Noble-metal nanocrystals with anisotropic shapes have received increasing interest owing to their unique properties. However, it remains challenging to induce anisotropic growth during a colloidal synthesis of noble-metal nanocrystals due to the constraint from their face-centered cubic lattice. In this study, we report a facile route to the preparation of Pt nanobars with aspect ratios tunable up to 2.1 by simply reducing a Pt<sup>(IV)</sup> 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<sup>(IV)</sup> 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 both particle coalescence and oxidative etching followed by selective atom deposition contributed to the anisotropic growth of Pt nanobars with lower symmetry relative to their cubic lattice.

Simple route to the synthesis of Pt nanobars and the mechanistic understanding of symmetry reduction

ACS Fall 2021

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