A preparative method to control the shape of platinum (Pt) nanoparticles in
the presence of sodium polyacrylate (PAA) or poly(N-vinyl-2-pyrrolidone) (
PVP) is described. Regardless of the kind of protective polymer used, the d
ominant shape of Pt nanoparticles was controlled by changing the reduction
rate of Pt4+ ions. Tetrahedral particles predominated by using H-2 reductio
n of H-2[PtCl6]. Methanol reduction generated mainly truncated octahedral p
articles. It stems that the slow: H-2 reduction of pt(4+) ions favorably le
ads to the Formation of tetrahedral Pt nuclei enclosed with Foul {111} plan
es that have the lowest surface energy. The truncated octahedral nuclei are
formed by the faster reduction with methanol. The selective growth of the
{111} planes takes place at a lower polymer concentration anti results in t
he generation of cubic nanoparticles.