ELECTROCHEMICAL PREPARATION OF PLATINUM NANOCRYSTALLITES WITH SIZE-SELECTIVITY ON BASAL-PLANE ORIENTED GRAPHITE SURFACES

Platinum nanocrystals were deposited on basal plane oriented graphite surfaces from dilute (1.0 mM) PtCl62--containing electrolytes using a pulsed potentiostatic method. The deposition of platinum nanocrystals occurred via an instantaneous nucleation and diffusion-limited growth mechanism which resulted in narrow particle size distributions (relati ve standard deviation <35%) for mean crystallite diameters smaller tha n 40 Angstrom. The number of particles per unit area on these surfaces was 10(9)-10(10) cm(-2). Noncontact atomic force microscopy images re veal that platinum nanocrystals nucleated both at defect sites-such as step edges-and on apparently defect-free regions of the atomically sm ooth graphite basal plane. Using electron transparent graphite surface s, selected area electron diffraction analyses revealed that the struc ture of deposited platinum nanocrystals was fcc with a lattice constan t that was indistinguishable from bulk fcc platinum. Platinum nanocrys tals were not epitaxially oriented on the graphite basal plane surface .