Electroless reduction and precipitation of gold from acid solution by polypyrrole

Abstract

The oxidation of the 25% intrinsically oxidized polypyrrole, containing 25% [ = N-] and 75% [-NH-], and the subsequent reprotonation and reduction of the highly intrinsically oxidized polymer in acid gold solution were utilized for the spontaneous and sustained reduction of gold. The X-ray photoelectron spectroscopic (XPS) results indicate that only elemental gold [or Au(0)] accumulates on the polymer film or powder surfaces. The N1s core-level spectra of the protonated and deprotonated polypyrrole after metal reduction suggest that the intrinsic structure of the polymer at the polymer/Au interface remains intact, even at [Au]/[N] mol ratios substantially above 1. The process, however, is limited by the decreasing effective surface area of the polymer due to Au coverage. The Au reduction behavior of polypyrrole was also compared to that of polyaniline.