Techniques for the detection and development of part I. detection of ozone for water treatment part II. utilizing layer-by-layer thin films with long period grating fibers /

by Puckett, Sean D.

TECHNIQUES FOR THE DETECTION AND DEVELOPMENT OF: PART I. DETECTION OF OZONE FOR WATER TREATMENT PART II. UTILIZING LAYER-BY-LAYER THIN FILMS WITH LONG PERIOD GRATING FIBERS By Sean D. Puckett The major thrust of this dissertation is the study of a new type of optical sensor, the long period grating (LPG). As a general rule the evanescent wave from the LPG will not travel more than l/10 ?. Therefore, the use of novel nanomaterials to provide the selective coating on an LPG is required. The chapters in this dissertation either extend our knowledge of the LPG applicability to analytical measurements or the feasibility of using specific nanomaterials on LPG to create the desired sensor. The major findings in this dissertation are: 1. Gold nanoislands respond the same way as colloidial gold nanoparticle solutions. Both colloidial and nanoislands showed a reversible color change when exposed to ozone. 2. Ozone shifts the surface plasmon resonce of gold nanoparticles, but without aggregation which has been hypothesized as the primary reason for the surface plasmon resonance shifts. 3. The ozone surface plasmon resonace shift is reversible. 4. A flow-through LPG system was designed and demonstrated. 5. LBL coatings do work on LPG. 6. LPG/LBL systems did not respond in a way similar to prior membrane swelling systems thereby suggesting that the LBL was changing the refractive index in ways other than only swelling. The significance of findings 1-3 are that previous methods for ozone detection either were complex multi-step titrations or were non-reversible processes that destroyed the analytical reagents during measurement. The construction of a flow-through LPG system in findings 4, allows for more reproducible measurements. The flow-through cell also allows for more sensitive measurements, due to the elimination of strain measurements that would be present if the fiber is handled. Finally, the significance of findings 5 and 6 allow for the combination of a very sensitive refractive index sensor by amplifying optical changes in LBL film changes.