,优化确定了fsDNA的检测条件。发现在4×10-7~7×10-6g/mL范围内峰电流的增强与加入的核酸浓度呈线性关系：ΔIp/(uA)=3.20501CfsDNA(10-5g/mL)+ 1.05969,检测限为5.77×10-8g/mL,对模拟样品的测定令人满意;研究还发现芹菜素发生了3e传递行为,并有质子参与,且该行为受到扩散控制。通过循环伏安、紫外-可见光谱等方法对API与fsDNA间的作用机制进行了初步探讨,结果表明二者之间存在着静电作用,结合常数K=1.77×104L/mol。     

甲基红-H2O2-HRP伏安酶联免疫分析法测定HRP及其标记物

提出了一种新的辣根过氧化物酶的底物-甲基红,它本身具有电化学活性,能够在静汞电极上发生还原反应,产生灵敏的伏安电流信号.以H2O2为氧化剂,HRP能催化氧化还原反应的发生,使甲基红被氧化分解,其平衡浓度降低,对应的还原峰电流降低,峰电流的降低值与HRP的质量浓度在5.0×10-8～5.0×10-7g/mL之间呈线性关系,对2.0×10-7g/mL HRP进行11次测定的相对标准偏差为4.6%,方法的检出限为1.8×10-8g/mL.应用于IgG-HRP和Avidin-HRP的测定.     

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%.     

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.     

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).