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Platinum Metals Rev., 1996, 40, (4), 168

Controlling the Shape of Colloidal Platinum


Colloidal metal particles find use in optical, electronic and magnetic devices, as catalysts and photocatalysts. Their catalytic activity depends on the size and shape of the nanoparticles, so the ability to control these parameters is very desirable. Some success has been achieved in controlling the size distribution, stability and catalytic activity of the nanoparticles, but controlling shape has been more difficult.

Now, however, researchers from the Georgia Institute of Technology, Atlanta, U.S.A., and Hahn-Meitner Institut, Berlin, Germany, have synthesised colloidal platinum nanoparticles with controlled shapes (T. S. Ahmadi, Z. L. Wang, T C. Green, A. Henglein and M. A. El-Sayed, Science, 1996, 272, (5270), 1924–1926).

Platinum nanoparticles were prepared from a solution of K2PtCl4 and sodium polyacrylate (capping agent) in various concentrations of capping polymer to platinum cation. The platinum ions were then reduced by hydrogen gas. On changing the ratios of the concentrations at room temperature under the same conditions, the distribution of platinum nanoparticle shapes could be changed. Tetrahedral, cubic, irregular-prismatic, icosahedral and cubo-octahedral particle shapes were observed, with cubic and tetrahedral being predominant in some cases.