A fractal analysis of colloidal Au nanoparticle electrodes

An electrochemical fractal analysis of three types of colloidal Au nanoparticle electrodes is described. One type of electrode comprises multilayers of 12-nm diameter colloidal Au particles on glass substrates; another type consists of analogous films grown on conductive Au substrates. Plots of log(I) vs. log(t) data from electrochemical potential step experiments were used to determine Df, the fractal dimension. On the Au substrate, Df ranged from 2.16 to 2.47 for films consisting of 7–13 colloidal Au layers, respectively, while for the glass substrate Df varied from 1.54 to 2.33 over the same range of layers. A third type of Au nanoparticle-based electrode was prepared by enlargement of nanoparticles in Au colloid monolayers by exposure to NH2OH/Au3+. For these samples, Df varied from ca. 1.2 to 2.0. Df determination by atomic force microscopy gave values in the range of 2.3–2.4 for both types of nanoparticle electrodes on glass substrates, regardless of Au film thickness.