Electrochemical deposition of silver and platinum nano-crystallites on the atomically smooth graphite basal plane: Characterization, particle size control, and chemical applications

We have studied the electrochemical synthesis and characterization of nanoscale silver and platinum metal particles on atomically smooth graphite (HOPG) surfaces. Nanometer-scale metal particles possess chemical and physical properties which differ significantly from macroscopic phases. Our interest is in developing electrochemical methods for the preparation of metal nanostructures that are narrowly dispersed in size. Although the mechanism of electrochemical metal deposition has been investigated previously, it has so far not been possible to electrodeposit silver or platinum nanostructures on HOPG electrode surfaces. Non-contact scanning force microscopy (NM-AFM), involving orders of magnitude less force than conventional AFM, is employed to image the particles.; A potentiostatic pulse method has been employed to electrochemically deposit silver and platinum nanocrystallites on the atomically smooth graphite basal plane surface. The particle size can be controlled by varying the coulombic loadings.; A chemical application of electrochemically synthesizes silver nanocrystallites for the preferential SERS (surface enhanced Raman spectroscopy) of defect modes on thermally etched graphite surfaces has been implemented in this work. Highly oriented pyrolytic graphite (HOPG) surfaces, on which atomically well-defined roughness has been introduced via high temperature gasification reactions, are investigated by NC-AFM, and Raman spectroscopy both before and following the electrochemical deposition of silver nanocrystallites at these surfaces. The Raman spectroscopy of these surfaces was investigated, and compared with spectra from the nanocrystallite-modified but unetched HOPG basal plane surfaces, and thermally etched surfaces on which no silver was deposited. An important chemical application of Pt nanoparticles is catalytic activity. Cyclic voltammetry experiments have shown that the platinum nanoparticles in 0.5M {dollar}rm Hsb2SOsb4{dollar} will catalyze oxygen oxidation and hydrogen reduction.