AVS 61st International Symposium & Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS+2D-WeA

Paper PS+2D-WeA9
The Impact of Ambient Gas Chemistry on Lipopolysaccharide Deactivation and Polymer Modification by Plasma-Generated Radicals at Atmospheric Pressure

Wednesday, November 12, 2014, 5:00 pm, Room 305

Session: Plasma Processing for 2D Materials, Coating, and Surface Modification
Presenter: Elliot Bartis, University of Maryland, College Park
Authors: E.A.J. Bartis, University of Maryland, College Park
A.J. Knoll, University of Maryland, College Park
P. Luan, University of Maryland, College Park
C. Hart, University of Maryland, College Park
D.B. Graves, University of California, Berkeley
I.V. Adamovich, The Ohio State University
W. Lempert, The Ohio State University
J. Seog, University of Maryland, College Park
G.S. Oehrlein, University of Maryland, College Park
Correspondent: Click to Email
In this study, lipopolysaccharide (LPS) -coated silicon substrates were exposed to the effluent of an atmospheric pressure plasma jet (APPJ) under a controlled environment to examine the effect of plasma-generated reactive species on the surface chemistry and biological activity. The goal of the present work is to understand the role of plasma-environment interactions in biodeactivation and surface modifications by regulating both the proximity of the plasma to the environment and the environmental gas chemistry. The APPJ is mounted inside a vacuum chamber that can be evacuated and refilled with any gas chemistry. By changing the APPJ geometry, the plasma plume can be either exposed or protected from the ambient. By adding small N2/O2 admixtures to Ar, we find that the O2 admixture in the APPJ is a major determining factor for both deactivation and surface modification as measured by an enzyme-linked immunosorbent assay and x-ray photoelectron spectroscopy, respectively. N2 admixture without O2 causes minimal deactivation, while N2/O2 admixtures deactivate more with increasing O2 content. For identical O2 feed gas flows, less deactivation occurs when N2 is also added, which demonstrates that nitrogen-based species quench reactive oxygen species (ROS) responsible for biodeactivation. After plasma treatments, a new chemical species was detected on LPS surfaces that was stoichiometrically verified as NO3. To determine if this species forms due to nitrogen and oxygen found naturally in LPS, we treated model polymer films of polystyrene, polypropylene, and poly(methyl methacrylate), as these materials contain solely carbon or only carbon and oxygen. We find that the formation of NO3 is generic to all surfaces even with no N2 in the feed gas. Thus, the reactive interaction of oxygen-based species with ambient N2 takes place, indicating that plasma-environment interactions create this moiety and providing insight into the mechanisms by which the APPJ modifies surfaces. For polystyrene films, oxygen uptake is dramatic with O/C ratios as high as 0.47 at the near surface. The oxygen uptake results in a variety of moieties including C-O, O-C-O, C-O-NO2, O-C=O, and O-(C=O)-O. APPJ treatments are also compared with a corona discharge to examine the role of long lived species such as ozone and NOx. Results from gas-phase characterization will also be discussed. The authors gratefully acknowledge financial support by the US Department of Energy (DE-SC0005105 and DE-SC0001939) and National Science Foundation (PHY-1004256).