Nanooptics and photonics
Interaction between Molecular Aggregates Incorporated in Layered Polymer Films
Pisklova P.V.1,2, Ropakova I.Yu.1, Viagin O.G.1, Yefimova S.L.1, Sorokin A.V.1 
1 Yu.V. Malyukin Nanostructured Materials Department, Institute for Scintillation Materials of NAS of Ukraine, Nauky Ave. 60, Kharkiv, 61072, Ukraine
2 Institute of Physics, University of Rostock, Albert-Einstein-Str. 23, 18059 Rostock, Germany
E-mail: polinkapisklova@gmail.com

Molecular aggregates of cyanine and some other dyes are nanosized luminescent clusters formed by organic molecules. They were discovered in the late thirties of the last centuries by E. Jelley and called in his honor J-aggregates [1]. Due to the high ordering of monomers within J-aggregates and strong intermolecular coupling between monomers, the electronic excitations of J-aggregates are the Frenkel excitons delocalized over a certain number of monomers. Thus, the exciton coherence length is one of the most important characteristics of J-aggregates, taking effect on the exciton bandwidth and exction lifetime. As a result, the spectroscopic properties of J-aggregates are quite different from that of the constituting molecules. J-aggregates are characterized by a narrow absorption band (J-band) red-shifted to the monomer one, nearly resonant luminescence with a much shorter luminescence decay time than that of monomers, due to the exciton superradiation effect. 
The unique features of J-aggregates provide their wide applications in various fields, such as photonics, sensorics, photovoltaics, etc. In particular, the strong photon absorption of J-aggregates and their high exciton mobility allow to realize an impressive energy transfer between J-aggregates and obtain a significant pumping of dyes gaining their bright luminescence. 
Some advantages can be obtained for J-aggregates placed into thin polymer films like layered polyelectrolyte ones. The additional dye pumping can be achieved by electromagnetic field confinement in the nanoscale region near the J-aggregates due to the formation of the surface exciton polariton in such molecular aggregates [2]. However, the features of such pumping in the case of J-aggregates used as the energy trap is not clear. 
Therefore, the present work is devoted to studying the interaction between two types of dyes, TDBC and TCC, with similar structures in aqueous solutions and thin polymer films. It has been experimentally confirmed that by placing the J-aggregates in different layers separated by polymer film spacer, efficient energy transfer can be achieved with TDBC J-aggregates as an energy donors and TCC J-aggregates as energy acceptors.

1.	 F. Würthner, et al. J-Aggregates: From Serendipitous Discovery to Supramolecular Engineering of Functional Dye Materials // Angew. Chemie Int. Ed. – 2011. – 50. – P. 3376–3410. 
2.	 A.V. Sorokin, et al. Unusual Enhancement of Dye Luminescence by Exciton Resonance of J-aggregates // Optical Materials. – 2019. – 96. – P. 109263.