Gold-decorated poly(3-alkylthiophenes)

Films of poly(3-alkylthiophenes) on glass substrates were oxidized with acetonitrile solutions of AuCl3 to yield electronically conductive materials containing the AuCl4- counterion, whereas oxidation with nitromethane solutions resulted in both AuCl4--doped polymer and electroless deposition of metallic gold, X-ray photoelectron spectroscopy (XPS) has been used to investigate the chemical nature of the counterion and the chemical evolution of interfaces during oxidation. XPS confirms AuCl4- as being the sole gold species present in films oxidized in acetonitrile. XPS of films oxidized using nitromethane solutions indicate that AuCl4- and Au(O) are present in the bulk and at the polymer/solution and polymer/ substrate interfaces immediately following oxidative doping. However, metallic gold continues to deposit at the polymer/solution interface well beyond the period required for complete oxidative doping, The localization of metallic Au at this interface was confirmed by XPS and depth profile Auger electron spectroscopic analysis, The electroless deposition process is autocatalytic in nature and leads to the formation of a homogeneous metallic layer which increases the conductivity of the film to values in excess of 10 000 Omega(-1) cm(-1). The high conductivity is solely due to the presence of the metallic layer, the underlying polymer film possessed a conductivity 15 Omega(-1) cm(-1). The solvent dependency of the electroless deposition process is due to the solvent's ability to coordinate with Au(I) intermediates, formed during oxidative doping, prior to disproportionation into Au(O).