Synthesis of Nanoparticles via Vapor Phase and Solution Phase Methods
Nanoparticles have increasing attention because of the size and shape-dependent properties, which differ from those of the corresponding bulk materials. These properties arise from their large surface area, quantum confinement, localized surface plasmon resonance and other phenomena that arise when materials are reduced in size below various critical length scales. This dissertation focuses on how to design and synthesize nano-strucutured quantum dots and metal nanoparticles. Two classed of synthesis methods, vapor phase methods and solution phase methods, were used here to produce nanoparticles. Vapor phase methods can often provide continuous, easy-controllable and reproducible processes; on the other hand, solution phase methods are usually carried out as batchwise and can produce monodisperse nanoparticles more easily. In the work reported in this dissertation, vapor phase method was applied to synthesize ZnS nanocrystals and nanospheres with hollow and porous structures. Solution phase method used to synthesize gold, silver, and gold-silver alloy nanoparticles. Size and localized surface plasmon resonance frequency of these particles could be tuned by varying the surfactants and composition of precursors in the synthesis. A simple and reproducible process was also designed to synthesize hybrid nanopaticles of Au and upconverting nanophosphors. The hybrid nanopaticles combine the properties of both components and their usefulness for multi-modal bioimaging was demonstrated.