CdS微球体的水热法制备及紫外-可见光谱分析

本文以水热法制得了CdS微球体，采用XRD、SEM、TEM等测试手段对产物进行了表征。实验结果表明，硫源、溶剂及其浓度对产物的形貌有显著影响。在180 ℃下，以硫脲为硫源，EDTA-二钠饱和水溶液为溶剂制得的CdS微球体具有良好的形貌，外形规则，直径大约2~5 μm。紫外-可见光谱分析表明CdS微球体的吸收峰与体相CdS相比出现了蓝移。     

Cu2+掺杂CdS纳米晶的制备与表征

以巯基乙酸为稳定剂,采用水相合成法制备了Cu2+掺杂的CdS纳米晶. 分别用电感耦合等离子体发射光谱仪、原子力显微镜测试技术对样品的化学成分及形状进行分析表征,研究了掺杂CdS纳米晶的荧光激发与发射光谱. 实验结果表明,在样品制备过程的溶液中回流2 h后,组成为Cd0.99Cu0.01S的样品形状有棒状和粒状2种,Cu2+的掺入使得CdS纳米晶的荧光发射光谱红移,没有掺杂的样品在回流前的最大发射波长在520 nm处,而组成为Cd0.99Cu0.01S和Cd0.98Cu0.02S的样品在回流前的最大发射波长分别为595和610 nm,通过改变Cu与Cd摩尔比可调控CdS纳米晶的发射波长范围.     

CdSe/CdS/SiO2复合纳米球的制备及发光性能

采用两相法合成了CdSe/CdS核-壳结构的量子点, 用氨水催化水解正硅酸乙酯制得复合结构的CdSe/CdS/SiO₂发光纳米球. 通过对量子点用量、氨水用量、反应时间及溶剂比例等实验条件的调节, 得到了单分散性较好, 尺寸在23~145 nm的复合发光纳米球. 利用紫外-可见吸收光谱和荧光发射光谱对其发光性能进行了研究, 同时利用透射电镜(TEM)观察复合纳米球的形貌. 结果表明, 复合发光纳米球样品的最高荧光量子产率可达8%.     

聚乙烯吡咯烷酮修饰的CdS纳米晶：多元醇合成、表征和可见光活性

采用溶剂热法合成了具有不同晶粒尺寸的聚乙烯吡咯烷酮（PVP）修饰的CdS纳米晶,并运用XRD,N₂物理吸附,TEM,IR,UV-Vis等手段进行表征。结果表明,所制得的样品均为聚乙烯吡咯烷酮(PVP)修饰的CdS纳米晶;添加四甲基氢氧化铵(TMAH)有利于获得晶粒尺寸较小的CdS纳米晶;受纳米晶粒尺寸的影响,CdS纳米晶的吸收边发生蓝移且可见光催化活性明显提高。     

利用牛血清蛋白合成CdS纳米棒和网状纳米线

采用简单易控、对环境友好的矿化方法, 利用牛血清蛋白(BSA)做模板, 通过Cd2+与硫代乙酰胺(TAA)反应制备了形貌均一的CdS纳米棒和网状纳米线. 分别采用透射电子显微镜(TEM)、X射线能谱(EDS)、X射线衍射(XRD)、荧光(PL)发射谱和导电原子力显微镜(C-AFM)等方法对不同实验温度下制备的CdS样品的结构形貌、成分组成和光学性质及微区电子传输行为进行了表征. 结果表明: 在实验反应温度为20 ℃时, 得到的产物为单分散性好的CdS 纳米棒, 长度为250 nm, 直径为30 nm; 在50 ℃时, 得到网状CdS纳米线, 其长度为2-3 μm; CdS纳米棒和网状纳米线均为立方相闪锌矿结构. 荧光性质的测试表明, CdS纳米棒和网状纳米线具有优良的荧光性能, 电流-电压(I-V)特性的表征表明CdS纳米线具有很好的电导特性.     

巯萘剂表面修饰的CdS纳米微粒的合成及发光特性

用疏萘剂(TN)作为表面修饰剂,在甲醇溶液中合成了CdS/TN纳米微粒,用TEM测得纳米微粒呈球形,其粒径约10nm,吸收光谱和荧光光谱研究表明,[S^2-]/[TN]浓度比、TN和镉离子的浓度对CdS/TN纳米微粒的粒径及发光特性具有显著影响,且随着条件的改变,CdS/TN纳米微粒的发射波长红移100nm,表现出明显的量子尺寸特性.XPS显示所制得表面修饰纳米微粒的核为CdS.     

CdS:Mn纳米棒的溶剂热合成与发光性质

近年来,一维纳米材料已成为广泛的研究热点.其中,Ⅱ-Ⅵ族掺杂半导体发光材料是一个重要的研究方向.研究者已通过不同的方法合成ZnS或CdS基掺杂纳米发光材料,以期得到基质与发光中心之间有效的能量传递,以及控制基质本身的缺陷发光.溶剂热便是其中一种较新的合成方法,通过它可以在相对温和的反应条件下得到均一的、结晶度较高的产品,在硫化物纳米发光材料的合成方面具有一定的优势.本文以乙二胺为溶剂,采用溶剂热方法制备出CdS︰Mn纳米棒,并系统研究了反应温度、硫镉比和反应时间对CdS︰Mn纳米晶的结晶度和发光性质的影响.(1)反应温度的影响.当[Cd(CH3COO)2]=0.0278mol·L-1,[TAA](硫代乙酰胺)=0.0556mol·L-1,[Mn(CH3COO)2]=0.000278mol·L-1时,分别在130,190,220,230,250℃恒温反应10h.随着反应温度的升高,CdS︰Mn纳米晶的结晶度逐渐提高.因为Mn2+掺杂进入CdS晶格,CdS纳米棒沿[001]晶向的生长优势逐步减弱并最终消失.在130～220℃之间,样品的发光强度变化不大.在220℃以上,样品的发光强度随反应温度的升高而迅速降低.(2)硫镉比的影响.当[Cd(CH3COO)2]=0.0278mol·L-1,[Mn(CH3COO)2]=0.000278mol·L-1时,改变TAA的浓度,分别采用0.5︰1,1︰1,1.5︰1,2︰1的硫镉摩尔比,在130℃恒温反应10h.发现随着硫镉比的提高,CdS︰Mn纳米晶的结晶度逐渐提高.当反应物中硫过量时,晶格缺陷以及表面悬空键数量降低,产品的发光强度随硫镉比升高而逐步提高.(3)反应时间的影响.当[Cd(CH3COO)2]=0.0278mol·L-1,[TAA]=0.0556mol·L-1,[Mn(CH3COO)2]=0.000278mol·L-1时,分别在130℃恒温反应1.5,2.5,4,6,10h.当反应时间少于4h时,CdS︰Mn纳米晶的结晶度迅速提高;而在4～10h之间,产品的结晶度变化不大.TEM图像显示了CdS︰Mn纳米棒的形成过程,只有当反应时间达到4h以上时,才能得到棒状产品.随着反应时间的延长,产品的发光强度先急剧降低,而后略微升高,这可能与纳米棒形成过程中产生的大量表面态有关.通过发光性质的研究,发现CdS基质的缺陷发光得到很好的抑制,产品在室温下即具有绝对优势的Mn2+发光(593nm),归于Mn2+的d-d(4T1-6A1)跃迁.激发光谱表明,本文所讨论的样品均显示出CdS基质的宽吸收,CdS基质与发光中心Mn2+之间存在有效的能量传递.综合考虑产品的形状与发光性质,当采用2︰1的硫镉比,不需要任何其他添加剂,在130℃反应10h制得Mn2+掺杂浓度为1%的CdS纳米棒,其在593nm附近的发光强度较强.CdS︰Mn纳米棒在纳米尺度电子和光子设备中具有潜在的应用价值.     

聚乙烯烷酮修饰CdS纳米微粒的制备及其光电转移特性

以聚乙烯烷酮（PVP）为修饰剂,制备了CdS纳米微粒。实验结果表明PVP与CdS纳米微粒间存在着强的相互作用,PVP和CdS纳米微粒的荧光都在很大程度上发生淬灭。其原因在于作为修饰剂的PVP与CdS纳米微粒子间发生了特殊缔合．受激时形成共振激发态,电子能量弛豫被延迟。     

用离子液前驱体合成高荧光性能的ZnO和CdS纳米材料

合成了含Cd和Zn的离子液,使其提供金属离子,与Na2S反应制备离子液包裹的半导体纳米材料．X射线衍射和透射电子显微镜分析结果显示：在Cd离子液与Na2S反应中,得到的是尺寸在5～6nm、离子液包裹CdS纳米晶,而在Zn的体系中,最终产物为尺寸在1μm左右六方盘形貌的ZnO颗粒．用热力学和结晶动力学详细讨论了造成Cd和Zn体系在反应条件相同时,产物的形貌和结构差别的原因．荧光性质的测试结果表明：该方法制备的ZnO和CdS纳米粒子具有很好的荧光性能．     

CdTe量子点的无机合成及其荧光性质

以Na HTe为碲源,巯基乙酸为稳定剂,在水溶液中制得Cd Te前驱体(A);A分别采用微波辐射加热法(1)、水热合成法(2)和水浴回流法(3)制备了三种水溶性Cd Te纳米量子点(Cd Te-1t~Cd Te-3t),其结构经XRD和TEM表征。利用UV-Vis和荧光发射光谱考察了反应时间(t)对Cd Te-1t~Cd Te-3t荧光性质的影响。实验结果表明:在反应条件[微波功率400 W,温度96℃,微波辐射5 min]下,可快速制得Cd Te-15,量子产率41.16%,粒径3.2 nm,抗光漂白性能较好;延长反应时间,Cd Te-1t~Cd Te-3t的特征发射峰和特征吸收峰均红移,量子产率先增加后降低。     

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%.     

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.     

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.     

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.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.