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941.
Ranganathan Velu 《Tetrahedron letters》2010,51(33):4331-9264
The aza-crown ether acridinedione-functionalized gold nanoparticles (ACEADD-GNPs) 6 have been synthesized and investigated as a fluorescent chemosensor for metal ions. A blue shift along with an intensity enhancement of emission and color change are observed in the presence of both Ca2+ and Mg2+ ions. The enhanced fluorescence intensity is attributed to the photoinduced electron transfer (PET) suppression through space and color change of the suspension from red to blue due to shifted surface plasmon resonance (SPR) with aggregation of nanoparticles by the sandwich complexation. 相似文献
942.
The formation mechanism for multiply charged ions (Cq+ and Oq+ (q = 2–4)) were investigated using a dual polarity time-of-flight mass spectrometer when diethyl ether clusters interacted with nanosecond laser pulse. The signal intensity of multiply charged ions and electron energy was measured experimentally. It was shown that the intensity of multiply charged ions increased about 50 times when laser intensity increased from 7.6 × 109 to 7.0 × 1010 W/cm2, then saturated as laser intensity increased further. It is interesting that the evolution of the mean value of electron energy was same to that of multiply charged ions. The theoretical calculation showed the ionization potential of atomic ions could be significantly decreased due to the effect of Coulomb screening especially at low laser intensity. It indicated that the electron ionization combined with Coulomb screening effect could explain the production of multiply charged ions in nanosecond laser field. 相似文献
943.
944.
Density Functional Theory and post‐Hartree Fock calculations reveal an unusual energy profile for Zn? S and Zn? N bond dissociation reactions in several [Zn(SR)4]2? and [Zn(Im)(SR)3]? complexes. The Zn? S bond dissociation in tetrathiolate dianions, which is highly exothermic in the gas phase, proceeds through a late transition state which can be rationalized on the basis of an avoided crossing resulting from Coulomb repulsion between the anionic fragments and ligand‐to‐metal charge‐transfer in the [Zn(SR)4]2? complexes. When solvation models for water, DMSO, or acetonitrile are included, some complexes become stable while others are metastable, so this constitutes the first theoretical model which is in full agreement with the experimental data for various [Zn(SR)4]2?, [Zn(SR)3]?, and [Zn(Im)(SR)3]? complexes. The analysis given here indicates that the Zn(Cys)4 and Zn(His)(Cys)3 cores of numerous proteins are metastable with respect to Zn? S and Zn? N bond dissociation, respectively. This is consistent with the kinetic lability at the zinc‐centers and illustrates that in nature, thermodynamic stability is imparted upon the zinc cores by the protein environment. 相似文献
945.
In this article, we describe the analysis of aptamers for Hg2+ ions through CE with LIF (CE‐LIF) detection using 2% poly(ethylene oxide) solutions containing OliGreen (fluorophore). In the presence of an EOF, DNA strands migrating against the EOF were detected at the cathode end. Four DNA strands – T33, T5C28, T5C5T23, and T15C5T13 – could not be separated through CE‐LIF in the absence of Hg2+. At 0.3 mM Hg2+, however, all four were partially separated within 20 min, with SDs of the migration times all being less than 2.5%. From the CE, fluorescence, and ellipticity data, we concluded that the conformations of these four DNA strands all changed from random‐coil to folded structures as a result of T–Hg2+–T bonding. In addition, we found that this CE approach provided different electropherograms patterns for T7, T15, and T33 in the absence and presence of Hg2+, indicating various interactions of the DNA strands with Hg2+. Using this simple, high‐resolution CE approach, we also demonstrated that adenosine triphosphate has a stronger interaction with the adenosine triphosphate aptamer than with either the platelet‐derived growth factor aptamer or T33. This CE approach holds great potential for screening aptamers for small solutes, studying the catalytic activity of DNAzymes, and evaluating the biological functions of microRNA. 相似文献
946.
Two novel mono-nuclear zinc(Ⅱ) complexes with oligoaniline-functionalized terpyridine ligands have been synthesized and verified by 1H-NMR,13C-NMR,Elemental Analysis (EA) and X-ray Diffraction (XRD). The UV-vis spectra show the ligand-centered (LC) π-π* transitions and intra-ligand charge transfer (1ILCT) transitions,and the 1ILCT band red-shifts with the increasing number of aromatic amine groups in the ligands. Complex [Zn(L1)2](PF6)2 with an aromatic amine group in ligand shows a strong emission peak at 523 nm in the MeCN solution at 293 K and a blue-shifted band at 517 nm in the alcoholic glass at 77 K. However,for complex [Zn(L2)2](PF6)2 containing aniline dimer modified ligand,no apparent emission can be observed in the MeCN solution at room temperature due to a PET non-radiative decay pathway. Both of them show multiplicate redox processes based on oligoaniline and terpyridine units. The shifts of redox potentials also reflect the D-A interactions between the oligoaniline units and [Zn(TPY)2]2+ core. 相似文献
947.
The title compound,[Zn2(H2C4BIm)(ox)2]·2H2O(1,H2C4BIm = 2,2'-(1,4-bu-tanediyl)bis(1H-benzimidazole),has been synthesized by the hydrothermal reaction of Zn(NO3)2·6H2O with H2C4BIm and Na2C2O4 in water solution.It crystallizes in the triclinic system,space group P1 with a = 9.445(9),b = 9.598(9),c = 14.962(14) ,α = 72.160(10),β = 79.905(12),γ = 83.680(11)°,Mr = 633.18,V = 1269(2) 3,Z = 2,Dc = 1.657 g/cm3,F(000) = 644,μ = 1.953 mm-1,the final R = 0.0671 and wR = 0.1689.X-ray crystal structure analysis revealed that 1 is a 3D network with(203)2(20)3 topology in which the ZnII atom can be considered as a 3-connected node and both ox2-and H2C4BIm serve as the linear linkers. 相似文献
948.
Water-soluble CdSe quantum dots (QDs) were synthesized using mercaptosuccinic acid (MSA) as a stabilizer. The growth process and characterization of CdSe quantum dots were determined by transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, Ultraviolet-visible (UV-vis) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Results demonstrated the MSA-capped CdSe QDs were highly crystalline and possessed good optical properties. Further, the resulting products could be used as fluorescent probes to detect Cu2+ ions in physiological buffer solution. The response was linearly proportional to the concentration of Cu2+ ion in the range 2×10−8- 3.5×10−7 mol L−1 with a detection limit of 3.4 nmol L−1. 相似文献
949.
A generalization of the original Jensen-Shannon divergence (JSD) is presented in this work, which gives rise to a non-extensive one-parameter divergence providing a powerful dissimilarity measure between electronic distributions. The analysis performed in this study employs the JTD measure to compare one-particle densities of neutral and ionized atomic systems, that generalizes and improves some previous results based on other measures of divergence. Such an improvement mainly arises from the capability of JTD to modify, by means of its order parameter, the relative contribution of specific relevant regions of the atomic densities under comparison, in both position and momentum spaces. Relevant information of the ionization processes attending to structural pattern and periodicity is found, as well as the strong correlation between extremal values of the neutral-cation JTD and those of the atomic ionization potential. Similar conclusions are obtained from processes involving an anion. The analysis includes a study of the dependence of JTD on its order for fixed atomic couples. 相似文献
950.
Theoretical calculations employing the modified over-barrier model to investigate single and double ionization cross sections of helium in collisions with highly charged ions are presented in the strong perturbation region. It shows the velocity and charge state dependences of cross sections, which coincides with the available experimental data. In order to determine the reliability of this model for partially stripped projectiles, the cross-section ratios have been measured for CZp+, OZp+-He (Zp=1-4) by the coincidence technique in the velocity range of 1-4.5 a.u. The calculated results are approximately in agreement with the experimental data. 相似文献