Photodegradation and self-healing in a Rhodamine 6G dye and Y$_2$O$_3$ nanoparticle-doped polyurethane random laser

TL;DR

This study demonstrates self-healing in a Rhodamine 6G dye and nanoparticle-doped polyurethane random laser after photodegradation, showing recovery of emission intensity and spectral changes, with insights into the underlying molecular mechanisms.

Contribution

It reports the first observation of self-healing in a dye-doped random laser, revealing recovery of lasing performance post-photodegradation and analyzing the molecular processes involved.

Findings

Emission intensity recovers after irradiation

Dye molecules form dimers and trimers during irradiation

Polymer host undergoes irreversible damage by photooxidation

Abstract

One of the fundamental difficulties in implementing organic dyes in random lasers is irreversible photodegradation of the dye molecules, leading to loss of performance and the need to replace the dye. We report the observation of self-healing after photodegradation in a Rhodamine 6G dye and nanoparticle doped polyurethane random laser. During irradiation we observe two distinct temporal regions in which the random lasing (RL) emission first increases in intensity and redshifts, followed by further redshifting, spectral broadening, and decay in the emission intensity. After irradiation the emission intensity is found to recover back to its peak value, while still being broadened and redshifted, which leads to the result of an enhancement of the spectrally integrated intensity. We also perform IR-VIS absorbance measurements and find that the results suggest that during irradiation some of the dye molecules form dimers and trimers and that the polymer host is irreversibly damaged by photooxidation and Norrish type I photocleavage.