纳米Ca0.8Zn0.2TiO3∶Pr3+, Na+荧光粉的合成和红色发光性质

采用溶胶-凝胶法在较低温度下合成了Ca0.8Zn0.2TiO3∶Pr^3＋,Na^＋纳米荧光粉.金属离子预先分散在溶有柠檬酸的乙二醇溶液中.通过TG-DSC,XRD和SEM对前驱物的分解、晶化和颗粒大小进行了研究.TG-DSC和XRD表明材料的组成随灼烧温度而变化;SEM表明1000 ℃合成材料的粒径在100 nm以下.与高温固相法合成的材料相比,激发光谱主峰发生蓝移,红色发射峰617 nm显著增强.     

溶胶-凝胶法合成纳米铬酸锶镧的工艺研究

以硝酸镧、硝酸铬、硝酸锶为原料，乙二醇为分散剂，柠檬酸为胶溶剂，用溶胶-凝胶法合成纳米级的铬酸锶镧粉体。利用TG，DSC，XRD分析研究了粉料的晶化过程。利用HREM分析了煅烧温度、含锶量对粉料粒径的影响。研究表明，获得纳米晶的最佳烧结温度在800℃。随着锶掺杂量的增加，粉料的粒径逐渐变小。     

聚合物前驱体方法低温合成LiTaO3纳米粉体

采用聚合物前驱体方法,以柠檬酸为配位剂,乙二醇为酯化剂,低温合成纳米LiTaO3粉体.以红外光谱和拉曼光谱研究了柠檬酸与金属离子的配位情况.当柠檬酸和金属离子物质的量的比为2.5:1、柠檬酸和乙二醇的物质的量比为1:2时可形成稳定的Li-Ta前驱体溶胶.用差热.热重对凝胶前驱体的热分解历程进行分析,采用X射线衍射和红外光谱对Li-Ta凝胶前驱体及不同温度下煅烧所得粉体的相组成进行分析.结果表明,凝胶前驱体经600℃下煅烧2 h可以得到纯钙钛矿型纳米LiTaO3粉体.平均粒径为60～80 nm.     

明胶对纳米二氧化钛相变和光催化活性的影响

以明胶为分散剂采用溶胶-凝胶法制备了纳米晶TiO₂粉末.通过XRD、TG-DTA、AFM、N₂吸附-解吸等手段,考察了明胶对TiO₂煅烧过程中相变和平均粒径的影响;用光催化降解甲基橙检测了明胶用量对样品光催化活性的影响.结果表明:明胶的存在抑制了TiO₂由无定形向锐钛矿的相变,降低了锐钛矿向金红石的相变温度;同时,TiO₂纳米晶的平均粒径也随明胶用量的增加而减小.600℃煅烧样品的光催化活性随明胶用量的增加而提高;800℃煅烧样品在m_G:m_TBOT(明胶与钛酸四丁酯的质量比)=1:8时,具有最高的光催化活性.     

Y2O3和CeO2复合掺杂ZrO2纳米晶的制备与表征

以ZrOCl2.8H2O,Y2O3,Ce（NO3）3.5.5H2O为原料,NH3.H2O作沉淀剂,少量表面活性剂PE作分散剂,采用反向共沉淀-喷雾干燥法,结合物理、化学分散技术,成功地制备了Y2O3,CeO2复合掺杂ZrO2纳米粉末。通过DSC-TG,XRD,XPS,BET和SEM等方法对所制得粉末进行了表征。结果表明：以Ce0.1Y0.1Zr0.8O1.95化学计量比制备的多元氢氧化物胶体经过喷雾干燥处理后,在500℃基本完成水合氧化物的分解,577℃附近完成由非晶相向立方相的转变;经过580-1000℃煅烧后,CeO2和Y2O3已经完全固溶到ZrO2中,形成类质同相体,该粉末系列均属于立方相萤石结构;掺杂进入ZrO2晶格中的Ce呈＋4价形式存在;比表面积由22.0 m^2.g^-1（580℃煅烧）减至4.97 m^2.g^-1（1000℃煅烧）;SEM结果显示800℃煅烧的该粉末颗粒尺寸分布均匀,多呈类球状,且粒径在50-80 nm。     

在乙二醇溶液中合成复合金属醇盐和纳米NiFe2O4

在乙二醇溶液中用电化学法制备了镍、铁醇盐配合物NiFe2(OCH2CH2OH)8,将其溶液水解、真空干燥后在400℃煅烧2 h,得到纳米级NiFe2O4粉体.产物NiFe2(OCH2CH2OH)8通过红外光谱(FTIR)和拉曼光谱(Raman)进行表征,纳米NiFe2O4通过X射线粉末衍射(XRD)和电子显微镜(TEM、SEM)进行表征.实验表明,前驱体中含有OCH2CH2OH基团,可以有效克服水解与煅烧过程中的团聚现象,经400 ℃煅烧2 h得到的纳米NiFe2O4粉体,颗粒分散较好、纯度高,粒径在25～40 nm.     

纳米二氧化钛的制备及其光催化性能

分别采用水热法和溶胶-凝胶法制备了TiO2纳米粉体;利用X射线衍射仪和扫描电镜分析了两种方法制备的TiO2粉体的形貌和晶体结构,并测定了纳米TiO2粉体对罗丹明B的光催化降解活性.结果表明:采用水热法制备的TiO2纳米粉体含有锐钛矿相和金红石相,粒径较小,大约为50nm,而且分散均匀,光催化性能良好;采用溶胶-凝胶法制备的TiO2粉体经过550℃煅烧后仍然为锐钛矿相,而且粒径较大,大约为80nm.     

熔盐法可控合成球形CeO_2的研究

以NaCl-KCl为熔盐,采用熔盐法制备了球形CeO_2纳米粉。在实验过程中,通过改变NaCl-KCl与Ce之间的比例、煅烧温度、煅烧时间等工艺参数,考察了熔盐法制备工艺参数对CeO_2粉末的形貌、颗粒尺寸和分散性的影响,以此实现了球形CeO_2的可控合成。通过SEM,XRD和激光粒度分析仪等测试方法对其颗粒形貌、分散性、物相、粒径等性能进行了表征。结果表明:通过控制制备条件,可以获得分散性良好、结晶完整的不同粒径的球形CeO_2纳米粉。当NaCl-KCl与Ce比为3∶1,煅烧温度为800℃,保温2 h时,获得的CeO_2纳米粉粒径约为85 nm。     

煅烧工艺对纳米MgO粒径及活性的影响

以六水合氯化镁和碳酸钠为原料,乙二醇为介质,采用直接沉淀法制备了纳米MgO粉体。通过热重分析确定了前驱物的煅烧温度范围,采用柠檬酸值法、静态除氟测定了煅烧产物的活性,并与普通MgO的活性进行了比较,X射线衍射法计算了煅烧产物的平均粒径,探讨了煅烧温度和保温时间对纳米MgO粒径及活性的影响。结果表明:当煅烧温度为430℃和保温时间为1.5h时,得到的纳米MgO活性最高(CAA值为14.35s),粒径较小15.77nm;而当煅烧温度为450℃和保温时间为1.5h时得到的纳米MgO活性较高(CAA值为23.44 s),粒径最小11.47nm。可见,煅烧工艺对纳米MgO粒径及活性影响很大,超细MgO并不一定是高活性MgO。另外,探讨了碱式碳酸镁低温分解机理。     

红色长余辉发光材料Ca2Zn4Ti15O36∶Pr3+的合成和发光性质

分别采用高温固相法和溶胶-凝胶法合成了新型红色长余辉发光材料Ca2Zn4Ti15O36∶Pr. 高温固相法合成Ca2Zn4Ti15O36需要在1200 ℃灼烧96 h才能形成纯物相. 热重分析曲线和X射线衍射分析结果表明 溶胶-凝胶法制得的前驱体在700 ℃灼烧12 h开始形成Ca2Zn4Ti15O36物相; 在1000 ℃灼烧24 h得到Ca2Zn4Ti15O36纯物相; 最佳反应温度为1000 ℃, 激活剂Pr3+的最佳浓度为0.6mol%, 发光强度比高温固相法增强了510%.     

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.     

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.     

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.     

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.     

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.