GOLD-DECORATED POLY(3-ALKYLTHIOPHENES)

Films of poly(3-alkylthiophenes) on glass substrates were oxidized wit h acetonitrile solutions of AuCl3 to yield electronically conductive m aterials containing the AuCl4- counterion, whereas oxidation with nitr omethane solutions resulted in both AuCl4--doped polymer and electrole ss deposition of metallic gold, X-ray photoelectron spectroscopy (XPS) has been used to investigate the chemical nature of the counterion an d the chemical evolution of interfaces during oxidation. XPS confirms AuCl4- as being the sole gold species present in films oxidized in ace tonitrile. XPS of films oxidized using nitromethane solutions indicate that AuCl4- and Au(O) are present in the bulk and at the polymer/solu tion and polymer/ substrate interfaces immediately following oxidative doping. However, metallic gold continues to deposit at the polymer/so lution interface well beyond the period required for complete oxidativ e doping, The localization of metallic Au at this interface was confir med by XPS and depth profile Auger electron spectroscopic analysis, Th e electroless deposition process is autocatalytic in nature and leads to the formation of a homogeneous metallic layer which increases the c onductivity 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 proces s is due to the solvent's ability to coordinate with Au(I) intermediat es, formed during oxidative doping, prior to disproportionation into A u(O).