Advisor

Rolf Konenkamp

Date of Award

1-1-2011

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Physics

Department

Physics

Physical Description

1 online resource (vii, 60 p.) : ill. (some col.)

Subjects

Triethanolamine, Humidity, NO₂, Nitrogen dioxide -- Measurement -- Equipment and supplies, Chemical detectors -- Design and construction, Conducting polymers

DOI

10.15760/etd.418

Abstract

Triethanolamine (TEA) is a semiconducting polymer which exhibits a resistance change when exposed to various gases. The polymer also exhibits a number of reactions with nitrogen dioxide, with the reaction products being heavily dependent on the presence or absence of water vapor. Previous studies have attempted the incorporation of a TEA-carbon nanoparticle composite as the active sensing layer in a chemresistive sensor for detection of NO₂. The incorporation of carbon nanoparticles in the polymer nanocomposite was thought to amplify the sensor's response. There are a number of chemical reactions that can occur between TEA and NO₂, with the reaction products being heavily dependent on the presence and amount of water vapor in the environment. Because of this influence, it becomes necessary to know to what degree the presence of water vapor interferes with the sensing response. In this work we show that the sensor exhibits a reversible resistance change as background humidity changes. This sensitivity to humidity changes is so large that it renders undetectable any resistance change that could be caused by the reaction of TEA with NO₂. Furthermore, we show that the presence of low levels of NO₂ do not interfere with adsorption of water vapor. The detection mechanism is based on measuring resistance changes in the TEA film due to the adsorption/desorption of water vapor. The sensing response can be described by Langmuir adsorption by using a site-based model for the polymer film resistance. Breakdown of the polymer film over time due to continuous adsorption of water vapor, as well as photodegradation of the polymer film, will be discussed. SEM images will also be presented showing growth of crystallites on the electrode walls, as well as experimental results demonstrating degradation of the sensing film during sensor operation.

Description

Portland State University. Dept. of Physics

Persistent Identifier

http://archives.pdx.edu/ds/psu/7375

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