金纳米粒子比色法检测卡那霉素的研究

运用金纳米粒子(AuNPs)比色法,构建了两种简单、快速、灵敏测定卡那霉素(KM)的新方法。方法一基于荷负电AuNPs与质子化的KM阳离子结合,AuNPs由酒红色变为蓝紫色,紫外吸收波长红移,吸光度降低。结果表明,吸光度比值(A620/A520)与KM的浓度在0.1~4.0μmol/L范围内存在良好的线性关系,其检出限(S/N=3)为33nmol/L。方法二基于核酸适配体AuNPs比色法测定KM。当不含KM时,核酸适配体与互补链形成稳定的双链DNA,高浓度NaCl溶液导致AuNPs团聚,颜色从酒红色变为蓝紫色。加入KM,适配体与KM结合,释放出单链DNA吸附于AuNPs表面使其保持稳定,颜色不发生变化。结果表明,吸光度比值((A0-A)/A)与KM的浓度在0.02~0.3μmol/L范围呈良好的线性,其检出限(S/N=3)为8nmol/L。建立的两种方法均可用于牛奶样品中KM的检测。方法一操作简单,但选择性较差;方法二检测KM的线性范围、检出限和选择性均较方法一更好。这两种方法可望用于其他抗生素的快速检测。     

紫外光谱法测定印制线路板废水中的铜

白杨素在紫外区内具有强吸收,Cu2+加入后会导致其吸光度显著下降,且吸光度的降低与Cu2+的浓度呈良好的线性关系,基于此建立了紫外光谱法测定Cu2+的新方法。通过对缓冲溶液体积、p H、白杨素浓度等进行考察和优化,在p H 8.28、9.0×10-2mol/L的六亚甲基四胺(HM TA)-HCl缓冲溶液中,4.0×10-8~1.0×10-6mol/L范围内,Cu2+浓度与吸光度降低成正比,线性方程为ΔA=0.508 c-0.0147(10-6mol/L)(R=0.99604),检出限为7.08 nmol/L(S/N=7),对4.0×10-8mol/L Cu2+溶液平行测定7次,ΔA的相对标准偏差为4.0%。对印制线路板废水中的铜进行了测定,测得结果与EDTA滴定法基本一致。     

基于银汞齐抑制三角纳米银刻蚀比色法检测水中汞离子

构建了一种基于汞离子存在下,银汞齐的形成抑制了三角纳米银被氯离子刻蚀的比色法检测水中汞离子的方法。当汞离子不存在时,由于氯离子的刻蚀,纳米银的形状由三角形纳米盘变成圆盘,溶液颜色由蓝色变成黄色。当汞离子存在时,汞离子被还原成汞原子强烈吸附在纳米三角银表面,汞充当纳米三角银的保护剂,抑制了氯离子对纳米三角银的刻蚀。随着汞离子浓度的增大,纳米三角银在450 nm处表面等离子共振峰发生红移,并伴随着颜色从黄色变为棕色,紫色,最后变为蓝色。在最佳反应条件下,该方法的线性范围为5~100 nmol/L,检出限为0.83 nmol/L。其它重金属离子对汞离子检测无干扰。将该方法用于实际水样中汞离子的检测,得到了满意的结果。     

甲烷氧化菌素催化纳米金合成

甲烷氧化菌素(methanobactin,mb)是具有过氧化氢还原酶活性的荧光肽.从甲基弯菌Methylosinus trichospo-rium IMV3011限铜培养介质中分离mb,采用紫外可见全波长扫描法观察mb催化对苯二酚还原氯金酸合成纳米金的作用和影响,当mb/氯金酸/对苯二酚反应液中mb的浓度分别是2.5×10-5mol/L、5.0×10-5mol/L和1.0×10-4mol/L时,形成的纳米金溶液的特征峰分别是561.5 nm(OD561=0.158)、548.0 nm(OD5 48=0.426)、536.5 nm(OD5 36=0.541),特征峰波长减小,对应的吸光值增大,表明mb能够催化对苯二酚还原氯金酸合成纳米金,并且可以通过调控mb的浓度控制纳米金的合成量及粒径大小.     

纳米银比色法检测多巴胺

在银纳米粒子存在下, 多巴胺可还原硝酸银生成银, 导致银纳米粒子粒径增大, 从而使溶液颜色发生改变. 基于此, 提出了一种用于检测多巴胺的纳米银比色法. 随着多巴胺浓度的增大, 溶液的颜色由浅黄色逐渐变为深黄色, 银纳米粒子溶液的吸收峰发生红移且吸光度增大. 在最优实验条件下, 该方法检测多巴胺的线性范围为0.05~16 μmol/L, 检出限为0.04 μmol/L. 该方法操作简单、 灵敏且选择性良好, 可用于人血清中多巴胺的检测.     

基于金纳米粒子探针比色法检测乙基谷硫磷

基于乙基谷硫磷在酸性条件下可以诱导金纳米粒子（AuNPs）发生聚集,建立了以AuNPs为探针、结合比色和分光光度法检测乙基谷硫磷的方法。通过改变氯金酸和还原剂柠檬酸钠的比例,制备了不同粒径的AuNPs。酸性溶液中乙基谷硫磷分子中-P=S键发生质子化,形成的-SH与Au形成S-Au键,使AuNPs发生聚集,溶液颜色由红色转变为蓝色。考察了乙酸-乙酸钠缓冲溶液的pH和浓度以及乙基谷硫磷与AuNPs的作用时间对AuNPs聚集程度的影响。在优化条件下,吸光度比值（A694 nm/A524 nm）与乙基谷硫磷浓度在0.392～0.603μmol/L范围内具有良好的线性关系,检出限为0.0782μmol/L。     

纳米金探针瑞利共振散射法测定针剂中盐酸普鲁卡因

采用葡萄糖还原氯金酸的方法制得粒径约15nm的纳米金,在pH3.54酸性介质中它可以与盐酸普鲁卡因作用形成体积更大的纳米金聚集体。这种聚集体的形成可以使纳米金的瑞利共振散射强度急剧增强,其最大散射峰位于354nm左右。在适当的条件下,相对散射强度(ΔI)与盐酸普鲁卡因的浓度成正比。采用标准加入法,对针剂中的普鲁卡因进行测定,得到满意结果。线性范围0～40μg/L(r=0.9996);对含盐酸普鲁卡因30μg/L的溶液平行测定的相对标准偏差为2.51%(n=11);检出限(3σ)为16ng/L;测定限(10σ)为54ng/L。     

5-（5-氯-2-吡啶偶氮）-2,4-二氨基甲苯褪色光度法测定牛血清蛋白

在pH 2.4的Britton-Robinson(B-R)缓冲溶液中,5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯(5-Cl-PADAT)与牛血清蛋白相互作用形成复合物而导致溶液吸收光谱发生变化,用分光光度法对光谱变化进行了研究.5-Cl-PADAT溶液在430 nm处有一个强的特征吸收峰,当在其溶液中加入牛血清蛋白后,溶液发生褪色现象,吸收峰强度降低,且没有新的吸收峰出现,吸光度降低值(ΔA)与牛血清蛋白的浓度(c)成正比.在选择的最佳试验条件下,牛血清蛋白浓度与ΔA的线性方程为ΔA=0.8141c+0.0041(r=0.9996),线性范围为1.071×10-9～5.902×10-9 mol/L,检出限为5.36×10-10 mol/L,该方法的回收率为96.9%～107.1%,测定结果的相对标准偏差为1.4%～2.3%(n=6).     

免标记比色核酸适配体传感器同步快速检测孔雀石绿和无色孔雀石绿

研究以双特异性核酸适配体A3作为传感探针、纳米金（AuNPs）为指示剂、NaCl溶液为聚集诱导剂,构建了一种新型的免标记AuNPs比色生物传感器,可实现水产品中孔雀石绿（MG）和无色孔雀石绿（LMG）的同步、快速、可视化检测。该方法的检测原理是核酸适配体A3对MG和LMG有双特异性识别能力,可作为MG和LMG理想的识别受体。它可通过静电作用吸附到AuNPs表面,保护AuNPs并抑制高盐溶液诱导的聚集,AuNPs溶液颜色不变,即为红色;当加入靶标MG或LMG后,该核酸适配体能够与靶标特异性结合,并从AuNPs表面上解离,AuNPs失去保护作用而在高盐溶液诱导下发生聚集,溶液颜色由红变蓝。根据颜色变化,可通过肉眼定性或通过光谱仪定量分析MG和LMG的残留量。该方法首先将50 μL的核酸适配体A3（终浓度150 nmol/L）与150 μL的AuNPs（终浓度1.25 nmol/L）混合,室温孵育6 min。随后加入50 μL待测液,室温孵育30 min。最后加入50 μL NaCl（终浓度150 mmol/L）,4 min后观察溶液颜色变化,并分别测定MG和LMG在520 nm和650 nm下的吸光度值。结果表明,在最佳反应条件下,该方法能够特异性检测MG和LMG,而对磺胺嘧啶（SDZ）和硝基呋喃妥因（NFT）无交叉反应;当MG、LMG的浓度为0~17.5 μmol/L时,吸光度比值与靶标浓度呈现良好的线性关系,相关系数（R ² ）分别为0.9938和0.9715。MG和LMG的检出限分别为6.93 nmol/L和6.38 nmol/L,加标回收率分别为88.60%~93.30%和101.80%~107.00%,相对标准偏差（RSD）分别为2.27%~3.55%和2.62%~3.75%。该方法操作简单,快速和灵敏,可为水产品中MG和LMG的同步快速检测提供一种新方法。     

纳米金光度法测定药物中盐酸小檗碱

氯金酸用葡萄糖还原制得纳米金,最终获得浓度为2.4×10-4mol.L-1且呈酒红色的纳米金悬浮溶液。试验证实纳米金颗粒被均匀地分散在悬浮溶液中,其吸收光谱中在525 nm波长处出现一吸收峰。当在纳米金悬浮溶液中加入盐酸小檗碱,由于两者间的静电结合导致溶液在525 nm波长处的吸光度降低,且其降低的幅度与盐酸小檗碱浓度在2.0×10-7～3.0×10-6mol.L-1范围内呈线性关系,其检出限(3S/N)为1.7×10-8mol.L-1。应用此方法分析了3个批号的药物盐酸小檗碱或片剂样品,所测得的结果与按药典方法测得结果相符。     

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.