Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session FT3: Liquids II |
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Chair: Andrey Starikovskiy, Princeton University Room: Nassau Room |
Tuesday, October 1, 2013 3:30PM - 4:00PM |
FT3.00001: Atmospheric Pressure Glow Discharge with Liquid Electrode Invited Speaker: Fumiyoshi Tochikubo Nonthermal atmospheric pressure plasmas in contact with liquid are widely studied aiming variety of plasma applications. DC glow discharge with liquid electrode is an easy method to obtain simple and stable plasma-liquid interface. When we focus attention on liquid-phase reaction, the discharge system is considered as electrolysis with plasma electrode. The plasma electrode will supply electrons and positive ions to the liquid surface in a different way from the conventional metal electrode. However, the phenomena at plasma-liquid interface have not been understood well. In this work, we studied physical and chemical effect in liquid induced by dc atmospheric pressure glow discharge with liquid electrode. The experiment was carried out using H-shaped Hoffman electrolysis apparatus filled with electrolyte, to separate the anodic and cathodic reactions. Two nozzle electrodes made of stainless steel are set about 2 mm above the liquid surface. By applying a dc voltage between the nozzle electrodes, dc glow discharges as plasma electrodes are generated in contact with liquid [1]. As electrolyte, we used aqueous solutions of NaCl, Na$_2$SO$_4$, AgNO$_3$ and HAuCl$_4$. AgNO$_3$ and HAuCl$_4$ are to discuss the reduction process of metal ions for synthesis of nanoparticles (NPs). OH radical generation yield in liquid was measured by chemical probe method using terephthalic acid. Discharge-induced liquid flow was visualized by Schlieren method. Electron irradiation to liquid surface (plasma cathode) generated OH$^-$ and OH radical in liquid while positive ion irradiation (plasma anode) generated H$^+$ and OH radical. The generation efficiency of OH radical was better with plasma anode. Both Ag NPs in AgNO$_3$ and Au NPs in HAuCl$_4$ were synthesized with plasma cathode while only Au NPs were generated with plasma anode. Possible reaction process is qualitatively discussed. The discharge-induced liquid flow such as convection pattern was strongly influenced by the gas flow on the liquid surface. \\[4pt] [1] N. Shirai et al., Plasma Sources Sci. Technol. 20 (2011) 034013. [Preview Abstract] |
Tuesday, October 1, 2013 4:00PM - 4:15PM |
FT3.00002: Plasma processes in water under effect of short duration pulse discharges Elchin Gurbanov It is very important to get a clear water without any impurities and bacteria by methods, that don't change the physical and chemical indicators of water now. In this article the plasma processes during the water treatment by strong electric fields and short duration pulse discharges are considered. The crown discharge around an electrode with a small radius of curvature consists of plasma leader channels with a high conductivity, where the thermo ionization processes and UV-radiation are taken place. Simultaneously the partial discharges around potential electrode lead to formation of atomic oxygen and ozone. The spark discharge arises, when plasma leader channels cross the all interelectrode gap, where the temperature and pressure are strongly grown. As a result the shock waves and dispersing liquid streams in all discharge gap are formed. The plasma channels extend, pressure inside it becomes less than hydrostatic one and the collapse and UV-radiation processes are started. The considered physical processes can be successfully used as a basis for development of pilot-industrial installations for conditioning of drinking water and to disinfecting of sewage. [Preview Abstract] |
Tuesday, October 1, 2013 4:15PM - 4:30PM |
FT3.00003: ABSTRACT WITHDRAWN |
Tuesday, October 1, 2013 4:30PM - 4:45PM |
FT3.00004: Investigation of OH Radical Generation Rate in Liquid induced by Non-equilibrium Atmospheric Pressure Plasma Jet Irradiation Tatsuo Ishijima, Yuko Imazawa, Kazuaki Ninomiya, Kenji Takahashi, Yasunori Tanaka, Yoshihiko Uesugi Non-equilibrium atmospheric pressure plasma jet (NAPPJ) is one of the convenient tools to supply reactive species to liquid under atmospheric pressure condition. Since a wide range of excitation frequencies is used to produce NAPPJs such as DC to microwave, it is necessary to obtain quantitative estimates of reactive species generation rate in liquid when the NAPPJ is irradiate to liquid surface. We have investigated hydroxyl radicals (OH) generation rate in liquid as one of a fundamental reactions using a chemical dosimetry technique based on a terephthalic acid (TA) when a pulsed 2.45 GHz microwave plasma jet (MWPJ) and low frequency ($\sim$20 kHz) plasma jet (LFPJ) source were used. Both MWPJ and LFPJ were produced at a He gas flow rate of less than 8 slm into a quartz tube. In order to evaluate the applicability of TA technique, the irradiation distance between the quartz nozzle edge and liquid surface was carefully investigated, taking into account linear dependence on irradiation time. As a result, we have found that OH generation rate of MWPJ was about 3 times lower than that of LFPJ in present operating conditions. [Preview Abstract] |
Tuesday, October 1, 2013 4:45PM - 5:00PM |
FT3.00005: Fabrication of hybrid nanostructures by liquid plasma for biomedical applications Sri balaji Ponraj, Xiujuan Jane Dai, Luhua Li, Zhiqiang Chen, Jayanth Surya Narayanan, Jagat Kanwar, Johan Du Plessis Liquid plasma, generated by a nanosecond pulsed generator at atmospheric pressure, was used to treat bamboo-like boron nitride nanotubes (BNNTs). It was observed that the length of the BNNTs was reduced and found more cup like structures called boron nitride nanocups (BNNCs). Interestingly, a new peak appeared at 406.86 eV in the N1s X-ray photoelectron spectrum, which seems to be attributable to the oxidation of nitrogen (N-O) in BNNTs. The C1s spectrum showed that oxygen functional groups were introduced onto the BNNT/BNNC surface. The liquid plasma was also used to assemble gold nanoparticles onto the treated BNNTs/BNNCs. This hybrid nanostructure was fabricated efficiently, compared with normal equilibrium conditions. The pH values and conductivity of all samples were measured. After plasma treatment, the pH values were greatly reduced and conductivity was significantly increased. We propose that the plasma acid, hydrogen peroxide, OH$^{-}$, H ions and radicals formed in liquid plasma as well as the pulsed electric field contribute to the oxidation of nitrogen, reduced length of the BNNTs(forming BNNCs), surface functionalization, and to the fabrication of hybrid nanostructure. The cytotoxic tests for these hybrid nanostructures is underway. [Preview Abstract] |
Tuesday, October 1, 2013 5:00PM - 5:15PM |
FT3.00006: Plasma electrolysis using atmospheric dc glow discharge in contact with liquid for synthesis of metal nano-particles Naoki Shirai, Yudai Shimokawa, Takuya Aoki, Satoshi Uchida, Fumiyoshi Tochikubo For the synthesis of metal nanoparticles in aqueous solution, we propose dual plasma electrolysis, which consists of Hoffman electrolysis apparatus with two atmospheric glow discharge plasmas as electrodes instead of conventional metal electrodes immersed in a liquid. The plasma anode irradiates positive ions to the solution surface while the plasma cathode irradiates electrons to the solution surface. The dual plasma electrolysis system enables us simultaneously to investigate the influence of electron and positive ion irradiation to a solution surface on metal nanoparticle generation at the same current. We used aqueous solutions of AgNO$_{3}$, HAuCl$_{4}$ and their mixture. In dual plasma electrolysis with AgNO$_{3}$, Ag nanoparticles were only synthesized on the plasma cathode side. This means that Ag nanoparticles are generated via the reduction of Ag$^{+}$ by electrons. With HAuCl$_{4}$ solution, Au nanoparticles were synthesized on both the plasma anode and plasma cathode sides. Ion irradiation with the plasma anode is more effective than electron irradiation for Au nanoparticle synthesis. This finding suggests that positive ions from the plasma trigger the dissociative reaction of AuCl$_{4}^{-}$ at the plasma-liquid interface. [Preview Abstract] |
Tuesday, October 1, 2013 5:15PM - 5:30PM |
FT3.00007: On The Possibility of Preferential Reactions at Plasma-Liquid Interface Due To Electric Double Layer Tatsuru Shirafuji, Fumiyoshi Tochikubo Plasmas in and in contact with liquid have attracted much attention because of their possible application fields such as nano materials synthesis, surface modification, water treatment, sterilization, recycling of rare materials, and decomposition of toxic compounds. The most important part in the plasmas in contact with liquid is the interface between the gas-phase plasma and liquid. According to electrochemistry, a nano-scale electric double layer (EDL) is formed on the top surface of the liquid. Thus, in a plasma treatment of liquid medium, gas-phase active species in the plasma primarily encounter the liquid-phase species in the EDL. For the purpose of precise control of plasmas in contact with liquid, we must pay attention to the formation and behavior of the EDL. In this work, numerical simulation of the EDL in contact with a dielectric barrier discharge has been performed. Preferential appearance of positive or negative ions has been observed on the top surface of the liquid depending on the mass ratio of the positive and negative ions in the liquid, and on the frequency applied. This means that the preferential reactions can be realized between gas-phase plasma species and liquid phase ions. [Preview Abstract] |
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