Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Chemistry

Supervisor

Corrigan, John F.

Affiliation

University of Waterloo

2nd Supervisor

Workentin, Mark S.

Co-Supervisor

Abstract

In nanocluster research, easy modification of the cluster surface while maintaining the cluster core remains a key challenge. Herein we report the synthesis, structure, and properties of four targeted Ag20 nanoclusters (NCs) with surface azide moieties, two of which have 8 azide moieties, [CO3@Ag20(StBu)10(m-N3-C6H4COO)8(DMF)4] and [CO3@Ag20(StBu)10(p-N3-C6H4COO)8(DMF)4], and two of which have 6 azide moieties, [CO3@Ag20(StBu)10(m-N3-C6H4COO)6(NO3)2(DMF)4] and [CO3@Ag20(StBu)10(p-N3-C6H4COO)8(NO3)2(DMF)4]. These Ag20 NCs with surfaces azide moieties are the first examples of Ag nanoclusters that can undergo cluster surface strain-promoted azide alkyne cycloaddition (CS-SPAAC) click reactions, introducing new functionality to the cluster surface. Reactivity was screened on the 8-azide NCs using a model strained cyclooctyne framework in exo-bicyclo[6.1.0]non-4-yn-9-ylmethanol (BCN) and a ferrocene functionalized derivative. Reaction products and parent clusters were characterized by UV-Vis., FT-IR, and NMR spectroscopies. The structure of the parent clusters and presence of surface azides was further confirmed by SCXRD analysis and XPS. Both tested clusters were found to be amenable to CS-SPAAC reactions with retention of the NC frameworks.

Summary for Lay Audience

Silver is a metal that is known to many people in everyday life from its use in jewelry and ornamentation, but also has a rich history in areas such as commerce (as a currency), culture (where different religions have associated it with God and made idols from it), medicine (where small silver molecules have applications in anti-cancer, anti-bacterial, anti-fungal drugs as examples) and analog photography. In more recent history, silver quantum dots became a large area of research interest in the 1990’s because of their unique light emitting and semi-conducting properties, making them potential candidates for both medical imaging and solar power applications. However, a silver quantum dot is not a single substance but actually a group of substances of varying sizes with a small range. Because of this it is difficult to precisely change the properties and structures of these substances and account for that change. From this research, the desire to more finely control the structure of silver clusters and devise atomically precise formulae came, and was fulfilled by the advent of silver nanoclusters. Silver nanoclusters are smaller than quantum dots, but have a specific chemical formula and so a silver nanocluster refers to a single atomically defined substance. This means that any changes to the nanocluster can be exactly detailed since it changes the chemical formula of the cluster, and so relationships between composition and the properties of the nanocluster can be established. The surface attachments on cluster surfaces can both introduce cluster surface functionality and can change the composition and shape of the cluster core due to their differing stabilizing effects. Since nanoclusters are not easily modified after they are assembled, it would be beneficial to put groups on the cluster surface, that can easily and efficiently react with complementary molecules to deliver additional function. In this thesis I was able to make and characterize, for the first reported time, silver nanoclusters with surface azide groups and showed that they react with alkynes to add functionality to silver nanocluster surfaces.

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