Gold nanorods: Synthesis, structural manipulation, and self -assembly
Khanal, Bishnu Prasad
Zubarev, Eugene R.
Doctor of Philosophy
This work describes methods for the synthesis, structural manipulation, and self-assembly of one-dimensional gold nanostructures. The thesis begins with an efficient technique for the synthesis and separation of gold nanorods from a complex mixture, which has been a long standing challenge in the field of inorganic nanocrystals. The key aspect of our approach is the combination of partial oxidative dissolution and gravitational sedimentation of gold nanostructures. In addition, the length of nanorods can be tuned using reversible elongation and shortening of rods when Au (I) and Au (III) ions are used, respectively. The synthesis of extremely long gold nanowires measuring up to ∼25 µm was accomplished by this novel synthetic approach. The width of gold nanowires can also be precisely controlled by adjusting the concentration of Au (I) ions in the growth solution. This thesis also describes a procedure for the large scale synthesis of gold nanorods. The gram quantity of nearly monodisperse single crystalline nanorods was synthesized by slow reduction of Au (I) ions on the surface of pre-formed gold nanorods. This results in the amplification of nanorods without the formation of any undesirable shapes. Finally, the surface functionalization technique described in this thesis allows for the synthesis of polymer-functionalized gold nanorods. Our investigation revealed their unique ability to undergo spontaneous self-organization into ring-like superstructures. This process is templated by water microdroplets which condense from the air when a volatile organic solvent evaporates. This self-assembly does not require any lithographic technique and can organize millions of gold nanorods into rings in a matter of seconds.