Metal nanoparticles have a large surface area to volume ratio compared to their bulk counterparts, which makes them attractive to use as catalysts. Atoms on the surface of metal nanoparticles are very active due to their high surface energy resulting from their unsatisfied valency. First synthesis of gold nanoparticles with different shapes and bimetallic structure are explored in detail. Then an experimental method which could distinguish between the two mechanisms (homogeneous or heterogeneous) by using hollow plasmonic gold nanocatalyst is developed. Furthermore the catalytic activity of gold nanocages was changed by adding an inner platinum or palladium nanoshell. Results suggested that adding palladium inner shell increased the activity of gold nanocages towards the reduction nitro groups to amino groups. Controlling the selectivity of the catalyst is an important goal of catalysis research. Lastly selectivity of the plasmonic nanocatalyst (Gold sphere-Gold shell Nanorattles) with multiple plasmon modes was studied for photo-dimerization of nitro groups into azo dimers were studied on gold nanocatalyst surface. Results showed that selectivity can be controlled by changing the wavelength of the light exciting surface plasmon.