Synthesis, Size-selective Separation and Characterization of Colloidally Stable, Water-soluble Silicon Nanocrystals

In the field of silicon nanocrystals (ncSi), polydispersity, pH-independent aqueous colloidal stability, near-infrared (NIR) to visible photoluminescence tunability and cytotoxicity present significant challenges in the elucidation of important size-dependent physical, chemical, and biological properties. This thesis outlines some contributions towards understanding and addressing these challenges with special consideration towards biological fluorescent cell labelling. We begin by demonstrating the synthesis of polydisperse ncSi functionalized with 10-undecenoic acid (ncSi:UDA) which are size-separated using two different size-separation methods: size-selective precipitation and sucrose density gradient ultracentrifugation. Further improvements are then made on the pH-independent colloidal stability of ncSi:UDA by coupling the carboxylic acid terminus to poly(ethylene glycol) (ncSi:UDAPEG). Finally, the colloidal stability of NIR-emitting ncSi:UDA is investigated through the synthesis and hydrolysis of ethyl 10-undecenoate-functionalized ncSi (ncSi:EUD).M.Sc