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31.
32.
Although Brust-Schiffrin two-phase synthesis is a popular method for synthesizing ligand-protected metal nanoparticles with an average size of less than 5 nm, the details on how the reactions can be controlled from a mechanistic point of view are still unclear, therefore hindering efforts to synthesize monodisperse metal nanoparticles. It was recently discovered that this method is basically an inverse-micelle-based synthesis (Li, Y.; Zaluzhna, O.; Xu, B.; Gao, Y.; Modest, J. M.; Tong, Y. Y. J. J. Am. Chem. Soc.2011, 133, 2092). In this letter, the critical role of water and the structure of inverse micelles in typical synthesis of gold nanoparticles were further investigated. We found that (1) water encapsulated in the inverse micelles of [TOA](+) that also hosted metal ions formed a hydrophilic microenvironment that acted as a reaction-enabling proton-accepting medium for the thiol protons (RS-H) and (2) not only the presence but also the amount of water in the reaction medium has a profound effect on the Au(I) precursor species (a pure [TOA][AuX(2)] complex or a mixture of a [TOA][AuX(2)] complex and polymeric [Au(I)SR](n) species), the reduction of Au(III) by thiols, and the formation of uniform small metal nanoparticles. A quantitative analysis of the (1)H NMR of the encapsulated water enabled an estimation of the size and composition of the involved inverse micelles. 相似文献
33.
Sakai N Lista M Kel O Sakurai S Emery D Mareda J Vauthey E Matile S 《Journal of the American Chemical Society》2011,133(39):15224-15227
Facile access to complex systems is crucial to generate the functional materials of the future. Herein, we report self-organizing surface-initiated polymerization (SOSIP) as a user-friendly method to create ordered as well as oriented functional systems on transparent oxide surfaces. In SOSIP, self-organization of monomers and ring-opening disulfide exchange polymerization are combined to ensure the controlled growth of the polymer from the surface. This approach provides rapid access to thick films with smooth, reactivatable surfaces and long-range order with few defects and high precision, including panchromatic photosystems with oriented four-component redox gradients. The activity of SOSIP architectures is clearly better than that of disordered controls. 相似文献
34.
Feyer V Plekan O Kivimäki A Prince KC Moskovskaya TE Zaytseva IL Soshnikov DY Trofimov AB 《The journal of physical chemistry. A》2011,115(26):7722-7733
Core-level X-ray photoemission and near-edge X-ray absorption fine structure spectra of 5-methylcytosine, 5-fluorocytosine, and isocytosine are presented and discussed with the aid of high-level ab initio calculations. The effects of the methylation, halogenation, and isomerization on the relative stabilities of cytosine tautomers are clearly identified spectroscopically. The hydroxy-oxo tautomeric forms of these molecules have been identified, and their quantitative populations at the experimental temperature are calculated and compared with the experimental results and with previous calculations. The calculated values of Gibbs free energy and Boltzmann population ratios are in good agreement with the experimental results characterizing tautomer equilibrium. 相似文献
35.
Periodic mesoporous organosilica with a heterocyclic bridging group of large molecular weight, tris[3-(trimethoxysilyl)propyl]isocyanurate, is reported. Incorporation of an organic moiety into the silica framework afforded material attractive for adsorption of mercury and related heavy metal ions from aqueous solutions. 相似文献
36.
Travnikova O Liu JC Lindblad A Nicolas C Söderström J Kimberg V Gel'mukhanov F Miron C 《Physical review letters》2010,105(23):233001
Dissociative nuclear motion in core-excited molecular states leads to a splitting of the fragment Auger lines: the Auger-Doppler effect. We present here for the first time experimental evidence for an Auger-Doppler effect following F1s → a(1g)* inner-shell excitation by circularly polarized x rays in SF(6). In spite of a uniform distribution of the dissociating S-F bonds near the polarization plane of the light, the intersection between the subpopulation of molecules selected by the core excitation with the cone of dissociation induces a strong anisotropy in the distribution of the S-F bonds that contributes to the scattering profile measured in the polarization plane. 相似文献
37.
Crack analysis of linear coupled thermoelasticity in two-dimensional, isotropic, non-homogeneous and linear elastic functionally graded materials subjected to thermal shock is performed by using a boundary-domain element method. The material parameters are assumed to be continuous functions of the spatial coordinates. Fundamental solutions of linear coupled thermoelasticity for the corresponding isotropic, homogeneous and linear elastic solids in Laplace-transformed domain are applied in the boundary-domain integral formulation. A collocation method is implemented for the numerical solution. Numerical examples for an exponential gradation of the material parameters are presented and discussed. The influences of the material gradation on the stress intensity factors are investigated. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
38.
We present the results for thermal expansion coefficients of Sn2P2S6 crystals determined both in the crystallographic system and the system based on eigenvectors of thermal expansion tensor. Peculiarities of temperature evolution of the indicative surface of thermal expansion tensor for Sn2P2S6 are discussed, including the region of their ferroelectric phase transition. 相似文献
39.
Wen Li Edita Mjekiqi Wessel Douma Xin Wang Dr. Oksana Kavatsyuk Prof. Dr. Ronnie Hoekstra Dr. Jean-Christophe Poully Dr. Thomas Schlathölter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16114-16119
Vacuum ultraviolet photoionization of a gas-phase oligonucleotide anion leads to the formation of a valence hole. This hole migrates towards an energetically favorable site where it can weaken bonds and ultimately lead to bond cleavage. We have studied Vacuum UV photoionization of deprotonated oligonucleotides containing the human telomere sequence dTTAGGG and G-quadruplex structures consisting of four dTGGGGT single strands, stabilized by NH4+ counter ions. The oligonucleotide and G-quadruplex anions were confined in a radiofrequency ion trap, interfaced with a synchrotron beamline and the photofragmentation was studied using time-of-flight mass spectrometry. Oligonucleotide 12-mers containing the 5'-TTAGGG sequence were found to predominantly break in the GGG region, whereas no selective bond cleavage region was observed for the reversed 5'-GGGATT sequence. For G-quadruplex structures, fragmentation was quenched and mostly non-dissociative single and double electron removal was observed. 相似文献
40.
Oksana Kharchenko Vitaliy Smokal Oksana Krupka Pavlo Virych Natalia Kutsevol 《Molecular Crystals and Liquid Crystals》2020,699(1):51-56
AbstractThe thermostability of polysterene with/without new styrylquinoline containing methacrylic fragments has been described in the present work. Polystyrene and copolymers based on styrene and new methacrylic styrylquinoline containing monomers were synthesized by free radical thermoinitiated polymerization in the presence of 2,2′-azobisisobutyronitrile (1?wt%) as initiator at inert atmosphere. The impact of 2-[2-(4-methoxyphenyl)ethenyl]quinolin-8-yl 2-methylpropyl-2-enoate (М1), 2-(2-phenylethenyl)quinolin-8-yl 2-methylpropyl-2-enoate (М2), 2-[2-(4-nitrophenyl)ethenyl]quinolin-8-yl 2-methylpropyl-2-enoate (М3) on thermal stability of polystyrene was investigated. The thermostability of polystyrene and copolymers ST:M1, ST:M2, ST:M3 were studied by dynamic thermograviametric analysis. It was shown that destruction of polystyrene with corresponding units M1-M2 starts at 41–42°С higher, than reference polystyrene. 相似文献