| The continued understanding of the geochemistry of extreme environments requires tools that are able to deliver high-quality measurements. Ion-selective electrodes were successfully deployed as chemical sensors in an extreme environment during NASA's 2007 Phoenix mission to Mars. Unfortunately, ISEs have proved difficult to miniaturize and further develop to the level where the "next-generation" of planetary instrumentation is heading. One of these instruments, called Nernst, is a microfluidic total-analysis system, which uses an array of electrochemical sensors for analyte detection.;In order to meet the demand for high-quality robust chemical sensors capable of analysis in microfluidic channels, sensors based on carbon nanostructures are developed and characterized. The focus of this work is three- fold: to understand the chemical and electrochemical properties or carbon nanostructures, especially graphene oxide and carbon nanofibers; to apply the knowledge gained into developing novel sensors for a microfluidic total analysis system; and to develop and demonstrate a microfluidic total analysis system.;The chemical and electrochemical characterizations are focused on understanding how the electrochemistry of these unique materials can be used to develop novel sensors. This is targeted on understanding the electrochemical behavior of GO in aqueous solutions, and the investigation of carbon structures within plasticized membranes. GO's aqueous electrochemistry is dominated by its acidity in solution, and is related to the stabilizing double-layer. In addition, it was discovered that GO could behave like an ionic additive within ion-selective membranes.;Two types of novel sensors based on carbon nanofibers are prepared and characterized here: a solid-state reference electrode, which is in essence a sensor with no response, and solid-state ion-selective electrodes using ionophore- modified carbon nanofibers. The solid-state reference electrode provides minimal response towards all tested ionic species, redox molecules and pH, and is demonstrated for dynamic potential techniques. The solid-state ISE is able to maintain excellent response and selectivity over a period of 75 days.;Finally, the development and demonstration of a novel microfluidic total analysis system is discussed. The bottom-up design of the instrument is discussed from its infancy as a flow-cell into its current state as a lab-on-a-chip, and preliminary data using solid-state ISEs is obtained. |
