Unusual temperature dependence of the fluorescence decay in heterostructured stilbene

Abstract

The fluorescence decay kinetics of solid stilbene demonstrate elongation of the excitation lifetime with a temperature increase. This unusual dependence can be explained by fluorescence from a thermalized exciton distribution in aggregated stilbene clusters.

Two phases of trans-stilbene in a polystyrene matrix

“…A polystyrene matrix (Scheme 1) is used as a solid solvent because it is transparent in the spectral region to the red from 280 nm and has minimal effects on both absorption and fluorescence in the case of a single, non-aggregated sample. 25 Films were prepared in a UV-isolated room using chloroform solutions (initial PS concentration for all solutions was the same, 8 mg mL −1 ) by spin-coating (1000 rpm for 40 s, with KW-4A apparatus) onto clean 15–24 mm quartz substrates. The average film thickness ranged from 120 to 160 nm.…”

“…It is demonstrated that this type of excitonic dynamics dominates over different single-molecular excitation decay pathways in the solid phase. 25 However, detailed studies of aggregate formation of Tstilbene molecules is still lacking. Here, we present comparative studies of the absorption and fluorescence spectra as well as the fluorescence kinetics of Tstilbene solutions in a polystyrene (PS) matrix as a function of the solute concentration.…”

“…From our recent studies it has been found that the temperature dependence of the steady-state and time-resolved fluorescence of solid-state systems and films of Tstilbene is attributed to cooperative exciton state formation in condensed phases, when the molecular isomerization process is suppressed. 25 For comparison, time-resolved fluorescence measurements have also been performed for stilbene solutions in chloroform and for stilbene in a polystyrene matrix, which specifically behaves as a highly viscous solution. Sensitivity of the fluorescence decay lifetimes for different samples at various temperatures suggests the emergence of aggregation-induced exciton diffusion in solid forms of Tstilbene, which specifically shapes the fluorescence spectrum.…”

“…It is demonstrated that this type of excitonic dynamics dominates over different single-molecular excitation decay pathways in the solid phase. 25…”

Excited state relaxation in cationic pentamethine cyanines studied by time-resolved spectroscopy

“…The assumptions about the nature of the emission from PMDs at low temperatures are based on the features of the one-dimensional structure of these dyes: the dependence of the electronic properties in the ground state and excited states on this structure [21], the manifestation of collective electronic excitations [22][23][24], the dependence of electronic properties on solvation processes that change at low temperatures [25]. The parameters of J o u r n a l P r e -p r o o f 5 quantum-chemical calculations for various molecular geometries [13][14][15]26,27] provide excellent supplementary insight to such spectral studies.…”