Size Classification of Au Nanometer-sized Particles by DMA and Their Application as a Catalyst

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Au nanometer-sized particles were generated by evaporation-condensation method, and their particles size distributions were measured by a Differential Mobility Analyzer (DMA) system. As a result of raising the Au particles generator temperature from 1000 to 1100 ℃, the generation of Au particles with 1.7 nm to 3.5 nm in size was experimentally confirmed. Good correlation was obtained when we compared the mean diameter D_<m,TEM> which was calculated from the TEM observation of particles with the D_<DMA> which was DMA targeted size. Consequently, we concluded that our DMA system was available to classification of the nanometer-sized particles. As application as a catalyst, we confirmed the generation of Au nanometer-sized particles ranging from 1.7 to 10 nanometers in size which might show high catalytic activity. The size distribution of these particles was controlled by changing the furnace temperature, although the particle concentration decreased with the decrease in the furnace temperature. The morphology of Au particles was found to be not spherical from the TEM observation. In order to generate the spherical Au nanoparticles, we installed reheating furnace between the outlet of particle generator and the aerosol charger, It was experimentally confirmed that shape of Au particles with 4.3 nm in size tended to be sphere by this processing. The catalytic performance of thus treated Au nanometer size-selected particles are now under way.