The hybrid nanomaterials based on inorganic matrix and organic compound with customizable properties have practical potential in the field of new developments in biological and chemical sensors, photonic and solar cell devices, as well as laser media. The optical properties of molecular clusters so called J-aggregates embedded in nanoporous aluminum oxide in presence of silver plasmonic nanoparticles were studied. The unique technique for obtaining nanoporous aluminum oxide on the island silver film was proposed. The optimal parameters of the impregnation of nanopores in the ethanol solution of pseudoisocyanine dye for the J-aggregate formation have been studied. The resonant transfer of optical energy from the oxygen vacancy in aluminum oxide to organic molecules was observed in the resulting hybrid films.
Nanoscale molecular clusters are fascinating fluorescent nanomaterials formed by highly ordered assembly of organic dyes with the optical properties strongly different from those of monomolecules. Hybrid films formed by pseudoisocyanine dye coated metal nanoparticles on a sapphire substrate or nanoporous alumina on an aluminum substrate were studied with steady‐state and time-resolved spectroscopy. On-surface reaction caused isomerization of cyanine molecules as well as self-assembly into molecular nanoclusters, so called J‐aggregates. The excitonic band of clusters had been strongly coupled to plasmonic response of metal nanoparticles. The dynamics of the strong coupling regime was directly analyzed depending on environmental conditions (temperature and presence of gas analyte). The energy transfer of the optical excitation from oxygen vacancies of alumina to the molecular clusters was observed depending on the anodization conditions of the aluminum substrate. Such unique feature should provide a new approach to develop new sensors.
The hybrid systems consisting of noble metal nanoparticles with plasmon resonances and organic cyanine dye, which are able to delocalize and migrate the energy of excitons on a large number of aggregated molecules of the structure, can be used to study the plasmon-exciton interaction. The position as well as the region of overlap of the absorption of the exciton band and the plasmon resonance of the nanoparticles in the form of island film allows observing both weak and strong coupling. The influence of overlap between the J-aggregate band of cyanine dyes with different length of the conjugation chain and nanoparticle plasmon resonance on the optical properties of hybrid structures was studied. Inhomogeneous ensembles of noble nanoparticles were obtained as an island films on the sapphire substrates by thermal deposition in vacuum. The homologous series of dicarbocyanine, monocarbocyanine and pseudoisocyanine dyes was used for forming J-aggregates in ethanol solution without adding salt by the original technique. Dye solution was spincoated on the island film to obtained hybrid structure. The plasmon resonance of the island film was broadened due to the large dispersion of the nanoparticles in size. So strong and weak plasmon-exciton coupling can be observed in hybrid structures due to overlap of the absorption bands of island film and exciton-transition in J-aggregates. The influence of near field of noble nanoparticles on enhancement of dye molecule absorption is observed in hybrid films with dicarbocyanine and monocarbocyanine. The surface molecular concentration was monitored, in the experiment there was no significant increase of the number of adsorbed molecules on island film in comparison with clean dielectric substrate. Spectral dip at the wavelength of the maximum absorption of the J-aggregate was observed for hybrid films with pseudoisocyanine.
Hybrid nanostructures that couple plasmon and exciton resonances generate hybridized energy states, which may result in unusual light-matter interactions. In our work we studied island films from the inhomogeneous ensemble of gold nanoparticles obtained by thermal vacuum deposition, spin-coated with a molecular layer of cyanine dye, in which Jaggregates were formed. The influence of the cyanine dye length chain of conjugation and the thickness of the island film on the optical properties of the hybrid structure was studied. The increase of the molecule absorption is observed for pseudoisocyanine, in comparison with mono- and dicarbocyanine dyes. The transparency in the absorption spectrum of a hybrid film with pseudoisocyanine was observed at a wavelength of 583 nm corresponding to the maximum of the Jaggregate band, which can be explained by the strong coupling of the exciton transition in the J-aggregate with the plasmon resonance of nanoparticles.
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.
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