巯基丁二胺镍(Ⅱ)自组装单分子层H2O2传感器研究

采用巯基丁二胺镍(Ⅱ)(NiL-SH)自组装单分子层修饰金电极,制得测定H2O2的电流型生物传感器.NiL-SH在电极表面有一对可逆的氧化还原峰.传感器对H2O2的还原显示出快速电催化响应(＜10 s),采用电子扫描电镜(SEM)和光电子能谱(XPS)对电极表面进行了表征,且计算了其自身电化学反应性质.研究了各种因素如pH、工作电位等对传感器响应电流的影响.循环伏安法测定H2O2的线性范围为5.0×10-6～3.0×10-3 mol/L(r=0.999),检出限为2.0×10-6 mol/L.该电极显示出模拟酶特性,测定米氏常数KMapp＝2.78 mmol/L.对传感器的稳定性,灵敏度和选择性进行研究,并应用于实际样品测定.     

石墨烯-聚多巴胺纳米复合材料制备过氧化氢生物传感器

通过合成具有仿生功能的石墨烯-聚多巴胺纳米材料,将其与辣根过氧化酶组装到电极表面,以对苯二酚为电子媒介体制备H2O2传感器.此修饰电极对H2O2具有良好的电催化活性,检测的线性范围为5.0×10-7～3.3×10-4 mol/L;线性回归方程为Y=29.69x+ 0.04577,相关系数为R=0.9995;检出限为3.7×10-7 mol/L(S/N=3).     

基于三维有序大孔金电极的过氧化氢无酶传感器

采用反相胶体-晶体模板技术以及电化学沉积法制得了三维有序大孔金膜修饰电极,并对修饰电极进行了表征,在此基础上构建了新型的H2O2无酶传感器。研究表明,此传感器在1×10-6～5.5×10-5mol/L和8×10-5～1.3×10-3mol/L范围内对H2O2还原峰电流有良好的线性响应;检出限为3.3×10-7mol/L(S/N=3),具有良好的稳定性和重现性。     

基于碳纳米管-纳米二氧化锰增强的H2O2修饰电极的研制

将碳纳米管(CNT)和纳米二氧化锰(Nano-MnO2)分散在壳聚糖(CHIT)溶液中,用涂敷法固定到玻碳电极表面,制成修饰电极.由于碳纳米管具有良好的电子传递性能,使纳米二氧化锰对H2O2的电催化活性明显提高,通过循环伏安法、计时电流法对传感器的性能进行了研究.在最佳测试条件下,该传感器对H2O2的线性范围为1.5×10-6 ～5.0×10-2 mol/L,检出限为4×10-7 mol/L.用于实际样品的测定,结果满意.     

基于硫堇/碳纳米管修饰金电极的过氧化氢生物传感器

制备了以硫堇(TH)、纳米金(Nano-Au)及多壁碳纳米管(MWNT)修饰的H2O2生物传感器.探讨了工作电位、温度、pH对电极响应的影响,考察了电极的重现性、抗干扰能力及使用寿命.该传感器具有线性范围宽、检出限低、灵敏度高、稳定性好和抗干扰能力强等特点.其线性范围为7.0×10-7～4.0×10-3 mol/L;检出限为2.3×10-7 mol/L;灵敏度为0.13 A/(mol L-1 cm2);达到稳定电流所用时间《9 s.米氏常数为0.62 mmol/L,表明所固定的酶具有较高的生物活性.     

L-半胱氨酸/辣根过氧化物酶/纳米银/辣根过氧化物酶修饰电极循环伏安法测定过氧化氢

在金电极表面自组装L-半胱氨酸,再分别吸附辣根过氧化物酶(HRP)和纳米银,制得L-半胱氨酸/辣根过氧化物酶/纳米银/辣根过氧化物酶修饰电极。采用循环伏安法研究了修饰电极的电化学特性,探讨了pH值、温度对电极响应的影响,考察了电极的重复性、稳定性及选择性。实验结果表明,HRP在修饰电极表面能进行有效和稳定的电子转移,HRP保持了其对H2O2还原的生物催化活性。该电极对H2O2检测的线性范围为8.6×10-7～1.3×10-3mol/L,r=0.9985,检出限(S/N=3)为1.6×10-7mol/L。该电极具有稳定性好、线性范围宽、检出限低等优点,同时具有一定的抗干扰能力。     

基于胆碱修饰层为基底的纳米金固定过氧化物酶修饰电极的研究

玻碳电极上共价修饰上单分子层胆碱(Ch)可以显著提高电极的活性。本研究利用该电极上胆碱层带有的正电荷,牢固吸附带负电荷的纳米金溶胶,继而利用纳米金颗粒良好固载辣根过氧化物酶(HRP),制备出了基于HRP酶直接电化学的H2O2传感器。以阻抗谱、循环伏安等方法表征了修饰电极的性质。结果显示,该电化学传感器具有良好的催化活性,电活性HRP的表面浓度(Γ*)为1.2×10-9mol/cm2,米氏常数KMapp=1.55±0.11 mmol/L。该修饰电极在H2O2浓度1.2×10-6~3.2×10-3mol/L范围内有线性响应,检出限(S/N=3)为4.0×10-7mol/L。本修饰电极制备简单,选择性高,稳定性好,可以作为进一步构筑生物传感器的基础。     

基于石墨烯-壳聚糖-辣根过氧化物酶的H2O2生物传感器的研制

制备了石墨烯-壳聚糖(GR-CS)纳米复合材料,并将之与辣根过氧化物酶(HRP)混合,构建了基于石墨烯-壳聚糖-辣根过氧化物酶的生物传感器(GR-CS-HRP/GC)。探针及循环伏安研究表明,该界面具有优异的电子传导能力、较大的比表面积和良好的生物相容性,对H2O2的还原显示出较好的电催化活性,在工作电位为-0.2 V,0.05 mol/L的磷酸盐缓冲盐溶液(PBS,pH 6.8)中,该酶传感器对过氧化氢响应灵敏度高,检测范围宽,测定H2O2的线性范围为5.0×10-7～2×10-3mol/L(相关系数为0.998)。检出限为2.0×10-7mol/L(S/N=3)。并且表现出良好的稳定性和高选择性。该电极用于实际样品中H2O2的测定,结果令人满意。     

碳纳米管/TiO2薄膜固定酶的生物传感器及电催化氧化H2O2的研究

采用酸性溶胶法在碳纳米管上负载纳米TiO2颗粒,并制备了CNT-TiO2薄膜固定辣根过氧化物酶的生物传感器。研究了该生物传感器在磷酸盐缓冲溶液中对H2O2的电催化氧化作用及实验条件的影响。结果表明该生物传感器对H2O2表现出良好的电催化性能,在最佳实验条件下,对H2O2检测的线性范围为:4.2×10-7mol/L~3.2×10-3mol/L。检出限为:7.22×10-8mol/L。     

PB/Au/CILE的制备与应用

混合离子液体(N-丁基吡啶六氟磷酸盐,[BuPy][PF6])与石墨粉,制备了离子液体碳糊电极(CILE),再采用电沉积法制得PB/Au/CILE修饰电极,研究了该修饰电极的电化学行为及其对H2O2的电催化,建立了H2O2的计时安培测定新方法。结果表明:在该修饰电极上PB产生了一对准可逆的氧化还原峰,并对H2O2表现出良好电催化作用,安培法测定H2O2的线性范围为5.0×10-6～1.55×10-4mol/L,检出限为1.0×10-6mol/L(S/N=3)。连续10次测定5.0×10-6mol/L H2O2峰电流的RSD为2.1%。     

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.