The molecular mechanisms of platinum cluster nucleation and growth in solution and on biopolymers have been investigated by means of first-principles molecular dynamics. In contrast with the classical picture where clusters nucleate by aggregation of metallic Pt(0) atoms, it was found that Pt-Pt bonds can form between dissolved Pt(II) complexes after only a single reduction step. Furthermore, small clusters were observed to grow by addition of unreduced [PtCl 2 (H 2 O) 2 ] complexes, in agreement with an autocatalytic growth mechanism. Moreover, Pt(II) ions covalently bound to biopolymers were found to act as preferential nucleation sites for the formation of clusters. This is a consequence of the presence of heterocyclic donor ligands which both enhance the electron affinity of the metal nuclei and induce the formation of metal-metal bonds that are stronger than those obtained in solution. In fact, in metallisation experiments a clean and purely heterogeneous metallisation of single DNA molecules leading to thin and uniform Pt cluster chains extending over several microns was obtained.
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Ciacchi et al. (2003) studied this question.