2012 Theses Doctoral

Nanomaterials from Nanocomponents: Synthesis and Properties of Hybrid Nanomaterials

Akey, Austin Joseph

This thesis consists of two series of investigations into two different classes of hybrid nanomaterials, their formation and properties. In the first part of this thesis, hybrid nanomaterials composed of cadmium selenide nanoparticles and single-walled carbon nanotubes (SWNTs) are discussed; a novel synthetic method for these hybrids is presented, and an anomalous photoluminescence behavior is examined. Our experiments show that SWNTs can be decorated with CdSe nanoparticles at high loading densities, following the removal of the nanoparticle surface ligands and replacement with pyridine. The resulting hybrids are thermally stable up to 350ºC and mechanically stable against sonication.

The photoluminescence Stokes shift in the bound nanoparticles is shown to be reduced relative to that of unbound nanoparticles. This difference is attributed to Forster resonance energy transfer from the nanoparticles to the nanotube, leading to hot luminescence in the nanoparticles. The second part of this thesis focuses on formation strategies and mechanisms for nanoparticle superlattices. Supercrystals, as they are called, are formed using lithographically-patterned reservoirs and capillary channels, giving control over both supercrystal dimensions and placement; these supercrystals form within a few hours, much faster than those previously reported. These results are extended to the formation of large-area (> 10 µm lateral dimension) thick (> 1 µm) supercrystals on substrates, and the formation mechanism probed by in situ small-angle x-ray scattering. Both monocomponent and binary supercrystals are examined.