Rhodium Decahedral Nanocrystals: Facile Synthesis, Mechanistic Insights, and Experimental Controls

Decahedral nanocrystals have received great attention owing to their unique symmetry and strain-energy distribution. In contrast to other noble metals, it has been difficult to synthesize decahedral Rh nanocrystals. We report a robust, one-pot method based on polyol reduction for the facile synthesis of Rh decahedral nanocrystals in high purity, with sub-20 nm sizes. The success of the synthesis relied on our ability to manipulate reduction kinetics by systematically tuning experimental parameters. We found that the yield of Rh decahedral nanocrystals could be maximized by optimizing: i) the concentration of Rh(acac)₃ (metal precursor); ii) the molecular weight and amount of poly(vinyl pyrrolidone) (colloidal stabilizer/capping agent); and iii) the chain length of the polyol (solvent/reducing agent), with tetraethylene glycol being the best. We believe the mechanisms elucidated herein can be extended to other syntheses to produce metal nanocrystals with multiply twinned structures.