Fabrication of MEH-PPV/SIO₂ and MEH-PPV/TIO₂ Nanocomposites with Enhanced Luminescent

摘要

Thin films of composites made by incorporation of silicon oxide (SiO₂) or titanium oxide (TiO₂) nanoparticles into poly[2-methoxy-5-(2'-ethylhexoxy-p-phenylene vinylene] (MEH-PPV) were deposited by spin-coating from p-xylene solutions and their optical properties were investigated. SEM images showed that different extents of aggregates were formed for two kinds of nanocomposites. The UV-vis absorption spectra of MEH-PPV/SiO₂ and MEH-PPV/TiO₂ films showed a small red shift (~ 5 nm) as compared with that of pristine polymer. However, the structure of MEH-PPV was not affected as revealed by infrared and Raman experiments. This result is different from that obtained in PPV/oxide nanocomposites in which, the conjugated length of PPV main chain was reduced. Similarly, a small red shift was found in PL emission spectra with increasing the content of oxide nanoparticles. The PL degradation experiments showed that blending with SiO₂ nanoparticles could enhance the luminescent stability of MEH-PPV. By blending with 8% SiO₂ nanoparticles of 20 nm diameter, the PL intensity of MEH-PPV film attained 46% of the original one, while it decreased to 20% for pristine MEH-PPV after four weeks of exposure to ambient air. The effect of TiO₂ nanoparticles to stabilize MEH-PPV thin films is though less important than that of SiO₂.