荧光碳量子点的特性及检测巯基化合物的研究进展

巯基化合物是生物体内一类重要的抗氧剂,包括半胱氨酸、同型半胱氨酸、谷胱甘肽等生物硫醇类化合物,在体内参与一系列典型的生化反应,有助于维持正常的生理功能,当含量异常会导致多种疾病.因此,定量检测巯基化合物在相关疾病研究和诊断方面具有重要的意义.目前,利用高选择性、高灵敏度的荧光探针检测巯基化合物已成为前沿课题之一.碳量子点(CDs)因具有优良的荧光稳定性、极好的生物相容性、耐光漂白以及易制备等优良的性能,作为一类荧光探针检测巯基化合物得到了广泛的应用.类似于其他纳米探针,当荧光CDs用于检测巯基化合物时,基于信号检测的竞争机制,引入猝灭剂和巯基化合物竞争性结合荧光碳量子点,由于巯基化合物的高亲和力和强亲核性,使荧光恢复.本文综述了碳量子点的制备和特性,以及在检测巯基化合物方面的研究进展.     

基于菁染料高选择性检测半胱氨酸的近红外荧光探针

本文设计合成了以菁染料为荧光团,以4-(三氟甲基)苯硫基为半胱氨酸响应识别基团的近红外荧光探针(Cy-CF_3)。利用探针分子Cy-CF_3与半胱氨酸和谷胱甘肽反应发生的机理不同,实现了对半胱氨酸特异性识别。探针分子Cy-CF_3与半胱氨酸发生芳香亲核取代反应生成巯基取代产物,进一步通过分子内重排反应生成氨基取代产物Cy-Cys。光谱研究结果表明,探针分子Cy-CF_3与半胱氨酸作用后发生明显的吸收波长蓝移(160nm),并且可观察到明显的颜色变化;荧光光谱中,随着半胱氨酸的加入,探针分子Cy-CF_3在780nm处的近红外荧光显著增强。Cy-CF_3能高选择性检测半胱氨酸,并且不受其它氨基酸尤其是结构类似的谷胱甘肽干扰。探针分子Cy-CF_3被成功地应用于活体细胞中检测半胱氨酸。     

荧光可视化技术在食品分析中的应用进展

介绍了常见的荧光可视化传感器(比率、纸基、分子印迹荧光传感器),荧光可视化传感机制(荧光共振能量转移、内滤效应、光诱导电子转移、聚集诱导猝灭、聚集性诱导发射、分子内电荷转移、金属-配体电荷转移等)及其判定方法，综述了量子点(普通量子点和生物质量子点)、有机荧光物质和金属荧光纳米团簇等发光物质作为荧光可视化探针在食品分析中的应用，并对其发展前景进行了展望(引用文献69篇)。     

巯基类荧光探针的研究进展

生物硫醇类物质,如半胱氨酸、高半胱氨酸、谷胱甘肽等,在生命体中有至关重要的生理和病理作用.因此,近几年对生物硫醇的研究成了一大热点.目前巯基类荧光探针的设计主要是基于巯基的强亲核性.根据荧光探针与巯基反应的不同的机理,综述了近几年关于检测硫醇的荧光探针的合成报道,从迈克尔加成、醛基的环化、裂解、取代和其他几个方面对探针的检测限、响应时间、当量比、选择性、稳定性等进行了综述.     

绿色、经济合成荧光碳纳米粒子并以此为探针实现对汞离子的灵敏性及选择性检测

汞离子(Hg2+)是最危险的污染物之一。荧光检测法已被证明是具有高灵敏度、可实现快速分析并对样品破坏性较小的有效方法。大量的荧光探针包括有机小分子、金属纳米簇和半导体量子点等已被广泛用于荧光检测Hg2+。然而这些荧光材料通常具有合成步骤     

有机巯基小分子生物荧光探针研究进展

生命体内许多重要的巯基小分子,如半胱氨酸(Cysteine,Cys)、同型半胱氨酸(Homocysteine,Hcy)和还原谷胱甘肽(Glutathione,GSH)等,在维持生命体系中的氧化还原平衡发挥着重要作用。因此,定量检测和专一性识别巯基生物分子在生物医学研究中具有非常重要的意义。荧光分析法具有操作简便、灵敏度高、选择性好、实时检测以及对生物体损伤小等优点而受到广泛关注。双光子荧光探针技术相对于单光子荧光技术具有长波吸收,短波发射、高度的三维空间选择性、大的穿透深度、避免荧光漂白和光致毒以及降低组织自发荧光干扰等特点,在生命科学领域具有广阔的应用前景。介绍了有机单光子和双光子巯基小分子荧光探针的研究现状,同时展望了有机巯基小分子荧光探针未来的研究方向。     

宽pH响应范围的比率荧光纳米探针的构建

基于化学剥离法制备MoS_2量子点,以荧光素和罗丹明B为pH荧光响应基团,经巯基共价修饰在MoS_2量子点表面后构建了宽pH检测范围的比率荧光纳米探针dl-MoS_2。对其光谱学性质和pH响应荧光性质进行了研究。结果表明,dl-MoS_2具有pH选择性识别作用,且对pH响应范围可以通过荧光配体和罗丹明配体的比例进行调节,当荧光素配体与罗丹明配体的摩尔比为1:10时,制备得到的dl-MoS_2探针具有最宽的pH响应范围(pH 4～9),该方法能有效的扩宽荧光探针的pH检测范围。进一步研究表明,dl-MoS_2探针对pH的检测可用作生命体内pH成像检测的荧光探针。     

CdTe量子点DNA荧光纳米探针的合成及表征

采用水相合成法合成了巯基乙酸(TGA)修饰的水溶性CdTe量子点,通过反相微乳液法制备了二氧化硅及壳聚糖修饰的核壳型复合荧光纳米粒子,将其与DNA吸附连接,得到CdTe量子点DNA荧光纳米探针。用扫描电镜、透射电镜、荧光光谱、红外光谱、紫外光谱、ζ电位等测试方法对产物的理化性质进行了分析表征。结果表明制备了表面富含氨基的复合荧光纳米粒子,其对DNA具有良好的吸附作用。     

分子印迹荧光探针在农药检测中的应用进展北大核心CSCD

分子印迹聚合物由于可特异性地从样品溶液中富集目标物,已被广泛应用于粮食、果蔬等食品以及水、土壤等环境中农药的提取和检测.将分子印迹技术和量子点修饰技术相结合形成的分子印迹荧光探针,可以实现对目标物的高灵敏快速检测.据此,对分子印迹技术的原理、制备方法及应用进行了概述,并进一步阐述了量子点修饰的分子印迹荧光探针在农药检测中的应用和展望.     

金属增强量子点荧光

量子点具有亮度高和稳定性好等优异的光学性质,在生物检测、活体成像及光电器件开发等领域有着广泛的应用。然而,当前水相量子点尤其是水相近红外荧光量子点的荧光发射强度相对较低,且荧光稳定性有待进一步提高。金属可以使其邻近荧光物质的激发效率提高且辐射衰减速率增加,荧光发射强度较之自由态荧光发射增强,产生金属增强荧光效应。采用金属纳米结构增强量子点的荧光有望为解决上述问题提供有效途径。本文详细介绍了量子点发光机理及金属增强量子点荧光机理,在此基础上讨论了影响金属增强量子点荧光的关键因素,并对相关研究现状及挑战进行了简短的评述。我们相信随着纳米科技的快速发展,金属增强量子点荧光在不远的将来会吸引越来越多的关注并展现出独特的潜力。     

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%.     

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.     

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.     

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.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

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.