电化学溶解钛金属直接水解法制备纳米TiO_2

纳米材料是目前材料科学的热点 .TiO2作为一种重要的无机功能材料 ,具有温敏、气敏、光催化等功能 ,广泛用于光电材料、涂料、传感器、介电材料、催化剂及载体等重要领域 .由于其各种应用都与粉体的性能有直接关系 ,因此研究纳米 TiO2的制备方法具有重要的实际意义 [1].近年来 ,纳米 TiO2粉体制备方法有了很大的发展 ,如 TiCl4气相水解沉淀法 [2],乳浊液法和 Ti(OC4H9)4水解沉淀法 [1],喷雾热解法 [3],放电爆炸法 [4],反应电极埋弧法 [5],溶胶凝胶 (Sol gel)法 [6]等 ,其中溶胶凝胶法是制备纳米材料的有效方法 .但这些方法存在…     

光致变色WO3/4,4'-BPPOBp超晶格薄膜的制备

具有光致变色和电致变色特性的三氧化钨薄膜因其巨大的应用前景而倍受人们关注[1-4].其制备方法一般为物理沉积方法和化学沉积方法等.其中化学方法包括喷射裂解法[5],化学气相沉积法[6,7],电化学沉积法[8]和溶胶凝胶法[9]等.利用超分子化学自组装技术构建用有机组分调控的光致变色纳米超晶格薄膜材料,是研制光致变色功能薄膜材料的新方法.本文采用溶液中相反电荷聚电解质超分子自组装的方法(ＰＥｓ法)[10],制备了ＷＯ3/4,4′ＢＰＰＯＢｐ超晶格薄膜.采用紫外可见吸收光谱和小角Ｘ射线衍射谱对薄膜的结构和分子的排列方式进行了研究.1　实验…     

微波辐射下碘代芳烃与乙酰乙酸乙酯反应研究

2-芳基乙酸及乙酸酯具有显著的生物生理活性[1],是合成异黄酮[2]、异喹啉[3]衍生物的重要原料.苯乙腈水解法、苯乙酰胺水解法都曾用于芳基乙酸的合成[4].二羰基化合物的直接芳基化是合成该类化合物的最直接有效的方法.这些方法一般需要过渡金属催化剂的催化和配体的参与[5].     

高能机械球磨法制备V-Ti-O超细微粒催化剂

负载型V2O5/TiO2氧化物催化剂因具有优良的催化性能而广泛地用于烃类选择性氧化[1,2]和氮氧化物选择性催化还原(SCR)[3]. 迄今,所研究的负载型V2O5/TiO2氧化物催化剂大多是采用浸渍法制备的[2,4～6],通过调整催化剂的组成[2,5]、引入适当的助剂组分[2,6]和选择适宜的反应操作条件[2,5]可进一步优化其催化性能.     

WO3纳米管的模板法制备及表征

0引言 WO3纳米材料具有光致变色、电致变色、气致变色等特性,可用于光学信息和储存显示器、pH值探测器、气敏传感器、灵敏窗口等[1,2];并且在太阳能的储存与利用、光电转换、光催化降解大气和水中的污染物等方面有着广阔的应用前景[3,4],成为近几年重点研究的半导体材料之一.以前纳米WO3的制备主要集中在薄膜上,其薄膜的制备工艺已经相当成熟,主要包括蒸发法、溅射法、CVD法、喷涂法、阳极氧化法、溶胶-凝胶法等[3].     

场放大样品进样-压力辅助毛细管区带电泳测定饮用水中的百草枯

1 引 言 百草枯属有机杂环类季铵盐除草剂,由于它具有优良的除草效果,已广泛应用于多种作物的杂草防治.百草枯具有极强的水溶性,极易迁移至水体环境中,从而对饮用水的质量安全构成潜在威胁.目前,百草枯的残留检测方法主要有分光光度法[1]、液相色谱-质谱联用法[2]、气相色谱质谱联用法[3]和毛细管电泳法(CE) [4～6].采用分光光度法测定百草枯,不仅操作繁琐费时,而且灵敏度低.采用气相色谱法测定百草枯,通常需要衍生化,应用较少[3].采用液相色谱法测定百草枯,通常需要在流动相中添加离子对试剂[2].毛细管电泳具有分离效率高,分析速度快等优点,已被广泛用于水样中百草枯残留的测定.然而,毛细管电泳灵敏度不高,极大地限制了其在实际样品分析中的应用.场放大样品进样(FASI)是一种简单有效的在线富集方法,其富集倍数可达1000倍[7],可有效提高毛细管电泳技术的灵敏度,因此应用较为广泛.本实验建立了场放大样品进样-压力辅助毛细管区带电泳法(CZE),用于测定饮用水中百草枯的残留量.     

LaMnO_3稀土纳米材料及催化性能

钙钛矿型复合氧化物（ ABO3）有稳定的结构和良好的高温性能,其中 La-Mn-O系列的钙钛矿材料具有很好的催化活性,但采用固相反应等方法制备的样品其比表面一般不超过 10 m2· g－ 1,反应活性受到限制 [1].纳米材料粒径较小,比表面较大,具有独特的物理化学性能,是一种有应用前景的新型催化材料 .目前,纳米材料的制备方法有喷雾冷冻干燥法 [2]、 共沉淀法 [3]或溶胶-凝胶法 [4－ 7]等 .本文用 NaOH-Na2CO3共沉淀法制备出纳米级 LaMnO3钙钛矿,并研究了其对 CO、 HC和 NO的催化性能 .1实验1.1样品制备　　纳米钙钛矿粉末制备方…     

基于多酸簇的有机/无机杂化的分子材料

多酸及其盐-POMs,是由钨、钼、钒、铌、钽等过渡金属元素的氧化物阴离子簇所构成的一大类具有确定的组成与结构的无机化合物.它们种类繁多、结构复杂多样,具有纳米范畴的分子尺寸,拥有丰富多彩的光、电、磁等物理性质,及奇特的催化、生理和药理活性[1,2].多酸分子表面的氧原子在一定的条件下可以被有机配体所取代[3],因此可以用于开发具有特殊功能的有机/无机杂化的分子材料.本文将要介绍我们最近在这一领域所取得的重要进展[4～8]:采用DCC脱水法,我们发展了制备多酸的有机亚胺衍生物的新的合成化学(见图1)[4,5].以含碘或乙炔官能团的六钼酸根芳香亚胺衍生物作为分子构件,通过Pd催化的碳-碳偶联反应,我们以可控方式制备了有机共轭体系与多酸簇共价键联的杂化分子材料[6],组装出了哑铃状的分子纳米杆(见图2)[7],并制备了主链含多酸簇的有机/无机杂化的聚合物[8].     

高分子保护沉淀法制备超细纳米氧化镁

纳米氧化镁具有不同于本体材料的光、电、磁、化学特性,特别是超细纳米氧化镁由于其颗粒直径小、比表面积大,具有高纯度、高硬度和高熔点,高的反应活性,强吸附性,良好的低温烧结性,高电阻率等优良性质,可用于高绝缘材料,高质量的陶瓷材料,高性能阻燃纤维,环境保护的吸附剂、负载型甲醇和低碳醇合成的催化剂载体等领域,是一种有广泛应用价值的新型无机材料[1￣5]。已见报道的纳米氧化镁的制备方法有电子束蒸发法[6]、化学气相沉积法[7]、金属醇盐水解法,化学沉淀法[8,9],固相法[10],燃烧法[11],溶胶-凝胶法[12,13]等,然而由于氧化镁容易发生…     

铈(Ⅳ)-亚硫酸钠体系流动注射化学发光法测定叶酸

叶酸又称蝶酰谷氨酸,是一种维生素B族类的抗贫血药,尤适用于孕妇和婴儿红细胞性贫血[1].目前,测定叶酸的方法多为荧光法[2]、高效液相色谱法[3-6]、紫外分光光度法[7]、电化学法[8]、原子光谱法[9,10]等.化学发光法测定叶酸的文献也曾有报道[11,12],它们分别采用的是鲁米诺体系和高锰酸钾体系,但这些方法的检出限比较高.     

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.     

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 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.