A hybrid Electrochemical-Chemical (E/C) method is employed to synthesize epitaxially-oriented CdS nanocrystallites - size selectively - on graphite surfaces. The E/C synthesis involves three steps (as shown schematically below): 1) Cadmium metal nanocrystals (NCs) are electrochemically deposited on the graphite basal plane surface; 2) Cadmium NCs are oxidized at high pH to Cd(OH)₂ , 3) Upon immersion of the Cd(OH)₂ NCs in an aqueous sulfide solution, displacement of OH^- by S^2- occurs yielding wurtzite phase NCs of the semiconducting salt, cadmium sulfide.

Dispersions of E/C-synthesized CdS nanocrystallites having mean diameters ranging from 20Å to 80Å were prepared and characterized using non-contact scanning force microscopy, transmission and high resolution electron microscopy, selected area electron diffraction (SAED), and micron-scale spatially resolved photoluminescence spectroscopy. The SAED data demonstrate that individual CdS nanocrystals are oriented with the c-axis of the crystallite perpendicular to basal plane (i.e. (0001)), and NCs located within the boundaries of a single grain on the graphite basal plane possess identical azimuthal orientations. Photoluminescence spectra reveal transitions which are assigned to band-gap and surface trap states.