Charge transport and electrochromism in novel nanocomposite films of poly(3,4-ethylenedioxythiophene)-Au nanoparticles−CdSe quantum dots

Abstract

Nanocomposite films of Poly(3,4-ethylenedioxythiophene)-Au−CdSe have been fabricated for the first time by first growing a porous PEDOT layer in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and then introducing the film to a mixed colloid of Au nanoparticles (NPs) and CdSe quantum dots (QDs), thereby imparting a uniform confinement of Au NPs/CdSe QDs nanocomposite to the bulk of the polymer film by the virtue of affinity that Au has for the sulfur on the thiophene rings. Progressive luminescence quenching and absorption enhancement of CdSe QDs as a function of Au NPs incorporation in the CdSe colloid confirmed the direction of charge transfer from CdSe QDs to Au NPs. The optimized composition of Au−CdSe based on a maximum charge transfer was utilized for the formation of the nanocomposite with PEDOT. The loss of electrons from CdSe in the nanocomposite was also reflected in the core level signals of Se 3d corresponding to oxidized states of Se²⁺ and Se⁰. The charge propagation from CdSe to Au to PEDOT through Fermi-level equilibration was also confirmed by luminescence and absorption spectroscopy. The effect of Au−CdSe on electrochromic performance of the nanocomposite film was realized in terms of a superior optical density change, larger coloring efficiency (300 cm² C⁻¹, λ = 550 nm), and faster color-bleach kinetics when compared with the electroactivity of the control PEDOT film, grown without the inclusion of any nanomoiety.