O. M. Perelygina

High precision nanoscale AFM height measurements of J-aggregates

Atomic force microscopy (AFM) was used to obtain high-resolution images of nanosized organic J-aggregate molecular crystals of 3,3′-di(gamma-sulfopropyl)-5,5-dichlorotiamonomethinecyanine (TC) and 3,3′-bis(2-sulfopropyl)-5,5′,6,6′-tetrachloro-1,1′-dioctylbenzimidacarbocyanine (C8S3) and precise height measurements of J-aggregates monolayers were conducted. It was found that TC J-aggregates obtained both in the solution bulk and by self-assembly on the mica surface are extended monolayer sheets of high mechanical flexibility. The height of TC is 1.05 ± 0.05 nm, which corresponds to the crystallographic size of a single molecule along the short axis. A model of asymmetric single-layer molecular packing is suggested in which sulfopropyl groups are located on the same side of the layer plane. In the case of C8S3, narrow multilayer ribbonlike structures with heights of 3 to 30 nm were observed. The heights are strictly quantized with a step of 3 nm. A bilayer model of C8S3 molecular packing in J-aggregates is discussed with partially interpenetrating monolayers with hydrophobic sides oriented face to face. A model of structural C8S3 units as “elementary ribbons” with the transverse dimensions of 3 × 4 nm is suggested on the basis of the comparison of AFM data with electron microscopy data from other works.

Tubular structure of J-aggregates of cyanine dye

1 A heightened interest in certain supramolecular organic structures is associated with their unusual optical and electronic properties. These structures include J aggregates of cyanine dyes that represent a variation of micro and nanosized molecular crystals with strong and narrow absorption band (J band) in the visible range shifted toward longer wavelengths as compared with the spectrum of monomers [1, 2]. Owing to high electron–hole conductivity and special spectral properties caused by excitation of delocalized Frenkel excitons, J aggregates are promising organic systems for application in different optoelectronic devices [3–7].

Crystalline structure of two-dimensional cyanine dye J-aggregates

A crystallographic analysis of optical fluorescent images of two-dimensional polygonal structures of J-aggregates of 3,3′-di(γ-sulfopropyl)-5,5′-dichlorothiamonomethinecyanine (MCD) cyanine dye has been performed. In aqueous solutions, MCD forms striplike J-aggregates in the form of extended strips with parallel sides and an oblique or right-angled end. It is found that the acute angle in oblique J-aggregates has a single value close to 45°. The staircase model of molecular packing in oblique J-aggregates is proposed with a slippage angle of 25° expected from the molecular simulation. Within this model the sides of aggregates are formed by the [100] and

Molecular nanocrystals in polyaniline-based light-emitting diode structures

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Crystallography and Molecular Arrangement of Polymorphic Monolayer J-Aggregates of a Cyanine Dye: Multiangle Polarized Light Fluorescence Optical Microscopy Study

faces, and the acute angle between them is equal to the experimentally observed angle. Right-angled rectangular J-aggregates are presumably described by the ladder model.

Polymorphism of 2D monolayer J-aggregates of cyanine dyes

Experimental data on electroluminescence of new light emitting materials, semiconducting organic polymers doped with nanosized J-aggregates of cyanine dyes, are described. OLED structures are considered. New light-emitting diode structures are developed. Polyaniline electroluminescence band is observed. High-resolution atomic force microscopy (AFM) is used to study J-aggregate structures. The AFM procedure is improved to increase accuracy in determination of J-aggregate dimensions. Certain supramolecular species are long ribbons with high flexibility.

Molecular arrangements in polymorphous monolayer structures of carbocyanine dye J-aggregates

It is found that one of the types of molecular organic nanocrystals, the so-called J-aggregates, is able to modify optoelectronic properties of electroactive polymers. It is intrinsic that the polyaniline interpolymeric complex, known as p-type semiconductor, turns into electroluminescent material in the presence of J-aggregates of 3,3-di(gamma-sulfopropyl)-5,5-dichlorotiamonomethincyanine triethylammonium salt. During the studying of new organic light-emitting diode structures, in which the polyaniline/J-aggregates polymeric composite forms both recombination and emitting layers, a polyaniline intrinsic electroluminescence spectrum is obtained. The electroluminescence band completely coincides with the polyaniline photoluminescence spectrum; it has maximum at 400 nm. The electroluminescence mechanism in the studied nanocomposites is discussed.

Molecular Arrangements in Two-Dimensional J-Aggregate Monolayers of Cyanine Dyes

566 An important line in the design of new high-molecular-weight structures with electroluminescent properties is the study of electroactive polymer composites containing a particular type of organic nanosized crystals with semiconductor properties known as J aggregates. Such polymer composites possess a number of advantages as compared to polymer systems doped with low-molecular-weight luminophores or inorganic nanosized particles [1, 2]. We have developed and studied electroluminescent layers doped with nanocrystals of cyanine dye (CD) J aggregates. These particles are efficient luminophores [3] and are used as spectral sensitizers of photographic materials [4].