Nanomaterials such as carbon nanotubes, gold nanorods, magnetic nanocrystals,
and binary nanocrystal superlattices have exciting potential applications. However,
before these ideas can be applied, it is imperative to fully understand the materials
synthesis.
Multiwall carbon nanotubes were synthesized in supercritical toluene using
cobaltocene, nickelocene, ferrocene, or metal nanocrystals as catalysts. Toluene served
as both the solvent and carbon source for nanotube growth. The reaction was optimized
by introducing supplemental carbon sources; either hexane or ethanol increased the yield
relative to pure toluene and catalytic amounts of water minimized carbon filament and
amorphous carbon formation.
Gold nanorods were synthesized by the colloidal seed-mediated, surfactantassisted
approach using cetyltrimethylammonium bromide (CTAB) obtained from ten
different suppliers. The gold nanorod yield depended strongly on the CTAB used: with
the same recipe, three of the CTABs produced only spherical particles, whereas the other CTABs produced nanorods with nearly 100% yield. Inductively coupled plasma mass
spectrometry revealed a trace iodide impurity in the CTABs that did not yield nanorods.
Further experiments introducing potassium iodide to the nanorod synthesis verified the
detrimental effect of iodide on nanorod formation.
Multifunctional colloidal core-shell nanoparticles of magnetic nanocrystals or
gold nanorods coated with a fluorescent dye (Tris(2,2 -bipyridyl)dichlororuthenium(II)
hexahydrate) doped silica shells were also synthesized. The as-prepared magnetic
nanocrystals were initially hydrophobic and silica coated using a microemulsion
approach, while the gold nanorods were hydrophilic and silica coated using a Stöber
process. These colloidal heterostructures have the potential to be used as dual-purpose
tags, exhibiting a fluorescent signal that could be combined with either dark-field optical
contrast or enhanced contrast in magnetic resonance imaging.
Binary superlattices (BSLs) of large iron oxide and small gold nanocrystals were
assembled by slow evaporation of colloidal dispersions on tilted substrates. SEM and
grazing incidence small angle X-ray scattering (GISAXS) confirmed the BSLs were
simple hexagonal AB2 superlattices with long range order. GISAXS also revealed that
the superlattice was slightly contracted perpendicular to the substrate as a result of
solvent drying during the deposition process. Additionally, in some BSLs nearly periodic
superlattice dislocations consisting of inserted half-planes of gold nanocrystals were
observed. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/6634 |
| Date | 23 October 2009 |
| Creators | Smith, Danielle Kristin |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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