Self-assembly of extended, high-density gold nanoparticle monolayers on silicon dioxide

Interest in gold nanoparticles in the 1 to 2 nm core diameter range has steadily increased over the last two decades because they possess useful electronic properties at room temperature. Gold nanoparticle-based electronic devices exhibit Coulomb blockade, which may be harnessed to produce single electron transistors or single molecule sensors. To exploit the useful properties of gold nanoparticles, methods of forming the desired particles must be developed and the particles must be functionalized to enable self-assembly into functional devices.; In this work, a synthetic method was developed that resulted in 1.5 nm diameter gold nanoparticles. These particles have an easily displaced ligand shell that allows them to be exchanged with thiols to yield functionalized gold nanoparticles. The synthetic access to functionalized nanoparticles was necessary to allow the use of functional group interactions to drive the self-assembly of gold nanoparticle monolayers on silicon dioxide.; High-density gold nanoparticle monolayers were formed on the native oxide of silicon using the strong bonds formed between phosphonic acid-functionalized gold nanoparticles and HfOC12 modified-silicon dioxide. We demonstrated that functional group interactions could be used to direct assembly of nanoparticle monolayers on chemically patterned surfaces.; To exploit the electronic properties of these nanoparticle monolayers, assembly must be carried out on insulating substrates, so the techniques used to form monolayers on the native oxide of silicon were adapted to thermal silicon oxides. A method consisting of a combination of oxygen plasma and wet chemical treatments was developed to restore surface silanol density to the thermal oxides to enhance their reactivity toward HfOC12. Monolayers formed on these surfaces that were composed of gold nanoparticles with thin ligand shells exhibited linear current-voltage curves at room temperature and Coulomb blockade at low temperatures. Monolayers formed from gold nanoparticles with thicker ligand shells showed Coulomb blockade at room temperature.; Finally, new methods for forming physisorbed gold nanoparticle monolayers on surfaces were developed. In one case, interparticle hydrogen-bonding was used to form monolayers of 1.2 run particles on silicon dioxide. In other experiments, centimeter-scale monolayers of 0.8 nm particles were assembled on the surface of water and transferred to silicon dioxide. This dissertation includes my previously published and co-authored materials.