Ag/SiO2复合薄膜的紫外光还原制备及其光学性能

采用溶胶凝胶法(sol-gel)制备不同Ag掺杂量的Ag/SiO2复合薄膜,通过紫外辐射技术对薄膜进行了还原处理,采用XRD、SEM、IR、UV-Vis、Raman和荧光光谱(PL)等技术对薄膜样品结构进行了表征和光学性能测试.XRD结果表明,复合薄膜样品中的Ag纳米粒子呈面心立方相,利用谢乐公式计算出金属银的平均晶粒尺寸约为10.2 nm;SEM结果显示,所得Ag/SiO2复合薄膜均匀性良好,薄膜中绝大部分纳米颗粒尺寸较小,薄膜约厚1μm;UV-Vis结果表明,随着,nAg/nSi的增加,Ag纳米粒子在420 nm附近的表面等离子共振吸收峰逐渐增强,并伴有一定的红移;PL谱表明,由于Ag纳米粒子的表面等离子共振,薄膜样品在442 nm处发出强光,并且随着Ag浓度增大,发光强度略有降低,出现蓝移;从Raman光谱可以看出由于Ag纳米颗粒表面局域电磁场增强造成的表面增强的拉曼散射(SERS).     

纳米金汞核-壳粒子的电化学制备及其光谱性质

在聚乙烯吡啶修饰导电玻璃电极表面进行了金纳米粒子的二维单层结构组装,通过电沉积方法在金粒子表面制备了纳米汞壳层.研究结果表明,汞壳层的形成导致了内部金粒子表面等离子体共振的谱峰红移和强度衰减.吸附于汞壳表面的结晶紫分子因可承受被金核增强的电磁场,而使其拉曼散射得到极大的增强.     

帽状锌纳米结构的制备及其表面等离子体共振特性

利用真空热蒸发法在二氧化硅纳米粒子单层膜上沉积锌薄膜制备了帽状锌纳米结构. 采用透射电镜(TEM)、扫描电镜(SEM)、X射线衍射(XRD)和紫外-可见吸收光谱(UV-Vis)对样品的形貌、结构和光学特性进行了表征和研究. SEM照片表明所得到的复合纳米粒子为不完全包裹的帽状结构, 且其表面较粗糙. XRD分析结果显示在二氧化硅纳米粒子上沉积的锌膜呈多晶六角密堆结构. 吸收光谱研究表明, 帽状锌纳米结构在570～760 nm范围内具有明显的由纵向双极子表面等离子体共振引起的吸收峰, 且随着锌帽层厚度的增加或二氧化硅内核粒径的增大, 该吸收峰逐渐红移; 当内核粒径增大到500 nm时, 帽状锌纳米结构在412 nm附近还出现了一个四极子共振峰.     

帽状锑纳米粒子的制备及表面等离子共振特性的研究

采用热蒸发法在SiO₂自组装单层膜上制备了帽状锑纳米粒子,通过扫描电镜(SEM)、原子力显微镜(AFM)、X射线衍射仪(XRD)和紫外-可见-近红外(UV-Vis-NIR)分光光度计对帽状复合纳米粒子的表面形貌、结构以及表面等离子共振特性进行了研究和表征。结果表明,制备的复合纳米粒子呈帽状,表面等离子共振峰具有明显的可调谐性,当二氧化硅粒径增大或锑帽层厚度增加时,等离子共振吸收峰位置红移。     

Au/Pt纳米柱阵列电极的制备及光电催化氧化甲醇性能

利用纳米压印、 电沉积和气相沉积方法构筑了有序均一的Au及Au/Pt纳米柱阵列电极. 通过反射光谱观测到580和660 nm附近的特征吸收谱峰, 并基于有限元电磁场(FEM)理论模拟, 确定其表面等离激元共振(SPR)性质分别对应于纳米柱柱顶的电偶极模式(584 nm)、 电四极模式(638 nm)以及表面等离激元极化子(666 nm). 制备的等离激元纳米柱电极用于甲醇光电催化氧化反应时, SPR效应能显著地增强甲醇的电催化氧化电流. 当表面负载2 nm的金属Pt时, 光电催化氧化甲醇活性最高, 光照使氧化电流增加, 同时甲醇的氧化峰电位随光强的增加逐渐负移, 证明SPR弛豫产生的热空穴参与到光电协同甲醇氧化中. 在恒电流甲醇氧化实验中, 光照使表面氧化反应时间延长6倍, 减小了CO的毒化, 证明SPR对于电极表面产生一定的清洁作用.     

单金纳米棒的光散射分析化学:径向比与分析灵敏度的关系

单纳米颗粒作为信号感应单元在化学与生物传感应用中已引起广泛关注.本文通过暗场显微成像(iDFM)研究了不同径向比金纳米棒的光散射性质.将iDFM与扫描电子显微镜(SEM)结合表征种子生长法制备的金纳米棒,结果发现,因局域表面等离子体共振而展示出的红色散射光随单个金纳米棒的径向比增大逐渐红移,且金纳米棒对其周围介质折光率(RI)变化的敏感程度随径向比增大而增大.这一结果对设计高灵敏的生物纳米传感器、提高分析检测的灵敏度具有很好的指导意义.     

金纳米粒子表面自组装巯基十一烷醇单分子层体系的制备及其光散射特性研究

采用柠檬酸钠还原法制备了水相金纳米粒子, 通过巯基的自组装, 成功获得了巯基十一烷醇(MUN)单分子层保护的金纳米粒子. 用紫外可见光谱、透射电子显微镜、激光散射粒度分析、同步散射光谱和发射光谱等手段对组装前后的金纳米粒子的性质进行了研究. 结果表明: 制备的金纳米粒子最大吸收波长518 nm, 形状规则, 粒度均匀, 平均粒径为14.6 nm, 每个粒子含有约9.64×10⁴原子; 组装之后的金纳米粒子表面等离子体共振吸收峰红移17.0 nm, 平均粒径增大为20.2 nm, 组装层的平均厚度2.8 nm, 与MUN分子长度相当, 结合量实验证明每一个金纳米粒子可以结合约7.52×10³个MUN, 表面覆盖率为83.6%, 粒子分散均匀, 稳定性增强可长期保存; 同步散射光谱变化和发射光谱中分频、差频和倍频峰的存在证明, 金纳米粒子组装前后均具有非线性光学特性.     

PyDDP修饰的金纳米颗粒的制备及其吸收红移机制

用柠檬酸三钠还原四氯化金制备了金纳米颗粒,并用双十八烷氧基二硫代磷酸吡啶盐（PyDDP）对其进行修饰. 红外吸收光谱表明PyDDP与金颗粒表面以共价键方式结合；透射电子显微镜（TEM）的结果表明, 所得到的PyDDP修饰的纳米金颗粒尺寸与修饰前基本相同; PyDDP修饰的金纳米粒子表面等离子吸收发生了较大幅度的红移.利用偶极子模型结合配位理论解释了PyDDP修饰的金纳米颗粒发生红移的机制.     

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.     

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.     

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.