Au nanoparticle (Au NP) assemblies have attracted tremendous interests in various research fields owing to their unique optical properties, in which the electromagnetic fields are greatly enhanced between internal gaps. As incorporation of catalytic active metals such as Pd and Pt into Au NP assemblies, these hetero-nanostructures show excellent catalytic performances for photo-reduction reactions. In this study, I suggest the new synthetic method for the stable Au NP trimers in aqueous solution to control the galvanic replacement kinetics between Ag nanoprisms and Au precursors. Also, the Au@M (M= Pd, Pt) core shell NP trimers were successfully synthesized using Au NP trimers as templates. Au@M NP trimers effectively induce change of the plasmonic resonant energy decay mechanism and thus increment of absorption energy compared to Au NP trimers. This surprising property of Au@M NP trimers enables induce plasmon-driven photoreduction with efficient plasmonic energy transport on their catalytic surfaces. In-situ surface-enhanced Raman spectroscopy (SERS) monitoring shows the plasmon-mediated reduction of 4-nitrobenzenethiol on Au@M NP trimers. As a result, I could conclude that modification of the geometries and compositions with Au NP assemblies could enhance the catalytic activity. We expect that our synthetic strategies may facilitate designing new plasmonic hetero-nanostructures with desired functionalities.