Ponsford, Daniel; (2025) Cucurbituril and selenium-based nanomaterials. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Nanoparticles of selenium and its compounds have a vast range of applications. As a biologically essential element, selenium plays an important role in a number of physiological functions, whilst silver selenides exhibit excellent thermoelectric properties. As a result, the ability to functionalise selenium nanoparticles is highly desirable. In this thesis, the first supramolecular binding interaction between selenium nanoparticles and the macrocycle cucurbit[7]uril (CB7) is reported, and confirmed by aggregation experiments. This interaction, along with the encapsulation properties of CB7, was harnessed to synthesise selenium nanoparticles (Se NPs) functionalised with 5-fuorouracil (FU), which exhibited significantly higher antimicrobial and cytotoxic action against E. coli and MCF7 cells, respectively (compared to the effects of nanoparticles and 5-fluorouracil independently). The minimum inhibitory concentration (MIC) against E. coli for both CB7-FU-Se NPs and FU-Se NPs was 16.5 μg mL-1, half that of the corresponding samples without FU. In terms of cytotoxicity, the cell viability of MCF7 cells in the presence of CB7-FU-Se NPs was 60% less than for cells incubated with FU-Se NPs after 24 hours, at selenium concentrations of 20 μg mL-1. Subsequently, the non-covalent cucurbituril-selenium interaction was utilised to prepare silver selenide nanoparticles, which were themselves used to fabricate flexible films with excellent thermoelectric properties. Thermoelectric materials generate a voltage when subjected to a temperature gradient, offering various ways to capture heat energy which would otherwise be wasted, and will be crucial in the global transition towards renewable energy sources. In this case, a film with a high power factor of 2.74 mW m-1 K-2 was constructed from the hollow silver selenide nanoparticles which formed in the presence of CB7. The exploration of the interaction between CB7 and selenium nanomaterials in this work lays the foundation for the facile generation of functional materials for a wide range of applications in the future.

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