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http://hdl.handle.net/11375/28046
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DC Field | Value | Language |
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dc.contributor.advisor | Kruse, Peter | - |
dc.contributor.author | Angizi, Shayan | - |
dc.date.accessioned | 2022-10-25T15:16:32Z | - |
dc.date.available | 2022-10-25T15:16:32Z | - |
dc.date.issued | 2022 | - |
dc.identifier.uri | http://hdl.handle.net/11375/28046 | - |
dc.description.abstract | Since the discovery of thermodynamically stable monolayer graphene, it has succeeded in overtaking a number of conventional materials in chemical sensing applications due to its exceptional chemical and electrical properties. In addition to being electrically conductive, graphene also has a large surface area which facilitates faster electronic interaction with analytes. In spite of graphene's inherent potential for chemical sensing, its application to aqueous electrolytes has been limited by an incomplete understanding of its interactions with the electrolytes’ environmental parameters. This thesis focuses on mechanisms through which graphene-based solid-state sensors (i.e., chemiresistors, Schottky diodes) respond to changes in aqueous electrolytes. Multiple environmental parameters, including pH, ionic strength, oxidation-reduction potential, as well as a target analyte (free chlorine), were chosen to examine their impacts on the performance of devices. To begin, graphene's pH response was explored, showing that its pH sensitivity is strongly defect-dependent. The graphene defectivity was determined with the aid of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). As revealed by measurements of the oxygen-to-carbon ratio (O/C) in XPS and the D-band/G-band intensity ratio (ID/IG) in Raman, graphene responds to pH in two main defectivity regions. In a low defect region, the graphene surface was shown to mainly interact with corresponding ions (i.e., H3O+ and OH−) through an electrostatic gating effect. However, in the high defect region, the response is dominated by protonation-deprotonation of oxygen-based functional groups. Therefore, the modulation of defectivity resulted in the change in pH responsivity. According to this result, we demonstrated that thermally reduced graphene oxide could be highly pH-sensitive to the pH range of 3-10 by dominating the defect induced pH response. Aside from pH, the impacts of changes in ionic strength, DO, and ORP of the electrolytes were investigated. We demonstrate that graphene chemiresistive devices can be used to investigate deviations in experimental screening lengths from the theoretical Debye length. We also present an overview of ion arrangements in the proximity of graphene, emphasizing the importance of DO in the Stern layer. Lastly, the development of an ultra-sensitive water quality sensor was shown by utilizing monolayer graphene in Schottky diodes. For the case study, free chlorine, a primary disinfectant of water, was chosen as the target analyte. Schottky diodes are demonstrated to offer sensitivity and LOD values competitive with current literature when environmental parameters are taken into account. I believe that this thesis provides a deeper understanding of graphene's applicability in aqueous media and opens new research avenues in graphene/aqueous interfacial interactions. | en_US |
dc.language.iso | en | en_US |
dc.title | The role of environmental parameters in the interactions of aqueous electrolytes with graphene solid state devices | en_US |
dc.type | Thesis | en_US |
dc.contributor.department | Chemistry | en_US |
dc.description.degreetype | Thesis | en_US |
dc.description.degree | Doctor of Science (PhD) | en_US |
dc.description.layabstract | This thesis aims to investigate the interfacial interactions between graphene-based water quality devices and aqueous electrolytes to enhance the functionality of graphene derivatives in aqueous environments. The study focuses on the mechanisms through which graphene devices respond to changes in electrolyte parameters such as pH, oxidation-reduction potential (ORP), dissolved oxygen (DO) and ionic strength. In order to investigate the possible interference of these environmental parameters with the detection of analytes in water, multiple graphene devices (such as chemiresistive and Schottky diodes) were fabricated to better understand how graphene perceives aqueous electrolytes. This thesis explores four groups of interfacial interactions: electrostatic gating effect, surface charge transfer, substitutional doping, and ion trapping, and strives to manufacture sensitive water quality sensors based on graphene. | en_US |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Angizi_Shayan_202210_Doctor of Philosophy.pdf | 32.12 MB | Adobe PDF | View/Open |
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