非共价方法分离金属型和半导体型单壁碳纳米管

目前商品化生产的单壁碳纳米管(SWNTs)都是金属型和半导体型碳管的混合物,极大地限制了其在微电子等领域的研究和应用。非共价分离方法既能保持SWNTs特有的电子结构又可实现可逆分离,是目前研究最多的分离方法。本文在介绍SWNTs的结构与导电性能关系的基础上,概述了金属型和半导体型SWNTs的表征原理和方法,并对各种非共价分离SWNTs的方法进行了综述和比较。     

DNA共价修饰单壁碳纳米管电极的制备及与VB6 相互作用的研究

利用单壁碳纳米管(SWNTs)上的羧基与DNA末端的氨基形成酰胺共价键从而共价修饰SWNTs,制备了新型DNA共价修饰SWNTs电极.傅立叶红外光谱表明DNA共价结合在SWNTs上,用扫描电镜(SEM)表征了SWNTs、DNA共价修饰的SWNTs的结构与形貌.循环伏安法(CV)研究了DNA修饰SWNTs电极的电化学特性,通过改变扫描速率,发现DNA修饰电极的过程属于扩散控制过程.维生素B6(VB6)与SWNTs上DNA的相互作用研究结果表明:DNA分子共价修饰在SWNTs上后仍具有生物活性,且能够与其他生物分子发生相互作用.     

聚氨酯/碳纳米管复合材料制备的研究进展

综述了聚氨酯/碳纳米管复合材料制备研究中碳纳米管的修饰方法及其复合材料的制备方法。碳纳米管的修饰方法包括共价修饰和非共价修饰,两种方法都可以有效改善碳纳米管在聚氨酯中的分散性。然而,共价修饰法会削弱碳纳米管的强度,非共价修饰层则容易脱落。因此,人们发展出了复合修饰法。该复合材料中的制备方法包括溶液共混法、熔融混合法和原位聚合法。评述了未来的发展趋势,提出朝简单、环保的方向改进碳纳米管的修饰方法,形成系统化的碳纳米管分散性评价的量化标准,发展出适应复合材料工业化生产线的制备方法,将是今后研究的重点。     

非离子型水溶性卟啉功能化单壁碳纳米管的研究

合成了两种非离子型水溶性卟啉分子,并利用它们对单壁碳纳米管(SWNTs)进行了非共价表面修饰。功能化后SWNTs能够在水中均匀分散。紫外-可见光谱、荧光光谱、透射电镜的测试结果均证明非离子型水溶性卟啉分子与SWNTs之间存在强烈的相互作用。其中,含有柔性烷基取代链的卟啉分子因与SWNTs之间存在π-π和疏水双重相互作用,所形成的复合物在水中表现出更好的分散稳定性。这种既具有水溶性又具有生物相容性和良好稳定性的功能化SWNTs,在生物医药领域具有潜在的应用前景。     

碳纳米管微结构的改变对其容量性能的影响

以KOH为活性剂，通过在高温下将碳纳米管进行活化处理来实现对碳纳米管管壁结构的改变，得到了比表面积和孔容分别是活化处理前约3倍和1.5倍的活性碳纳米管.将活化处理前后两种碳纳米管分别制作成电化学超级电容器电极，在充满氩气的无水手套箱组装成模拟电化学超级电容器，在恒流充放电模式下进行电化学可逆容量的测试，发现活性碳纳米管的电化学容量远高于活化前碳纳米管，是它的2倍.从而发现碳纳米管被打断，管壁变粗糙的活性碳纳米管比一般碳纳米管更适合用于电化学超级电容器电极材料.     

活化条件对活性碳纳米管比表面积的影响

以KOH为活化剂, 研究了多壁碳纳米管在制备活性碳纳米管过程中四个重要影响因素: 活化剂用量、活化温度、活化时间和活化过程中保护气体的流速对所得活性碳纳米管BET比表面积的影响并解释了原因. 研究表明上述四个因素都会对活性碳纳米管的比表面积产生较大的影响, 其中活化剂用量的影响最大, 在研究范围内可引起比表面积增大约241 m²•g^-1. 在这四个影响因素中除活性碳纳米管的比表面积随活化温度的增加而不断增加外, 其他三个影响因素的变化都会使活性碳纳米管的比表面积出现最大值, 而且四个影响因素的改变, 都不改变活性碳纳米管的孔洞主要是中孔和大孔的特点.     

碳纳米管共价功能化*

碳纳米管由于其独特的结构与优异的各项性能,在许多领域具有巨大的应用潜力,已引起了广泛的关注。由于碳纳米管不溶于水和有机溶剂,极大地制约了其性能应用,因此碳纳米管的功能化就成为目前研究的热点。本文侧重于碳纳米管的共价功能化,详细讨论了碳纳米管不同位置共价功能化的研究进展。     

碳纳米管的活化处理及对其电化学容量影响的研究

采用KOH为活性剂,对碳纳米管进行活化处理,经透射电子显微镜和高分辨透射电子显微镜从不同角度观察,发现得到了两端开口,管长较短,管壁粗糙的活性碳纳米管．用氮气自动吸附仪测试了活化前后两种碳纳米管的比表面积,发现活性碳纳米管具有比活化前碳纳米管更高的有效比表面积,将这两种碳纳米管分别作为电极材料应用于电化学超级电容器,经测试,发现活化后的碳纳米管的电化学容量大大提高,在有机电解液中达到了50F／g．     

活性碳纳米管的制备及其在有机电解液中的电容性能研究

以KOH为活化剂对碳纳米管进行化学活化制备双电层电容器用高比表面积活性碳纳米管. 采用TEM和N₂吸附法表征活性碳纳米管的结构, 采用恒流充放电、循环伏安、交流阻抗等评价其在1 mol•L^－1 Et₄NBF₄/PC中的电容性能. 随活化剂用量增大、活化温度升高和活化时间的延长, 活性碳纳米管的比表面积和比电容都呈增大的趋势. 活化剂用量为3∶1, 800 ℃活化4 h制备的活性碳纳米管的比表面积663 m²•g^－1, 比活化前提高了3倍, 其比电容达57.2 F• g^－1, 比活化前提高了2倍. 将活性碳纳米管的比电容与其比表面积相关联, 发现两者之间具有非常好的线性关系, 并分析了原因.     

碳纳米管和碳纳米管-四氢呋喃水合物的储氢特性

研究了单壁碳纳米管(SWNTs)干法储氢和碳纳米管(SWNTs)-四氢呋喃(THF)水合物法储氢的过程. 结果表明, 实验所用的SWNTs在16.5 MPa压力下, 温度为0.5 ℃时, 氢气的吸附存储量为0.75%(质量分数), 经浓酸处理后, 氢气的存储量可以达到1.15%, SWNTs-THF水合物法储氢量为0.37%, 与碳纳米管干法储氢相比, 储氢量有所降低.     

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.     

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.