AVS 61st International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThA

Paper PS-ThA7
Gas Chromatography and Mass Spectrometry Characterization of Nanoparticle-Producing Atmospheric-Pressure Microplasmas

Thursday, November 13, 2014, 4:20 pm, Room 305

Session: Plasma Processing of Nanoparticles and Nanomaterials
Presenter: Jonathan Cole, Case Western Reserve University
Authors: J. Cole, Case Western Reserve University
R.M. Sankaran, Case Western Reserve University
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Plasma processes are becoming increasingly important for the production of nanoparticles by homogeneous nucleation.1,2 The high-purity conditions that have made plasmas essential for thin film etching and deposition in the semiconductor industry similarly allow nanoparticles to be synthesized without organic stabilizers or other types of contaminants. In addition, high temperature and/or pressure materials such as silicon and diamond can be produced in plasmas because of non-equilibrium conditions. A novel class of plasmas for nanoparticle synthesis is microplasmas. Microplasmas operate stably at atmospheric pressure as a result of pd scaling (p being the gas pressure and d the electrode gap), eliminating the need for vacuum infrastructure. In addition, particle nucleation, growth, and agglomeration are controlled by the rapid quenching that results from the small volume and flow-through geometry.

Here, we present gas chromatography and mass spectrometry measurements of atmospheric-pressure microplasmas with reaction chemistries relevant to nanoparticle synthesis by homogeneous nucleation. We focus on two different gas chemistries that are used to produce nanoparticles: 1) metal-organic vapors that allow the synthesis of metal nanoparticles, such as Ni and Fe, and 2) hydrocarbon gases that allow the synthesis of carbon nanoparticles, including nanodiamonds. Measurements are performed on the effluent at the exit of the microplasma. To sample gases at high pressure (>1 atmosphere), we have built a mass spectrometry system consisting of an open ion source, quadrupole trap, 1-300 AMU detection range RGA (Dycor Technologies, Ltd.) and capillary inlet. The gas chromatography system (Shimadzu, Inc.) is equipped with a recently developed barrier ionization discharge detector, which is capable of universal detection of molecular gases with sensitivity at the ppm and ppb levels. The results are thus comprehensive, but restricted to the neutral vapor or gas molecule reaction products because of the high sampling pressure. Important insight is nonetheless obtained about reactant conversion, gas product selectivity, process efficiency, and influence of plasma characteristics. The gas chemistry studies are complemented by optical emission spectroscopy (Ocean Optics, Inc.) and scanning mobility particle sizer spectrometry (TSI, Inc.) of the nanoparticle aerosol. Materials analysis of collected product by high resolution transmission electron microscopy is also carried out in support of the in situ measurements.

References

1

U. Kortshagen, J. Phys. D 42, 113001 (2009).

2D. Mariotti and R. M. Sankaran, J. Phys. D 43, 3223001 (2010).