He Li

Date of Award

12-2009

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Carl P. Tripp

Second Committee Member

Raymond C. Fort, Jr.

Third Committee Member

Bruce L. Jensen

Abstract

The motivation of this thesis is to develop and investigate the merits of infrared spectroscopic based methods that could be used as a detector/identifier in biological detection systems. The methods described in this thesis are based on Attenuated Total Reflection (ATR) because of the requirement of detection of spores in water. It is noted that in our work we use benign Bacillus globigii spores as a stimulant of the target Bacillus anthracis spores for obvious health and safety reasons. The use of ATR requires concentrating the spores onto the surface of internal reflection elements (IRE). In chapter 3, an electrostatic method for concentrating Bacillus globigii spores on the ZnSe IRE with alumina coating is presented. The amount of spores adsorbed on the alumina/IRE passed through a maximum near pH 5 because of a compromise between the attractive force for spore-alumina interaction and the repulsive force for spore-spore interactions. Two main drawbacks to this approach are mass transport limited detection and nonreusable coating. In chapter 4, an electric field assisted ATR was developed and no coating of the IRE was required. Application of the electric field without flow leads to a rapid adsorption of the spores on the IRE. The spores adsorb through Van der Waal's forces and are not removed by reversing the field direction. Nevertheless, the spores could be easily and rapidly removed by flowing in a new sample. Three key advantages of the E-field ATR method are: (1) no coating, (2) rapid adsorption and (3) easy cleaning. The work in chapter 5 explores the packing arrangement of kaolin particles on a ZnSe IRE under an applied electric field. The packing geometry of kaolin on the surface can be altered by applying an electric field under certain conditions. Polarized IR spectroscopic measurement and AFM show that kaolin deposition rearranges a flatter orientation on the surface under E-field and no flow. The work in chapter 5 demonstrates the potential use of electric field for controlling filter cake formation which, in turn, could find use in the coating industry.

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