Nanometric urchin like monometallic and bimetallic alloy particles of Cu and Pt were tailored via a green aqueous approach utilizing starch, a well known green stabilizing agent and ascorbic acid at room temperature. The fabricated Pt and Cu monometallic and Pt/Cu bimetallic (B1 and B2) alloy nanoparticles are well crystalline and adopted identical average particle size of about 23 nm as measured via transmission electron microscopy. The bimetallic systems display remarkable light promoted activities in degradation of organic pollutant, malachite green, to its mineralized products which was otherwise very slow. The photo degradation reaction follows first order kinetics and apparent rate constant for catalysis reaction follows the trend: k((app)B2 NPs) > k((app)B1 NPs) > k((app)Pt NPs) k((app)Cu NPs). Shifting of surface d band center and lower photo-induced electrons and holes recombination rate seem to play important roles in enhancing catalytic property of the bimetallic systems. (C) 2016 Elsevier Ltd. All rights reserved.