Shape-Controlled Synthesis and Self-Assembly of Metallic Nanoparticles

Abstract

Noble metal nanoparticles have been studied extensively for their promising chemical and physical properties. These properties can be effectively controlled by tailoring their size and shape. Achieving control of the size and shape of noble metal nanoparticles is actively pursued for various applications such as catalysis.

This thesis is concerned with the size and shape controlled synthesis of ruthenium and bimetallic palladium-ruthenium core-shell nanoparticles. Using one-pot synthesis in a closed pressure reaction vessel (Fischer-Porter method), the effect of variables on solution-phase synthetic reactions were investigated. The sizes and shapes of nanoparticles were regulated in a one-pot synthesis approach. The seeded-growth method is another approach which can realise precise size and shape control, especially in bimetallic nanoparticle synthesis. In this thesis, I used this approach to deposit palladium atoms on prepared ruthenium nanoparticles. The nanoparticles were characterised by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and selected area electron/ X-ray diffraction (SAED, XRD).

Chapter 1 and Chapter 2 of this thesis give an overview of research into size and shape controlled synthesis of nanoparticles as well as the method and techniques for synthesis, characterisation and analysis of nanoparticles.

Chapter 3, Chapter 4 and Chapter 5 of this thesis detail the research into ruthenium nanoparticles. In Chapter 3, ruthenium nanoparticles were synthesised with their size and shapes closely controlled. The variables were investigated to understand their effects on synthesised morphologies as well as size monodispersity.

Chapter 4 describes the growth mechanism of unique shape ruthenium nanoparticles. To investigate the formation of these ruthenium nanoparticles synthesised in the previous chapter, time resolved reactions were designed to isolate intermediate species. All the experimental results obtained in different steps have been analysed. The process to form the different shapes of the ruthenium nanoparticles is discussed, and the growth mechanism is summarised.

In Chapter 5, the shape of the ruthenium nanoparticles was varied based on Chapter 3 and Chapter 4. In the same chapter, formation of superlattices using ruthenium nanoparticles, which have been synthesised in the previous chapters, was studied. In Chapter 6, ruthenium nanoparticles with faceted shapes were used for directing the overgrowth of a secondary metal (palladium). Synthetic variables were investigated to understand and control the overgrowth. At the end of this chapter, the overgrowth of the palladium shell is discussed and summarised.

Finally, Chapter 7 provides an overall discussion and conclusion of this research. The key variables for shape controlled overgrowth based on noble metals such as ruthenium and palladium as well as self-assembly are summarised. Consideration on future work and potential interests of research based on this thesis are also discussed in details in this chapter.

Part of the work from Chapter 3 and 4 was published in the Journal of the American Chemical Society.