Organic nanoclusters, so-called J-aggregates, composed of cyanine dyes possess properties different from constituting molecules. There is a growing interest in the study of organic dyes conjugates with metal nanoparticles. The combination of unique properties of J-aggregates and plasmonic nanoparticles allow novel effects to be observed in such systems. The optical properties of molecular layer of cyanine dyes and its J-aggregates, coated on the island films in the form of a heterogeneous ensemble of silver or gold nanoparticles, were studied by absorption and fluorescent spectroscopy, as well as AFM. The original method for obtaining cyanine J-aggregates on metallic films without use of salt and water was developed. The molecular nanoclusters obtained on silver island film were stable for a week, while aggregation of cyanine molecules was much smaller on gold island films. The absorption spectrum of the organometallic film is not a simple sum of the spectra of its components. The absorption of dye molecules increases several times in the presence of silver nanoparticles in comparison with gold island film. Besides, the induced transparency is observed at the absorption maximum of J-aggregates, which can indicate the interaction between the plasmons of metal nanoparticles and the excitons of the J-aggregate.
The optical properties of organometallic films of silver nanoparticles and J-aggregates of pseudoisocyanine dye have been studied to observation of the plasmon-exciton interaction. The original method for obtaining J-aggregates on inhomogeneous island silver films without use of salt and water was developed. Owing to the broad bandwidth of inhomogeneous plasmon resonances; it is possible to study the interaction of nanoparticles and J-aggregates, obtained in the spin-coated layer on the silver island film. The absorption spectrum of the organometallic film is not a simple sum of the spectra composing its components. The absorption of dye molecules increases several times in the presence of silver nanoparticles, which is due to the influence of the near fields of the latter. The spectral dip in the absorption maximum of the J-aggregate of pseudoisocyanine was observed; it became more symmetrical with an increasing equivalent thickness of the island film.
The optical properties of hybrid film based on plasmon Ag nanoparticles of different size and cyanine dyes with different
length of conjugation chain depending on the relative position of the plasmon resonance and the absorption of organic
molecules were studied. The absorption spectra of the films revealed several molecular forms, such as all-trans- and cisisomers,
dimers and J-aggregate, which also exist in pure organic films without Ag nanoparticles. It’s shown that the
absorption of aggregate bands increased after exposure by nanosecond laser on the hybrid films due to photo-induced
additional self-organization of aggregates. In the presence of Ag nanoparticles, laser radiation leads to the change of
molecular forms at a comparatively low threshold.