Development of new silicon quantum dots-polymer composite nanoparticles via miniemulsion polymerisation :synthesis and characterizations

Abstract

The research presented throughout this dissertation demonstrates the potential of miniemulsion polymerization to co-encapsulate silicon quantum dots (SiQDs) within polymeric nanoparticles and shows that the optical properties of SiQDs can be manipulated by their co-encapsulation with metal nanoparticles. In Chapter 1, the current state of the art in the preparation of inorganic/polymer composite nanoparticles via miniemulsion polymerization, utilizing inorganic species ranging from semiconductor nanocrystal quantum dots, metal nanoparticles, magnetic and oxide nanoparticles, is reviewed. A brief discussion on the properties of SiQDs, which are the inorganic entities of interest in this work, is presented. Chapter 2 describes the synthesis and characterization of encapsulated alkylated SiQDs within polymer nanoparticles composed of the monomers styrene and 4-vinylbenzaldehyde via miniemulsion polymerization. It was shown that the polymer nanoparticle surfaces, which display aldehyde groups, can be further decorated with organic molecules through the formation of imine, oxime or hydrazone bonds. The preparation of two-component polymer composite nanoparticles encapsulating both SiQDs and gold nanoparticles (AuNPs) is presented in Chapter 3. These Au-Si polymer composite nanoparticles display plasmon-enhanced fluorescence of the SiQDs attributable to the localized surfaced plasmon resonance of AuNPs co-encapsulated within the polymer nanoparticles. A preliminary study of Au-Si polymer composite nanoparticles in inkjet printing is also discussed. Chapter 4 presents the development of multicomponent polymer composite nanoparticles which co-encapsulate SiQDs and Au-Ag alloys NPs encoded with Raman-active molecules within polymer nanoparticles. The multicomponent polymer composite nanoparticles exhibit the simultaneous effects of surface-enhanced Raman scattering and metal-enhanced fluorescence as a consequence of the close proximity of the co-encapsulated SiQDs and Raman-active Au-Ag NPs. In Chapter 5, the conclusions and future directions of this study are discussed. This research moves iii towards the development of novel inorganic/polymer composite nanoparticles which may offer potential as new chemical probes with applications in biology, sensing and anti-counterfeiting.