The Surface Passivation and Potential Sensing Applications of Silicon Nanocrystals

Abstract

Silicon nanocrystals (SiNCs) have been explored as active materials in a variety of prototype applications including photovoltaics, electronics, photonics, and sensors based on their optical and electronic properties. Using SiNCs are appealing because their source material (i.e., silicon) is abundant, they exhibit limited toxicity, and their optical as well as electronic properties are tunable. To further the advancement of SiNC-based applications, there is a need to develop surface functionalization methods that provide stability and render the SiNCs solution-processable. This must be achieved while maintaining, and even tailoring SiNC optical response. This thesis consists of two overarching themes: the surface passivation of SiNCs (Chapters 2-3) and the development of SiNC-based sensors (Chapters 4-5). Chapter 2 investigates the hydrosilylation of SiNCs with a variety of alkenes and alkynes using two common radical initiators (i.e., azobisisobutyronitrile and benzoyl peroxide). Chapter 3 examines the use of a compact fluorescent light source for the generation of thiyl radicals from two disulfide containing ligands (i.e., lipoic acid and dibutyl disulfide) to promote radical initiation of the SiNC surface to generate Si-S surface bonds. Chapter 4 describes the development of a luminescent paper-based sensor using dodecyl functionalized SiNCs for its optical response towards nitro-group containing high energy compounds (i.e., trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN)). Ester functionalized SiNCs were embedded into polydimethylsiloxane (PDMS) based-substrates for the optical detection of biogenic amine vapors released during food spoilage in Chapter 5. Finally, in Chapter 6, a summary of the findings of SiNC surface passivation and sensors is presented, followed by possible future research directions in these areas.