421 research outputs found

    Optical Properties and XPS-Characterization of Ag/Au Bimetallic Nanoparticles in Porous Sol-Gel Silica Films

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    Ag/Au bimetallic nanoparticles (BMNP) in porous sol-gel silica films on glass substrates were obtained via hydrolysis of tetraethylorthosilicate (TEOS) in presence of template agent Pluronic P123 and definite amounts of AgNO3 and HAuCl4 by dip-coating procedure followed by a UV-irradiation and thermal treatment. UV-vis spectroscopy was employed to follow the changes in the position and intensity of the surface plasmon resonance band of the resulting BMNP, SEM was employed for morphology investigation. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical states of Au and Ag as well as the surface composition of the resultant films. By utilizing the charging characteristics of the films prepared on a silicon wafer, via application of an external voltage bias, it was found that the Au and Ag nanoparticles are retained within the silica matrix and demonstrate similar charging behavior. Depending on the coating sequences of glass substrates by the silica sol precursors (Au/SiO2 or Ag/SiO2), resultant BMNP within silica film have alloy (Au/SiO2-Ag/SiO2) or core-shell (Ag/SiO2-Au/SiO2) structure.Біметалічні наночастинки (БМНЧ) Ag/Au, інкорпоровані в пористу золь-гель кремнеземну плівку, були одержані шляхом гідролізу тетраетилортосилікату (ТЕОС) в присутності темплатного агента Pluronic P123 з додаванням AgNO3 і HAuCl4; нанесення плівок на субстрат проводилося методом "dip-coating" з наступним УФ-опроміненням і термообробкою. УФ- видима спектроскопія застосовувалася для реєстрації положення і інтенсивності максимумів поверхневого плазмонного резонансу БМНЧ, а рентгено-фотоелектронна спектроскопія - для визначення хімічного стану Au і Ag та встановлення поверхневого складу плівки. При використанні методики зарядження плівок на кремнієвій підкладинці шляхом накладання зовнішнього електричного потенціалу було встановлено, що наночастинки Au і Ag зв’язані з силікатною матрицею та демонструють однаковий відгук на накладений зовнішній негативний потенціал. В залежності від послідовності нанесення прекурсорів (Ag/SiO2 або Au/SiO2) на підкладинку, БМНЧ, які містяться в матриці кремнеземної плівки, формують структуру типу сплав (Au/SiO2-Ag/SiO2) або ядро-оболонка(Ag/SiO2-Au/SiO2).Биметаллические наночастицы (БМНЧ) Ag/Au, инкорпорированные в пористую золь-гель кремнеземную пленку, были получены путем гидролиза тетраэтилортосиликата (ТЭОС) в присутствии темплатного агента Pluronic P123 с добавлением AgNO3 и HAuCl4; нанесение пленок на субстрат производилось методом "dip-coating" с последующим УФ-облучением и термообработкой. УФ-видимая спектроскопия использовалась для регистрации изменений в положении и интенсивности максимумов поглощения полос поверхностного плазмонного резонанса БМНЧ, а рентгено-фотоэлектронная спектроскопия – для определения химического состояния Au и Ag и установления поверхностного состава пленки. C помощью методики заряжения пленок на кремниевой подложке путем наложения внешнего электрического потенциала было установлено, что наночастицы Au и Ag связаны с силикатной матрицей и демонстрируют одинаковый отклик на приложенный внешний негативный потенциал. В зависимости от последовательности нанесения прекурсоров (Ag/SiO2 или Au/SiO2) на подложку, БМНЧ в матрице кремнеземной пленки образуют структуру типа сплав (Au/SiO2-Ag/SiO2) или ядро-оболочка (Ag/SiO2-Au/SiO2)

    Sol-gel synthesis, optical properties, morphology and photocatalytic activity of titania films modified with ethanolamines as nitrogen source

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    In this work the titania films modified with ethanolamines are synthesized by sol-gel method using two different routes. Introduction of template during sol ripening leading to the formation of porous structure and a single stage synthesis resulting in non-porous surface are proposed. The optical properties and calculated band-gap values of the films are presented. The titania particle size of the modified films is increased in comparison with the bare one as results of Root mean square (RMS) and Roughness average (Ra) values. The influence of the synthesis conditions and structure of ethanolamines on the photocatalytic activity under visible light are reported.В данной работе синтезированы пленки диоксида титана, модифицированные этаноламинами. Описан золь-гель метод с использованием различных. Введение темплата во время созревания золя приводит к образованию пористой структуры, а предложенный одностадийный синтез формирует непористую поверхность. Исследованы оптические свойства пленок и рассчитаны их величины ширины запрещенной зоны. Размер частиц модифицированных пленок диоксида титана возрастает по сравнению с немодифицированным, как показано представленными значениями RMS и Ra. Изучено влияние условий синтеза и структуры этаноламинов на фотокаталитическую активность под видимым светом.Синтезовано плівки діоксиду титану, модифіковані етаноламінами. Описано золь-гель метод з використанням різних підходів. Введення темплату під час дозрівання золю призводить до утворення пористої структури, а запропонований одностадійний синтез формує непористу поверхню. Досліджено оптичні властивості плівок та розраховано їхні величини ширини забороненої зони. Розмір частинок модифікованих плівок діоксиду титану зростає в порівнянні з немодифікованим, як показано представленими значеннями RMS і Ra. Вивчено вплив умов синтезу і структури етаноламінів на фотокаталітичну активність під видимим світлом

    Morphology and optical properties of thin silica films containing bimetallic Ag/Au nanoparticles

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    We have studied the optical spectra in the UV and visible regions, the morphology by scanning electron microscopy (SEM), and the X-ray photoelectron spectra (XPS) of bimetallic Ag/Au nanoparticles incorporated into transparent silicate films in the sol-gel transition stage. The bimetallic nanoparticles, obtained by a combination of photoreduction and thermal reduction, form structures of the alloy or core-shell type. © 2008 Springer Science+Business Media, Inc

    Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

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    We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

    Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

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    This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

    Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

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    The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

    Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

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    A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

    Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

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    A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

    Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

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    Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

    Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

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    This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review
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