The role of surface chemistry in defining the energetics and kinetics of single electron tunneling through individual gold nanoparticles

by McConnell, Wyatt Parks

MCCONNELL, WYATT PARKS. The role of surface chemistry in defining the energetics and kinetics of single electron tunneling through individual gold nanoparticles. (Under the direction of Dr. Daniel L. Feldheim.) The properties of nanoscale materials are often dominated by their surface chemistry due to their increased surface-to-volume ratio. Metal nanoparticles with diameters smaller than ~12nm show a technologically relevant non-linear current-voltage response known as single electron tunneling. Gold nanoparticles offer an excellent platform for understanding how the surface chemistry of the metal island in a single electron-tunneling device can affect the current response of the structure. This is because the surfaces of these particles can be custom tailored using thiol-based self-assembled monolayer protocols that have been extensively developed for planar gold substrates. This dissertation describes STM measurements of single electron tunneling through individual gold nanoparticles of various sizes and surface chemistries in both air and solvent at room temperature and pressure. The voltage step-width of the resulting coulomb staircase was shown to be dependent on particle size. Solution experiments show that the energetics of single electron tunneling of particles with certain surface chemistries is dependent on the composition of the solution, while other surface chemistries can produce particles that give a stable single electron tunneling response in a wide variety of local chemical environments. Using acid and base terminated surface chemistries, particles were made that showed a defined response to a specific change in the local solution pH. The kinetics of single electron tunneling was also shown to be highly dependent on the chemical bond formed between the capping ligand and the metal particle.