Potassium tetrachloroplatinate is used in the preparation of platinum (Pt) nanoparticles. Ligands like ammonia or triphenyl phosphine can able to replace the chloride ligands to afford various derivatives. The replacement by ammonia results in the preparation of cisplatin, which is used in the cancer treatment. Further, it is used as catalyst in the hydroarylation reaction. Cisplatin and potassium tetrachloroplatinate are shown to bind to DNA that encapsulates SWNTs in aqueous solution. The bound platinum salt can then be reduced to decorate the DNA-encapsulated SWNTs with platinum nanoparticles. The unique combination of catalytic activity of nanoscale platinum, biological functionality of DNA, and optoelectronic properties of SWNTs suggests a myriad of applications including fuel cells, catalysts, biosensors, and electrochemical devices.