Date of Award

1997

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

Keywords

Chemistry, Analytical.

Supervisor

Aroca, R.

Rights

info:eu-repo/semantics/openAccess

Abstract

This thesis deals with the preparation of two thin film devices, in particular a nitrogen dioxide (NO$\sb2$) gas sensor and a rechargeable lithium battery. A number of different thin film preparation techniques were used for a variety of applications and the resultant films were characterized by spectroscopic and electrochemical methods. The NO$\sb2$ gas sensor was based on Langmuir-Blodgett (LB) monolayer films of the sandwich molecule europium bisphthalocyanine (EuPc$\sb2$). The intense UV-visible absorption spectrum of a monolayer of the EuPc$\sb2$ dye molecules was recorded before and after exposure to NO$\sb2$ gas. It was noted that with time the film spectrum returned to its original colour, thus indicating the process to be reversible. The powerful spectroscopic technique of surface enhanced Raman scattering (SERS) was also utilized for film characterization. As with the absorption spectroscopy, the SERS experiments also indicated a reversible NO$\sb2$ adsorption-desorption process. An interdigitated gold electrode was used to measure the electrical conductivity of LB monolayers of EuPc$\sb2.$ The activation energy for conduction for this molecular semiconductor was determined to be 0.27 eV from thermal conductivity experiments. Upon exposure to NO$\sb2$ gas, the conductivity of the film increases considerably until it reaches saturation. Kinetics studies indicated that the conductivity changes resulted from two sources: the adsorption of NO$\sb2$ molecules on the surface, and the absorption of the molecules into the film. While the spectroscopic experiments suggested this process to be completely reversible, the electrical measurements indicated that heating was required to remove the residual absorbed NO$\sb2.$ Thin film cathodes for a rechargeable lithium battery were fabricated by the magnetron sputtering technique. The cathodes were deposited from a sample of the LiMn$\sb2$O$\sb4$ pure spinel material. The Li-Mn-O film was characterized by grazing angle x-ray diffraction, Raman and infrared spectroscopies. Electrochemical analyses of the films deposited on aluminum gave charge/discharge capacities of around 78.9 mA h g$\sp{-1}.$ Tests showed that these cells suffered from very high impedance most likely due to a high degree of polarization at the cathode:substrate interface. Deposition of a gold film onto the aluminum substrate proved to greatly reduce the impedance losses, resulting in an improvement in the total charge capacity of the cathode film to 211 mA h g$\sp{-1}.$Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1996 .B47. Source: Dissertation Abstracts International, Volume: 59-08, Section: B, page: 4068. Adviser: Ricardo Aroca. Thesis (Ph.D.)--University of Windsor (Canada), 1997.

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