Synthesizing, separating, and isolating monodisperse monolayer protected gold nanoparticles

This dissertation describes work done that has led to obtaining near monodisperse samples (ie. core size) of Monolayer Protected Gold Nanoparticles (MPCs).; Chapter 1 outlines the importance of our present work and previous research performed by other groups striving to obtain individual isolated sizes of nanoparticles. The different properties that nanoparticles possess when fractionated into separate sizes are discussed. A brief description of the technique that our research group has developed for effective fractionation of monolayer protected clusters (MPCs) is reported along with an overview of the previously used processes that attempt to isolate and separate the different sizes of nanoclusters.; Chapter 2 describes poly-disperse samples of Au nanoparticles protected with monolayers of hexanethiolate ligands (C6 MPCs) and with mixed monolayers of hexanethiolate and mercaptoundecanoic acid (C6/MUA MPCs) that have been separated using reversed phase HPLC. Spectral detail of eluted peaks and quantized double layer charging features in the differential pulse voltammetry of collected fractions were used to show that the elution order of C6 MPCs was smallest MPCs first, whereas the smallest C6/MUA MPCs were eluted last.; Chapter 3 discusses how the nucleation-growth-passivation Brust reaction has been modified so as to enrich the product in useful quantities of a 38-atom gold nanoparticle coated with a hexanethiolate monolayer. Compositional evidence is presented that establishes the product as a Au38(C6)24 hexanethiolate monolayer protected cluster (MPC), based on transmission electron microscopy, laser ionization-descrption mass spectrometry, thermogravimetric analysis, and elemental analysis. Reversed phase HPLC confirms the relatively good mono-dispersity of the MPC products.; Chapter 4 discusses reversed-phase HPLC chromatographic separations of Au MPCs in the size range 1--2 nm (diameter) that are detected electrochemically (ECLC) on the basis of double layer charging of the metal-like nanoparticles by the detector electrode. The ECLC experiment estimates the nanoparticle sizes from the electrochemical responses by hydrodynamic current-potential curves.; Chapter 5 discusses directions taken to understand ultra high-resolution HPLC results achieved from separation of the near-monodisperse Au38 C6 MPC sample obtained in Chapter 3. Analytical methods include LCEC, Spectroelectrochemistry, core charging, and synthetic techniques.