THE SHAPE AND STRUCTURE OF GOLD PARTICLES GROWN AT DIFFERENT ELECTRODE-POTENTIALS

The crystal characteristics of gold particles grown on an amorphous ca rbon film in a 10(-3)-10(-5)M HAuCl4 solution at different electrode p otentials have been studied by means of electron microscopy and electr on diffraction. The results show that the gold particles grown at diff erent electrode potentials have different shapes, i.e., the particles formed at negative potential (versus SCE) consist mainly of icosahedra l and decahedral particles, while at positive potential (versus SCE) f ee octahedral single crystal particles are dominant. Decahedral partic les grown to 80 nm and icosahedral particles grown to 32 nm were obser ved at negative potentials. At positive potentials the icosahedral and decahedral particles only grew to about 10 nm. From these results it is clear that at negative potentials the gold particles prefer the gro wth of decahedral and icosahedral structures, but at positive potentia ls the fee crystal structure is preferred. The characteristics of the gold particles depend upon the electrode potential at which the partic les are grown, but it is not influenced by the concentration of the HA uCl4 electrolyte. The results will be discussed in relation to the pot ential-dependent surface reconstruction of Au(111), Au(110) and Au(100 ) surfaces.