氧化锌纳米棒的制备和生长机理研究

ZnO nanorods are prepared by different assistants (cetyltrimethylammonium bromide，trisodium citrate and ethylene diamine anhydrous) favored hydrothermal synthesis with Zn(OH)₂ colloid as the precursor. The samples are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the as-synthesized ZnO nanorods are of uniform size with 25 nm in diameter and 200～300 nm in length. The effects of the different assistants to the morphology, size and mechanism of nano-ZnO are discussed.     

溶剂热制备氧化锌纳米线

ZnO nanowires were synthesized mildly through an absolute alcohol solvothermal process at 120 ℃ for 12 h using ZnAc₂·2H₂O and NaOH as raw materials and PEG400 as a soft template. The cyrstal structure and morphology of the nanowires were characterized by XRD, SEM, TEM and HRTEM. The results indicate that the diameter of ZnO nanowires is 40 nm, the length can reach 2 μm and the nanowires are of high purity, homogeneity and well crystallinty. The influence of the various factors on the formation of ZnO nanowires and formation mechanism were also discussed.     

ZnO纳米线的电化学制备研究

High-quality ZnO nanowires have been synthesized at relatively low temperature via one-step electrochemical anodization technique. In this method, Zn sheet acted as the anode and Pb sheet served as the counter electrode, and the complex solution of HF-C₂H₅OH-H₂O was used as electrolyte. ZnO nanowires were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED) and X-ray Diffraction (XRD). The results show that the nanowires were wurtzite crystalline ZnO, and the ZnO nanowires with the diameters of 70 nm and 30～40 nm were obtained by adjusting preparation conditions, respectively.     

CeOHCO3和CeO2束状纳米结构的制备及表征

The cantaloupe-like particles of CeOHCO₃ were synthesized in aqueous solution by using cetyltrimethylammonium bromide (CTAB) as soft template. Then, the bunchiness rods of CeO₂ were obtained by calcining CeOHCO₃ at 450 ℃. The results of thermogravimetric/differential thermal analysis reveal that an endothermic reaction with decomposition is involved in the transformation process from CeOHCO₃ to CeO₂. By scanning electron microscopy and X-ray diffraction analysis, it is found that the orthorhombic phase CeOHCO₃ particles are constituted of short nanorods with diameters ranging from several tens nm to over 100 nm, and the cubic phase CeO₂ rods are composed of small particles with diameter ca. 15 nm. From the results of UV-Vis absorption and photoluminescence analysis, it is found that the CeO₂ possess abundant defects, and the band gaps of the CeO₂ and CeOHCO₃ are ca. 2.70 eV and 3.87 eV, respectively.     

反相微乳液法合成SrTiO3纳米棒

SrTiO₃ nanorods were synthesized in cetanyl trimethyl ammonium bromide (CTAB) reverse microemulsion containing CTAB, n-hexanol, n-octane and water with Ba(OH)₂ as reactants. The effects of different conditions such as ω₀ [ω₀=n_H2O/ n_CTAB], aging time and the concentration of reactants on the formation of the nanorods were studied. Transmission electron microscope (TEM), electron diffraction (ED) and X-ray diffraction(XRD)were used to characterize the morphology and the structure of the synthesized nanorods. The results show that SrTiO₃ nanorods with a length of 260～2 000 nm and a diameter of 50～100 nm belonging to single crystal are single cubic system. The molar ratio of Sr to Ti of products is 1.0 as determinded by ICP.     

高分子自组装ZnO纳米带合成过程的研究

ZnO nanobelts were synthesized from zinc acetate (Zn(CH₃COO)₂) and polyvinyl alcohol(PVA) at about 300 ℃, 400 ℃, and 550 ℃. The products were characterized by scanning electron microscope(SEM) and transmission electron microscope(TEM). The ZnO nanobelts were typically 10～30 μm in length and 30～8 000 nm in width. The results show that the ZnO Y-nanobelts were formed owing to dislocation structure. The thermal treatment of 120 ℃ and enough time for growth of the crystal are essential to ZnO nanobelts synthesis.     

羟基功能化离子液体中Ag纳米材料的制备及结构表征

Ag nanoparticles were prepared using hydroxyl-functionalized ionic liquids as reductant and reaction medium. Nanoparticles with different particle sizes were obtained by using ionic liquids with different structures, while nanorods were harvested when the reaction temperature was increased. The materials obtained were investigated by XRD and TEM. The results indicate that the crystal is in face-centred cubic structure for both of Ag nanoparticles and nanorods, and the diameter of Ag nanoparticles prepared in 1-ethoxyl-3-methyl imidazolium tetrafluoroborate ([C₂OHmim]BF₄), 1-(4′-hydroxyl)butyl-3-methyl imidazolium tetrafluoroborate ([C₄OHmim]BF₄) and 1-(6′-hydroxyl)hexyl-3-methyl imidazolium tetrafluoroborate ([C₆OHmim]BF₄) ionic liquid is about 25, 15 and 10 nm, respectively. And the diameter of Ag nanorods is about 200 nm and 2 μm in length. Finally, the formation mechanism of Ag nanoparticles and nanorods is proposed.     

Synthesis of porous hematite nanorods loaded with CuO nanocrystals as catalysts for CO oxidation

Porous hematite (α-Fe2O3) nanorods with the diameter of 20-40 nm and the length of 80-300 nm were synthesized by a simple surfactant-assisted method in the presence of cetyltrimethylammonium bromide (CTAB).The α-Fe2O3 nanorods possess a mesostructure with a pore size distribution in the range of 5-12 nm and high surface area,exhibiting high catalytic activity for CO oxidation.CuO nanocrystals were loaded on the surface of porous α-Fe2O3 nanorods by a deposition-precipitation method,and the catalysts exhibited superior activity for catalytic oxidation of CO,as compared with commercial α-Fe2O3 powders supported CuO catalyst.The enhanced catalytic activity was attributed to the strong interaction between the CuO nanocrystals and the support of porous α-Fe2O3 nanorods.     

95 ℃水溶液体系中TiCl4溶胶水解法制备纯金红石纳米粉体(英)

Titanium dioxide (TiO2) nanoparticles of rutile phase were synthesized by hydrolysis of TiCl₄ at 95 ℃ in aqueous solution. The samples as prepared and calcined at 500 ℃ were characterized by XRD, TG-DTA and TEM. The sample as prepared was of imperfect rutile structure, and its morphology was rod-like with a diameter of 10～20 nm, a length of 20～80 nm and an aspect ratio of 2～4. The structure of the sample calcined at 500 ℃ was a perfect rutile one, and its morphology was rod-like with a diameter of 15～25 nm, a length of 25～105 nm and an aspect ratio of 2～4. These results indicate that calcination temperature has a positive effect on the structure and the size of rutile nanocrystals, and has no effect on the aspect ratio of rutile nanocrystal. A model for the formation mechnism of rutile nanocrystal in aqueous solution under hydrolysis conditions has been proposed.     

简捷水热前驱物技术制备钛酸钡纳米棒与纳米球

A facile synthesis route has been developed to prepare barium titanate nanoparitcles via a low temperature (120 ℃) hydrothermal decomposition of single-source metal-organic precursor. A mixture of tetramethylammonium hydroxide (TMAH) and distilled water was used as reaction media, and Barium titanium ethyl-hexano- isoproxide [BaTi(O₂CC₇H₁₅)(OC₃H₇)₅] was used as precursor. The architecture of products can be selectively controlled from nanorods to nanospheres by adjusting the precursor′s concentration in the reaction system. Powder X-ray diffraction (XRD) analysis indicated that the products were in cubic phase. Transmission electronic microscopy (TEM) observation showed that the nanospheres were 30～50 nm in diameter, and the nanorods were 5～10 nm in diameter and 100～600 nm in length, respectively. Phase transformation behavior of the as-prepared products was also investigated.     

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.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.