Mechanisms of reversible photodegradation in disperse orange 11 dye doped in PMMA polymer

TL;DR

This study investigates the reversible photodegradation mechanisms of disperse orange 11 dye in PMMA, revealing the role of dye concentration, polymer environment, and excited states in degradation and recovery processes.

Contribution

It introduces a detailed energy level diagram and a hypothesis explaining the reversible degradation pathways specific to dye-polymer systems, highlighting the polymer's role.

Findings

ASE originates from a state that forms dimers or aggregates upon relaxation

High dye concentration and polymer environment are crucial for reversible degradation

A proposed energy level diagram describes decay and recovery processes

Abstract

We use amplified spontaneous emission (ASE) and linear absorption spectroscopy to study the mechanisms of reversible photodegradation of 1-amino-2-methylanthraquinone (disperse orange 11-DO11) in solid poly(methyl methacrylate). Measurements as a function of intensity, concentration, and time suggest that ASE originates in a state (be it a tautomer or a vibronic level) that can form a dimer or some other aggregate upon relaxation, which through fluorescence quenching leads to degradation of the ASE signal. Whatever the degradation route, a high concentration of DO11 is required and the polymer plays a key role in the process of opening a new reversible degradation pathway that is not available at lower concentrations or in liquid solutions. We construct an energy level diagram that describes all measured quantities in the decay and recovery processes and propose a hypothesis of the nature of the associated states.