The development of lifetime-based, imaging, fiber-optic sensors

The following dissertation describes the development of luminescence lifetime-based, fiber-optic sensors for remote and in-situ imaging. The work described includes the development and characterization of a lifetime-based, fiber-optic water sensor for measurement of relative humidity and water content in organic solvents; a description of the sensing chemistries that were developed and modified for the applications included here; the development of a lifetime-based, fiber-optic imaging sensor system for remote and in-situ measurements; and the incorporation of a fiber-optic, dimension reduction array into the lifetime imaging system allowing simultaneous, multi-wavelength spectroscopic imaging.; A single point fiber-optic water sensor that can be used to measure water content in organic solvents and relative humidity of air was developed as an initial step toward a lifetime imaging system to monitor water diffusion inside thin Nafion™ membranes. The sensor is based on the luminescence lifetime quenching of ruthenium(II) bisphenanthrolinedipyridophenazine immobilized in a lithium hydroxide pre-treated Nafion™ membrane that is mechanically attached to the distal tip of an optical fiber. The second major part of this dissertation describes the development of a lifetime-based, imaging, fiber-optic sensor system that is useful for remote, in-situ, and small spatial scale (9 μm) measurements. Optimization of the data collection parameters to maximize the confidence in the lifetime images derived from a curve fit of the data is discussed and the method is compared to lifetime images calculated using the Rapid Lifetime Determination method. Lifetime imaging sensors were developed for several analytes including moisture, pH, and oxygen. We demonstrate the application of these sensors to in-situ , small scale measurements by imaging the development of a micrometer scale pH gradient in a sample cell. Incorporation of a recently described fiber-optic dimension reduction array into this optical fiber lifetime imaging system allows lifetimes of multi-wavelength spectra to be collected simultaneously for all points in an image while preserving the spatial information. The usefulness of dimension reduction is demonstrated for multi-analyte lifetime imaging sensors and deconvolution of lifetime images. The compromises that must be considered when incorporating dimension reduction into lifetime imaging are discussed.