A Simple Route to the Synthesis of Pt Nanobars and the Mechanistic Understanding of Symmetry Reduction.

Noble-metal nanocrystals with anisotropic shapes have received increasing interest owing to their unique properties. Here we report a facile route to the preparation of Pt nanobars with aspect ratios tunable up to 2.1 by simply reducing a Pt (IV) precursor in N,N -dimethylformamide (DMF) at 160 °C in the presence of poly (vinyl pyrrolidone) (PVP). In addition to its commonly observed roles as a solvent and a reductant, DMF could also decompose to generate CO, a capping agent capable of selectively passivating Pt{100} facets to promote the formation of nanobars. The size and aspect ratio of the nanobars could be tuned by varying the amount of Pt (IV) precursor involved in the synthesis, as well as the concentration of PVP because of its dual roles as a stabilizer and a co-reductant. Our mechanistic study indicated that the anisotropic growth resulted from both particle coalescence and localized oxidative etching followed by preferential growth.