| This dissertation consists of two distinct parts: An Optical Waveguide Strain Sensor comprises Part 1, and An Electrochemical Oxygen Sensor comprises Part 2.; The optical waveguide strain sensor examined in this work consists of a polyimide coated fused silica capillary tube which serves as a waveguide in which an optical signal is attenuated in an amount proportional to applied bending strain. The capillary is incorporated into an optical fiber fink, making possible continuous monitoring and damage assessment of structures such as bridges and buildings. By applying thin films to the surfaces of the waveguide, the strain gage can be optimized for specific strain ranges. This optical strain sensor exhibits advantages in comparison to commercially available metal foil (resistance) strain gages, including gage factors 100 times larger and temperature insensitivity for operating temperatures ranging from --25°C to +51°C.; The electrochemical oxygen sensor consists of a glassy carbon (GC) electrode coated with either of two electrocatalytic polymer films: poly(1,2-phenylenediamine) (PPD) or poly(2,3-diaminophenazine) (PDAP). Either polymer film catalyzes the reduction of oxygen to hydrogen peroxide in acidic aqueous media. In addition, relative to bare GC, the polymer films increase cathodic peak current by a factor of 3, shift the cathodic peak potential positively by 300 mV, and improve cathodic peak shape. Visible reflectance spectra reveal structural differences reveals between the two films, despite the fact that both are similar in their electrocatalytic behavior. Although either 1,2-phenylenediamine (PD) or 2,3-diminophenazine (DAP) may be electropolymerized onto GC for subsequent use in oxygen determination, DAP is preferred for use because it is more stable in solution and its spectrum exhibits a higher degree of conjugation. The in situ electropolymerization of DAP results in a polymer coating which is strongly adherent, stable, suitable for prolonged use, and highly effective in the electrocatalysis of oxygen reduction. |
