Photoinduced charge separation of self-organized semiconducting superstructures composed of a functional polymer-TiO2 hybrid

摘要

The incorporation of TiO_2 nanoparticles into long (several micrometers) fibers of a gel-forming poly(para-phenylene vinylene) (PPV) derivative is described. For that purpose, a PPV-block-dopamine polymer is synthesized, which is used to coat TiO_2 nanoparticles leading to well-dispersed nanoparticles and fluorescence quenching of the polymer. Independently, the homopolymer gels in various organic solvents are observed to form long fibers. By mixing the PPV homopolymer with the TiO_2-PPV hybrid, we are able to incorporate the nanoparticles into the fibrous network, as shown in transmission electron microscopy (TEM) images. Photoinduced charge separation is measured by Kelvin probe force microscopy. Upon illuminating the polymer fibers, positive charges are observed, even at distances of around 300 nm. From these results, charge transport along the polymer fibers is inferred. A semiconducting poly(para-phenylene vinylene) PPV block copolymer carrying dopamine anchor groups, which self-assembles into nanosized fibers, is presented. TiO_2 nanorods can be functionalized and incorporated into the fibers. Using photoluminescence spectroscopy and Kelvin probe force microscopy, charge transfer between these two materials can be observed and a positive charging over a range of up to 300 nm within the polymer fibers can be observed.