exhibits the UV–vis spectrum of the Pt–Ag bimetallic sample synthesized by the sequential reduction of Ag (I) followed by Pt (IV) at 0 and 4 h of sonication. Inset in Fig. 1c shows the time evolution of UV–vis absorbance of bimetallic synthesis at 0.0, 3.0, 3.5 and 4.0 h.