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排序方式: 共有131条查询结果,搜索用时 15 毫秒
41.
Measurement of transition dipole moments in lithium dimers using electromagnetically induced transparency 总被引:1,自引:0,他引:1
Qi J Spano FC Kirova T Lazoudis A Magnes J Li L Narducci LM Field RW Lyyra AM 《Physical review letters》2002,88(17):173003
We have observed electromagnetically induced transparency in a Doppler broadened molecular cascade system using fluorescence detection. We demonstrate that the power-dependent splitting of lines in the upper-level fluorescence excitation spectrum can be used as a new spectroscopic tool for the measurement of molecular transition dipole moment functions. 相似文献
42.
卟啉纳米材料制备及在可视化传感器中的应用 总被引:1,自引:0,他引:1
在水/油体系中,利用表面活性剂辅助自组装制备出5,10,15,20-四苯基卟啉锌(ZnTPP)和5,10,15,20-四苯基卟啉钴(CoTPP)纳米材料,改变陈化时间制备多种形貌卟啉纳米材料,如纳米球、纳米棒和纳米片等。利用紫外-可见光谱和荧光光谱分析两种卟啉纳米材料的光学性质,ZnTPP纳米材料的荧光强度是其单体的4.5倍,具有良好光敏性。基于两种卟啉纳米材料构建可视化阵列芯片对挥发性气体己醛检测,卟啉纳米的响应度是它们单体的2倍。 相似文献
43.
Namuswe F Kasper GD Sarjeant AA Hayashi T Krest CM Green MT Moënne-Loccoz P Goldberg DP 《Journal of the American Chemical Society》2008,130(43):14189-14200
Iron peroxide species have been identified as important intermediates in a number of nonheme iron as well as heme-containing enzymes, yet there are only a few examples of such species either synthetic or biological that have been well characterized. We describe the synthesis and structural characterization of a new series of five-coordinate (N4S(thiolate))Fe(II) complexes that react with tert-butyl hydroperoxide ((t)BuOOH) or cumenyl hydroperoxide (CmOOH) to give metastable alkylperoxo-iron(III) species (N4S(thiolate)Fe(III)-OOR) at low temperature. These complexes were designed specifically to mimic the nonheme iron active site of superoxide reductase, which contains a five-coordinate iron(II) center bound by one Cys and four His residues in the active form of the protein. The structures of the Fe(II) complexes are analyzed by X-ray crystallography, and their electrochemical properties are assessed by cyclic voltammetry. For the Fe(III)-OOR species, low-temperature UV-vis spectra reveal intense peaks between 500-550 nm that are typical of peroxide to iron(III) ligand-to-metal charge-transfer (LMCT) transitions, and EPR spectroscopy shows that these alkylperoxo species are all low-spin iron(III) complexes. Identification of the vibrational modes of the Fe(III)-OOR unit comes from resonance Raman (RR) spectroscopy, which shows nu(Fe-O) modes between 600-635 cm(-1) and nu(O-O) bands near 800 cm(-1). These Fe-O stretching frequencies are significantly lower than those found in other low-spin Fe(III)-OOR complexes. Trends in the data conclusively show that this weakening of the Fe-O bond arises from a trans influence of the thiolate donor, and density functional theory (DFT) calculations support these findings. These results suggest a role for the cysteine ligand in SOR, and are discussed in light of the recent assessments of the function of the cysteine ligand in this enzyme. 相似文献
44.
Single crystals of a new beta-octamolybdate salt containing protonated 1,4-diazabicyclo[2.2.2]octane cations were prepared under mild hydrothermal conditions. This compound, [C6H13N2]2[C6H14N2][Mo8O26], was then used as a starting material in the synthesis of [C6H13N2]6[Mo16O53F2].4H2O, which contains previously unreported [Mo16O53F2]12- anions. The structure-directing properties of gamma-[Mo8O26]4-, a likely intermediate in this pH-dependent transformation, are responsible for the site selection of the fluoride incorporation. [Mo16O53F2]12-, the largest reported polyoxofluoromolybdate cluster, expands upon the limited number of such anions in the literature. The structures of both compounds were determined using single-crystal X-ray diffraction. 相似文献
45.
46.
采用具有紫外光聚合性能的聚乙二醇(PEG)基水凝胶材料, 通过紫外光聚合作用快速加工双层水凝胶微流控芯片, 并验证了其对肿瘤细胞代谢液进行检测的可行性. 与传统微流控芯片材料相比, 该水凝胶芯片材料具有更好的生物相容性及可操控性, 可直接加工成形, 在生物学领域特别是细胞培养过程控制方面具有良好的应用前景. 实验结果表明, 该水凝胶微流控芯片可在微尺度空间有效模拟细胞生长环境, 并实现对细胞连续捕获后的原位培养. 将该芯片与卟啉可视阵列传感器系统结合, 经代谢特征分析可有效区分不同种类肿瘤细胞, 实现芯片细胞培养平台上的细胞代谢指纹快速可视化传感检测. 相似文献
47.
Rutherford backscattering and channeling spectrometry (RBS/C) are used to identify the crystalline quality (Xmin = 4.87%) Of an InN thin film as a function of depth, and make a non-destructive quantitative analysis of the structure, in order to analyze the tetragonal distortion of the InN thin film at the depth determined. 相似文献
48.
Hernan Sanchez Casalongue Amy Narducci Sarjeant Alexander J. Norquist 《Journal of solid state chemistry》2009,182(6):1297-11620
The role of charge density matching in the formation of templated molybdates under mild hydrothermal conditions was investigated through the use of a series of structurally related amines: piperazine, 1,4-dimethylpiperazine, 2,5-dimethylpiperazine and 2,6-dimethylpiperazine. A series of reactions was conducted in which the relative mole fractions of each component were fixed at 2.5 MoO3:1 amine:330 H2O:2 H2SO4 in order to isolate the effects of the amine, the only variation between reactions was the structure of the amine. Four distinct polyoxomolybdates anions were observed, ranging from zero-dimensional β-[Mo8O26]4− molecular anions to [Mo3O10]n2n− and [Mo8O26]n4n− chains and [Mo5O16]n2n− layers. The primary influence over the structure of the molybdate anion is charge density matching with the protonated amine, which was quantified through surface area approximations based upon both calculated molecular surfaces and polyhedral representations of each anion. Secondary influences include amine symmetry and hydrogen-bonding preferences. The synthesis and characterization of two new compounds are reported. Crystal data: [C6H16N2][Mo3O10]·H2O (1), triclinic, P-1 (no. 2), a=8.0973(7) Å, b=8.8819(9) Å, c=11.5969(11) Å, α=71.362(9)°, β=82.586(8)°, γ=74.213(8)°, Z=2, R/Rw=0.0262/0.0564, and [C6H16N2]2[Mo8O26] (2), monoclinic, P21/n (no. 14), a=7.9987(11) Å, b=12.5324(19) Å, c=16.003(3) Å, β=97.393(14)°, Z=2, R/Rw=0.0189/0.0454. 相似文献
49.
50.
本文引入并论证了描述动态位错场的张量势(A与B)的规范交换问题,而且证明这种变换可采取这样的形式:B′=B+▽F, A′=A-ρ?/(?t)▽G,x′=x-ρ?/(?t)F,其中xi=eiklAkl。至于F与G,则为带有很大任意性的时空坐标的矢量函数,但它们要满足以下关系式:F=▽×G,▽2F-1/Gt2-(?2/?t2)F=0.进
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