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161.
Haes AJ Zhao J Zou S Own CS Marks LD Schatz GC Van Duyne RP 《The journal of physical chemistry. B》2005,109(22):11158-11162
A novel method to produce solution-phase triangular silver nanoparticles is presented. Ag nanoparticles are prepared by nanosphere lithography and are subsequently released into solution. The resulting nanoparticles are asymmetrically functionalized to produce either single isolated nanoparticles or dimer pairs. The structural and optical properties of Ag nanoparticles have been characterized. Mie theory and the Discrete Dipole Approximation method (DDA) have been used to model and interpret the optical properties of the released Ag nanoparticles. 相似文献
162.
Oxyallyl cations generated in situ from dihaloketones have been found to undergo the Favorskii rearrangement in preference to an intramolecular Type-II 4 + 3 cycloaddition reaction in trifluoroethanol and hexafluoropropan-2-ol solvents, generating acrylate esters with high cis selectivity. A synthetic alternative to the intramolecular Type-II 4 + 3 cycloaddition has been developed on the basis of intramolecular enolate alkylation to close a 7-membered ring with an exocyclic double bond. 相似文献
163.
Thomas Geiger Richard Nottenberg Mary-Lou Plaprat Michael Grtzel 《Helvetica chimica acta》1982,65(8):2507-2516
Light-induced interfacial electron transfer from two p-InP electrodes differing in the amount of majority carrier doping to a number of electron relays ( R ) dissolved in aqueous solution was investigated. The material with the lower carrier density (0.71 × 1018 cm?3) exhibited much better wavelength response and quantum yield for electron transfer than the electrode doped with 2.3 × 1018 cm?3 charge carriers. Using cobalt (III) sepulcrate, Co (sep)3+, as an electron relay a polychromatic light to electrical energy conversion efficiency of 18% was obtained. The potential of this relay for use in a regenerative photoelectrochemical cell is briefly discussed. 相似文献
164.
Ellis MJ Antonyuk SV Strange RW Sawers G Eady RR Hasnain SS 《Inorganic chemistry》2004,43(24):7591-7593
Copper nitrite reductases contain both an electron-transfer type 1 Cu site and a catalytic type 2 Cu site. We have mutated one of the type 2 copper ligating histidines to observe the effect on catalytic turnover. This mutation has created a unique site where Cu is ligated by 2 His Nepsilon2 atoms alone. 相似文献
165.
Dendritic nanowire ultraviolet laser array 总被引:16,自引:0,他引:16
Yan H He R Johnson J Law M Saykally RJ Yang P 《Journal of the American Chemical Society》2003,125(16):4728-4729
Self-organized dendritic crystal growth is explored to assemble uniform semiconductor nanowires into highly ordered one-dimensional microscale arrays that resemble comb structures. The individual ZnO nanowires have uniform diameters ranging from 10 to 300 nm. They are evenly spaced on a stem with a regular periodicity of 0.1-2 micrometer. Under optical excitation, each individual ZnO nanowire serves as a Fabry-Perot optical cavity, and together they form a highly ordered nanowire ultraviolet laser array. 相似文献
166.
Most common diseases appear to result from complex, poorly understood interactions between genetic and environmental factors. Relatively few factors have been unequivocally linked with disease risk or outcome. Evidence from various studies using different experimental approaches has been interpreted as showing that, apart from its harmful effects on the pathogenesis of the common skin cancers, ultraviolet radiation (UVR) may exert a beneficial effect on development of various internal cancers and other pathologies. This concept is supported by parallel studies showing that hypovitaminosis D is linked with increased risk of various diseases including insulin resistance and multiple sclerosis. These findings suggest that, first, host factors such as skin pigmentation that affect UVR-induced synthesis of vitamin D and, second, polymorphism in genes that mediate the effectiveness of vitamin D action are susceptibility candidates for a variety of diseases. Collectively, these data suggest the hypothesis that, via effects on vitamin D synthesis, UVR exposure has beneficial effects on susceptibility and outcome to a variety of complex diseases. We describe evidence from studies in various diseases, but mainly from prostate cancer patients, that supports this hypothesis, but we emphasize that, although supportive data are available, the concept is unproven. Indeed, other explanations are possible. However, given the potentially important public health implications of the hypothesis and the potential for the development of novel therapeutic modalities, we believe the concept is worthy of further investigation. 相似文献
167.
Richard Partch Egon Matijevi Anthony W. Hodgson Barlow E. Aiken 《Journal of polymer science. Part A, Polymer chemistry》1983,21(4):961-967
A procedure was developed by which polymer colloids can be prepared by polymerizing aerosol droplets of monomers with an initiator in the vapor state. This work describes the formation of poly(p-tertiarybutylstyrene) particles by exposing the corresponding monomer droplets to trifluoromethanesulfonic acid. It was found that the monomer-to-initiator mass ratio is the critical factor in determining the uniformity and morphology of the particles. Under ideal conditions spheres of narrow size distribution are obtained. Otherwise porous particles or soft particles with whiskers may develop. The aerosol was prepared in a falling film generator, but other procedures for producing monomer droplets may be used. 相似文献
168.
The application of Ag(I) catalysis of S2O82? to the oxidation of organic carbon to CO2 for determination of dissolved organic carbon in aqueous samples is described. The resulting method combines to a significant degree the speed of high-temperature combustion methods and the sensitivity of wet chemical oxidation. For some samples, a higher oxidation efficiency has been observed than with an uncatalyzed wet chemical oxidation method. 相似文献
169.
170.
[reaction: see text] The 3-quinuclidinone-catalyzed (pK(BH) = 7.5) enolization of cyclobutanone (1) in D(2)O at 25 degrees C, I = 1.0 (KCl) was followed by deuterium incorporation, which was determined by (1)H NMR. The second-order rate constant for the buffer-catalyzed deprotonation of 1 was found to be k(B) = 3.3 x 10(-4) M(-1) s(-1), which is compared to rates for acetone and 2-(2'-oxopropyl)benzaldehyde under similar conditions. The data shows that ring strain has very little effect on the energy barrier to deprotonation of 1 vs the unstrained systems. 相似文献