双盘状ZnO的可控制备

采用水热法制备了形貌可控、 尺寸均一的双盘状ZnO. X射线粉末衍射(XRD)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等测试结果表明, 制备的ZnO具有六方纤锌矿结构, 由2个直径约为4 μm, 厚度约为600 nm的圆盘复合而成. 考察了反应温度和乙酸锌与柠檬酸钾的摩尔比对产物形貌与尺寸的影响, 实现了双盘状ZnO的可控合成, 并初步探讨了其形成机理. 荧光光谱显示, 双盘状ZnO的紫外发射峰半高宽约为10 nm, 比块体ZnO的紫外发射峰半高宽(18 nm)窄, 表明双盘状ZnO具有更好的光学特性.     

Co掺杂ZnO纳米棒的水热法制备及其光致发光性能

以Zn(NO3)2·6H2O 和Co(NO3)2·6H2O为原料, 通过水热法在较低温度下制备了纯ZnO和Co掺杂的ZnO(ZnO:Co)纳米棒. 利用XRD、EDS、TEM和HRTEM对样品进行了表征, 结合光致发光(PL)谱研究了样品的PL性能. 结果表明, 水热法制备纯ZnO和ZnO:Co纳米棒均具有较好的结晶度. Co2+是以替代的形式进入ZnO晶格, 掺入量为2%(原子分数)左右. 纯的ZnO纳米棒平均直径约为20 nm, 平均长度约为180 nm; 掺杂样品的平均直径值约为15 nm, 平均长度约为200 nm左右; Co掺杂轻微地影响ZnO纳米棒的生长. 另外, Co掺杂能够调整ZnO纳米棒的能带结构、提高表面态含量, 进而使得ZnO:Co纳米棒的紫外发光峰位红移, 可见光发光能力增强.     

氧化石墨烯改性ZnO/CeO2复合纳米材料的制备及其紫外屏蔽性能研究

以六水硝酸锌、六水硝酸铈、氧化石墨烯为原料,采用溶胶凝胶法制备了氧化石墨烯(GO)改性ZnO/CeO_2复合纳米紫外屏蔽剂。采用X射线衍射(XRD)、扫描电镜(SEM)、傅立叶变换红外光谱(FTIR)、紫外可见分光光度计(UV-Vis)等测试手段对产物的结构、组成及形貌进行表征,研究了氧化铈与氧化锌摩尔比、GO投入量、屏蔽剂用量以及pH值对复合纳米材料紫外屏蔽性能的影响,探索了氧化石墨烯改性ZnO/CeO_2复合纳米的最佳制备条件。结果表明:氧化石墨烯改性ZnO/CeO_2复合纳米材料中GO、CeO_2、ZnO的平均粒径分别为8. 3、15. 4、37. 5 nm。当pH 6. 0、氧化铈与氧化锌摩尔比为4∶1、GO投入量为2. 0g、屏蔽剂用量为0. 06 g/L时,紫外屏蔽性能强弱顺序为:氧化石墨烯改性ZnO/CeO_2复合纳米材料 GOZnO/CeO_2复合纳米材料 CeO_2 ZnO。     

醇热法制备ZnO纳米棒及其发光性能

在常压条件下,以油酸为分散剂一步反应醇热法制备ZnO纳米棒,利用XRD、SEM、TEM、HRTEM和FTIR等分析技术对产物进行了表征,对产物退火前后的光致发光性能进行了测试,并对ZnO纳米棒生长机理进行讨论. 结果表明,ZnO纳米棒沿[001]方向择优取向生长,直径为10～15 nm,长度为150～200 nm,油酸与ZnO表面Zn(Ⅱ)以螯合键形式相结合,具有良好的近紫外发光性能. 随着退火温度升高,产物深能级发光强度先降低后增加.     

ZnO纳米片自组装空心微球的无模板水热法制备与发光性质

报道了一种简单的制备ZnO纳米片自组装成空心微球的无模板水热法. 即通过醋酸锌与水和乙二醇混合溶剂(V_水/V_乙二醇 = 1/20)在100℃水热反应12 h合成了ZnO空心微球. 利用扫描电子显微镜、透射电子显微镜、X 射线衍射仪和红外光谱对产物进行了表征和分析. 结果表明, 所制备ZnO空心微球的直径为2~5 μm, 它是由直径为10~20 nm纤锌矿结构的ZnO纳米片自组装而成. 研究了水与乙二醇的体积比及反应时间对产物形貌的影响, 结果表明乙二醇在ZnO纳米片的形成与自组装过程中起着关键作用, 并提出了可能的生长机理. 在波长为300 nm光的激发下, 发现ZnO空心微球具有发光峰位于397 nm强的紫外光发光和486 nm弱的蓝绿光发光, 这两种发光分别起源于ZnO宽带隙的激子发射和氧空位与间隙氧之间的跃迁.     

ZnO纳米环的可控合成

以六次甲基四胺(Hexamethylenetetramine, C6H12N4)和水合硝酸锌[Zn(NO3)2·2H2O]为原料, 表面活性剂聚丙烯酰胺-氯化二烯丙基二甲基铵[poly(acrylamide-co-diallyldimethylammonium chloride, 缩写为PAM-CTAC]为形貌控制剂, 采用液相沉淀法合成了ZnO纳米环. 产物的结构与形貌经X射线粉末衍射(XRD)和扫描电子显微镜(SEM)表征. 研究了不同实验条件(如表面活性剂的浓度、反应物浓度、反应温度和反应时间等)对产物形貌与尺寸的影响. 讨论了PAM-CTAC作用下ZnO纳米环可能的形成机理. 结果表明, 合成产物为六方Wurtzite型结构的ZnO纳米环, 环内径约为220 nm, 壁厚约为70 nm. 反应物浓度、反应温度对ZnO纳米环的形成以及纳米环的尺寸都有一定的影响, 但起关键作用的是PAM-CTAC. 通过改变PAM-CTAC的浓度, 能有效地实现ZnO纳米环的可控合成. 室温荧光光谱显示, ZnO纳米环的紫外发射峰具有较窄的半高宽(FWHM)(约7 nm), 表明合成产物具有较窄的尺寸分布.     

加热覆盖有ZnCl2溶液的锌片制备ZnO亚微米棒阵列

将表面覆盖有ZnCl2溶液的锌片加热到400 ℃反应1 h, 在锌片上生长出了ZnO亚微米棒阵列. 采用扫描电镜、透射电子显微镜和X射线衍射仪对所制备的产物进行了表征和分析. 结果表明产物为六方相纤锌矿单晶结构的ZnO亚微米棒, 其直径和长度分别为300～650 nm和6 μm, 提出了ZnO亚微米棒可能的生长机理. 在波长为300 nm光的激发下, 发现了ZnO亚微米棒阵列具有发光峰位于395 nm强的紫外光发光和位于490 nm弱的蓝绿光发光, 这两种发光分别起源于ZnO宽带隙带边发射和ZnO中相应的缺陷结构.     

旋涂水溶液前驱体制备氧化锌薄膜及其性质

通过旋涂法, 采用Zn(OAc)2·2H2O和聚环氧乙烷(PEO)的水溶液为前驱体在不同的热处理温度下制备了ZnO薄膜. PEO的加入增加了溶液的成膜性, 其较低的热分解温度有利于制得纯净的ZnO薄膜. 文中考察了在不同热处理温度下制备的ZnO薄膜的形貌、结晶性、带隙(Eg)以及电导性. 原子力显微镜(AFM)测试表明在热处理温度为400、450和500 ℃制备的ZnO薄膜的粗糙度均方根值分别为3.3、2.7和3.6 nm. 采用透射电子显微镜(TEM)测试发现ZnO薄膜中含有大量纳晶粒子. 通过测试ZnO薄膜的UV-Vis吸收光谱, 根据薄膜位于373 nm处的吸收带边计算得到ZnO的带隙为3.3 eV. 通过对薄膜的电流-电压(I-V)曲线的测试计算得到在热处理温度为400、450和500 ℃制备的ZnO薄膜的电阻率分别为3.3×109、2.7×109和6.6×109 Ω·cm. 450 ℃时制备的ZnO薄膜的电阻率最小, 主要是由于较高的热处理温度有利于提高薄膜的纯度、密度和吸附氧. 而纯度较高、密度较大的薄膜电阻率比较小; 吸附氧含量增加, 晶界势垒增大, 电阻率增大. 因此在纯度和吸附氧的双重作用下450 ℃时制备的ZnO薄膜的电阻率最小, 而500 ℃时制备的ZnO薄膜的电阻率最大.     

ZnO纳米棒薄膜的湿化学法制备及光致发光特性

在80 ℃水浴下, 采用简易的湿化学法在不导电玻璃基底上制备了ZnO纳米棒阵列, 利用X射线衍射仪(XRD)和场发射扫描电镜(FE-SEM)对样品的结构形貌进行了表征. 结果表明, 晶化30 min所得产物为六方纤锌矿相的ZnO纳米棒, 直径大约为80~90 nm. 为了分析不同的低温退火温度和退火气氛对其光致发光性能的影响, 研究了ZnO纳米棒薄膜在不同的后处理条件下的光致发光谱(PL). 实验结果表明, 在O₂气氛下于450 ℃退火1 h后, ZnO纳米棒薄膜的红光发射(约650 nm)强度相对在空气和5%H₂/95%N₂气氛下退火的样品变得更强, 而且该样品的激发波长范围(200~370 nm)与近紫外发光二极管(LEDs)的发射波长范围(350~420 nm)匹配得很好.     

分级多孔结构ZnO微球的制备及其光电性能

采用简单的低温化学溶液沉积方法制备了分级多孔ZnO微球。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电镜(TEM)、N2吸附脱附以及紫外-可见分光光度计(UV-Vis)等对样品进行了表征。结果显示产物为分级多孔结构的ZnO微球,由直径约10~20 nm ZnO颗粒组装而成,比表面积为40 m2.g-1。把多孔ZnO微球用作染料敏化太阳能电池(DSCs)光阳极,结果表明,该光阳极在增强对入射光的散射作用的同时,为染料分子的吸附提供了较大比表面积,从而提高了DSCs的光伏性能。     

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%.     

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.     

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.