功能化石墨烯固定酪氨酸酶修饰电极的制备、表征及其对对苯二酚的测定

酪氨酸酶通过乙二胺作为悬臂分子稳定地固定到功能化氧化石墨烯上,再将该杂化材料修饰玻碳电极表面制成新型生物传感器。酪氨酸酶固定在氧化石墨烯上的物理化学行为通过X射线光电子光谱和电化学阻抗进行表征,显示功能化氧化石墨烯可以促进固定酶的活性位点与修饰电极之间的电子传递。通过循环伏安法研究该电极的直接电化学和电催化行为,表明其电化学行为是一个直接的吸附控制氧化还原反应。在优化实验条件下,对苯二酚在3.0~200.0μmol/L浓度范围内与其氧化峰电流呈良好的线性关系,检出限(S/N=3)达1.0μmol/L。该生物传感器显示了较好的重现性、稳定性及选择性,在实际水样检测中得到良好应用。     

血红蛋白在二维纳米金Langmuir—Blodgett单层膜修饰电极上的直接电化学

利用Langmuir-Blodgett(LB)技术在氧化铟锡(ITO)电极上制备了分散均匀的二维纳米金单层膜,并将血红蛋白(Hb)直接固定于该修饰电极表面,研究了Hb在电极上的直接电化学行为.实验结果表明:纳米金可以改善Hb和电极间的直接电子传递,提高电子传递效率.Hb/Nano-Au修饰电极在pH 5.0～9.0范围内的式电位与溶液pH呈线性关系,斜率为-57 mV/pH,说明Hb的电子传递过程伴随质子转移;该修饰电极对H2O2具有良好的催化作用,在0.1 mol/L pH 7.0 的磷酸盐缓冲溶液(PBS)中,H2O2在2.5×10-6～4.1×10-4 mol/L浓度范围内与响应电流呈良好的线性关系,检出限为6.2×10-7 mol/L;其异相电子转移速率常数为0.66 s-1,米氏常数为0.20 mmol/L.     

壳聚糖-纳米金-葡萄糖氧化酶生物传感器的制备及其应用于葡萄糖的测定

采用了一种简便快捷的电沉积方法制备了壳聚糖-纳米金复合膜并应用于葡萄糖生物传感器的构建.氯金酸和壳聚糖的混合液在玻碳电极表面电化学还原为金纳米粒子,再将葡萄糖氧化酶通过戊二醛交联的方式固定在纳米金复合膜修饰的玻碳电极表面,制成一种新型的葡萄糖氧化酶生物传感器.该传感器对葡萄糖的响应十分快速,在5 S内即达到平衡.测定葡萄糖的线性范围为20μmol·L-1～5 mmol·L-1,检出限(3S/N)为12μmol·L-1.     

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。     

纳米铂颗粒修饰薄膜金电极的新型葡萄糖传感器研究

在没有引入电子媒介体条件下,为了提高传感器的响应灵敏度,降低工作电位,利用电化学沉积法在薄膜金电极表面修饰纳米铂颗粒,并通过戊二醛固定酶的方法制备了一种新型生物传感器。研究了在薄膜金电极上修饰纳米铂颗粒前后传感器对低浓度葡萄糖的响应影响。结果表明,纳米铂颗粒修饰后所制备的葡萄糖传感器工作电位下降为0.4 V,测定葡萄糖的检出限从100μmol/L下降到10μmol/L。传感器对10~1300μmol/L低浓度葡萄糖的响应灵敏度为50.8 nA/(cm2μmol/L);响应时间30 s;r为0.9974;传感器精密度为2.1%,并具有较好的稳定性。     

细胞色素c在Fe_2O_3修饰电极上的直接电化学和电催化特性

采用全氟磺酸树脂Nafion将金属氧化物Fe2O3颗粒细胞色素c(Cyt c)固定玻碳电极(GCE)表面,制备了Nafion-Cyt c-Fe2O3修饰的玻碳电极,构建了基于直接电子传递的过氧化氢生物传感器。在0.10mol/L pH7.0的磷酸盐缓冲溶液中,修饰电极的循环伏安曲线上显示出一对准可逆的氧化还原峰,式量电位为22mV。Cyt c在修饰电极表面的异相电子转移速率常数为1.21s-1。修饰后的电极对过氧化氢有良好响应,响应时间小于10s,电极的安培响应与过氧化氢浓度在2.0×10-6～3.0×10-3mol/L范围内成线性关系,检出限为1.0×10-6mol/L,米氏常数为1.35mmol/L,显示出较好的亲和力。     

葡萄糖氧化酶在石墨烯-纳米氧化锌修饰玻碳电极上的直接电化学及对葡萄糖的生物传感

采用滴涂法和电沉积法制备了石墨烯/纳米氧化锌复合膜修饰玻碳电极,再将葡萄糖氧化酶固定在修饰电极表面制成了电化学生物传感器,用于葡萄糖的灵敏测定。用循环伏安法在-0.7～-0.1 V范围内研究了葡萄糖氧化酶在修饰电极上的直接电化学行为。结果表明,石墨烯/纳米氧化锌复合膜能很好地保持葡萄糖氧化酶的生物活性,并显著促进了其电化学过程。在0.1 mol/L磷酸盐缓冲溶液(pH 7.0)中,固定在修饰电极上的葡萄糖氧化酶呈现出一对近乎可逆的氧化还原峰,并且对葡萄糖的氧化具有良好的催化作用。葡萄糖氧化酶在修饰电极上的电子转移常数ks为1.42 s-1,修饰电极对葡萄糖催化的米氏常数Kampp为14.2μmol/L。线性范围为2.5×10-6～1.5×10-3mol/L,检出限为2.4×10-7mol/L(S/N=3)。此修饰电极具有良好的导电性能、稳定性和重现性,可用于实际样品的分析测定。     

四羧基酞菁钴(Ⅲ)/Fe3O4/金胶共固定修饰免疫传感器检测尿样中核基质蛋白22

同时固定四羧基酞菁钴Ⅲ(CoPc)和HRP标记核基质蛋白22抗体(HRP-Ab-NMP22)于自组装在金电极表面的Fe3O4/Au胶上,构建了一种快速测定膀胱肿瘤患者尿液中NMP22抗原(NMP22)含量的安培免疫传感器。CoPc可被用作电极表面HRP的电子传递媒介体。当该传感器在含NMP22尿样的溶液中温育后,NMP22与HRP-Ab-NMP22免疫结合导致HRP的活性中心与CoPc之间的电子传递部分阻碍,使HRP对H2O2电催化还原电流Io降低。ΔIo与NMP22浓度在1.2~200μg/L呈线性关系;检出限为0.5μg/L。该传感器对NMP22响应灵敏,较ELISA法提高了检测速度,有望用于膀胱肿瘤的体外诊断。     

电沉积纳米NiO_x无酶葡萄糖传感器的性能

利用电沉积法在ITO电极表面修饰了一薄层NiOx,通过循环伏安和计时电流等方法研究了该修饰电极的电化学特性。实验表明:该修饰电极对葡萄糖有良好的催化作用,对葡萄糖检测的线性范围为0.001~1.0 mmol/L,检出限为0.3μmol/L(S/N=3),灵敏度为65.26μA·(mmol/L)-1,响应时间为3 s。传感器可用于实际样品的测定。     

基于胱胺/壳聚糖/酶标纳米金自组装的的酪氨酶传感器的研制

通过自组装技术构制了一种简单有效的酪氨酸酶传感器。该法先通过戊二醛交联将壳聚糖固定在胱胺修饰的金丝电极上,进而通过氨基与纳米金的强力相互作用将酶标纳米金固定在壳聚糖层上。结果表明,酪氨酸酶能很好地保持其生物活性,所构制的传感器达到95%稳定状态电极的时间在15s以内。酚类化合物是通过酶催化产生的醌在-100mV(相对饱和甘汞电极)直接还原而测定的,传感器对邻苯二酚、苯酚、对甲基苯酚测定的灵敏度依次为2.216,4.828,4.885μA·μmol-1L.cm-2,检测限依次为0.32,0.60,0.18μmolL-1。二周后活性仍保持原有活性的75%。     

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%.     

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.     

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.     

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.     

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.