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991.
Jian-How WongSzetsen Lee 《Physica B: Condensed Matter》2012,407(2):232-234
We report the use of silver (Ag) colloids in the spectroscopic differentiation of methyl red (MR) isomers (o-MR, m-MR, p-MR) by fluorescence techniques. Under different pH conditions, the formation of MR-Ag complex has an impact on the fluorescence band shapes and peak position shift, which are distinctive between MR isomers. The fluorescence quenching between 400 and 414 nm accompanied by simultaneous enhancement between 510 and 541 nm changes with pH are closely related to energy transfer efficiency and the interaction between the MR isomers and the Ag surface. 相似文献
992.
In the present work, mesoporous silica nanoparticles (MSNs) with well-ordered hexagonal structure were synthesized using Sodium Carboxy Methyl Cellulose. The MSNs were characterized by scanning electron microscopy, dynamic light scattering, powder XRD, nitrogen physisorption and Transmission electron microscopy. The MSNs were also functionalized with thiol groups and its capacity toward adsorption of a large cation, i.e. lead was investigated. Scanning electron microscopy reveals that MSNs have semi-spherical shapes. The XRD pattern of the calcined sample shows at least five well-defined peaks which point out that silicate nanoparticles have hexagonal array of pores as MCM-41 structure. The nitrogen adsorption isotherm displays a type IV isotherm according to the IUPAC classification. A sharp inflection in capillary condensation/evaporation step specifies that well-ordered MCM-41 nanoparticles were synthesized. TEM image shows the well-ordered hexagonal structure of MSNs. The adsorption capacity of functionalized MSNs was higher than functionalized MCM-41 in which one reason for such behavior might be explained by higher accessibility of pores of functionalized MSNs. This approach was carried out using relatively low-cost and nonhazardous reactants in concentrated reaction medium and also the yield of this approach was high up to 96% by weight. 相似文献
993.
994.
Dmitriy A. Sibgatulin Dmitriy M. Volochnyuk Eduard B. Rusanov Alexander N. Chernega 《Journal of fluorine chemistry》2010,131(2):234-237
The reaction of a set of enamines with methyl trifluoropyruvate and its imine was investigated. As a result, a simple procedure for synthesis of trifluoromethylated 2-pyrrolidone and 2-pyrrolone derivatives has been developed. 相似文献
995.
The interactions of brilliant cresyl violet (BCV) with herring sperm DNA in γ-cyclodextrin (γ-CD) supramolecular system were studied by UV-vis absorption spectroscopy and cyclic voltammetry (CV). Both UV-vis absorption and CV data show that the interaction of BCV with DNA depends on the concentration ratio of BCV to DNA (R), the initial concentration of BCV and γ-CD. The binding constants of BCV monomer, (BCV)2 dimer and (BCV)2-γ-CD inclusion complex with DNA are 1.64 × 105, 2.56 × 104 and 2.32 × 103 M−1, respectively. It was observed that γ-CD can affect the interactive mode of BCV with DNA. If R is larger than 0.5, the (BCV)2-γ-CD inclusion complex will retain intact and bind to DNA via the electrostatic attraction forces. By contrast, when R is smaller than 0.5, the inclusion complex will be partially dissociated and the free BCV monomer is intercalated into the double-helix structure of DNA attributing to the more favorable microenvironment of DNA for the BCV monomer. Our work postulates the importance of the initial concentration of dye and host molecule on the interaction of dye with DNA in living bodies. 相似文献
996.
An enyne dimer (1) of methyl propiolate was reacted with amines to form dimethyl (E,E)-2-amino-2,4-hexadiene dioates with remarkable chemospecificity, regiospecificity, and stereospecificity. This enyne was also reduced by Ph3P stereospecifically to form dimethyl (E,E)-muconic ester. Hydrogenation of the conjugated amino-diene led to an efficient production of dimethyl α-aminoadipate. A lactam of dimethyl α-aminoadipate was obtained in high yield by simply varying the hydrogenation conditions. 相似文献
997.
998.
<正>4-Amino-3-mercapto-6-methyl-l,2,4-triazin-5(4H)-one 1 converted to 4-amino-6-methy-3-(methylthio)-1,2,4-triazin-5(4H)-one by methylation with methyl iodide.Controlled hydrazination of the resulting compound afforded 4-amino-3-hydrazinyl-6- methyl-l,2,4-triazin-5(4H)-one 2 as a building block,to the synthesis of some novel derivatives of[1,2,4]triazino- [4,3,b][1,2,4,5]tetrazepine 3-6,by the reaction with 3-chloropentane-2,4-dione,chloro acetonitrile,1,3-dichloroacetone,and methyl bromoacetate.This general synthetic procedure can be extended to the preparation of wide variety of tetrazepines using 1,2- bielectrophiles derivatives. 相似文献
999.
在弱酸性条件下,甲基蓝(MB)可以通过静电和疏水作用聚集到血红蛋白(Hb)上并形成离子缔合物,不仅使得吸收光谱发生变化,而且使得共振瑞利散射增强。据此发展了一种测定Hb的RRS便捷方法,其线性范围和检出限分别为0.2~20μg/mL和0.012μg/mL。与RRS法相比,分光光度法的线性范围和检出限分别为8~60μg/mL和0.688μg/mL(344 nm),5~60μg/mL和0.398μg/mL(408 nm)。此RRS法可用于尿样中Hb的痕量检测。实验考察了体系的吸收、散射光谱性质和最佳聚合条件,并在最佳条件下研究了分析参数及作用机理。并初步讨论了有机小分子对体系的影响,结果表明分子间氢键是主要作用力不容忽视。 相似文献
1000.
改性H-ZSM-34上氯甲烷催化转化制低碳烯烃 总被引:1,自引:0,他引:1
比较了几种典型的沸石分子筛在氯甲烷转化制乙烯、丙烯和丁烯等低碳烯烃反应中的催化性能, 发现H-ZSM-34具有较佳的催化活性和选择性. 经乙二胺四乙酸二钠(Na2H2EDTA)水溶液处理, 并经离子交换及焙烧后, H-ZSM-34上氯甲烷转化制低碳烯烃的催化性能显著改善. 当Na2H2EDTA浓度为0.1 mol/L, 反应温度为673 K, CH3Cl分压9.2 kPa时, C2-C4烯烃选择性和收率分别达82%和61%. 研究还发现, Ce修饰H-ZSM-34催化剂同样可改善氯甲烷制低碳烯烃的选择性和收率. 表征结果表明, Na2H2EDTA处理和Ce修饰均降低了H-ZSM-34的酸性. 酸性的降低可抑制低碳烯烃的氢转移反应, 继而避免了其进一步转化为低碳烷烃. 相似文献