量子点:FRET的新发展

荧光共振能量转移(FRET)技术作为一种高效的光学“分子尺”,在生物大分子相互作用、免疫分析、核酸检测等方面有广泛的应用。但是许多有机染料吸收光谱较窄而发射光谱较宽,并且光漂白现象比较严重,使得FRET的应用受到了限制,因此迫切需要寻找新的能量供-受体对。由于量子点(QDs)相对于有机染料有很多优点,可以较好地应用于FRET,可能成为FRET领域发展的一个有意义的新方向,近来已引起了人们的关注。本文就FRET的原理以及量子点应用于FRET的最新进展情况做了评述。     

量子点:FRET的新发展

荧光共振能量转移(FRET)技术作为一种高效的光学“分子尺“,在生物大分子相互作用、免疫分析、核酸检测等方面有广泛的应用.但是许多有机染料吸收光谱较窄而发射光谱较宽,并且光漂白现象比较严重,使得FRET的应用受到了限制,因此迫切需要寻找新的能量供-受体对.由于量子点(QDs)相对于有机染料有很多优点,可以较好地应用于FRET,可能成为FRET领域发展的一个有意义的新方向,近来已引起了人们的关注.本文就FRET的原理以及量子点应用于FRET的最新进展情况做了评述.     

量子点在法庭科学手印显现中的研究进展

随着纳米技术的进步,纳米颗粒正在被逐步应用到法庭科学领域的手印检验之中。近年来,半导体量子点因其良好的荧光特性而备受国内外法庭科学家的推崇,但大多数半导体量子点具有毒性,且会对环境造成污染,这些问题制约了半导体量子点在法庭科学领域中的应用。与传统有机染料和金属内核的半导体量子点相比,碳量子点具有毒性低、污染小、生物相容性优异的特点,现已应用于医学、生物、化学等多个领域。本文综述了半导体量子点在手印显现中的应用,介绍了碳量子点的研究进展,并指出碳量子点显现手印是今后法庭科学领域的重要研究方向。     

NEWS

荧光检测法是一种高灵敏度的分析监测方法。很多荧光物质,如有机染料和半导体量子点等已广泛应用于Hg2+的检测。但是,普通有机染料和量子点的发光寿命比较短,通常会受到背景信号干扰,从而影响检测方法的灵敏度。最近,湖南大学     

CdTe/CdS量子点的合成及用于HeLa细胞的免疫标记与成像

自1998年,Alivisatos~([1])和Nie~([2])小组成功地将量子点作荧光探针应用于鼠组织细胞核HeLa细胞的免疫标记后,量子点在细胞标记、活体和组织成像、生物大分子定性定量分析等方面显示出极大的发展潜力.与传统的有机染料荧光探针相比,量子点具有激发光谱宽、发射光谱对称、半峰宽窄,发射波长可调,以及光化学稳定性高等特点.这些优异特性使得量子点在生物学领域展示了广泛的应用前景.     

CdS量子点与曙红Y间的荧光共振能量转移研究

在水溶液中,量子点与有机荧光染料之间可能发生荧光共振能量转移(FRET)。本文以发射波长470nm的Cd S量子点为供体,曙红Y为受体,建立了Cd S量子点-曙红Y的FRET体系,研究了该体系的FRET参数。该体系受体供体数目比为8,猝灭效率为45.6%,增强效率为20.1%;供体-受体间的距离为4.4nm;临界能量转移距离为2.4nm。     

用于生物标记的半导体量子点研究

半导体量子点的独特光学性质使之成为理想的荧光探针材料,在生物医学领域具有广阔的应用前景.本文评述了目前量子点合成、表面修饰、结合生物分子的方法,以及半导体量子点在生物标记应用中相对于传统有机染料的优点.     

基于Mn掺杂ZnS量子点的室温磷光传感应用的研究进展

与一般有机染料分子相比,半导体材料量子点具有优异的光学性能,在多个领域得到了广泛的应用.量子点具有窄而对称且可调的发射波长、宽激发强吸收、抗光漂白能力强以及水溶性好等诸多优势,引起了研究者广泛关注.为了增加量子点的斯托克斯位移从而很好地避免量子点的自猝灭现象,引入掺杂物是一种很有效的方式.掺杂量子点不仅保留了量子点原有的优点,而且还赋予量子点额外的优异性能.如Mn掺杂ZnS量子点生物相容性好,不含Cd和Hg等有害元素,而且Mn2+的加入使其具有优异的室温磷光特性.磷光检测能很好地避开生物背景荧光的干扰,使得Mn掺杂ZnS量子点能够广泛应用于磷光生物分析.本文综述了Mn掺杂ZnS量子点在室温磷光分析中的研究进展,着重介绍了几种具有启发意义的设计策略,包括其发光机理以及应用于离子、分子以及生物大分子等的检测.     

基于Ⅰ型核壳量子点的宽光谱响应的高效能量转移体系

针对常规F?rster共振能量转移(FRET)体系中能量转移效率低的问题,合成了可见光吸收的Ⅰ型CIS@Zn S核-壳量子点作为能量供体,近红外方酸(SQ)染料作为能量受体,采用超声自组装的方式首次制备了光谱匹配、间距可调的高效FRET能量转移体系.超快/时间分辨光谱证明了CIS和SQ之间的FRET能量转移机制:CIS*+SQ→CIS+SQ*.荧光猝灭动力学数据显示,CIS@Zn S与SQ之间的能量转移对量子点的尺寸存在依赖性,由CIS@Zn S尺寸增加引起的荧光量子产率和供体-受体间距的增加使得体系的FRET能量转移效率(ηFRET)先增大后减小,并且在壳层反应时间为20min时体系的ηFRET值达到最佳值62.8%.该研究对于开发新型、高效、全谱响应的太阳能电池将具有一定的理论及实际应用价值.     

CdTe量子点-罗丹明6G荧光共振能量转移体系的构建及其应用研究

采用巯基化合物修饰的CdTe量子点构建了量子点(供体)-罗丹明6G(受体)荧光共振能量转移体系, 研究了CdTe量子点与牛血清白蛋白(BSA)的相互作用. 结果表明, CdTe量子点与BSA相互作用后提高了CdTe量子点-罗丹明6G 体系的荧光共振能量转移(FRET)效率, 减小了CdTe量子点和罗丹明6G分子间的距离(r), 证实BSA是通过其色氨酸(Trp)残基与CdTe量子点表面金属发生配位作用而直接结合到量子点表面的.     

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.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

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.