Electroless plating of palladium and copper on polyaniline films

Abstract

Electroless plating of copper on polyaniline (PANI) films of different intrinsic oxidation states, viz., the emeraldine base (EB), the nigraniline (NA) and the leucoemeraldine (LM) states, in the complete absence of surface sensitization by SnCl2 was explored. The process consisted of two steps. The first step involved electroless deposition of palladium on PANI film in Pd(NO3)2 nitric acid solution. The Pd-laden films were subsequently used for the electroless plating of copper. It was found that electroless deposition of Pd and Cu occurred efficiently only on the fully reduced LM film surface. X-ray photoelectron spectroscopy was employed for the characterization of surface compositions and chemical states of the polymer films and the metals during the two electroless deposition processes. The quantitative changes in N1s core-level spectra and the evolution of Pd 3d and Cu 2p core-level spectra on the polymer films during the two-step process were carefully monitored. In Pd(NO3)2 nitric acid solution, all three types of the PANI films were protonated. Nevertheless, coupled Pd reduction occurred only on the LM film surface. The metallic Pd atoms on the LM film surface initiated the subsequent electroless plating of copper. The reduction of Cu(II) ions to Cu metal proceeded via the Cu(I) state. The effect of [Pd]/[N] mole ratio of the Pd-laden LM film on the rate of electroless plating of copper was also investigated.