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Daqing Zhang, Devananda Gangadean, Abdullah Alkhateeb, Radhakrishnan Padmanabhan, and David N. McIlroy Department of Physics, University of Idaho, Moscow, Idaho 83844-0903 (Received 28 March 2005; accepted 2 August 2005)

Production of gold nanoparticles with the specific goal of particle size control has been investigated by systematic variation of chamber pressure and substrate temperature. Gold nanoparticles have been synthesized on SiO2 nanowires by plasma-enhanced chemical vapor deposition. Determination of particle size and particle size distribution was done using transmission electron microscopy. Average nanoparticle diameters were between 4 and 12 nm, with particle size increasing as substrate temperature increased from 573 to 873 K. A bimodal size distribution was observed at temperatures 艌723 K indicating Ostwald ripening dominated by surface diffusion. The activation energy for surface diffusion of gold on SiO2 was determined to be 10.4 kJ/mol. Particle sizes were found to go through a maximum with increases in chamber pressure. Competition between diffusion within the vapor and dissociation of the precursor caused the pressure effect.

I. INTRODUCTION

In the United States, the chemical industry produces over 7000 different products worth an estimated $375 billion per year and generates 10% of the nation’s total exports.1 Eighty percent of processes in the chemical industry use catalysts, and current global catalyst markets are in excess of $20 billion.2 Another major application for catalysts is for carbon monoxide reduction in automobile exhaust systems. The majority of pollution emitted from automobiles is generated in the first 5 min that the engine is running and is a direct result of the inactivity of the current Pt- or Pd-based catalysts below 473 K.3 A possible solution to the limitations presented by existing catalyst materials is the use of Au-based catalysts. In its bulk form Au is very unreactive. However, when the diameter of gold particles is