Date of Award

2018

Degree Type

Thesis

Degree Name

Master of Science in Chemical Engineering (MSChE)

Department

Chemical Engineering

First Advisor

Otto Gregory

Abstract

At the University of Rhode Island’s Sensors and Surface Technology Partnership, a sensor platform has been fabricated that is capable of detecting explosive vapor at the ppb level. This sensor utilizes differential signal processing between a catalyzed microheater and a bare reference microheater to detect heat effects from catalyst-analyte interactions. The reaction mechanism behind these catalytic heat effects is highly debated and was originally thought to be due to chemisorption and catalytic decomposition of explosive vapor molecules [1]. The true mechanism of detection has been proven to be oxidation or reduction of the metal oxide catalyst to higher or lower oxidation states.

This mechanism was revealed thanks to the increased sensitivity of the thermodynamic sensor created by the significant decrease in thermal mass to the nickel microheater platform. This increased sensitivity allowed for the detection of heat effects at significantly lower temperatures thus new trends in sensor behavior were observed as sensors using different metal oxide catalysts were swept from room temperature to 500°C. Activation energy calculations for SnO2 reduction, Cu2O oxidation, and ZnO reduction were consistent with activation energy values presented by literature. Further evidence that these metal oxide catalysts are changing oxidation state was presented through SEM imaging of a tin oxide catalyst.

Sensor selectivity was also investigated relating to the differentiation between different explosive compounds such as TATP or 2,4-DNT. Reference sensors not employing a metal oxide catalyst are not responsive to TATP however a small heat effect is observed when the sensor is subjected to 2,4-DNT vapor. In order to identify specific explosive compounds, “fingerprint” plots were created using multiple different catalysts exposed to the same analyte. Plots were created for TATP, DADP, and 2,4-DNT and each plot has unique features. These features allow for the differentiation between individual explosive compounds.

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