CdTe量子点修饰电极的阳极电致化学发光

制备了CdTe量子点/Nafion修饰玻碳电极(CdTe QDs/Nafion/GCE),并研究了该修饰电极在中性磷酸盐缓冲溶液(PBS)中的电致化学发光(ECL)行为。结果表明,三丙胺(TPA)作为共反应剂存在时,QDs/Nafion/GCE在中性PBS中可以产生强的阳极电化学发光信号。考察了量子点的用量、Nafion的用量、pH、电解质等条件对ECL的影响。抗坏血酸对QDs/Nafion/GCE的ECL具有抑制作用,且抑制程度与抗坏血酸浓度呈线性关系,为利用电致化学发光法检测抗坏血酸提供了新方法。     

硅量子点为共反应剂的联吡啶钌电致化学发光研究及对多巴胺的检测

利用水热法合成了水溶性硅量子点(SiQDs),并探究了联呲啶钌(Ru(bpy)23-)在硅量子点修饰玻碳电极(SiQDs/GCE)上的电致化学发光(ECL)行为.结果表明,在中性条件下,SiQDs能够作为共反应剂明显增强Ru(bpy)32+的阳极ECL信号.研究了SiQDs修饰量、缓冲溶液pH等因素对该体系ECL信号的...     

肌红蛋白在Nafion/Fe3O4- CdTe/CdS量子点复合膜内的直接电化学及其应用于H2O2的生物传感

利用磁性纳米Fe3O4和CdTe/CdS量子点结合Nafion的良好成膜性,将肌红蛋白(Mb)固定在玻碳 电极表面制备成Nafion/Fe3O4 - CdTe/CdS - Mb/GCE修饰电极.在pH 7.0的0.1 mol/L磷酸盐缓冲溶液 (PBS)中,固定在膜内的Mb表现出良好的直接电化学性质,在-0.351...     

磁性量子点电致化学发光法测定李氏禾提取液中的过氧化氢

利用巯基乙酸水热法合成出表面修饰—COOH的CdTe量子点,并将CdTe量子点(QDs)连接在Fe3O4纳米粒子表面,制备出CdTe/Fe3O4磁性量子点。通过磁力将磁性量子点修饰于石墨电极表面。在pH7.5的PBS缓冲溶液中,H2O2可使CdTe量子点产生电致化学发光,H2O2浓度在4～100μmol/L范围内与CdTe量子点的电致化学发光强度呈良好的线性关系,检出限为0.24μmol/L。据此建立了测定样品中过氧化氢含量的电致化学发光分析法,并成功地应用于李氏禾草汁原液中过氧化氢含量的测定。该研究借助纳米Fe3O4的磁力特征,使敏感膜易于形成和更新分离,简化了实验操作,同时起到增强发光强度的作用。     

南京大学鞠熀先研究组近期的研究成果介绍

量子点的电致化学发光(ECL)技术集成了发光分析的高灵敏度和电化学分析的电位可控性的优点,已成为分析化学工作者十分感兴趣的研究领域之一。最近,南京大学生命分析化学教育部重点实验室鞠熀先研究组对量子点的阴极和阳极ECL性质进行了深入地研究,探讨了发光机理,并成功地将其应用于生物分析和实际样品的检测。图1裸电极和QDs膜修饰石墨充蜡电极在氧气饱和的磷酸缓冲溶液(pH7.0)中的循环伏安(a,b)和ECL(c,d)曲线该研究组于2004年提出第一支量子点水相电致化学发光传感器,并用于H2O2检测(Anal.Chem.2004,76:6871~6876)。通过构建仿生…     

金纳米球/氮掺杂石墨烯量子点固载Ru(bpy)3^2+电致化学发光法检测邻苯二酚

利用还原法制得金纳米球(Au NPs),与氮掺杂石墨烯量子点(NG QDs)杂化后,再以壳聚糖胶黏剂并通过静电作用使Ru(bpy)3^2+负载于其表面形成复合膜,制备了一种新型的固相电致化学发光(ECL)传感器。研究发现,与单一材料相比,Au NPs和NG QDs杂化复合材料作为载体显著提高了发光试剂Ru(bpy)3^2+的ECL信号。根据环境污染物邻苯二酚对该修饰电极ECL信号较强的阻抑作用,建立了测定领苯二酚的新体系。结果表明,Au NPs/NG QDs/Ru(bpy)3^2+修饰电极的ECL信号变化值与邻苯二酚的浓度负对数在5.0 nmol/L^10μmol/L之间呈良好的线性关系,检出限为3.0 nmol/L(r=0.9992)。对5.0μmol/L的邻苯二酚进行10次重复测定,相对标准偏差为4.6%,常见的共存物质不干扰测定,表明该方法的选择性较好。采用该修饰电极成功测定了河水中的邻苯二酚含量。     

基于血红蛋白/硒化镉量子点多层膜的H2O2生物传感器

合成了水溶性硒化镉(CdSe)量子点,利用组装技术和静电吸附作用,将带正电荷的血红蛋白(Hb)和带负电荷的CdSe量子点层层组装到壳聚糖(chit)修饰的玻碳电极(GCE)表面,构建基于{Hb/CdSe}n多层膜的无电子媒介体的电流型生物传感器({Hb/CdSe}3/chit/GCE).运用紫外-可见吸收光谱、电致化学发光、交流阻抗和循环伏安技术来表征修饰膜,并研究传感器的作用机理、性能及分析应用.结果表明:与量子点薄膜法及量子点/血红蛋白复合物法等固载血红蛋白的其他方法相比,层层组装法能显著提高血红蛋白的固定量,保持血红蛋白的生物活性,增强传感器的灵敏度和稳定性.传感器检测H2O2的线性范围为4.0×10-8～4.8×10-6 mol·L-1(r=0.999 1),检测限为2.0×10-8mol·L-l.多层膜的电致化学发光研究,表明修饰电极有望用于电致化学发光传感器的制备.     

氮掺杂石墨烯量子点/Ru(bpy)_3~(2+)体系电致化学发光法检测邻苯二酚

采用简单的方法合成了氮掺杂石墨烯量子点(NG QDs),并分别用荧光光谱仪和透射电子显微镜进行了表征。研究了NG QDs对Ru(bpy)_3~(2+)电致化学发光(ECL)体系的增敏作用。实验优化了体系pH、Ru(bpy)_3~(2+)用量、NG QDs用量以及扫速等条件。在最优条件下,根据邻苯二酚对NG QDs/Ru(bpy)_3~(2+)耦合ECL体系信号的猝灭作用,建立了测定邻苯二酚的新方法。邻苯二酚浓度(1.0×10~(-8)～1.0×10~(-5) mol/L)的对数值与ECL信号强度差之间呈线性关系,检测限低至5.0×10~(-9) mol/L,而且选择性和重现性好,实际样品检测结果令人满意。     

基于L-半胱氨酸/CdTe量子点修饰电极的电化学传感器的制备及其对Pb~(2+)的检测

成功制备了由L-半胱氨酸和CdTe量子点作为修饰材料的电化学传感器并用于水体中Pb~(2+)的检测。巯基丙酸修饰的CdTe量子点通过水相合成,表面含有大量羧基,与L-半胱氨酸表面的氨基形成酰胺键,修饰于金电极表面。通过荧光分光光度计、透射电子显微镜、红外光谱、X射线衍射对L-Cys/CdTe QDs复合材料进行表征。采用循环伏安法(CV)研究了L-Cys/CdTe QDs修饰成分在金电极上的电化学性能及CdTe量子点的最佳自组装时间。采用差分脉冲溶出伏安法(DPSV)研究了铅离子在修饰电极上的电化学行为。在优化实验条件下,Pb~(2+)浓度在1.0×10~(-6)~1.0×10~(-2) mol/L范围内与其峰电流呈良好的线性关系,相关系数(r2)为0.993 8,检出限(3σ,n=5)为4.0×10~(-7) mol/L。该传感器具有良好的重现性和稳定性,有望用于实际水样中铅离子的检测。     

构建新型固相电致化学发光传感界面用于检测三丙胺

通过静电作用将带正电的Ru(bpy)23+和带负电的纳米铂制备成铂钌纳米复合物(Ru-PtNPs),并将其滴涂在Nafion分散的多壁碳纳米管(MWCNTs-Nafion)复合膜修饰的玻碳电极上,制备了一种新的基于联吡啶钌的固相电致化学发光(ECL)传感器。利用扫描电镜以及电致化学发光的方法对传感界面进行表征。实验结果表明,通过此种方式可将大量的发光试剂Ru(bpy)23+固载到电极表面,并对三丙胺(TPA)保持良好的电催化活性,Ru-PtNPs/MWCNTs-Nafion修饰电极在0.1 mol.L-1磷酸盐缓冲溶液(PBS,pH 7.4)中对TPA的响应有很好的灵敏度和稳定性,线性范围为6.67×10-7～1.00×10-3mol·L-1,检出限(S/N=3)为3.3×10-7 mol·L-1。     

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.     

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).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.