Chemical detection technologies: Optical sensors and ion-mobility systems

The field of analytical chemistry requires instrumentation and methodology that is capable of chemical measurements outside of the laboratory. Two technologies that provide these capabilities are optical sensors and ion-mobility spectrometry. Optical sensors are a broad range of detectors that provide flexible methods of analysis for a variety of target species. In their most common form, they utilize a chemical indicator that is sensitive to the target species and allows concentrations of the chemical of interest to be measured, often remotely. Ion mobility spectrometry is a second technique that is capable of chemical analysis in the field. In this case, however, volatile analytes are introduced for gas-phase measurements that separate the ions by size. Both of these techniques offer extremely portable and flexible analytical solutions.; This document describes the construction and characterization of both optical sensors and an ion-mobility spectrometer. First, novel optical sensors derived from fiber optics are considered. An initial study uses photoluminescent quantum dots to create a novel temperature sensor. The second project involves fiber-optic sensors with sensing regions that can be tens of meters in length, produced by simple modification of their plastic cladding. These fiber-optic sensors are constructed so fluorophores that act as indicators of humidity and carbon dioxide are incorporated into the fiber-optic itself. Finally, a third fiber-optic sensor is described that is composed of a temperature-sensitive core, covered with a humidity-sensitive coating. Dual-parameter sensors such as this are an important development, as the temperature sensitivity of the core provides a means to correct for the influence of temperature on humidity measurements.; A second set of projects concerns the design and construction of an atmospheric-pressure ion mobility spectrometer. The spectrometer is designed with a unique ion gate that enhances the resolution of the instrument. After construction, the ion-mobility instrument was used in two detection schemes that employ a correlation technique called the Hadamard Transform and a novel phase-resolved detection method. These two methods are shown to enhance the signal-to-noise ratio of analyte detection. Furthermore, the use of phase-resolved analysis enhances the resolution of the instrument, which aids in identification of unknown compounds.