Gold-Decorated Poly(3-alkylthiophenes)

Abstract

Films of poly(3-alkylthiophenes) on glass substrates were oxidized with acetonitrile solutions of AuCl 3 to yield electronically conductive materials containing the AuCl 4counterion, whereas oxidation with nitromethane solutions resulted in both AuCl 4 --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 AuCl 4 -as being the sole gold species present in films oxidized in acetonitrile. XPS of films oxidized using nitromethane solutions indicate that AuCl 4 -and Au(0) 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 Ω -1 cm -1 . The high conductivity is solely due to the presence of the metallic layer, the underlying polymer film possessed a conductivity 15 Ω -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(0).

Reductive deposition of Au³⁺(aq) on o×idized silicon surfaces

“…Successful methods of preparation usually involve vapour-deposition or deposition from solution via chemical and (or) electrochemical routes. An electroless deposition of zerovalent gold nano-clusters was reported using electroactive poly(3-alkylthiophenes) from a solution of the polymer and AuCl 4 -in nitromethane (5). Similar studies were reported using other electroactive polymers, such as, polyaniline and polypyrrole (6).…”

Preparation of Gold Nanoparticles on Ultrathin Films of Polythiophene and Polythiophene Derivatives

“…For the synthesis the work and reviews of Schmid et al, [1,2] and for the assembly of gold nanoparticles the review of Daniel et al [3] should be mentioned. Holdcroft et al [4,5] examined the oxidation of poly(3-hexylthiophene) (PHT) with gold trichloride in water-free solvents. The use of thick polymer films (Ͼ1 µm) yielded sandwich structures consisting of an oxidised PHT film, covered with a continuous gold layer.…”

“…However, thinner polymer films (Ͻ0.25 µm) yielded only an irregular, nonuniform covering with gold. Holdcroft et al [5] proposed the following reaction [Equation (1)]. …”

“…[5] To obtain gold nanoparticles rather than nonuniform gold films, the polymer film has to be even thinner than the 0.25 µm that Holdcroft et al used. For micro-and optoelectronic applications it is necessary to chemically deposit adhesive films especially on insulating substrates.…”

“…Then the following reactions would be possible Equation (2) and Equation (3). Equation (2) was proposed by Freund et al, [6] while Equation (3) was derived from Equation (1), which was proposed by Holdcroft et al, [5] assuming that HAuCl 4 can be regarded as the hydrochloride of AuCl 3 . The reduction of HAuCl 4 requires the incorporation of a dopant anion into the oxidised polymer to achieve charge neutrality.…”