Functional Nanoparticles: Synthesis and Application
Open Access
- Author:
- Fleming, David Andrew
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 14, 2006
- Committee Members:
- Mary Elizabeth Williams, Committee Chair/Co-Chair
Thomas E Mallouk, Committee Member
Christine Dolan Keating, Committee Member
William O Hancock, Committee Member - Keywords:
- nanoparticles
colloid - Abstract:
- Nanoparticles have attracted much attention due to their potential applications in, for example, magnetic recording, optical detection and medical diagnostics. The control of nanoparticle size, shape and composition is essential because each affects physical properties, while control over surface functionality is necessary to realize potential uses. As a result, the synthesis and chemical surface modification of noble metal and magnetic nanoparticles is therefore presented. Au nanoparticles with diameters ranging from 4 - 15 nm and with low polydispersity were synthesized in molten trioctylphosphine oxide/hexadecylamine solutions through the amine mediated reduction of Au(acac)PPh3. The rate of particle growth and subsequent aggregation was strongly dependent on the relative concentrations of protecting ligands and was monitored by both transmission electron microscopy and UV-visible absorption spectroscopy. This scheme was subsequently amended to the growth of thiol, amine, or phosphine protected Au seeds. An aqueous route for the production of gold-coated ã-Fe2O3 and partially oxidized Fe3O4 through hydroxylamine iterative seeding was also explored. Au shell growth was confirmed by transmission electron microscopy and tracked via UV-Vis spectroscopy. Core/shell particle magnetic properties were investigated using SQUID magnetometry and where shown to remain constant during Au deposition. Place exchange reactions were used to functionalize FePt with electroactive groups. Here, ferrocene thiol was incorporated into the FePt supporting ligand monolayer. Cyclic voltammetry revealed that particle motion was mass transport limited, and a diffusion coefficient was calculated. Microelectrode voltammetry revealed that applied magnetic fields did not effect particle diffusion. Au particles were also subject to place exchange with ù-bromo-functionalized thiol and the Br termini were subsequently converted to azides. These were then reacted with a series of alkynyl-derivatized small molecules in nonpolar solutions which led to their attachment through the formation of a 1,2,3-triazole ring. These click reactions were used to impart chemical functionality to the Au particles, which was assessed using fluorescence spectroscopy and cyclic voltammetry. The ability of electrostatically stabilized Au nanoparticles to selectively deposit onto amine-patterned glass substrates is lastly investigated. In addition, the syntheses of several classes of noble metal particles again functionalized via place exchange were implicated for additional attachment chemistries. Strategies aimed at directing the assembly of these particles to specific areas of patterned substrates were likewise investigated.