The Phosphorescence of Adsorbed Acriflavine¹

The Triplet State and Molecular Electronic Processes in Organic Molecules

“…Teplyakov (390) has since shown that 30-35 passes of zone-refining is sufficient to eliminate these effects from the solution spectrum of phenanthrene. A similar nonexponential decay of acriflavine phosphorescence observed by Kato and Koizumi (183) has been attributed to inhomogeneities in the rigid medium (329).…”

Molecular Photophysics of Acridine Yellow Studied by Phosphorescence and Delayed Fluorescence: An Undergraduate Physical Chemistry Experiment

“…Although eq 3 indicates that a single, first-order rate constant should account for the triplet state decay, the individual decay curves in Figure 3 are not well modeled by single exponential functions over their entire range. Since the local environment surrounding some of the dye molecules in the glass may differ from the average, shorter triplet lifetimes are observed for these molecules owing to site-specific interactions (14)(15)(16). To discriminate against any residual prompt fluorescence and the shorter-lived excited-state emission, the first 150 ms of each decay curve was omitted from the analysis.…”

Photophysical and Photochemical Effects of Dye Binding*

“…The lifetime of phosphorescence of acriflavine dye molecules adsorbed on silica gel increases as the concentration of adsorbed dye molecules increases [5], and in this system the rate constant for population of the triplet state from the first excited singlet increases forty-fold between -100°C and room temperature; the authors consider that thermal excitation from the lowest vibrational level of the excited singlet state is necessary in order to reach a D* + D' crossing point. Of course the observation of an increase in the quantum yield of phosphorescence with an increase in the concentration of adsorbed dye molecules would afford a more direct confirmation of the energy transfer mechanism of populating the triplet state.…”