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29 Sep 2008

Volume 93, Issue 13, Articles (13xxxx)

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Appl. Phys. Lett. 93, 132101 (2008); http://dx.doi.org/10.1063/1.2988720 (3 pages)

Yueh-Nan Chen and Lukas Gilz
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Plasma-liquid electrochemistry: Rapid synthesis of colloidal metal nanoparticles by microplasma reduction of aqueous cations

Carolyn Richmonds and R. Mohan Sankaran

Appl. Phys. Lett. 93, 131501 (2008); http://dx.doi.org/10.1063/1.2988283 (3 pages) | Cited 35 times

Online Publication Date: 1 October 2008

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We demonstrate operation of an aqueous electrochemical cell with an atmospheric-pressure microplasma cathode and a solid metal anode for the rapid production of colloidal metal nanoparticles. Microplasmas are miniaturized versions of low-pressure glow discharges that operate nonthermally at high pressures ( ∼ 1 atm) and contain energetic electrons. Aqueous metal cations are directly reduced by electrons in the microplasma without the presence of a solid cathode or chemical reducing agents. Kinetic studies performed by UV-visible absorbance spectroscopy suggest that particle nucleation and growth are coupled to redox reactions initiated in the electrochemical cell through plasma-liquid interactions.
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82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
82.45.Fk Electrodes
82.70.Dd Colloids
82.80.Dx Analytical methods involving electronic spectroscopy
62.50.-p High-pressure effects in solids and liquids
82.30.-b Specific chemical reactions; reaction mechanisms

Direct measurements of the energy flux due to chemical reactions at the surface of a silicon sample interacting with a SF6 plasma

R. Dussart, A. L. Thomann, L. E. Pichon, L. Bedra, N. Semmar, P. Lefaucheux, J. Mathias, and Y. Tessier

Appl. Phys. Lett. 93, 131502 (2008); http://dx.doi.org/10.1063/1.2995988 (3 pages) | Cited 10 times

Online Publication Date: 2 October 2008

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Energy exchanges due to chemical reactions between a silicon surface and a SF6 plasma were directly measured using a heat flux microsensor (HFM). The energy flux evolution was compared with those obtained when only few reactions occur at the surface to show the part of chemical reactions. At 800 W, the measured energy flux due to chemical reactions is estimated at about 7 W cm−2 against 0.4 W cm−2 for ion bombardment and other contributions. Time evolution of the HFM signal is also studied. The molar enthalpy of the reaction giving SiF4 molecules was evaluated and is consistent with values given in literature.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.60.Cx Enthalpies of combustion, reaction, and formation

Absolute atomic oxygen density profiles in the discharge core of a microscale atmospheric pressure plasma jet

Nikolas Knake, Kari Niemi, Stephan Reuter, Volker Schulz-von der Gathen, and Jörg Winter

Appl. Phys. Lett. 93, 131503 (2008); http://dx.doi.org/10.1063/1.2995983 (3 pages) | Cited 24 times

Online Publication Date: 3 October 2008

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The micro atmospheric pressure plasma jet is an rf driven (13.56 MHz, ∼ 20 W) capacitively coupled discharge producing a homogeneous plasma at ambient pressure when fed with a gas flow of helium (1.4 slm) containing small admixtures of oxygen ( ∼ 0.5%). The design provides excellent optical access to the plasma core. Ground state atomic oxygen densities up to 3×1016 cm−3 are measured spatially resolved in the discharge core by absolutely calibrated two-photon absorption laser-induced fluorescence spectroscopy. The atomic oxygen density builds up over the first 8 mm of the discharge channel before saturating at a maximum level. The absolute value increases linearly with applied power.
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52.80.Pi High-frequency and RF discharges
52.75.-d Plasma devices
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