Controlling the Photoluminescence from a Laser Dye through the Oxidation Level of Polypyrrole.

In situ spectroelectrochemistry was used to study the emission of the laser dye oxazine 720 (oxa720) embedded into a polypyrrole (ppy) matrix. The photoluminescence (PL) of the dye was found to be controlled by the oxidation level of ppy. It is suggested that a Förster resonance energy transfer (FRET) mechanism is involved in the potential-controlled PL. FRET calculations were used to determine the dependence of the apparent distance between the dye molecules and the polymer chain with the oxidation level of ppy. In the reduced state, at 0.9 V, an efficient FRET process quenches the PL from the dye due to the short distance between the dye molecules and the polymer chains. In the oxidized state, at þ0.9 V, the FRET efficiency is only 24% leading to higher PL intensity, due to the larger distance between the donor (oxa720) and the acceptor (ppy).