石墨烯-二氧化锰-离子液体修饰玻碳电极同时测定尿液中尿酸、抗坏血酸、黄嘌呤

采用滴涂法将石墨烯-二氧化锰分散液于玻碳电极上,然后利用循环伏安法将1-辛基-3-甲基咪唑六氟磷酸盐修饰,制得石墨烯-二氧化锰-离子液体修饰电极。研究了修饰电极对尿酸、抗坏血酸和黄嘌呤混合物电化学行为,实验结果表明,在pH 5. 0的0. 2 mol/L的磷酸缓冲溶液中,尿酸、抗坏血酸和黄嘌呤在修饰电极上有较好的电化学行为,3种分析物浓度分别在0. 5～45μmol/L,2. 5～25μmol/L,1. 0～100μmol/L范围内呈良好的线性关系,检出限分别为0. 031,1. 1,0. 21μmol/L。方法用于人体尿液中3种分析物同时检测,其RSDs均小于4. 7%,回收率分别为93. 6%～95. 3%,73. 0%～82. 0%,80. 0%～81. 8%。     

碳量子点/纳米金@碳纳米管修饰电极同时检测鸟嘌呤和腺嘌呤

制备了一种碳量子点(CQDs)/金纳米颗粒(AuNPs)@羟基化多壁碳纳米管(MWCNT-OHs)复合膜修饰电极用于鸟嘌呤(GA)和腺嘌呤(AE)的同时检测.与裸电极和其它修饰电极相比,复合膜修饰电极能显著提高GA和AE的氧化峰电流及峰电位差,能够对GA和AE同时高灵敏检测.研究了GA和AE在复合膜修饰电极上的电化学行为,结果表明,在0.2 mol/L PBS(pH 7.0)中,GA和AE的氧化峰电流与浓度分别在1～200 μmol/L和2～80μmol/L范围内呈良好的线性关系,检测限分别为0.9和1.8 μmol/L.将该修饰电极用于人体血清样品中GA和AE的同时电化学检测,加标回收率在90.4％～107.4％之间,证明了该修饰电极在生物样品分析领域的应用潜力.     

碳纳米管/对氯四苯基锰卟啉修饰电极同时测定二羟基苯异构体

制备了碳纳米管/对氯四苯基锰卟啉修饰的玻碳电极,研究了三种二羟基苯异构体在该修饰电极上的电化学行为。由于碳纳米管独特的性能及与对氯四苯基锰卟啉特殊的协同效应,异构体在该修饰电极上的氧化峰电流均显著增大。利用差分脉冲伏安法(DPV)可同时检测三种异构体,在pH=6.5的磷酸盐缓冲溶液(PBS)中,邻苯二酚(CC)、间苯二酚(RC)、对苯二酚(HQ)峰电流与其浓度分别在0.8～280.0μmol/L、1.5～85.0μmol/L和0.4～200.0μmol/L范围内呈良好的线性关系,其检出限分别为0.5μmol/L、1.0μmol/L和0.2μmol/L。该电极具有良好重现性和稳定性。     

基于CeO2/ERGO/SiO2复合膜修饰电极的制备及应用

采用三步化学合成法制备了二氧化铈/还原氧化石墨烯/二氧化硅球(CeO_2/ERGO/SiO_2)复合纳米粒子,用X-射线粉末衍射(XRD)技术对其进行了表征,并用于修饰电极(CeO_2/ERGO/SiO_2/CPE)的制备,研究了修饰电极的电化学行为及其对苯酚的电催化活性。在最优实验条件下,苯酚的浓度在0. 2～143μmol/L范围内,与峰电流呈良好的线性关系,线性方程为i(μA)=-4. 00 c(μmol/L)-16. 77,检出限为0. 1μmol/L。方法用于实际样品延河水中苯酚含量的测定,样品回收率在97. 0%～102. 8%之间。     

TiO2-石墨烯-Nafion复合膜修饰玻碳电极同时测定多巴胺和尿酸

利用在玻碳电极上修饰了TiO2-石墨烯-Nafion复合膜制得的修饰电极进行多巴胺(DA)和尿酸(UA)的同时测定。用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了该修饰电极的电化学行为。在pH为7.0的磷酸盐缓冲液(PBS)中,修饰电极对于DA和UA的电化学氧化具有良好的电催化性能。DA和UA的氧化峰电流分别在2～120和60～300μmol/L浓度范围内呈良好的线性关系,检出限分别为0.066和0.102μmol/L。实验结果表明,TiO2-石墨烯-Nafion复合膜修饰电极显著提高了检测的灵敏度,并表现出良好的选择性和重现性。     

多壁碳纳米管修饰玻碳电极伏安法测定香草醛

制备了羧基化多壁碳纳米管修饰玻碳电极(c-MWCNTs/GCE),采用循环伏安法在0.5 mol/L HCl中研究了食品添加剂香草醛的电化学行为。结果显示,该修饰电极对香草醛的电化学氧化具有良好的电催化作用,与裸玻碳电极相比电流响应显著增强。香草醛在该修饰电极上的氧化为不可逆的扩散控制过程。在最佳条件下,采用二阶导数线性扫描伏安法进行测定,香草醛的氧化峰电流与其浓度在0.1～6.0μmol/L和6.0～100μmol/L范围内呈良好的线性关系,检出限(S/N=3)为0.02μmol/L。该修饰电极具有良好的重现性(RSD=4.6%)和稳定性。方法应用于食品中香草醛的测定,回收率为96.3%～104%。     

纳米金/Nafion/石墨烯修饰玻碳电极检测对苯二酚的研究

采用一步电化学共还原的方法将纳米金(AuNPs)、Nafion、电化学还原石墨烯(ERGO)修饰到玻碳电极(GCE)表面,制成修饰电极AuNPs/Nafion/ERGO/GCE。以扫描电镜对其进行表征,用循环伏安法和微分脉冲伏安法研究对苯二酚在该修饰电极上的电催化行为。优化了实验参数,对苯二酚在2.0～100μmol/L及100～800μmol/L浓度范围内与其氧化峰电流呈良好的线性关系,检出限为0.3μmol/L。用该修饰电极成功地进行了实际水样中对苯二酚含量的测定。     

金纳米粒子/碳纳米管修饰电极对4 壬基酚的电催化氧化及检测研究

制备了金纳米粒子/碳纳米管修饰玻碳电极(AuNPs-CNTs/GCE),采用循环伏安法和线性扫描伏安法研究了4-壬基酚在修饰电极上的电化学行为,并建立了一种灵敏简便地检测4-壬基酚的电化学方法。优化了pH值、扫描速率、富集时间等测定参数,并计算出pH值与氧化峰电压、扫描速率与氧化峰电流之间的数量关系。在pH 10.0的BR缓冲溶液中,4-壬基酚在AuNPs-CNTs/GCE上出现灵敏的氧化峰,氧化电位为0.51 V。与裸玻碳电极(GCE)和单一碳纳米管修饰电极(CNTs/GCE)相比,AuNPs-CNTs/GCE明显提高了4-壬基酚的氧化电流。在优化实验条件下,4-壬基酚的浓度分别在0.05～4μmol/L和6～14μmol/L范围内与氧化峰电流呈良好的线性关系,检出限为0.023μmol/L,对于实际样品测定的回收率为95%～104%。该修饰电极具有良好的重现性和稳定性,可用于环境样品中4-壬基酚的直接检测。     

对硫磷在纳米氧化铝薄膜修饰电极上的电化学行为及其测定

制备了纳米氧化铝修饰玻碳电极(nano-Al2O3/GCE/CME),用循环伏安法(CV)、线性扫描伏安法(LSV)研究了对硫磷(TP)在nano-Al2O3/GCE/CME上的电化学行为.实验表明,该修饰电极与裸电极相比能显著提高TP的氧化还原峰电流并降低其氧化峰电位.在0.1 mol/L HAc-NaAc缓冲溶液(pH =5)中,TP在该修饰电极上产生1个不可逆的还原峰( Epc1=-0.567 V)和1对可逆氧化还原峰( Epa2=0.018 V和Epc2=-0.008 V) ,氧化峰电流与TP的浓度在2.5×10-9～1.0×10-7 mol/L和1.0×10-7～1.0×10-5 mol/L范围内具有良好的线性关系,回归方程分别为: ip(μA)=0.2529+4.201C(μmol/L), r=0.9984和ip(μA)=0.6752+0.3181C(μmol/L), r=0.9946.开路富集30 s后,检出限为1.0 ×10-9 mol/L(S/N=3).在1.0×10-5 mol/L TP试液中连续测定10次,其RSD为3.8%.用此方法测定了蔬菜中TP的含量,回收率为95. 6%～100.5% ,结果满意.     

共价有机骨架材料修饰碳糊电极电化学检测铜离子

利用溶剂热反应合成共价有机骨架材料TpBD-COF，通过扫描电子显微镜和红外光谱表征其形貌和结构。按照一定比例将石墨粉、 TpBD-COF、离子液体(BPPF6)和石蜡油混合研磨，制备COF-2-BPPF6-CPE碳糊电极，采用循环伏安法(CV)和差分脉冲伏安法(DPV)评估修饰电极的电化学性能。在pH 3.50的邻苯二甲酸氢钾缓冲溶液中，Cu²⁺在修饰电极上有灵敏的电流响应。COF修饰碳糊电极对Cu²⁺有更高的峰电流，且峰电流与Cu²⁺浓度在1～200μmol/L呈线性关系(R2=0.9997)，检出限为0.13μmol/L。利用该修饰电极，采用标准加入法对水样中的Cu²⁺进行测定，回收率为100.6%～101.2%，表明其可用于检测水体中的Cu²⁺。     

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%.     

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.     

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.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.