School of Chemistry - Theses
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ItemSynthesis and Modification of ZnSe NanoplateletsHan, Jiho ( 2021)Nanoplatelets (NPLs) are a class of nanoparticles which have garnered significant interest in the research community. Unfortunately, much of the focus has been on the usual workhorse material: cadmium selenide. Zinc selenide is a close relative of cadmium selenide, both belonging to the II-VI family of semiconductors, but little research exists on ZnSe NPLs beyond its initial synthesis. In this thesis, ZnSe NPLs are addressed from the bottom up. In Chapter 2, the formation mechanism of ZnSe NPLs and MSCs is investigated. The evolution of nanoparticles in the reaction is monitored while exploring the reaction space. It is demonstrated that the concept of surface reversibility can be used to predict the formation of NPLs and MSCs. Additionally, it is found that MSCs and NPLs compete in the reaction, and selective formation can be induced by varying selenium precursor and the ripening behaviour of the ligand. Along the way, five unreported ZnSe magic-sized clusters (MSCs) are found. Chapter 3 of the thesis is a demonstration of Mn 2+ doping into the ZnSe and ZnS NPLs. Mn 2+dopant incorporation can be confirmed via its photoluminescence and photoluminescence excitation spectra and the photostability is measured. Additionally, the unique Mn 2+ emission is used a probe to investigate the evolution of various ZnSe species. Finally, Chapter 4 is concerned with the post-synthetic shelling of ZnSe nanoplatelets. ZnSe NPLs as synthesized from literature are colloidally and photo-unstable. A common solution to this is to coat the surface of the nanocrystal with a suitable semiconductor material. By modifying the process introduced for CdSe NPLs, the synthesized ZnSe NPLs are shelled successfully via colloidal atomic layer deposition (C-ALD). This allows us to improve its photoluminescence properties and observe unique features associated with Type-II ZnSe/CdS heterostructures.
ItemIt’s hip to be square: a cyclobutene diester approach to alkyl citrate natural productsRobertson, Angus ( 2018)This thesis features an enatiospecfic synthesis of a key alkyl citrate retron that was leveraged in the total syntheses of squalene synthase inhibitors (-)-CJ-13,982, (-)-CJ-13,981 and (-)-L-731,120 (featured in Org. Let. 2018, 20, 4255–4258). This key retron was prepared in 7 linear steps, requiring only 4 purification, with a 40% yield from (S)-(+)-γ-hydroxymethy-γ-butyrolactone. The synthesis highlights the application of a formal [2+2] cycloaddition and a remarkable acid-mediated rearrangement sequence to furnish the correct stereochemistry and oxidation level of the citrate moiety. This thesis demonstrates the shortest enantiospecifc total synthesis of (-)-CJ-13,981 to date, via the use of this key citrate retron, affording this natural product in 7.7% total yield over 10 steps. Efforts towards the squalene synthase inhibitor (-)-L-731,120 and the viridiofungins, a family of serine palmitoyl transferase inhibitors that have activity inhibiting hepatitis C replication, are also featured.