Rapid detection systems for chemical warfare agents (CWA) are needed to reduce exposure threat. Current technologies are limited by the use of selective sensors that require pre-determined targets and an inability to adapt to environmental conditions. Electronic nose systems overcome this by utilizing multiple semi-selective chemical sensors simultaneously with conductive polymer-colloid materials of particular interest due to their response diversity and commercial availability. Previously, detection and discrimination of 5 CWA simulants and 8 interferent compounds was demonstrated with an array of chemiresistive sensors consisting of polymer-graphene nanoplatelet (GNP) composite coated interdigitated electrodes. Using 12 unique polymer-GNP coated sensors 95-100% classification accuracy was achieved. First the effect of these 12 polymers on classification accuracy was evaluated for down selection to reduce future device complexity. Using a random forest analysis the optimal polymers were identified for detection of the CWA simulants, interferents, and all analytes. Next the coating deposition, formulation, and thickness of sensor coatings with these down selected polymers was evaluated to improve sensor sensitivity and repeatability. All coatings were airbrushed to improve dispersion, uniformity, and sensor repeatability compared to dropcast and spin cast films. The optimal GNP-polymer weight ratio was investigated using 3-18% (w/w) solutions deposited on an interdigitated electrode array. Coatings were evaluated by measuring the response magnitude and signal to noise ratio (SNR) upon exposure to ethanol and dimethyl methylphosphonate (DMMP). Maximum response occurred near the percolation coefficient with the maximum SNR at a greater weight percent. The effect of thickness was evaluated by depositing solutions with different solids content. Thinner films maximize response magnitude due to the increased surface area to volume ratio for the sorption based reactions. However SNR is maximized with a slightly thicker coating by minimizing coating variations across the electrodes. The results demonstrate methods to optimize conductive polymer-colloid sensors for sensitive, robust CWA detection systems with applications to other analyte types.

Optimization of polymer-graphene nanoplatelet chemiresistive sensors for detection and discrimination of chemical warfare agents

255th National Meeting (2018)

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