Studies of nanoparticle reinforced polymer coatings for trace gas detection

With the goal of improving chemical detection methods for buried improvised explosive
devices (IED’s), the intention of this study is to show that functionalized nano-particles
improve the sensing properties of a polymer applied to gas sensors. The approach was
reinforcing the polymer, Nafion, with acid-functionalized carbon nanotubes (CNT’s).
Ammonia was chosen as the analyte for its similarity to IED byproducts without the
dangers of toxicity or explosion. Two sensor platforms were investigated: Quartz crystal
microbalances (QCM’s) and microcantilevers (MC’s). Preliminary evaluation of treated
QCM’s, via frequency analyzer, showed improvements in sensitivity and fast reversal of
adsorption; and suggested increased stability. Tests with coated MC’s also supported the
findings of QCM tests. Amplitude response of MC’s was on average 4 times greater
when the Nafion coating contained CNT’s. Quantitative QCM testing with gas-flow
meters showed that with CNT inclusion: the average number of moles adsorbed increased
by 35% (>1.2 times frequency response); sensitivity improved by 0.63 Hz/ppt on average; although the detection threshold decreased marginally; but reusability was
much better after extended exposures to concentrated ammonia.