Thesis
Heterogeneous nucleation at hydrophobic interfaces
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2021
- Thesis identifier
- T16137
- Person Identifier (Local)
- 201777586
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Crystal nucleation is a ubiquitous process that plays an important role in a range of environmental, biological and industrial processes. It is well accepted that nucleation most commonly occurs heterogeneously at interfaces, and a number of mechanisms have previously been explored that contribute to this effect. Nucleation experiments are often conducted in small scale experimental setups, where the interfaces present are significantly different to those present in normal, macroscale crystallisations. Despite the prevalence of heterogeneous nucleation, the effects of these very particular interfaces are often neglected when analysing the data from such experiments. This thesis will demonstrate the impacts that these interfaces can have on nucleation using a model system of aqueous glycine solution, and will demonstrate a novel concentration effect that facilitates heterogeneous nucleation and is distinct from previously investigated heterogeneous nucleation mechanisms. Results of experiments will be reported for glycine solutions with and without contact with a tridecane oil interface. These results demonstrate that the presence of the oil significantly increases the nucleation rate of glycine. This is a surprising result as the nonpolar hydrophobic tridecane interface would not be expected to enhance the nucleation of the highly polar, hydrophilic glycine. Classical molecular dynamics simulations reveal significantly enhanced vs depleted glycine concentrations at the oil–solution vs air–solution interfaces, respectively. It is proposed that this interfacial concentration effect facilitates heterogeneous nucleation, and that it is due to dispersion interactions between the interface and the solution molecules. To confirm this, model interfaces with tuneable interface–solution interactions were implemented to the molecular dynamics simulations. The solution composition at the interface was found to be strongly dependent on the strength of the dispersion interactions between the interface and the solution. In contrast, while the electrostatic interactions between the interface and the solution were also found to influence the interfacial solution composition, the observed effects are significantly weaker than those observed for the dispersion interactions. These effects have been observed for glycine solutions at a tridecane interface, however it is expected that the same mechanism will be present in a wide range of solution–interface systems. Deeper understanding of these efffects will allow for control over the interfacial concentration in order to design effective nucleants for the enhancement of nucleation, or to suppress nucleation for anti-fouling purposes.
- Advisor / supervisor
- Johnston, Karen
- Resource Type
- DOI
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PDF of thesis T16137 | 2022-01-18 | Public | Download |