Formation of the "J-aggregate-surfactant" complex for three cyanine dyes (L-21, LC-1 and PIC) in binary solutions containing cationic surfactant CPB at the concentration higher than the critical micelle concentration has been observed. The complex formation causes a significant increase of J-aggregate luminescence quantum yield and a decrease of radiative lifetime. The model of exciton self-trapping suppression in the "J-aggregatesurfactant" complex that causes changes of luminescence parameters has been proposed.

Using luminescent exciton traps, an efficiency of the exciton migration in J-aggregates of an amphiphilic analogue of pseudoisocyanine (amphi-PIC) dye in solutions, has been investigated. Applying a modified Stern−Volmer equation for analysis of the J-aggregate luminescence quenching by the trap, the quenching of 50% of amphi-PIC J-aggregate luminescence accessible for trapping at the ratio amphi-PIC/DiD = 120:1 has been revealed. To increase the exciton migration efficiency, the J-aggregate structure was improved by the formation of a “J-aggregate−surfactant” complex. The J-aggregate structure improvement is confirmed by the about 3 times increase in the exciton delocalization length that leads to the 1.3 times enhancement in the exciton migration efficiency in solutions with the surfactant. To the best of our knowledge, such a control of the exciton transport parameters in J-aggregates in solutions has not been demonstrated yet.

The diindolenine derivative of squaraine dye Sq-2Me has been used as an exciton energy trap (an energy acceptor) for amphi-PIC J-aggregates in a solution. Using the modified Stern-Volmer equation, parameters of the energy transfer have been obtained. It has been revealed that 50% of J-aggregate luminescence is quenched in a binary DMF/water solution at the ratio trap/amphi-PIC ) 1:80 that corresponds to the exciton migration over 20 delocalization segments within the J-aggregate.

Using a luminescent exciton trap, a mechanism of the exciton migration in disordered J-aggregates of amphiphilic analogue of pseudoisocyanine (amphi-PIC) dye has been investigated in the temperature range of 80−300 K. Due to a strong topological disorder in amphi-PIC J-aggregates observed in a binary dimethylformamide−water (DMF/W) solution with a low water content, two types of excitonic states have been revealed, delocalized exciton state that forms the main part of the J-aggregates absorption band (J-band) and a state of strongly localized excitons that forms the long-wavelength edge of the J-band. These excitonic states are characterized by the different mechanism of the exciton transport: a coherent mechanism for delocalized excitons and an incoherent one for localized excitons. As localized excitons provide a small contribution to the J-band and appear only at high degree of topological disorder, the coherent mechanism of the exciton transport in amphi-PIC J-aggregates has been concluded. Such a result is nontrivial due to a small delocalization length of excitons in amphi-PIC J-aggregates (11 monomers at 80 K) provided by the moderate energetic disorder and strong exciton−phonon coupling.

Optical spectroscopy experiments were used to study the features of cyanine dye 3,3'-dimethyl-9-(2-thienyl)-thiacarbocyanine iodide (L-21) aggregation in binary solutions DMF:Tris-HCl buffer (pH = 8) containing nucleic acids (DNA or RNA). The appearance of absorption and luminescence bands associated with J-aggregates and dimers that are formed within the minor groove of DNA has been observed. The model of L-21 J-aggregate structure is proposed. It has been found that dimers are the building blocks of L-21 J-aggregates. Disorientation in dimers caused by the minor groove curvature is reason of observation of Davydov splitting in absorption spectrum of L-21 J-aggregates. In the solution containing DNA the absorption and luminescence bands of L-21 J-aggregates exhibit the specific properties that allows the dye L-21 to be used as a fluorescent probe for DNA detection.