Morphology of platinum nanoparticles protected by poly(N-isopropylacrylamide)

Platinum nanoparticles were synthesized by reduction of a K2PtCl4 solution using a thermosensitive polymer, poly(N-isopropylacrylamide, NIPA) as a capping polymer. The Pt nanoparticles obtained at temperatures above and below the lower critical solution temperature (LCST) of NIPA showed clear differences. When the temperature is higher than the LCST, the particles obtained have clearer outlines as well as sharper size and shape distributions. By observation over time, it was also found that the shape distribution of the particles improved as the particles grew. These facts mean that the morphology of Pt particles is decided in the process of their growth, and the direction of the growth is controlled by the capping condition of the polymer, possibly through hydrophobic interaction.