Molecular structure and reversible photodegradation in anthraquinone dyes

Abstract

Reversible photodegradation is a process that has been observed in several dye molecules, but the underlying mechanisms are not still well understood. In this contribution, we characterize a series of anthraquinone dyes to determine how self-healing depends on molecular structure. Past studies have used probing techniques that rely on linear absorption, two-photon fluorescence, and amplified spontaneous emission. Each of these probes provide an indirect measure of the populations of the damaged and undamaged species, requiring calibrations or assumptions to be made that might affect the accuracy of the results. The present studies use fluorescence as a probe, which is shown to directly measure the undamaged population. It is found that certain anthraquinone classes share common structural features that are associated with self healing. Furthermore, the time and temperature dependence of photodegradation and self-healing is found to be consistent with the domain model of self healing.

Self-Healing Properties of 1-Amino,2,4-Dibromoanthraquinone Dye Doped in PMMA Polymer

“…CCrDM's estimation of the undamaged molecule fraction as a function of time at various depth.Figures 11,12,13 and 14 are consistent with each others and in accordance to our expectation. We can conclude that the more a layer of the dye is damaged, the CCrDM's estimation of the undamaged molecule fraction as a function of depth at various time.…”

“…The presence of isobestic points in the absorbance spectra indicate that the degraded species of the molecules must pass predominantly through at least one species of photodegradation. Table I shows some of the important properties of dye B at key wavelengths [12]:…”

“…Of all the anthraquinone molecules that are shown to undergo self-recovery [12], the 2,4-dibromo anthraquinone molecule is of a special type because of the relatively * dprabodh@wsu.edu † mgk.wsu@gmail.com heavier bromine atoms attached to the carbon atoms of the benzene rings. All the other dye molecules studied in the past have only nitrogen, oxygen or hydrogen on the benzene molecule.…”

“…In an attempt to understand its recovery properties, we measured its decay and the recovery rate as a function of temperature and concentration. The only disadvantage of fluorescence spectroscopy is self absorption because the sample by necessity has a thickness that exceeds the 1/e × the absorption length [12]. As a result, the fluorescence spectra partially overlaps with the absorption spectra.…”

Excited-State Intramolecular Hydrogen Transfer of Compact Molecules Controls Amyloid Aggregation Profiles

“…Photodegradation of photosensitizers during illumination was reported to yield unidentified fragments that can cause toxicity. 62 Thus, the toxicity of the compounds prepared with and without photoirradiation was determined in human neuroblastoma SH-SY5Y As described in Figure S10, the cells in the presence of both Group A and Group B without photoactivation exhibited greater survival of over ca. 80% at up to 25 μM.…”