XPS Studies of PtCl4 and H2PtCl6·6H20 doped polyacetylene

The PtCl₄ and H₂PtCl₆-6H₂O doped polyacetylene were studied by X-ray photoelection spectroscopy and transmission electron microscopy. We found that both Pt 4f and Cl 2p peaks could be resolved into two components both with a splitting of ca. 1.5 eV. The higher binding energy components of Pt 4f peak is attributed to Pt⁴⁺ and the lower binding energy one to Pt²⁺ species. From quantitative analysis of the results of decomposition of both Pt 4f and Cl 2p peaks it was found that an atomic ratio of chlorine to platinum for Pt²⁺ species is (Cl) / (Pt) = 2 and that for Pt⁴⁺ species is (Cl) / (Pt) = 6 for both PtCl₄ and H₂PtCl₆·6H₂O doped polyacetylene. The C 1s peaks could be decomposed into two components separated by ca. 1 eV. The intensity of the higher binding energy component increased with increasing dopant concentration. These indicate that the platinum salt doping proceeds through charge transfer from polyacetylene chain to platinum atom resulting in a partial reduction from Pt⁴⁺ to Pt²⁺ state. The existence of PtCl₂ cluster on the surface of the doped polyacetylene film was supported by transmission electron microscopy and electron diffraction observations. These results indicate that a random distribution of the dopant along the macromolecular chain, and the charge per carbon atom in the metallic region of doped polyacetylene has been estimated to be 0.2 |e|. From these results the mechanism of the PtCl₃ and H₂PtCl₆·6H₂O doping process in polyacetylene is clarified as follows: Thus the dopant anion in polyacetylene is PtCl,^2? for both PtCl₄ and H₂PtCl₆·6H₂O doping.