FY2010 - Oak Ridge National Laboratory

Seed Money Fund—
Environmental Sciences Division
We have succeeded in modifying the absorption spectrum in a controllable manner through laser
irradiation with a Nd:YAG second harmonic pumped dye laser. The modification process involves using
power thresholds sufficiently high so as to “burn” a spectral hole (transmission peak) in the otherwise
broad absorption curve at the wavelength of irradiation. Thus, we have demonstrated the use of this
process to engineer a film that absorbs at short wavelengths and transmits at higher ones.
For our next step, the modified films will be coated with a spacer layer of SiO 2 (to prevent fluorescence
quenching). A layer of fluorescent dye in a polymer matrix will then be spin coated on the sample. The
fluorescence from the sample will be measured to verify whether an enhancement in the fluorescence
quantum yield has been achieved. The sample will also be investigated for directional emission. Both
phenomena in conjunction should lead to a large increase in fluorescent downshifting efficiencies,
demonstrating the advantages of using plasmonic nanostructures towards augmenting downshifting
yields.
Theoretical modeling will also be performed to determine the optimum structures for maximizing the
quantum efficiency of the structure. The work will provide the proof of principle for the use of plasmonic
effects towards improved photocarrier generation in thin-film solar energy materials.
05892
Testing Nonthermal Plasma as a CWA Decontamination Method
Meng-Dawn Cheng
Project Description
The project was designed to test the feasibility of using cold plasma as an alternative to solution-based
methods for decontamination of chemical warfare agents (CWA) that deposited on the sensitive weapon
platforms and systems. The nonthermal or cold plasma was generated by an electrical or radiofrequency
powering method and contains a high level of reactive species such as free radicals. The reactive species
react with CWA and chemically “degrade” or “destroy” the agents in a short time (typically minutes); the
end-products of the decontamination are benign gas species such as carbon dioxide. Nonthermal plasma
decontamination leaves no residue trace on the material treated. We demonstrated the effectiveness of the
nonthermal plasma decontamination on the surface of C-17 polymer airframe composite material.
Mission Relevance
Use of a wet chemical-based method for decontamination of chemical and biological warfare agents
(CWA and BWA) has been known to cause significant material degradation and loss of tensile strength of
a stainless steel structure in previous tests. The solvent-based decontamination also leaves a significant
quantity of polluted water, potentially causing secondary pollution that could increase human exposure
and health risks. We tested an alternative method that is dry, potentially clean, and leaves no trace
residues—the Atmospheric Pressure Non-Thermal Plasma (APNTP) jet. The APNTP is scalable so it is
conceivable to scale up the technique for large areas to be decontaminated.
Results and Accomplishments
A bench-top commercial APNTP was used to produce the jet for this quick turn-around test. The jet has a
nozzle that produces a line-shaped jet. The initially proposed use of a pulsed high-power laser plasma as
one of two NTP power sources did not yield stable APNTP as expected. The laser approach created
breakdown successfully; however, the reactive species rapidly recombined, virtually eliminating the
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