Direct and one-step synthesis of polythiophene/gold nanoparticles thin films through liquid/liquid interfacial polymerization.

This work demonstrates a simple and one-step synthesis of polythiophene/gold nanoparticles (PT/Au) nanocomposite thin films, through a liquid-liquid (L/L) interfacial polymerization route. Starting from an aqueous solution of tetrachloroauric acid (acting both as metallic gold source and oxidizing agent to start the oxidative polymerization of thiophene), and a solution of thiophene in n-hexane, a biphasic L/L system was originated. In the following, the interface acted as a meeting-point for the reactants, and the polymerization reaction took place, leading to self-assembled PT/Au film between the two immiscible liquids. These films were easily deposited over different substrates (glass, silicon, plastics) and characterized through different techniques. The influence of both the reactants ratio and the reaction time on the structure and morphology of the films were evaluated. The films obtained with a shorter reaction time exhibited spherical gold nanoparticles (around 3 nm diameter) homogeneously dispersed into a polymeric matrix. The increase of both the reaction time and the thiophene/gold precursor ratio led to agglomerated and anisotropic gold structures wrapped by a thin layer of polythiophene. Overall, PT/Au films are transparent, homogeneous, stable, flexible and presented reversible electrochromic properties, which make them suitable for application in different systems and devices, as demonstrated here for electrochromic application.