基于银纳米粒子/氧化石墨烯复合薄膜制备TNP电化学传感器

利用改进的Hummers法制备了氧化石墨烯(GO), 以葡萄糖为还原剂直接在GO表面沉积银纳米粒子(AgNPs)得到性能稳定的AgNPs/GO纳米复合材料;基于该纳米复合材料修饰电极构建了一种新型的2, 4, 6-三硝基苯酚(TNP)电化学传感器。采用原子力显微镜(AFM)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见光谱(UV-Vis)和交流阻抗(EIS)等多种方法对纳米复合薄膜进行了表征;并研究了TNP在复合薄膜修饰电极上的电化学行为和动力学性质。结果表明, AgNPs/GO对TNP有较强的电催化活性, 在复合薄膜修饰电极出现一灵敏的氧化峰和3个还原峰;利用氧化峰可对TNP进行定量分析。同时整个电极过程明显不可逆, 电极反应受到吸附步骤控制;复合膜电极表面覆盖度为5.617×10^-8 mol·cm^-2, 在所研究电位下的速率常数为9.745×10^-5 cm·s^-1。在pH 6.8的磷酸缓冲液中, 当富集电位为-0.70 V, 富集时间为60 s;TNP氧化峰电流与其浓度在5.0×10^-9~1.0×10^-7 mol·L^-1范围内成良好线性关系, 相关系数为0.995 8, 检出限可达1.0×10^-9 mol·L^-1。所制备的电化学传感器稳定性和选择性较好;用于实际水样中TNP的现场快速检测, 加标回收率在 97.6%~103.9%之间。     

基于氧化石墨烯/碳纳米管复合薄膜修饰电极制备L-色氨酸电化学传感器

将Hummers法制备的单层氧化石墨烯(GO)与多壁碳米管(MWCNT)超声混合,得到性能稳定的GO/MWCNT复合纳米材料。以此纳米材料修饰玻碳电极,构建了一种新型L-色氨酸(L-Trp)电化学传感器。采用透射电镜(TEM)、循环伏安(CV)和交流阻抗(EIS)等方法对修饰电极进行了表征;并研究了L-Trp在修饰电极上的电化学行为和动力学性质。结果表明,L-Trp在GO/MWCNT修饰电极有一个灵敏的氧化峰(Epa=0.956 V);该氧化反应是一个2电子和2质子参与的不可逆过程,电极过程受到吸附步骤控制,其表观标准速率常数为9.613×10-4cm/s;利用该氧化峰可进行痕量L-Trp的检测。在pH 6.0磷酸盐缓冲液中,当富集电位为0.600 V,富集时间为25 s,扫速为100 mV/s时,L-Trp氧化峰电流与其浓度在1.0×10-6～1.0×10-4mol/L范围内呈良好线关系,相关系数为0.995,检出限可达3.50×10-7mol/L;所制备的电化学传感器稳定性较好,用于人体血清中L-Trp的现场快速检测,加标回收率为97.8%～104.2%。     

纳米二氧化铈修饰碳糊电极线性扫描伏安法测定苯酚

在0.01mol.L-1硼砂溶液(pH 9.18)中,用纳米二氧化铈修饰碳糊电极作为工作电极,线性扫描伏安法测定苯酚。伏安图上出现一灵敏的氧化峰,其峰电位为+0.56V(vs.SCE),峰电流与苯酚的浓度在1.0×10-7～2.0×10-4 mol.L-1范围内呈线性关系,检出限(3s/k)为5.0×10-8 mol.L-1。富集时间为30s,同时采用线性扫描伏安法研究苯酚在纳米二氧化铈修饰碳糊电极上的氧化还原反应,结果表明此电极反应为一不可逆的吸附过程。     

介孔炭/纳米金修饰玻碳电极的制备及其应用研究

制备了介孔炭/纳米金修饰玻碳电极,并对对苯二酚(HQ)在该修饰电极上的电化学行为进行了研究。与HQ在纯介孔炭材料修饰玻碳电极上的电化学响应相比,HQ在该修饰电极上的氧化峰和还原峰电流均大大增加,表明纳米金与介孔炭复合后对HQ具有良好的催化作用。HQ在该修饰电极上经过富集后,峰电流明显增大。采用循环伏安法对HQ电化学行为进行研究,结果表明,HQ在3.0×10-8~1.0×10-6mol/L和1.0×10-6~1.0×10-4mol/L浓度范围内与峰电流呈良好的线性关系,据此建立了检测HQ的电化学分析方法。该方法的相对标准偏差为0.69%,检出限(S/N=3)为1.0×10-8mol/L,具有较高的稳定性和灵敏度。     

多壁碳纳米管修饰玻碳电极测定铜离子

以多壁碳纳米管(MWCNTs)修饰玻碳电极为工作电极,采用阳极溶出线性扫描法研究了铜离子的电化学测定方法。探讨了MWCNTs修饰层数、富集电位、富集时间、溶液pH、支持电解质对峰电流的影响。实验表明,铜离子浓度在1.0×10-8~1.0×10-5mol·L-1范围内与峰电流呈良好的线性关系,检测限为2.0×10-9mol·L-1,且该电极具有良好的稳定性和抗干扰能力。     

氢氧化镍薄膜修饰玻碳电极的制备及其对L-赖氨酸氧化的电催化活性

采用恒电位沉积方法将氢氧化镍沉积到玻碳电极表面,得到稳定性高、催化活性好的氢氧化镍薄膜修饰玻碳电极;分析了影响薄膜形成过程的关键因素,确定了最佳薄膜制备方案;与此同时,将薄膜修饰玻碳电极用于生物样品L-赖氨酸的氧化测定,并探讨了其催化作用机理.结果表明,所制备的氢氧化镍薄膜修饰玻碳电极表面发生电化学反应[Ni(OH)2→NiOOH],从而促进电极表面的电子转移,实现对L-赖氨酸的电催化作用.当L-赖氨酸的浓度在1.0×10-4～4.0×10-7 mol/L范围内时,相应氧化峰电流与浓度呈线性关系,检出限达4.0×10-7 mol/L;据此可方便地制备稳定性好且灵敏度高的电流型传感器.     

基于Ag_2S-MWNTs的肌红蛋白直接电化学研究

制备了硫化银-多壁碳纳米管(Ag2S-MWNTs)纳米复合材料,构置了Mb-Ag2S-MWNTs-CHIT/GCE,并研究了肌红蛋白(Mb)在该修饰电极上的直接电化学和电催化行为。采用扫描电镜和透射电镜表征了Ag2SMWNTs的形貌,利用循环伏安法对Mb的电化学行为进行研究。Ag2S能够均一、稳定的在MWNTs表面生长,所构置的修饰电极在PBS中出现一对峰形良好的、准可逆的氧化还原峰,并对过氧化氢(H2O2)表现出良好的电催化作用,测定H2O2的线性范围为1.0×10-6~2.5×10-4mol·L-1,检出限为3×10-7mol·L-1(S/N=3)。Ag2S-MWNTs纳米复合材料能显著提高氧化还原蛋白质(酶)的直接电子传递速率,所构置的修饰电极可为制备基于蛋白质(酶)的第三代电化学生物传感器提供一良好的研究平台。     

羧基化碳纳米管修饰电极的制备及其对Vc的电催化性能

用羧基化碳纳米管修饰玻碳电极制备了一种新型的碳纳米管修饰电极(A)。利用循环伏安,交流阻抗法对A进行了表征。用线性扫描伏安(LSV)法研究了A对Vc的电催化行为,结果表明,在0.1 mol.L-1的醋酸缓冲液(pH5.8)中,当Vc在A表面于-1.0 V电位下富集30 s,电位扫速为100 mV.s-1时,Vc在LSV图上能出现一灵敏的电催化氧化峰,峰电位约为0.149 V;利用该氧化峰可以进行痕量Vc的测定;峰电流与Vc浓度在1.0×10-5mol.L-1～1.0×10-3mol.L-1内成良好线关系,其相关系数为0.996,检出限达1.0×10-6mol.L-1;A稳定性较好,可用于水果和蔬菜中Vc的现场快速检测,回收率96.0%～103.0%。     

银掺杂聚L-精氨酸修饰电极同时测定芦丁和抗坏血酸

用循环伏安法制备银掺杂聚L-精氨酸修饰玻碳电极(Ag-PA/GCE),研究了芦丁和抗坏血酸在该修饰电极上的电化学行为,建立了芦丁和抗坏血酸同时测定的新方法。在pH=2.5的磷酸盐缓冲溶液(PBS)中,于140mV·s-1的扫速下,芦丁产生一对氧化还原峰,其氧化峰电位为0.552V,还原峰电位为0.491V;抗坏血酸产生一个氧化峰,峰电位为0.281V。芦丁和抗坏血酸的△Epa=0.271V,用氧化峰不需分离可直接对芦丁和抗坏血酸进行同时测定,在最佳条件下,芦丁和抗坏血酸的线性范围分别5.0×10-7~2.0×10-5 mol·L-1和2.5×10-5~5.0×10-3 mol·L-1,检出限分别为1.0×10-7 mol·L-1和1.0×10-5 mol·L-1。方法可用于复方芦丁片中芦丁和抗坏血酸的同时测定。     

用银-色氨酸复合膜修饰玻碳电极循环伏安法测定去甲肾上腺素

在含有1.0mmol.L-1硝酸银、5.58×10-2 mol.L-1色氨酸的溶液中,于-0.8～1.8V(vs.Ag/AgCl)电位下,在玻碳电极表面电沉积一层银-色氨酸复合膜,制得银-色氨酸复合膜修饰玻碳电极(Ag-TRY/GCE)。采用扫描电镜对电极表面的性能进行表征,循环伏安法对其电化学性能进行研究。试验发现:在pH 6.0磷酸盐缓冲溶液中,去甲肾上腺素(NE)在修饰电极出现一对明显的氧化还原峰,氧化峰电位为0.306V,还原峰电位为0.368V,提出了用循环伏安法测定NE的方法。在试验条件下,氧化峰电流与去甲肾上腺素浓度在3.4×10-7～8.3×10-6 mol.L-1和8.3×10-6～1.1×10-4 mol.L-1两段范围内呈线性关系,检出限(3S/N)为4.3×10-8 mol.L-1。修饰电极用于药物中去甲肾上腺素的测定,加标回收率在95.6%～99.4%之间。     

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.     

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.     

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.     

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.     

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.