| The studies described in this dissertation focus on the development and application of ion-selective sensors. For these types of sensors to be useful for everyday applications, they must demonstrate selective responses to a specific analyte or class of analytes. The primary component of such devices that governs selectivity is an ionophore. These ionophores can be simple organic and inorganic molecules or can be larger biomolecules, however, the most important characteristic of the ionophore, regardless of what type, is that it strongly interacts with or binds to a specific ion.; Although some naturally occurring compounds have been employed as ionophores in sensors, the majority of useful ionophores that have been reported are the result of synthesis. When developing an ionophore for potential application in ion sensors, specific recognition principles such as ionophore geometry, topology, and acid/base chemistry must be considered to yield selective interactions with certain ions. In many cases, lessons exhibited in nature can also be employed in ionophore design to induce desired selectivity. The major focus, then, of the work described herein is on the development and evaluation of synthetic receptors that act as ionophores. For instance, Chapter 2 and Chapter 3 of this work describe mercuracarborand and molecular asterisk ionophores, respectively, that have been developed by the rational inclusion of important features into the molecular architecture. Similarly, Chapters 4 and 5 present studies of cyclic(bisguanidinium) and cyclosporin, respectively, which are ionophores that are based on biologically-inspired ideas. Furthermore, part of Chapter 5 is devoted to the comparison of potentiometric selectivity with results from mass spectrometry to evaluate the potential for using this technique in screening ionophore libraries created by combinatorial synthesis.; Chapter 6 of this work presents the integration of ion-sensing constructs with a microfluidic platform. Since sensors exist for a wide variety of both cations and anions, the incorporation of such sensors into microfluidic systems could result in a highly parallel means of analyzing for an array of ions in a single sample, or determining concentrations of a single analyte in a number of samples. Centrifugal microfluidics was chosen due to its operational insensitivity toward pH and ionic strength. |
