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71.
Raman mapping and in situ SERS spectroelectrochemical studies of 6-mercaptopurine SAMs on the gold electrode 总被引:1,自引:0,他引:1
Yang H Liu Y Liu Z Yang Y Jiang J Zhang Z Shen G Yu R 《The journal of physical chemistry. B》2005,109(7):2739-2744
The self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) were formed at the roughened polycrystalline gold surfaces in acid and alkaline media. The time-dependent Raman mapping spectral analysis in conjunction with the quantum calculations for the vibrational modes using ab initio BLYP/6-31G method suggested that both of the resulted 6MP SAMs adopted the same adsorption mode through the S atom of pyrimidine moiety and the N7 atom of the imidazole moiety anchoring the gold surface in a vertical way. The in situ surface-enhanced Raman scattering spectroelectrochemical experiment was conducted to examine the stability of the SAMs at various bias potentials. It was found that the detaching process of the 6MP SAMs from the surface involved one electron reduction as the voltage was applied at ca. 0.7 V vs a standard calomel electrode. 相似文献
72.
新型含氟聚芳醚酮的合成与表征 总被引:10,自引:0,他引:10
聚芳醚酮具有很高的热稳定性和优良的电性能及机械性能 ,已经被广泛应用于宇航、电子及核能等高技术领域 [1] .氟元素的引入可以降低材料介电常数、折光指数和吸水率 ,提高热稳定性、溶解性和阻燃性 ,增加材料透明度 ,使这类聚合物在光电子、光学和微电子等应用领域的研究倍受关注 [2~ 4 ] .本文在合成含三氟甲基苯侧基的聚芳醚酮 [5] 的基础上 ,设计并合成了新型的含氟量更高的单体和聚合物 ,并对其性能进行了初步研究 .1 实验部分1 .1 试剂与仪器 [3,5 -二 (三氟甲基 ) ]苯代对苯醌 (自制 ) ;锌粉 ,A.R.级 ,天津化学试剂一厂产品 ;… 相似文献
73.
本文合成了部分烷基化三氟乙酰化的β-环糊精手性固定相(DP-TFA-β-CD),并把它与普通聚硅氧烷OV-7混合制备出了柱效高、热稳定性好的手性石英毛细管柱。与直接涂DP-TFA-β-CD相比,混合固定相能在较短分析时间内对卤代烃、醇、酯、γ-内酯、胺等对映体有更好的拆分。 相似文献
74.
Weihua Di Xiaoxia Zhao Shaozhe Lu Haifeng Zhao 《Journal of solid state chemistry》2007,180(9):2478-2484
In this work, we used the solution precipitation route to synthesize Eu3+-doped YPO4·nH2O nanowires. The structure, morphology, composition, thermal behavior, and photoluminescence of as-synthesized product were characterized by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopic (FE-SEM) and photoluminescence (PL) spectra. The dependence of the structure, morphology, composition and luminescent properties on the thermal treatment was investigated. The results indicate that the aqueous synthesis has a better control on the structure, morphology, composition of the products, and that the heat treatment induces the transitions of the structure, composition, and luminescent properties. 相似文献
75.
76.
Dimethylformamide (DMF) acts as an efficient source of carbon monoxide and dimethylamine in the palladium-catalyzed aminocarbonylation (Heck carbonylation) of p-tolyl bromide to provide the dimethylamide. Addition of amines to the reaction mixture in excess delivers the corresponding aryl amides in good yields. The amines employed, benzylamine, morpholine, and aniline, all constitute good reaction partners. The reaction proceeds smoothly with bromobenzene and more electron-rich aryl bromides, but electron-deficient aryl bromides fail to undergo aminocarbonylation. The reactions are conducted at 180-190 degrees C for 15-20 min with microwave heating in a reaction mixture containing imidazole and potassium tert-butoxide: the latter is required to promote decomposition of the DMF solvent at a suitable rate. The beneficial effects of controlled microwave irradiation as an energy source for the rapid heating of the carbonylation reaction mixture are demonstrated. The carbonylation procedure reported herein, which relies on the in situ generation of carbon monoxide, serves as a convenient alternative to other carbonylation methods and is particularly applicable to small-scale reactions where short reaction times are desired and the direct use of carbon monoxide gas is impractical. 相似文献
77.
IntroductionInthcsclcctivcoxidationofalkanes.suchas'theoxidativccouplingofmcthanc(0CM)andthcoxidativcdch}'drogenationofcthanc(0DE)t0prcparccth}'lene.bothoxidcionsofthelatticeandtheox}'genspeciesovercataIystsuffocepla}'animportantrole.Althoughcxtcnsivcinvcstigationshavcbeengivcntothecharactcrizationofox}'gcnspccicsandthcreactionofox}'gcnspecicsx`ithalkanes,itisstilldifficulttosayt`hichoncsofox}'gcnspcciesarcthcactivcspecicsinthcactivation0falkancs.bccauscthenaturcofcatal}'stsandthecxperimcntc… 相似文献
78.
Determination of enantiomeric purity is most often done under overload conditions, which leads to deformed peaks. In general, the best resolutions are obtained when the small peak appears before the large peak in the electropherogram. To be able to determine the R(+)-impurity in the S(-)-form as well as the S(-)-impurity in the R(+)-form the elution orders have to be reversed. The present paper describes reversal of enantiomeric elution order for the basic analyte propranolol and the acidic analyte ibuprofen. For propranolol, a charged heptakis-(6-sulfo)-beta-cyclodextrin (CD) is used in the background electrolyte. For ibuprofen, a mix of the charged heptakis-(6-sulfo)-beta-CD and the uncharged heptakis-(2,3,6-tri-O-methyl)-beta-CD is used in the background electrolyte. The use of a coated capillary and reversal of the polarity shift the elution order, buffer composition is unchanged in both cases. The enantiomers of propranolol and ibuprofen are well separated on both the coated and uncoated capillaries. Detection limits of enantiomer impurities are investigated using spiked samples of both propranolol and ibuprofen. 相似文献
79.
Dispersion of MoO3, NiO, ZnO on rutile TiO2 with low specific surface area was studied with Mercury Porosimeter, SEM, XPS and Ammonia Extraction method. The dispersion thresholds of MoO3, NiO, ZnO on three rutile TiO2 carriers were obtained with XPS, and com-pared with those on anatase TiO2 with high specific surf are area. Ammonia Extraction method was used to identify the surface oxide species interarting with support surface in different strength and it was found that the proportions of oxides that can not be extracted by ammonia extraction are different for MoO3, NiO and ZnO which are supported on rutile TiO2. 相似文献
80.
A series of chiral aromatic imides and diimides were synthesized and their electrochemical, absorption, fluorescent, and chiroptical properties were examined for their potential application as molecular chiroptical switches. These compounds exhibit strong UV-vis absorptions, and can be electrochemically reduced to radical anions that absorb in the near infrared (NIR) region. Further reduction to the dianionic states results in new absorptions in the visible region. The changes in circular dichroism upon redox switching were apparent in the UV-vis region but were absent in the NIR region. 相似文献