Morphological selection of gold nanoparticles electrodeposited on various substrates

Gold nanoparticles with different morphologies (nanocrystallites, perfect nanospheres, plumbs, and nanoaggregates) have been electrodeposited on different substrates, namely, glassy carbon (GC), highly oriented pyrolytic graphite (HOPG), and Au(111) single-crystalline substrates. Au particles with particle size ranging from a few nanometers to a few micrometers have been prepared. The morphology of the electrodeposited Au particles was largely dependent on the nature of the substrate as well as the composition of the electrodeposition bath. For instance, the inclusion of iodide ions during electrodeposition was found to enhance two-dimensional (2D) growth of the Au nanoparticles, and particles with a relatively small particle size down to 10 nm were obtained. The inclusion of L-cysteine (as an additive) during the electrodeposition of the Au nanoparticles resulted in a significant influence on the morphology (and the particle size of the Au particles), which strongly depends on the nature of the substrate. Au nanoparticles with crystalline geometry were prepared on the Au(111) substrates in the presence of L-cysteine, while under the same experimental conditions Au aggregates of size up to 300 nm were electrodeposited on the GC substrates. Au particles with a perfect spherical shape were electrodeposited on the HOPG electrodes. X-ray diffraction measurements of the electrodeposited Au particles revealed significantly different crystallinity of the Au particles and in turn different ratios of the single-crystalline domains constituting the Au particles. The cyclic voltammetric response toward the oxygen reduction reaction at the different Au nanoparticles showed a versatile behavior ranging from a quasi-reversible two-electron reaction to an irreversible overall four-electron reaction in O-2-saturated 0.5 M KOH solution, demonstrating the entirely different electrocatalytic activity of the thus-prepared Au nanoparticles on different substrates. (c) 2005 The Electrochemical Society.