Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session ET1: Nanotechnologies I |
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Chair: Makoto Kambara, University of Tokyo Room: Amphitheatre 204 |
Tuesday, October 23, 2012 1:30PM - 2:00PM |
ET1.00001: Three-Dimensional Integrated Micro Solution Plasmas for Nano Materials Processing Invited Speaker: Tatsuru Shirafuji In contrast to the conventional solution chemistry, the solution plasma processing (SPP), which has been invented by Osamu Takai and Nagahiro Saito (Nagoya University), involves accelerated electrons which contribute to generate active chemical species, such as radicals, ions, UV photons and metastable excited atoms. Such active species are expected to enhance through-put of the solution chemistry and to promote the reactions which do not proceed without catalysts. In our previous work, we have successfully obtained glow discharges in water, and applied this technique to modify the surface of nano-materials. Since the previous solution plasma is ignited in a small volume between two stylus electrodes, actual treatment area or volume should be enlarged for practical industrial application. In the case of gas phase processes, large area processing is realized by producing large area plasmas. In the case of SPP, however, large volume plasma in liquid is meaningless, because the most important region is gas-liquid interface. Thus, preparation of large number of tiny plasmas (microplasmas) is rather important in the case of SPP. This can be named as ``integrated micro solution plasma.'' In order to realize the integrated micro-solution plasmas, we have recently utilized interfaces between a plane dielectric plate and porous dielectric material, and successfully obtained large area integrated micro solution plasmas in two dimensions. In this work, we report that three-dimensionally integrated plasmas can be obtained in a porous dielectric material, and demonstrate that Au nano-particles can be synthesized by using this technique. This work has been partly supported by the CREST/JST, the Knowledge Cluster Initiative Tokai Region Nanotechnology Manufacturing Cluster, Grant-in-Aid for Scientific Research on Innovative Areas ``Frontier science of interactions between plasmas and nano-interfaces'' by the MEXT, and Grant-in-Aid for Scientific Research (C) by the JSPS. [Preview Abstract] |
Tuesday, October 23, 2012 2:00PM - 2:15PM |
ET1.00002: Microplasma-liquid interactions for nanomaterials synthesis Jenish Patel, Paul Maguire, Davide Mariotti Interactions of microplasmas with solid, liquid and/or gas precursors provide new pathways for the synthesis and surface-engineering of nanomaterials. This study is focused on the plasma-induced non-euqilibrium liquid-chemistry (PiLC) as an effective approach to synthesize colloidal metal nanoparticles without using any reducing/capping agents. Highly dispersed gold and silver nanoparticles (NPs) were synthesized in aqueous solutions without any capping agents which explore the opportunities to functionalize the surface of these surfactant-free metal NPs for a better device applications. In particular, various sizes (5 nm to 100 nm) and shapes (e.g. spherical, hexagonal, pentagonal, triangular, etc.) of the gold nanoparticles (AuNPs) were formed with different concentrations of gold precursor. Moreover, conductivity, pH and temperature of the solutions were measured before and after the plasma processing, in order to realize the basic chemistry initiated by plasma in/at liquid surface. Especially, to understand the basic reduction process of AuNPs synthesis by plasma, we measured the presence the of hydrogen peroxide (H$_{2}$O$_{2})$ which is believed to be a strong reductant for gold and for the first time we demonstrated experimentally that H$_{2}$O$_{2}$ is the key factor that reduces the gold precursor to AuNPs. These investigations create the opportunities to understand how these microplasmas can be effectively explored to other materials synthesis/processing. [Preview Abstract] |
Tuesday, October 23, 2012 2:15PM - 2:30PM |
ET1.00003: Diamondoid synthesis by nanosecond pulsed microplasmas generated in He at atmospheric pressure Sven Stauss, Tomoki Shizuno, Fumito Oshima, David Z. Pai, Kazuo Terashima Diamondoids are $sp^3$ hybridized carbon nanomaterials that possess interesting properties making them attractive for biotechnology, medicine, and opto- and nanoelectronics. So far, larger diamondoids have been synthesized using the smallest diamondoid (adamantane) as a precursor. For this electric discharges and pulsed laser plasmas generated in supercritical fluids, and hot filament chemical vapor deposition have been used, but these methods are difficult to realize or very time-consuming. We have developed a more convenient approach where diamondoids are synthesized by high-voltage nanosecond pulsed microplasmas (voltage 15~kV$_{\rm p-p}$, frequency 1~Hz, pulse width 10~ns) generated in He at atmospheric pressure using point-to-plane tungsten electrodes. Adamantane was used as a precursor, and synthesis was conducted for 10$^5$ pulses at gas temperatures of 297, 373 and 473~K. Energy dispersive {X-ray} and micro-Raman spectroscopy were conducted to determine the composition of the products, and gas chromatography - mass spectra indicated the formation of diamantane. It was found that synthesis is more efficient at room temperature than at higher temperatures, and time-resolved optical emission spectroscopy suggest that the chemical reactions take place in the afterglow. [Preview Abstract] |
Tuesday, October 23, 2012 2:30PM - 2:45PM |
ET1.00004: Generation of plasmas in supercritical xenon inside microcapillaries for synthesis of diamondoid Fumito Oshima, Chikako Ishii, Sven Stauss, Kazuo Terashima Diamondoids are series of \textit{sp}$^{3}$ hybridized carbon nanomaterials that could be applied in various fields such as pharmacy and optoelectronics. In our previous studies, higher order diamondoids were synthesized in supercritical fluid (SCF) plasmas in a batch-type reactor using adamantane (C$_{10}$H$_{16})$, the smallest diamondoid, as a precursor and seed. However the yield was low and the selectivity was difficult to control. We have developed a continuous flow SCF microplasma reactor that allows discharge volume and residence time to be adjusted. The electrodes consist of a tungsten wire inserted into a fused silica capillary and a sputtered silver outside of the capillary. We dissolved adamantane in supercritical xenon near critical point, and then generated DBDs inside the capillary using a nominal constant xenon flow rate of 0$\sim $2.3 mL min$^{-1}$. Micro-Raman spectra of the synthesized products show peaks that are characteristic of hydrocarbons possessing \textit{sp}$^{3}$ hybridized bonds while gas-chromatography/mass spectrometry spectra indicate the synthesis of diamantane (C$_{14}$H$_{20})$ and possibly isomers of diamondoids consisting of up to nine cages, nonamantane. It is suggested that this type of SCF microplasma reactor might be effective not only for synthesis of diamondoids, but also other nanomaterials. [Preview Abstract] |
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