Nanocomposite films of a polyfluorene copolymer and carbazole-thiol-capped gold nanoparticles: Electrochemical crosslinking and energy-transfer properties

The preparation and properties of an electrochemically crosslinked Au nanoparticle/polyvinylcarbazole (PVK)/polyfluorene (PFC) nanocomposite film is described. Blends of the blue-light emitting PFC, PVK, and the 11-(9H-carbazol-9-yl)-undecane1-thiol-capped Au nanoparticles (CBZ-S-Au) were prepared as thin films by spin-coating and subsequent crosslinking by cyclic voltammetry (CV). The electrochemical properties are then evaluated on the basis of the redox behavior (reversibility) and electron-transport properties of the films. They are further characterized by UV-vis spectroscopy, photoluminescence spectroscopy, and atomic force microscopy (AFM). The large differences in photoluminescence properties of the CBZ-S-Au/PFCVK crosslinked copolymer composite film compared to the PFCVK polymer alone result in an efficient energy-transfer system, in which the excimer peak is almost totally quenched. This indicates a compatible match between the absorbance of the Au plasmons and the emission of the excimer energy trap from PF polymers. Furthermore, electrochemical crosslinking enhances this match both by shifting the absorbance to greater overlap and decreasing the Förster distance between the Au nanoparticle and the PFCVK polymer chains.