Raman vibrational evidence for the presence of conjugated regions in individual micron diameter polystyrene particles irradiated with visible radiation

Micron diameter particles containing or composed solely of polystyrene have been reported to become highly fluorescent shortly after immobilization in a visible optical trap (488.0 nm). It has been proposed that extensive regions of conjugation in the polymer backbone are responsible for this emission. Raman spectroscopic evidence is described in this report that confirms the presence of polymer backbone conjugation. In some experiments Raman signals were enhanced by incorporating silver nanoparticles into the micron-diameter polystyrene particles by photoreduction of silver ion. By monitoring the intensity changes of the C-H and C=C stretching regions while an individual particle is immobilized in the optical trap, the generation of extensive conjugation regions can be observed over time. In addition, the presence of the silver nanoclusters increased the rate and magnitude of the reactions that lead to polystyrene conjugation.