Poster: Hybrid polymer nanoparticles: synthesis and characterization

HERNÁNDEZ, LAURA I.; BERTOLOTTI SONIA G.; CHESTA, CARLOS A.; PALACIOS, RODRIGO E.; ROBERT, GODIN; COSA, GONZLAO

Corodba

Congreso; XI Encuentro Latinoamericano de Fotoquímica y Fotobiología (XI ELAFOT); 2012

Conjugated polymers are of great interest due to their application in optoelectronic devices such as organic photovoltaic cells (OPVs), polymer light-emitting diodes (PLEDs) and organic field-effect transistors (OFETs)[1]. Herein we describe the synthesis and characterization of hybrid nanoparticles (NPs) containing commercial conjugated polymers [such us: (poly [2-methoxy-5-(2-ethyl-hexiloxi)-P-phenylene vinylene] (MEH-PPV) and F8BT ()] and inorganic or organic dopants (such as TiO2 nanocrystals and organic dyes). Hybrid nanoparticles containing TiO2 nanocristals were formed by a controlled precipitation method [2] producing particles of diameters ranging from 25 to 90nm depending on the precipitation conditions. A comparative study of stationary and time-resolved fluorescence in solution indicates that the fluorescence of hybrid NPs depends on the amount of TiO2 present in a non-linear fashion. Charge transfer processes within the TiO2/MEH-PPV hybrid NPs were studied by single molecule fluorescence spectroelectrochemistry (SMS-EC).3 In the SMS-EC setup the particles are deposited over a transparent ITO Working Electrode (WE) allowing for the detection of the fluorescence intensity (IF) of individual particles (one at a time) while modulating the WE electrochemical (EC) potential (in a 3 electrode EC cell configuration). Preliminary results indicate that the fluorescence intensity is modulated by the applied EC potential (E). Fluorescence quenching is observed at potentials positive enough to electrochemically oxidate the polymer (E>0.7V). This quenching is assigned to the EC injection of positive charges into the polymer and consequent quenching of excitons. At potentials more negative than -0.6V a small IF increase is observed for a subensamble of particles. This increase is assigned to the elevation of the Fermi level of the TiO2 nanoparticles and the resulting slow down of the photoinduced electron transfer injection rate from the polymer to the semiconductor. In the case of conjugated polymer NPs doped with organic dyes a series of experiments were performed to evaluate their efficiency in the generation of Reactive Oxygen Species.