硼氢化钾还原-原子荧光光谱法研究纳米TiO2对Hg(Ⅱ)的吸附行为

以硼氢化钾还原-原子荧光光谱法(KBH4-AFS)为检测手段，研究了纳米TiO2(锐钛型)对Hg(Ⅱ)的吸附行为，考察了影响吸附和解脱的主要因素，并考察了共存离子的干扰影响。在较宽的pH范围内，纳米TiO2对汞具有良好的吸附性能。在优化的实验条件下，具有吸附容量较大和吸附速度较快的特点，该法测定汞的检出限为0．004ng/mL，相对标准偏差(RSD)为3．3％(n=9，ρ=0．05ng/mL)。将本法应用于标准样品GSS-8、GSS-4的测定，其测定值与标准值吻合。已应用于实际水样中汞的测定。     

氨基酸离子液体与碳纳米管协同作用下的葡萄糖氧化酶直接电化学

氨基酸离子液体（AAILs）由于其独特的化学和物理特性,特别是它突出的生物相容性和优异的绿色特性,已经引起了广泛的关注．本文设计了一种新型的基于氨基酸离子液体和碳纳米管（CNTs）复合物的电化学传感界面．其中,氨基酸离子液体被用作一种新型的葡萄糖氧化酶（GOD）溶剂．通过将碳纳米管修饰的玻碳（OC）电极浸泡在含有葡萄糖氧化酶的氨基酸离子液体溶液中,就可以方便的获得GOD—AAILs／CNTs／GC电极．我们研究了葡萄糖氧化酶在GOD．AAILs／CNTs／GC电极上的直接电化学,获得了一对可逆的氧化还原峰．同时固定在电极上的葡萄糖氧化酶仍然保持了它们的生物活性以及催化溶解氧还原的能力．在氨基酸离子液体和碳纳米管的协同作用下,该GOD．AAILs／cNTs／Gc电极展现了对葡萄糖良好的电催化活性,其检测线性范围为0．05～0．8mmol／L,检测限为5．5μmol／L（S／N=3）．尤其该传感器显示了良好的稳定性以及排除常见共存物尿酸和抗坏血酸干扰的能力．因此,对于氧化还原酶的直接电化学以及第三代酶传感器的制作来说,AAILs／CNTs复合物将会成为一种很好的生物相容性材料．     

用于示踪分析的固体汞合金电极线性扫描伏安法测痕量钼

研究了可用于示踪分析测定痕量钼的固体银汞合金电极催化伏安法.在H2SO4-苯羟乙酸-氯酸钾体系中,采用该电极于-0.165V(vs.SCE)处出现灵敏的还原峰,Mo的质量浓度在0～200 ng/mL范围内与峰高呈良好线性关系,检出限为0.42 ng/mL.该方法操作简便、快速,同时又可避免传统汞电极使用中带来的不便和毒性.对实际水样进行了测定.     

微波消解-氢化物发生原子荧光光谱法同时测定化肥中砷、汞含量

采用微波消解样品前处理手段以及双道原子荧光光度计,建立了微波消解一氢化物发生原子荧光光谱法同时测定化肥中砷、汞含量的方法。通过试验确定了样品前处理方法,对负高压、灯电流,载气、屏蔽气、原子化器高度、酸度等测试条件进行了优化。在优化的工作条件下,砷、汞含量分别在0-50ng／mL和0—1．0ng／mL范围内与荧光强度呈良好的线性关系,线性相关系数分别为0．9996,0．9996,检出限分别为0．085,0．008ng／mL,回收率分别为88．8％～107．4％,90．0％～120％,测定结果的相对标准偏差均小于7％（n=6）。     

汞(Ⅱ)-硫氰酸盐-维多利亚蓝4R体系的共振发光和二级散射光谱及其分析应用

研究了[Hg(SCN)₄]^-配阴离子与维多利亚蓝4R(VB4R)离子缔合反应体系的共振发光(RL)、二级散射(DS)和反二级散射(ADS)光谱,考察了它们的光谱特征、影响因素和适宜的反应条件。研究了RL、ADS和DS强度与汞(Ⅱ)浓度之间的定量关系;提出了用RL、ADS光谱测定痕量汞的方法。对汞(Ⅱ)的检测限分别为1.33ng/mL和1.83ng/mL,可用于水中μg/L级汞的测定,并对有关机理进行了初步的探讨。     

掺杂纳米普鲁士蓝溶胶-凝胶修饰葡萄糖生物传感器

采用溶胶-凝胶法制备了纳米普鲁士蓝微粒,将含纳米普鲁士蓝微粒的TiO2溶胶-凝胶固定在玻碳电极表面得到纳米普鲁士蓝修饰电极,该电极对H2O2产生灵敏的响应,线性范围为0．5～400μmoL／L,较常规普鲁士蓝修饰电极(线性范围为25～500μmol／L)灵敏。电极表面再用溶胶．凝胶法固定葡萄糖氧化酶后构建了葡萄糖生物传感器,响应范围0～20mmoL／L,葡萄糖氧化酶表观米氏常数为8．04mmoL／L。实验表明,该法适合于批量制作高灵敏和高重现性的生物传感器。     

基于胸腺嘧啶碱基错配的汞离子传感器研究进展

基于汞离子和胸腺嘧啶的质子取代反应,可形成T-Hg(Ⅱ)-T碱基错配结构,该结构可作为新型汞离子传感器的良好识别元件。相较于传统汞离子检测方法在效率与精度上的不足,以T-Hg(Ⅱ)-T碱基错配结构为识别基团的新型汞离子传感器具有一定优势。该文综述了以T-Hg(Ⅱ)-T结构为识别基团,以不同类型报告基团为基础的汞离子传感器的研究进展与趋势,从而为后续汞离子传感器的开发提供参考。     

催化光度法测定痕量钴的研究

研究了钴 (Ⅱ )离子在碱性介质中催化H2 O2 氧化 2 ,2′ 二甲基 4 ,4′ 二氨基联苯 (o Tolidine)的显色反应 ,发现当Co2 +浓度在 0 8～ 3 6ng mL时具有强烈的催化显色作用 ,而当Co2 +浓度在 0 0 4～0 2 4 μg mL时则对显色作用具有抑制效应。基于此研究了测定痕量Co(Ⅱ )离子的影响因素 ,建立了测定痕量Co2 +离子的催化光度法。测定的线性范围Co(Ⅱ )的浓度在 0 0 4～ 0 2 4 μg mL时 ,灵敏度为 3 1 6× 1 0 -6g L ;Co(Ⅱ ) 0 8～ 3 6ng mL时 ,灵敏度为 1 78× 1 0 -6g L。实验操作简便 ,应用于工业污水中痕量Co2 +离子的监测 ,结果满意。     

镉-向红菲啰啉体系吸附伏安法测定镉

在pH＝4.1的0．03mol／L邻苯二甲酸氢钾介质中，Cd（Ⅱ）-向红菲啉络合物于悬汞电极上在-0．65V（vs．SCE）电位处产生一灵敏的吸附还原峰，利用1．5次微分技术进行测定，络合物波峰峰值epp与Cd（Ⅱ）浓度在1．0×10－9～1．0×10－7mol／L范围内呈良好的线性关系，检出下限为7×10－10mol／LCd（Ⅱ），本文详细研究了测定镉的最佳条件，对络合物在汞电极上的电化学行为进行了初步探讨。方法用于环境水样中微量镉的测定，结果令人满意。     

双向溶出伏安法同时检测金和铜

本文首次提出双向溶出伏安法 ,并将该方法用于同时检测水溶液中的Au(Ⅲ )和Cu(Ⅱ ) .采用细菌修饰的碳糊电极做工作电极 ,于阳极富集 ,阴极溶出测定Au(Ⅲ ) ,同时在碳糊电极上再修饰上一层超细微粒金膜 .然后 ,在金电极上进行阴极富集 ,阳极溶出检测Cu(Ⅱ ) .该法仪器设备简单、操作简便 .Au(Ⅲ )与Cu(Ⅱ )的检测信号分别在阴极、阳极两个方向显示 ,分辨率高 .Au(Ⅲ )在 0 .2～ 1μg/mL、Cu(Ⅱ )在 2～ 10ng/mL浓度范围内 ,均有良好线性关系 ,其检测限依次为 2 0ng/mL和 0 .5ng/mL ,8次平行测定RSD小于 3%     

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.     

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.     

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.     

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.     

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.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.