The bark extract of Terminalia arjuna, a well known cardiac tonic, is rich in different types of plant secondary metabolites such as triterpenoids, saponines, tannins, flavanoids, etc. We have demonstrated the use of the bark extract for the synthesis of gold nanoparticles at room temperature under very mild conditions.  The synthesis of the gold nanoparticles was complete in several minutes and no extra stabilizing or capping agents were necessary.  The gold nanoparticles were characterized by HRTEM, AFM, Surface Plasmon Resonance Spectroscopy and X-Ray Diffraction studies.  The synthesized colloidal gold nanoparticles were used as a catalyst for the sodium borohydride reduction of 4-nitrophenol to 4-aminophenol. 

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