Coupled self-assembly and flow alignment of silver nanorods

Abstract

The recent development of facile routes for the production of inorganic nanorods, nanowires, and nanowhiskers has resulted in an array of materials with intriguing optical, electronic, magnetic and structural properties. However, the production of functional materials from these nanoscale building blocks often requires aligning the nanorods on the micro- to macro- scales. The theoretical foundation for self-assembly of anisotropic rigid materials in solution dates back to Onsager (1949), but understanding the liquid crystalline phase behavior of nanorod dispersions is a nascent field formed by the intersection of nanotechnology, liquid crystalline science and colloid science. This thesis reports the liquid crystalline assembly and flow alignment of silver nanorods. The techniques demonstrated for achieving liquid crystalline phases and shear alignment can be extended to any high aspect ratio rigid nanomaterial. The isotropic to biphasic phase transition was determined by optical microscopy and the biphasic to liquid crystalline phase transition was determined by both differential scanning calorimetry and optical microscopy. Aligned films were prepared and studied by surface enhanced Raman spectroscopy (SERS) and scanning electron microscopy (SEM). This work represents a significant step forward in developing a fundamental understanding about the impacts of nanorod concentration on liquid crystalline phase behavior as well as the potential for liquid crystalline dispersions of nanorods to be processed in to highly aligned macroscale coatings, films and fibers.