Size- and shape-controlled synthesis of various metal nanoparticles and their applications

Abstract

Controlling the size and shape of metal nanoparticles has been one of the most interesting research topics over the past decade, because the several properties of metal nanoparticles can be finely and widely tuned by controlling their size and shape. Thanks to these tunable properties, metal nanoparticles have been widely applied in various fields such as electronics, sensing, imaging, and biomedicine as well as catalysis. In this re-gard, tremendous efforts have been devoted to the synthesis of metal nanocrystals with different sizes and shapes, in order to study their growth mechanisms and to study their size- and shape-dependent properties as well as to fine-tune or enhance the properties. However, growth mechanisms for metal nanoparticles with dif-ferent shapes are still unclear and high-level synthetic control is also necessary. For this dissertation, I synthe-sized various metal nanoparticles with different sizes and shapes for the following purposes: i) to understand their formation mechanisms in order to facilitate better control over the size and shape of metal nanoparti-cles, ii) to study size- and shape-dependent properties of them, iii) to apply them to several applications. Chapter 1 introduces basic knowledge in this field that includes what is metal nanoparticle, shape- and size-dependent properties of metal nanoparticles, and how to control the size and shape of metal nanoparticles. Chapter 2-4 describe experimental results for this dissertation. More specifically, Chapter 2 presents shape evolution of Au nanoparticles. We found that rhombic dodecahedral Au nanoparticles in the early stage of the reaction transformed into Au octahedra with the other shapes. By stopping the reaction at certain times, Au nanoparticles with different shapes such as rhombic dodecahedral, truncated rhombic dodecahedral, rhombic cuboctahedral, truncated octahedral, and octahedral could be obtained. Their strong scattering ability arisen from the localized surface p...