Silver particles-modified polysulfonic acid-doped polyaniline layers: electroless deposition of silver in slightly acidic and neutral solutions

Polyaniline layers are produced by electrochemical polymerisation of aniline in the presence of small amounts of poly(2-acryalamido-2-methyl-propane-sulfonic acid) in an inorganic acid solution. Electroactivity and in situ conductance of the obtained polysulfonic acid-doped layers are studied in slightly acidic and neutral solutions. Electroless deposition of silver particles is carried out in silver-EDTA complex ion solutions at pH = 4.2 and pH = 6.6 by using the polyaniline layers as reductant. The amount of electroless-deposited silver is studied depending on: polymerisation charge used to synthesize the polymer layer, pH of the plating solution, metal ion concentration and dipping time. SEM shows in all cases a highly non-homogeneous distribution of the metallic phase over the surface, the most protruding fibrillar polymer structures favouring the electroless silver deposition. A linear dependence between amount of the polyaniline material and amount of deposited silver is found for the silver plating solutions with the highest investigated concentration (10 mmol l(-1)). At lower concentrations (2.0 and 0.4 mmol l(-1)), the same amount of silver becomes deposited on polymer layers with markedly different charges. The electroless deposition of silver in the solutions with lower acidity results in lower amounts of deposited silver at otherwise identical conditions. Effects such as charge transfer within the polymer phase and mass transport in the solution are addressed to explain the observed dependencies of the amount of deposited silver on concentration and pH in the different plating solutions.