Design, synthesis and applications of functional carbonaceous nanospheres

Abstract

Carbon nanoparticles have gained considerable attention due to their distinguishing features including hydrophobic, conducting and thermostable properties. Other features include the fine control over the ductile properties, porosity, and surface area of the nanoparticles. These features allow the nanoparticles to be designed for applications in drug and vaccine delivery, nanoreactors for catalytic reactions, electrode material for energy storage and conversion.With the advance in new synthetic techniques, carbon nanoparticles can now be designed with control over the particles morphology, which include microporous, mesoporous, hollow, core-shell and yolk-shell structures. However, due to the inert nature of carbon, there remains a great challenge to prepare carbon nanoparticles not only with a desired morphology and porosity, but with desired functionality. Accomplishing this will provide a powerful synthetic methodology to prepare the next generation of carbon nanoparticles, improving on the many known applications and possibly generate new technologies. This thesis aims to develop highly effective and facile methods to prepare carbon nanoparticles with not only controlled morphology and porosity, but producing composite nanoparticles (e.g. heteroatom-doping and metal nanoparticle inclusion) and greater surface functionality. The additional features have provided the design capability to develop better supercapacitors and nanocatalysts.The first aspect discussed in this thesis is the development of monodisperse Ag@carbon coreshell nanospheres by an extended Stöber method. The synthetic method is based on the the similarity between the organic sol-gel of resorcinol/formaldehyde (RF) resins and silicate solgel process. This important finding represents a unique method to make carbon nanoparticles with morphologies similar to that found with silica. In particular, the well-know Stöber method is extended to enable the preparation of Ag, AgBr@RF core-shell nanospheres, which after being carbonized under N 2 gas produced Ag@carbon core-shell nanospheres. The shape and thickness of the shell can be tuned by simply adjusting the synthesis parameters.The simple one-pot route can be extended to the preparation of core-shell spheres with other metals/metal oxides as cores. The rattle-type Ag, AgBr@meso-SiO 2 and yolk-shell structured Ag@carbon@meso-SiO 2 have been selectively synthesized by calcinations of double layered Ag, AgBr@RF@meso-SiO 2 under air or nitrogen respectively. This synthesis approach is considered to be low cost and more suitable for industrial production. Because of the II tunability and functionality of both cores and shells, these complex core-shell and yolk-shell spheres have the potential application as nanocatalysts, which have been confirmed by our preliminary photocatalysis study.The second aspect discussed in this thesis is the design and synthesis of N-doped mesoporous carbon nanosphere (N-MCN) via a dual surfactants soft template method for fuel cell applications. Here, the technique...