Carbon-based electrodes for environmental health applications
Date
2019
Authors
Berg, Kathleen E., author
Henry, Charles, advisor
Ackerson, Christopher, committee member
Krummel, Amber, committee member
Lear, Kevin, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Environmental risk factors of air pollution and unsafe water are leading contributors to human morbidity and mortality, causing millions of deaths and diseases annually worldwide. Fine particulate matter (PM2.5) air pollution is linked to millions of deaths worldwide annually along with millions of cardiovascular and respiratory diseases. Unsafe water can contain heavy metals, including manganese (Mn), which high doses are linked to a variety of neurological and developmental diseases in humans. Analytical methods for testing for environmental risk factors such as fine PM and Mn still need improving. The primary focus of the dissertation here was to use carbon-based electrodes for improvements on environmental risk factor applications. An electrochemical assay was developed and used to measure Mn(II) in aqueous samples with stencil printed carbon paste electrodes. Stencil printed carbon paste electrodes are a mixture of graphite and organic liquid; they are easy to fabricate, portable, and disposable. These electrodes also do not require modification before detecting Mn in aqueous samples, but 1,4-benzoquinone was added to the background electrolyte for improved precision. Mn was then detected in complex matrices of tea and yerba mate samples. The focus is shifted from Mn detection to air pollution applications. A commercially available stencil printed carbon electrode was used for the dithiothreitol (DTT) assay, which is an assay commonly used to estimate the health effects of air pollution samples. The presented, improved DTT assay reduces reagents and increases sample throughput, both of which will help enable larger scale air pollution studies to be executed in the future. The DTT assay was then further improved with a semi-automated system that further increases the sample throughput and reduces reagent volumes while reducing the required manual labor associated with liquid handling. The semi-automated system uses a custom carbon composite thermoplastic electrode (TPE). Changes were observed in the TPE response over time and are studied further. The dissertation shifts focus to a more fundamental electrode characterization of high performing TPEs that were previously used because TPEs have a vast array of potential analytical applications, including environmental risk factor applications. Atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM) were used for a thorough investigation of the local surface topography and electrochemistry of TPEs, which is needed to assess the cause of the excellent electrochemical properties. The evidence suggests that the TPEs behave as microelectrodes, which gives rise to their high electrochemical activity. The amount of potential applications from TPEs is then increased by modifying the surface. TPEs, while being high performing and easy to pattern, have previously been limited by their solvent compatibility to aqueous solvents. Presented here is an alternative fabrication, which makes TPEs polar organic solvent compatible, that greatly increases the number of applications. The TPEs were then modified and functionalized in acetonitrile as a proof of concept that TPEs can be used in non-aqueous solvents and can have modified surfaces, which can lead to more applications. The research here uses different carbon electrodes to advance method development of environmental risk factor quantification. Advances to Mn(II) detection and fine PM health impacts were made. Fundamental understandings were developed of carbon composite TPEs and then modified to show a large potential number of future applications for continual improvement of electrochemical sensing.