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Resumen del trabajo presentado a la 19th International Conference on Transparent Optical Networks (ICTON), celebrada en Girona (España) del 2 al 6 de julio de 2017., We report our recent results of investigation of the interactions between localized plasmons in gold nanorods and excitons in J-aggregates. We were able to track an anticrossing behavior of the hybridized modes both in the extinction and in the photoluminescence spectra of this hybrid system. We identified the nonlinear optical behavior of this system by transient absorption spectroscopy. Finally using magnetic circular dichroism spectroscopy, we show that nonmagnetic organic molecules exhibit magneto-optical response due to binding to a plasmonic nanoparticles. In our experiments, we also studied the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states.

Trabajo presentado a la 3rd International Conference on Applications of Optics and Photonics, celebrado en Faro (Portugal) del 8 al 12 de mayo de 2017., We investigated the interactions between localized plasmons in gold nanorods and excitons in J-aggregates and were able to track an anticrossing behavior of the hybridized modes both in the extinction and in the photoluminescence spectra of this hybrid system. We identified the nonlinear optical behavior of this system by transient absorption spectroscopy. Finally using magnetic circular dichroism spectroscopy we showed that nonmagnetic organic molecules exhibit magneto-optical response due to binding to a plasmonic nanoparticles. In our experiments we also studied the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states., We acknowledge financial support from Project Fis2016.80174-P (PLASMOQUANTA) from MINECO (Ministerio de Economía y Competitividad). L.L.-M. acknowledges funding from the European Research Council (ERC Advanced Grant 267867, Plasmaquo). This study was supported by the Ministry of Education and Science of the Russian Federation, grant no. 14.Y26.31.0011.

The interaction between the excitonic J-band of J-aggregate molecules and localized plasmonic resonances supported by metallic structures can be large enough to reach the regime of strong coupling, giving rise to two hybridized modes [1, 2]. The new hybrid system is often characterized in extinction measurements, where the strong coupling results in an avoided crossing of the two modes as the detuning of the plasmonic mode with respect to the excitonic transition is changed. In principle, the photoluminescence (PL) signal should also exhibit a characteristic anti-crossing signature, but, so far, it has been challenging to identify it in experiments [2, 3].

We experimentally and theoretically investigate the interactions between localized plasmons in gold nanorods and excitons in J-aggregates under ambient conditions. Thanks to our sample preparation procedure we are able to track a clear anticrossing behavior of the hybridized modes not only in the extinction but also in the photoluminescence (PL) spectra of this hybrid system. Notably, while previous studies often found the PL signal to be dominated by a single mode (emission from so-called lower polariton branch), here we follow the evolution of the two PL peaks as the plasmon energy is detuned from the excitonic resonance. Both the extinction and PL results are in good agreement with the theoretical predictions obtained for a model that assumes two interacting modes with a ratio between the coupling strength and the plasmonic losses close to 0.4, indicative of the strong coupling regime with a significant Rabi splitting estimated to be ∼200 meV. The evolution of the PL line shape as the plasmon is detuned depends on the illumination wavelength, which we attribute to an incoherent excitation given by decay processes in either the metallic rods or the J-aggregates., We acknowledge financial support from Projects FIS2013-41184-P and MAT2013-46101-R of the Spanish Ministry of Economy and Competitiveness (MINECO) and ETORTEK project NANOGUNE’14. R.E. acknowledges funding as Fellow Gipuzkoa of the Gipuzkoako Foru Aldundia through Feder Funds of the European Union “Una manera de hacer Europa”.

We studied the chiroptical properties of colloidal solution of CdSe and CdSe/ZnS quantum dots (QDs) with a cubic lattice structure which were initially prepared without use of any chiral molecules and coated with achiral ligands. We demonstrate circular dichroism (CD) activity around first and second excitonic transition of these CdSe based nanocrystals. We consider that this chiroptical activity is caused by imbalance in racemic mixtures of QDs between the left and right handed nanoparticles, which appears as a result of the formation of various defects or incorporation of impurities into crystallographic structure during their synthesis. We demonstrate that optical activity of colloidal solution of CdSe QDs with achiral ligands weakly depends on the QDs size and number of ZnS monolayers, but does not depend on the nature of achiral ligands or polarity of the solution., Project FIS2013-41184-P of the Spanish Minsitry of Economy and Competitiveness MINECO.

We report on direct formation of J-aggregates in cyanine dye solution by injection of colloidal CdTe quantum dots. The optical properties of formed J-aggregates have been investigated by absorption and photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. Quantum dots/J-aggregate system shows the enhanced absorption in visible and ultraviolet parts of the spectrum typical of quantum dots, along with the narrow emission linewidth and fast recombination rate characteristic of the J-band emitters. Our studies suggest electrostatic association between the J-aggregates and quantum dots, followed by highly efficient energy transfer. Copyright © 2012 American Scientific Publishers All rights reserved.

We have studied the photodynamic properties of novel CdTe quantum dots—methylene blue hybrid photosensitizer. Absorption spectroscopy, photoluminescence spectroscopy, and fluorescence lifetime imaging of this system reveal efficient charge transfer between nanocrystals and the methylene blue dye. Near-infrared photoluminescence measurements provide evidence for an increased efficiency of singlet oxygen production by the methylene blue dye. In vitro studies on the growth of HepG2 and HeLa cancerous cells were also performed, they point toward an improvement in the cell kill efficiency for the methylene blue-semiconductor nanocrystals hybrid system.

In this work we demonstrate the possibility to achieve efficient anti-Stokes photoluminescence emission and Raman scattering from semiconductor quantum dots deposited on spherical microcavity using excitation below the absorption edge of quantum dots. The largest spectral shift in photoluminescence spectra to shortwave region with respect to the excitation energy was found to be 380 meV, with periodic structure in optical spectra arising from the coupling between the emission from quantum dots and spherical cavity modes.

We present our recent results on the development and characterization of hybrid sytems consisting of plasmonic nanostructures and organic dye molecules in a J-aggregate state. The measured spectra exhibit a strongly suppressed signal at wavelengths which correspond to the J-aggregate band, which is indicative of strong interaction between the plasmonic and excitonic systems.

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.-- et al., 23rd Congress of the International Commission for Optics (ICO 23), The exceptional properties of localised surface plasmons (LSPs), such as local field enhancement and confinement effects, resonant behavior, make them ideal candidates to control the emission of luminescent nanoparticles. In the present work, we investigated the LSP effect on the steady-state and time-resolved emission properties of quantum dots (QDs) by organizing the dots into self-assembled dendrite structures deposited on plasmonic nanostructures. Self-assembled structures consisting of water-soluble CdTe mono-size QDs, were developed on the surface of co-sputtered TiO2 thin films doped with Au nanoparticles (NPs) annealed at different temperatures. Their steady-state fluorescence properties were probed by scanning the spatially resolved emission spectra and the energy transfer processes were investigated by the fluorescence lifetime imaging (FLIM) microscopy. Our results indicate that a resonant coupling between excitons confined in QDs and LSPs in Au NPs located beneath the self-assembled structure indeed takes place and results in (i) a shift of the ground state luminescence towards higher energies and onset of emission from excited states in QDs, and (ii) a decrease of the ground state exciton lifetime (fluorescence quenching)., Financial support from the European Science Foundation (ESF) through PLASMONBIONANOSENSE programme and Portuguese Foundation for Science and Technology (FCT) and FEDER through Projects PTDC-FIS-113199-2009 and Est-C/FIS/UI0607/2013 are gratefully acknowledged. DM, DS and YR acknowledge support from Project FIS2013-41184-P of the Spanish Ministry of Economy and Competitiveness MINECO.

Trabajo presentado a la 16th International Conference on Transparent Optical Networks (ICTON), celebrada en Grazer Messe (Austria) del 6 al 10 de julio de 2014., In this paper, we discuss our recent results on development and characterization of three-component hybrid systems consisting of plasmonic nanostructures and two different organic dye molecules in a J-aggregate state. The measured absorption spectra exhibit a strongly suppressed absorption at wavelengths which correspond to the J-aggregate absorption bands, manifesting strong interaction between the localized surface plasmon of the plasmonic and excitonic systems. The observed dips in absorption spectra of hybrid systems correspond to an average vacuum Rabi splitting of the order of 200 meV. These findings could pave the way towards development of novel sensing devices using strong light-matter interaction on the nanoscale.

Trabajo presentado a la 16th International Conference on Transparent Optical Networks (ICTON), celebrada en Grazer Messe (Austria) del 6 al 10 de julio de 2014., In this paper, we report on the optical activity (circular dichroism) properties of hybrid organic/inorganic structures consisting of dye molecules in J-aggregate states and silver nanoparticles. The most striking results of this study are formation of microspherical micelles in a system of interacting J-aggregates and silver nanoparticles and strong (up to 8 times) enhancement in the optical activity of complexes of J-aggregates and silver nanoparticles as compared to the CD signal from the original J-aggregates. These experimental results might have potential applications in chiral species sensing and can provide some insights on mechanisms of self-assembly of supermolecular structures and the induction of their optical activity.

Trabajo presentado a la 16th International Conference on Transparent Optical Networks (ICTON), celebrada en Grazer Messe (Austria) del 6 al 10 de julio de 2014., In this paper, we report on fabrication and optical properties of hollow poly(methyl methacrylate) (PMMA) microspheres loaded with CdSe/CdS core-shell quantum dots. The PMMA microspheres were fabricated using a spray-drying method and investigated using scanning electron microscopy, confocal microscopy, and fluorescent lifetime imaging microscopy. Micro-photoluminescence studies of individual microspheres were also performed revealing pronounced whispering gallery modes. This result demonstrates the high optical quality of the hollow microspheres and their potential application as optical microresonators

We report on development and characterization of Whispering Gallery Modes spherical microcavities integrated with organic dye molecules in a J-aggregate state. The microcavities are studied using micro-photoluminescence spectroscopy, and fluorescence lifetime imaging confocal microscopy. Directional emission of light from the microcavity is also experimentally demonstrated and attributed to the photonic jets generated in the microsphere., This work was in part financially supported by the ETORTEK2011–2013 project “nanoIKER” from the Department of Industry of the Basque Government.

Hybrid materials formed by semiconductor quantum dots and J-aggregates of cyanine dyes provide a unique combination of enhanced absorption in inorganic constituents with large oscillator strength and extremely narrow exciton bands of the organic component. The optical properties of dendrite structures with fractal dimension 1.7-1.8, formed from J-aggregates integrated with CdTe quantum dots (QDs), have been investigated by photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. Our results demonstrate that (i) J-aggregates are coupled to QDs by Förster-type resonant energy transfer and (ii) there are energy fluxes from the periphery to the centre of the structure, where the QD density is higher than in the periphery of the dendrite. Such an anisotropic energy transport can be only observed when dendrites are formed from QDs integrated with J-aggregates. These QD/J-aggregate hybrid systems can have applications in light harvesting systems and optical sensors with extended absorption spectra. © The Royal Society of Chemistry 2013., This research was supported by the ETORTEK 2011–2013 project “nanoIKER” from the Department of Industry of the Basque Government and by the Ministry of Education and Science of the Russian Federation Contract no. 8842 and 11.G34.31.0050. Financial support from the Portuguese Foundation for Science and Technology (FCT) and FEDER through Projects PTDC-FIS-113199-2009 and PEst-C/FIS/UI0607/2011 is gratefully acknowledged.

Hybrid materials formed by plasmonic nanostructures and J-aggregates provide a unique combination of localized and enhanced electro-magnetic field in metal constituent with large oscillator strength and extremely narrow exciton band of the organic component. The coherent coupling of the plasmons of the multi-spiked gold nanostars and the excitons of JC1 dye J-aggregates results in a Rabi splitting reaching 260 meV. Importantly, broad absorption features of nanostars extending over a visible and near-infrared spectral range allowed us to demonstrate double Rabi splitting resulting from the simultaneous coherent coupling between plasmons of the nanostars and excitons of J-aggregates of two different dyes.

Trabajo presentado a la 15th International Conference on Transparent Optical Networks, celebrada en Cartagena (España) del 23 al 27 de Junio de 2013., Recent results on development and characterization of WGM spherical microcavities integrated with organic dye molecules in a J-aggregate state are presented. The microcavities are studied using micro-photoluminescence spectroscopy, and fluorescence lifetime imaging confocal microscopy. Directional emission of light from the microcavity is also experimentally demonstrated and attributed to the photonic jets generated in the microsphere

We report on the chiroptical (circular dichroism) properties of hybrid organic/inorganic nano-and microstructures consisting of dye molecules in J-aggregate states (arranged in direct and reverse micelles) and silver nanoparticles. The main results are formation of micelles in a system of interacting J-aggregates and silver nanoparticles and strong (up to 8 times) enhancement in the optical activity of complexes of J-aggregates and silver nanoparticles as compared to the CD signal from the original J-aggregates. These experimental results might have potential applications in chiral species sensing and can provide some insights on mechanisms of self-assembly of supermolecular structures and the induction of their optical activity. © 2013 American Chemical Society., This work was in part financially supported by the ETORTEK 2011−2013 project “nanoIKER” from the Department of Industry of the Basque Government; D.S., Y.G., and Y.R. acknowledge the support received from the European Science Foundation (activity PLASMON-BIONANOSENSE) and Science Foundation Ireland (grant SFI 07/IN.1/I1862).

We report on the resonant modes in micro-luminescence spectra of whispering gallery microcavities combining dielectric microspheres and J-aggregates of cyanine dye. We use fluorescence lifetime imaging spectroscopy to study modification of spontaneous emission rate in J-aggregates attached to a microcavity. Directional emission of light from the integrated microcavity is experimentally shown in this work and attributed to the photonic jets generated in the microsphere. The results show that whispering gallery resonators with dye nano-aggregates can be used as micro-organic light-emitting devices.

We have studied the optical properties of a hybrid system consisting of cyanine dye J-aggregates (both PIC and TDBC) attached to a spherical microcavity. Instead of the commonly accepted chemical bonding of dye molecules to the surface of microspheres or deposition of dye-doped sol-gel film, in our experiments microspheres were coated with J-aggregate shell utilizing the layer-by-layer assembly of the ultrathin films. In this approach we aimed to take advantage of light confinement in the Whispering Gallery Modes (WGMs) microcavity by placing the emitter (shell of J-aggregates) just at the rim of the microsphere, where the resonant electromagnetic field reaches its maximum. A periodic structure of narrow peaks was observed in the photoluminescence spectrum of the J-aggregates, arising from the coupling between the emission of J-aggregates and the WGMs of the microcavity. The most striking result of our study is the observation of polarization sensitive mode damping caused by re-absorption of J-aggregate emission. This effect manifests itself in dominating emission from the transverse magnetic modes in the spectral region of J-aggregates absorption band where the transverse electric (TE) modes are strongly suppressed. Strong suppression of TE modes reflects preferential tangential orientation of transition dipole moment of J-aggregates in deposited microcavity shell. Observed polarization sensitive mode damping observed in the spectral region of high J-aggregate absorption can be used for suppression of unwanted modes in high Q optical resonators. We also demonstrate that the emission intensity can be further enhanced by depositing a hybrid layer of J-aggregates and Ag nanoparticles onto the spherical microcavity. Owing to the concerted action of WGMs and plasmonic hot spots in the Ag aggregates, we observe strongly enhanced Raman signal from the Jaggregates. Microcavities covered by J-aggregates and plasmonic nanoparticles could be thus useful for a variety of photonic applications in basic science and technology.

Highly luminescent semiconductor nanocrystals or quantum dots (QDs) possess a number of interesting and important properties that are tunable thanks to their size-dependent discrete electronic spectra. In this work we studied the optical properties of a novel type of hybrid structures that combine CdTe QDs with organic dye molecules (Pseudocyanine iodide) in a J-aggregate state. Due to the excitonic nature of electronic excitations, J-aggregates have the narrowest absorption and luminescence bands among organic materials, large oscillator strengths and giant third-order nonlinear susceptibility. In developed structures optical energy harvested by the quantum dots as artificial antennas then transferred to J-aggregates to enhance the photostability and efficiency of the carriers recombination. To fabricate CdTe/J-aggregates hybrid nanostructures we have used an approach based on electrostatic interaction between the positively charged dye and CdTe QDs capped with thioglycolic acid and, thus, carrying a negative charge. In order to develop an efficient hybrid material operating in the FRET regime, we carefully selected the PL colors (diameters) of the QD to be optically coupled with absorption of J-aggregates. We took advantage of extremely thin ligand shell (~0.5 nm) of CdTe QDs, which insures high efficiency of energy transfer. Formed QD/J-aggregate FRET system shows the broadband absorption in the visible and the ultraviolet part of the spectrum typical of QDs, along with the narrow emission linewidths characteristic of J-band emitters (~15 nm full width at half-maximum). We use absorption and photoluminescence spectroscopy and photoluminescence lifetime studies to conclude that efficiency of energy transfer is 95%. Also we report on development of active whispering-gallery microcavities integrated with with hybrid QDs/J-aggregate shell. Results of micro-PL spectroscopy and PL lifetime imaging confirm strong quenching of QDs emission and multifold shortening of their photoluminescence lifetime, which is consistent with highly efficient FRET in hybrid organic/inorganic semiconductor nanostructures coupled to microcavity modes.

Using electro-static assembly of complementary organic (cyanine dye) and inorganic (quantum dots) building blocks we report on formation of an advanced nanohybrid system with highly efficient nonradiative energy transfer properties. In contrast to previous approaches, formation of J-aggregates in cyanine dye solution was triggered by direct injection of as-synthesized colloidal CdTe quantum dots without any additional surface treatment. The optical properties of formed hybrid aggregates have been investigated by absorption and photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. A quantum dot/J-aggregate system shows the enhanced absorption in visible and ultraviolet parts of the spectrum typical of quantum dots, along with the narrow emission linewidth and fast recombination rate characteristic of the J-band emitters. These quantum dot/J-aggregate hybrid systems may have applications in light harvesting systems with the extended spectral absorption as well as optical sensors and optoelectronic devices. © The Royal Society of Chemistry 2012., This work was in part financially supported by Ikerbasque Visiting Fellowship (NG). DS and YR acknowledge the support received from the European Science Foundation (activity PLASMON - BIONANOSENSE).

In this paper, we report on development of active whispering-gallery microcavities integrated with shell of organic dye molecules in a J-aggregate state. Results of high-resolution micro-photoluminescence spectroscopy and photoluminescence lifetime imaging confirm strong coupling of J-aggregate emission to whispering gallery modes of spherical microcavity. Highly efficient luminescence from J-aggregate/microcavity system suggests that such photonic structures will find use as both microsensors and microlasers.

In this paper, we report on optical properties of a novel type of the hybrid nanostructures that combine CdTe colloidal quantum dots (QDs) with organic dye molecules in J-aggregate state. Formed QD/J-aggregate system shows the broadband absorption in visible and ultraviolet part of the spectrum typical of quantum dots, along with the narrow emission linewidth characteristic of J-band emitters (∼15 nm full width at a half-maximum (FWHM)). Highly efficient Forster energy transfer from an excited semiconductor quantum dot to an organic material paves the way for engineering a wide range of desired radiation rates, making these hybrid nanostructures promising for integration with whispering-gallery-mode (WGM) resonators. Photoluminescence spectroscopy and photoluminescence lifetime studies were used to conclude that the efficiency of energy transfer is ∼91%.

We have studied the photoluminescence and Raman spectra of a system consisting of a polystyrene latex microsphere coated by CdTe colloidal quantum dots. The cavity-induced enhancement of the Raman scattering allows the observation of Raman spectra from only a monolayer of CdTe quantum dots. Periodic structure with very narrow peaks in the photoluminescence spectra of a single microsphere was detected both in the Stokes and anti-Stokes spectral regions, arising from the coupling between the emission of quantum dots and spherical cavity modes.

Recent results on the development of active metallic nanocavities integrated with organic dye molecules in a J-aggregate state will be presented. Highly efficient SERS, the photoluminescence enhancement and photoluminescence lifetime modification have been observed at nanowire junctions.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License., Hybrid materials formed by plasmonic nanostructures and J-aggregates provide a unique combination of highly localized and enhanced electromagnetic field in metal constituent with large oscillator strength and extremely narrow exciton band of the organic component. The coherent coupling of localized plasmons of the multispiked gold nanoparticles (nanostars) and excitons of JC1 dye J-aggregates results in a Rabi splitting reaching 260 meV. Importantly, broad absorption features of nanostars extending over a visible and near-infrared spectral range allowed us to demonstrate double Rabi splitting resulting from the simultaneous coherent coupling between plasmons of the nanostars and excitons of J-aggregates of two different cyanine dyes., This work was supported by the ETORTEK 2011–2013 project ‘nanoIKER’ from the Department of Industry of the Basque Government and by the Visiting Fellowship program of Ikerbasque Foundation.