Composite Ag-Pt Nanoparticles in Aqueous Solution

It is shown that the saturation of an aqueous solution containing K2PtCl4 with hydrogen in the presence of 6.3 nm silver nanoparticles leads to the reduction of platinum on the silver surface and the formation of Ag/Pt core-shell nanoparticles. The Ag:Pt molar ratio is varied from 9:1 to 1:9 for synthesizing Pt shell layer of different thickness. An apparent shift of Ag surface plasmon band from 405 nm to 230 nm and broadening of one with decrease of Ag:Pt ratio was observed. The TEM images and SAED pattern of Pt@Ag nanoparticles has been obtained. The UV-Vis and TEM data confirms a formation of Ag/Pt coreshell nanoparticles. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3503

Search for the Decay τ−→4pi−3π+(π0)ντ\tau^{-}\to 4pi^{-}3\pi^{+}(\pi^{0})\nu_{\tau}

We have searched for the decay of the tau lepton into seven charged particles and zero or one pi0. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.61 fb^(-1). No evidence for a signal is found. Assuming all the charged particles are pions, we set an upper limit on the branching fraction, B(tau- -> 4pi- 3pi+ (pi0) nu_tau) < 2.4 x 10^(-6) at the 90% confidence level. This limit represents a significant improvement over the previous limit.Comment: 9 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

Measurement of prompt Jψ\psi pair production in pp collisions at \sqrt s = 7 Tev

Production of prompt J/ &#968; meson pairs in proton-proton collisions at s s&#8730; = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 fb &#8722;1 . The two J/ &#968; mesons are fully reconstructed via their decays into &#956; + &#956; &#8722; pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ &#968; pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/ &#968; transverse momentum ( p T J/ &#968; ) and rapidity (| y J/ &#968; |): | y J/ &#968; | 6.5 GeV/ c ; 1.2 4.5 GeV/ c . The total cross section, assuming unpolarized prompt J/ &#968; pair production is 1.49 ± 0.07 (stat) ±0.13 (syst) nb. Different assumptions about the J/ &#968; polarization imply modifications to the cross section ranging from &#8722;31% to +27%

Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV

The tt¯ charge asymmetry in proton-proton collisions at s&#8730; = 7 TeV is measured using the dilepton decay channel (ee, e &#956; , or &#956;&#956; ). The data correspond to a total integrated luminosity of 5.0 fb &#8722;1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = &#8722;0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt¯ system. All measurements are consistent with the expectations of the standard model

Reduction of Ag on polyacrylate chains in aqueous solution

Silver ions are reduced in aqueous solutions that contain sodium polyacrylate or partly carboxylated polyacrylamide or glutaric acid. The reducing agent is the hydrated electron generated amp; 947; radiolytically or hydrogen. Complexes of small silver clusters with the polyelectrolyte are formed in the early stages of reduction, the color of the solutions varying from rose to green or blue depending on the size of the complexed silver clusters. In the case of 10 carboxylated polyacrylamide, large colored complexes are not formed, which indicates that a high carboxylate density along the polymer chain is necessary for their formation. The complexes are stable toward heat 100 C and oxygen. In the later stages of reduction, the long wavelength absorptions of the silver amp; 8722;polyacrylate complexes disappear. The UV absorption bands of a magic cluster probably Ag9 are present during a short time interval, until the plasmon absorption band of metallic nanoparticles develops at 380 nm. The colored clusters react with ammonia and cyanide to form large silver particles through the intermediate stage of the magic cluste

The one electron reduction of Hg2 by 1 hydroxyalkyl radicals in aqueous solution a pulse radiolysis study

The rate constants for the reduction of the divalent mercury ion Hg2 by alcohol radicals, which are produced in acidic aqueous solutions containing methanol, ethanol or 2 propanol, are determined by optical absorption measurements to be 7.0 x 108, 3.8 x 108 or 3.1 x 108 dm3 mol 1 s 1, respectivel