Excitation Energy Transfer and Trapping in Dye‐Loaded Solid Particles

Abstract

The photophysics of several systems composed of a single dye or pairs of dyes attached to solid particles has been studied in the dry solid state at high dye concentrations taking into account light scattering and inner filter effects. Interaction among dye molecules and singlet-singlet energy transfer are relevant in these conditions, as has been demonstrated for pairs of dyes with suitable spectral overlap. For single dyes, after correction for radiative energy transfer, fluorescence quenching is observed as the surface concentration increases. This effect is explained by two different trapping models. Irrespective of the nature of the traps, concentration quenching may be of static (trap absorption) and dynamic (energy transfer) nature. The unraveling of energy trapping mechanisms is a key to the development of efficient photoactive solid materials.

Eosin Y Triplet State as a Probe of Spatial Heterogeneity in Microcrystalline Cellulose

“…At the lowest concentrations, the shape of thin layer spectra becomes constant, but a redshift with concentration remains. This effect, not attributable to reabsorption, is typical in this kind of system and reflects again the occurrence of weak interactions between singlet excited state molecules and neighboring ground state partners (11).…”

“…As singlet‐triplet transitions are forbidden, the interaction almost vanishes when a triplet dimer is formed (9). Even a random distribution of dye molecules noninteracting in the ground state can lead to the existence of close‐lying dye pairs, which may undergo exciton interactions and act as statistical traps of the singlet excitation energy (10,11).…”

Structural Confirmation of Lymphatic Outflow from Subconjunctival Blebs of Live Humans

“…However, the choice of tracer concentration can differ when imaging different parts of J o u r n a l P r e -p r o o f the body. First, fluorophores can exhibit unusual behaviors such as the inner-filter effect 24,25 where high concentrations can result in the fluorescent emission itself exciting nearby fluorophores. In this case, no fluorescent emission escapes and the solution appears dark.…”

Aqueous Angiography with Fluorescein and Indocyanine Green in Bovine Eyes

“…Fluorescent resonance energy transfer (FRET) is a commonly used strategy that intentionally takes advantage of fluorescent cross-talk for biological assays. 31 At higher concentrations, fluorescein is known to undergo an inner-filter effect 32,33 where the fluorescein emission itself, which can be as high as 650 nm and notably longer than typical fluorescein excitation wavelengths, can actually excite nearby fluorescein molecules. Therefore, we speculate that the ICG capture mode laser (786 nm) could have excited fluorescein when prepared in combination and caused fluorescein emission that further stimulated ICG.…”