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Discerning the kinetics of photoluminescence (PL) decay of packed quantum dots (QDs) and QD-based hybrid materials is of crucial importance for achieving their promising potential. However, the interpretation of the decay kinetics of QD-based systems, which usually are not single-exponential, remains challenging. Here, we present a method for analyzing photoluminescence (PL) decay curves of fluorophores by studying their statistical moments. A certain combination of such moments, named as the n-th order moments’ ratio, Rn, is studied for several theoretical decay curves and experimental PL kinetics of CdSe quantum dots (QDs) acquired by time-correlated single photon counting (TCSPC). For the latter, three different case studies using the Rn ratio analysis are presented, namely, (i) the effect of the inorganic shell composition and thickness of the core–shell QDs, (ii) QD systems with Förster resonance energy transfer (FRET) decay channels, and (iii) system of QDs near a layer of plasmonic nanoparticles. The proposed method is shown to be efficient for the detection of slight changes in the PL kinetics, being time-efficient and requiring low computing power for performing the analysis. It can also be a powerful tool to identify the most appropriate physically meaningful theoretical decay function, which best describes the systems under study., Funding from the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2020 is acknowledged. V.K. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement 101025664 (QESPEM). Y.P.R. acknowledges funding from the Basque Government for Consolidated groups of the Basque University (Grant IT 1526-22) and Basic and/or Applied Research Projects (Grant PIBA-2021-0026). Part of this work dealing with the synthesis of CdSe/ZnS and CdSe/ZnS/CdS/ZnS quantum dots was supported by the Russian Science Foundation (Grant 18-19-00588).

Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal–polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity., This work was supported by grant PID2019-111772RB-I00 funded by MCIN/AEI/10.13039/501100011033 and grant IT 1254-19 funded by Basque Government. The authors acknowledge the financial support of the European Commission (EUSMI, Grant 731019). S.B. is grateful to the European Research Council (ERC-CoG-2019 815128).

Polariton emission from optical cavities integrated with various luminophores has been extensively studied recently due to the wide variety of possible applications in photonics, particularly promising in terms of fabrication of low-threshold sources of coherent emission. Tuneable microcavities allow extensive investigation of the photophysical properties of matter placed inside the cavity by deterministically changing the coupling strength and controllable switching from weak to strong and ultra-strong coupling regimes. Here we demonstrate room temperature strong coupling of exciton transitions in CdSe/ZnS/CdS/ZnS colloidal quantum dots with the optical modes of a tuneable low-mode-volume microcavity. Strong coupling is evidenced by a large Rabi splitting of the photoluminescence spectra depending on the detuning of the microcavity. A coupling strength of 154 meV has been achieved. High quantum yields, excellent photostability, and scalability of fabrication of QDs paves the way to practical applications of coupled systems based on colloidal QDs in photonics, optoelectronics, and sensing., Comment: 14 pages, 3 figures

The interaction of several components in the strong coupling regime yielding multiple Rabi splittings opens up remarkable possibilities for studies of multimode hybridization and energy transfer, which is of considerable interest in both fundamental and applied science. Here we demonstrate that three different components, such as core−shell Au@Ag nanorods and J-aggregates of two different dyes, can be integrated into a single hybrid structure, which leads to strong collective exciton− plasmon coupling and double-mode Rabi splitting totaling 338 meV. We demonstrate strong coupling in these multicomponent plexitonic nanostructures by means of magnetic circular dichroism spectroscopy and demonstrate strong magneto-optical activity for the three hybridized states resulting from this coupling. The J-aggregates of two different nonmagnetic dyes interact with metal nanoparticles effectively, achieving magnetic properties due to the hybridization of electronic excitations in the threecomponent system., This work was supported by MINECO (Ministerio de Economiá y Competitividad), Spain, Projects FIS2016-80174-P (PLASMOQUANTA) and MAT2017-86659-R (MULTIMAGE). I.R.N. and Y.P.R. acknowledge support from the Ministry of Education and Science of the Russian Federation under Grant No. 14.Y26.31.0011 and funding from the Basque Government (Grant No. IT1164-19). This work was coordinated under the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency (Grant No. MDM-2017-0720).

Triethanolamine is a widely used model electron donor that enables a fast screening of the photocatalyst parameters in both, homogeneous and heterogeneous scenarios. We report a new role of triethanolamine in heterogeneous photoregeneration of cofactor molecules – nicotinamide adenine dinucleotide (NADH) – using state-of-the-art heterogeneous photocatalysts. In contrast to the common model involving the light-induced electrons and holes generation to reduce the substrate and oxidize triethanolamine simultaneously, we identified glycolaldehyde as a stable product of triethanolamine degradation capable of reducing NAD+. Triethanolamine, apart from playing a role of a precursor for reducing agent, maintains the alkalinity of the solution to drive the reduction. Our findings offer a fresh insight into the triethanolamine-assisted photocatalysis because glycolaldehyde as such have generally been neglected in mechanistic considerations. Moreover, a spatial and temporal decoupling of the photocatalyst from the substrate reduction reaction minimizes the product re-oxidation, thus implying a relevant feature for the real-world applications using a continuous flow setting., F. V. would like to thank ScotChem for the financial support. Y. R. would like to thank The Ministry of Education and Science of the Russian Federation (grant no. 14.Y26.31.0011).

Resonant interaction between excitonic transitions of molecules and localized electromagnetic field allows the formation of hybrid light–matter polaritonic states. This hybridization of the light and the matter states has been shown to significantly alter the intrinsic properties of molecular ensembles placed inside the optical cavity. Here, we have observed strong coupling of excitonic transition in a pair of closely located organic dye molecules demonstrating an efficient donor-to-acceptor resonance energy transfer with the mode of a tuneable open-access cavity. Analysing the dependence of the relaxation pathways between energy states in this system on the cavity detuning, we have demonstrated that predominant strong coupling of the cavity photon to the exciton transition in the donor dye molecule can lead not only to an increase in the donor–acceptor energy transfer, but also to an energy shift large enough to cause inversion between the energy states of the acceptor and the mainly donor lower polariton energy state. Furthermore, we have shown that the polariton-assisted donor–acceptor chromophores' role reversal or “carnival effect” not only changes the relative energy levels of the donor–acceptor pair, but also makes it possible to manipulate the energy flow in the systems with resonant dipole–dipole interaction and direct energy transfer from the acceptor to the mainly donor lower polariton state. Our experimental data are the first confirmation of the theoretically predicted possibility of polariton-assisted energy transfer reversal in FRET systems, thus paving the way to new avenues in FRET-imaging, remote-controlled chemistry, and all-optical switching., This study was supported by the Ministry of Education and Science of the Russian Federation (grant no. 14.Y26.31.0011). I. N. acknowledges the support from the Ministry of Higher Education, Research and Innovation of the French Republic and the University of Reims Champagne-Ardenne. The part of the work devoted to the microresonator development and adaptation was supported by the Russian Science Foundation (grant no. 21-79-30048). Y. R. acknowledges the support from the Basque Government (grant no. IT1164-19).

Excitons in semiconductor quantum dots (QDs) feature high values of the two-photon absorption cross-sections (TPACSs), enabling applications of two-photon-excited photoluminescence (TPE PL) of QDs in biosensing and nonlinear optoelectronics. However, efficient TPE PL of QDs requires high-intensity laser fields, which limits these applications. There are two possible ways to increase the TPE PL of QDs: by increasing their photoluminescence quantum yield (PLQY) or by further increasing the TPACS. Plasmonic nanoparticles (PNPs) may act as open nanocavities for increasing the PLQY via the Purcell effect, but this enhancement is strictly limited by the maximum possible PLQY value of 100%. Here we directly investigated the effect of PNPs on the effective TPACS of excitons in QDs. We have found that effective TPACS of excitons in a QD–PMMA thin film can be increased by a factor of up to 12 near the linearly excited gold nanorods (GNRs). Using gold nanospheres (GNSs), in which plasmons cannot be excited in the infrared range, as a control system, we have shown that, although both GNSs and GNRs increase the recombination rate of excitons, the TPACS is increased only in the case of GNRs. We believe that the observed effect of TPACS enhancement is a result of the nonlinear interaction of the plasmons in GNRs with excitons in QDs, which we have supported by numerical simulations. The results show the way to the rational design of the spectral features of plasmon–exciton hybrids for using them in biosensing and nonlinear optoelectronics., V. K. acknowledges support from the Russian Science Foundation (Grant No. 18-72-10143) for the part of the study related to the investigation of the effects of PNPs on the effective TPACS of excitons in QDs and numerical simulations of these effects. Support from the Ministry of Education and Science of the Russian Federation (Grant No. 14.Y26.31.0011) for the part of this study related to the synthesis and functionalisation of the QDs and engineering of hybrid QD-GNR materials is also acknowledged. Y. R. acknowledges the support from the Basque Government (grant no. IT1164-19). Y. R. and M. G. acknowledge the support from the Spanish MINECO (PID2019-111772RB-I00). I. N. acknowledges the Ministry of Higher Education, Research and Innovation of the French Republic and Université de Reims Champagne-Ardenne.

Strong exciton–plasmon interaction enables effective control of the photonic properties of hybrid organic–inorganic nanostructures encompassing light absorption, scattering and luminescence. Whereas the manifestations of light-matter interactions in the absorption and scattering are reasonably well understood their relation to the luminescence as well as luminescence properties themselves in strongly coupled plexcitonic hybrids is still largely underexplored especially for a system with a complex mechanism of hybridisation of states. Here we report on investigation of the interaction between localized and hybridized plasmons in gold nanostars and excitons in J-aggregates under ambient conditions. Our findings demonstrate the quality performance of the formed plexciton system with multiple hybridization channels in terms of the parameters of strong coupling, such as Rabi splitting (230 meV), coupling-strength-to-transition energy ratio (0.07), and cooperativity (2.03). The results of time-resolved experiments elucidate the observed enhanced spontaneous emission rate with regard to the Purcell effect, whose value was estimated from the extinction spectra of the strongly coupled plexciton system., Financial supports from Projects PID2019-111772RB-I00 of the Spanish MINECO and the Ministry of Science and Higher Education of the Russian Federation (Grant No. 14.Y26.31.0011) are acknowledged. Y. R. acknowledges the support from the Basque Government (grant no. IT1164-19). P.S. and I.N acknowledge support from the Russian Science Foundation (grant no. 21-79-30048) of the part of this work related to nanomaterials manufacturing and functionalisation. I.N. acknowledges support from the Université de Reims Champagne-Ardenne. A.S.-I. acknowledges the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency (Grant No. MDM-2017-0720).

Semiconductor quantum dots (QDs) are widely used in photovoltaic and optoelectronic devices due to their unique optical properties. Photoluminescence (PL) properties of QDs can be significantly improved by their electromagnetic coupling with plasmonic nanoparticles (PNPs). The excitation of resonant localized plasmon modes leads to the enhancement of the density of photon states and increase of electromagnetic field near the surface of PNPs, what boosts the acceleration of the exciton radiative decay, known as the Purcell effect. To study the dependence of the degree of acceleration of radiative decay rate (Purcell factor) on the distance between QDs and PNPs, we fabricated thin-film hybrid structures based on CdSe(core)/ZnS/CdS/ZnS(multishell) QDs and silver or gold PNPs with a controllable distance between these components. The change in the radiative decay rate of excitons was calculated from the PL intensities and lifetimes before and after the deposition of PNPs on top of the QD thin film covered by a poly(methyl methacrylate) (PMMA) spacer. For both PNP types, the PL lifetime of underlying QDs decreased, whereas the PL intensity of the latter decreased only slightly for gold PNPs and even increased for silver PNPs. This indicates the acceleration of QDs radiative decay (Purcell effect) mediated by exciton-plasmon interaction. The Purcell factor was higher for silver PNPs than that for gold PNPs, what can be explained by the better spectral overlap between the QDs PL band and silver PNPs absorbance and the absence of interband absorption in silver at the wavelength of QDs PL. The results of this study provide better understanding of the Purcell effects in hybrid materials based on QDs and PNPs.

Enhancement of the photoluminescence signal intensity from organic and inorganic fluorophores increases the sensitivity of operation of optical sensors, detectors, and photonic diagnostic assays. Here, we have engineered and compared optical and fluorescence-enhancing properties of two types of one-dimensional porous silicon photonic crystals: a transfer-printed microcavity based on the freestanding photonic crystal and a conventional “one-piece” microcavity created on a monocrystalline silicon substrate. Comparative analysis of the eigenmodes and the photonic bandgaps of both types of microcavities demonstrated a high quality of transfer-printed microcavities and good correlation of their reflection spectra with the spectra of “one-piece” microcavities. Moreover, embedding of a highly concentrated solution of quantum dots (QDs) in the eigenmode localization region of transfer-printed microcavity was followed by three-fold reduction of the full-width-at-half-maximum of their luminescence spectrum at the microcavity eigenmode wavelength, thus confirming a weak coupling regime of QD exciton and microcavity eigenmode interaction and significant enhancement of QD luminescence within the microcavity.

Today, lots of research address the phenomenon of interaction between light and matter. In particular, it is of a special interest to investigate light–matter interaction in one-dimensional resonators based on porous materials. In this case, one can embed emitting semiconductor particles into the porous resonator, where the excitons of these particles couple to the resonator eigenmode and luminescence intensity of the emitters is enhanced, allowing an increase in the sensitivity of optical sensors, detectors, and photonic diagnostic assays. A particular challenge is to place the emitters directly in the antinode region of the resonator eigenmode in order to maximize the coupling strength, which is sometimes a problem due to the spatial distribution of emitters away from the eigenmode localization region. Here, we have shown that the transfer-printing technique can be used to obtain structures based on freestanding porous silicon photonic crystals capable of precisely controlling the emitter spatial distribution about the eigenmode localization region. This, as well as the porosity of these structures and high adsorption capacity of porous silicon, allows the light–matter interaction in these hybrid structures to be used in sensing applications. We have shown that the transfer-printing method does not worsen the optical properties of the microcavities compared to the conventional electrochemical etching of the whole microcavity at a time. Furthermore, we have observed slightly better coupling of the exciton of the emitter to the eigenmode of the transfer-printed microcavity in the weak coupling regime.

Efficient biexciton (BX) photoluminescence (PL) from quantum dots (QDs) paves the way to the generation of entangled photons and related applications. However, the quantum yield (QY) of BX PL is much lower than that for single excitons (EX) due to efficient Auger-like recombination. In the vicinity of plasmon nanoparticles, the recombination rates of EX and BX may be affected by the Purcell effect, fluorescence quenching, and the excitation rate enhancement. Here, the effect of the plasmon resonance spectral position on the EX and BX PL is experimentally studied in two cases: when the plasmon band overlaps with the excitation wavelength and when it coincides with the QDs PL band. In the first case, the EX and BX excitation efficiencies are significantly increased but the EX QY reduced. As a result, the BX-to-EX QY ratio is higher than 1 at plasmon–exciton systems separations shorter than 40 nm. In the second case, the radiative recombination rates are enhanced by several orders of magnitude, which led to an increase in BX QY over distances of up to 90 nm. Finally, these two effects are obtained in the same hybrid structure, with the resultant increase in both excitation efficiency and QY of BX PL., They also acknowledge the financial support from theMinistry of Science and Higher Education of the Russian Federation (Grant Number: 14.Y26.31.0011) . Y.R. acknowledges the support from the Basque Government (IT1164‐19)

Hybridized plexcitonic states have unique properties which have been widely studied in recent decades in many research fields targeted at both fundamental science and innovative applications. However, to make these applications come true one needs to ensure the stabilization and preservation of electronic states and optical transitions in hybrid nanostructures, especially under the influence of external stressors, in regimes, that have not yet been comprehensively investigated. The present work shows that the nanohybrid system, composed of plasmonic nanoparticles and J-aggregates of organic molecules, displays outstanding resistance to harsh environmental stressors such as temperature, pH and strong light irradiation as well as demonstrates long-term stability and processability of the nanostructures both in weak and strong coupling regimes. These findings contribute to a deeper understanding of the physicochemical properties of plexcitonic nanoparticles and may find important implications for the development of potential applications in optoelectronics, optical imaging and chemo-bio-sensing and, in general, in the field of optical materials science., Authors acknowledge the financial support from the Ministry of Education and Science of the Russian Federation (grant no. 14.Y26.31.0011). Y. R. acknowledges the support from the Basque Government (grant no. IT1164-19). M. G. acknowledges support from the Basque Government (PIBA 2018-34), and Diputación Foral de Guipúzcoa (RED 2018, RED 2019). A. S. I. acknowledges the Maria de Maeztu Units of Excellence Programme – Grant No. MDM-2017-0720 Ministry of Science, Innovation and Universities.

International audience; Resonance interaction between a molecular transition and a confined electromagnetic field can reach the coupling regime where coherent exchange of energy between light and matter becomes reversible. In this case, two new hybrid states separated in energy are formed instead of independent eigenstates, which is known as Rabi splitting. This modification of the energy spectra of the system offers new possibilities for controlled impact on various fundamental properties of coupled matter (such as the rate of chemical reactions and the conductivity of organic semiconductors). To date, the strong coupling regime has been demonstrated in many configurations under different ambient conditions. However, there is still no comprehensive approach to determining parameters for achieving the strong coupling regime for a wide range of practical applications. In this review, a detailed analysis of various systems and corresponding conditions for reaching strong coupling is carried out and their advantages and disadvantages, as well as the prospects for application, are considered. The review also summarizes recent experiments in which the strong coupling regime has led to new interesting results, such as the possibility of collective strong coupling between X-rays and matter excitation in a periodic array of Fe isotopes, which extends the applications of quantum optics; a strong amplification of the Raman scattering signal from a coupled system, which can be used in surface-enhanced and tip-enhanced Raman spectroscopy; and more efficient second-harmonic generation from the low polaritonic state, which is promising for nonlinear optics. The results reviewed demonstrate great potential for further practical applications of strong coupling in the fields of photonics (low-threshold lasers), quantum communications (switches), and biophysics (molecular fingerprinting).

Plasmonic nanoparticles (PNPs) can significantly modify the optical properties of nearby organic molecules and thus present an attractive opportunity for sensing applications. However, the utilization of PNPs in conventional absorption, fluorescence, or Raman spectroscopy techniques is often ineffective due to strong absorption background and light scattering, particularly in the case of turbid solutions, cell suspensions, and biological tissues. Here we show that nonmagnetic organic molecules may exhibit magneto-optical response due to binding to a PNP. Specifically, we detect strong magnetic circular dichroism signal from supramolecular J-aggregates, a representative organic dye, upon binding to silver-coated gold nanorods. We explain this effect by strong coupling between the J-aggregate exciton and the nanoparticle plasmon, leading to the formation of a hybrid state in which the exciton effectively acquires magnetic properties from the plasmon. Our findings are fully corroborated by theoretical modeling and constitute a novel magnetic method for chemo- and biosensing, which (upon adequate PNP functionalization) is intrinsically insensitive to the organic background and thus offers a significant advantage over conventional spectroscopy techniques., We acknowledge financial support from Project Fis2016.80174-P (PLASMOQUANTA) from MINECO (Ministerio de Economia y Competitividad). L.L.-M. acknowledges funding from the European Research Council (ERC Advanced Grant 267867, Plasmaquo).

Studies of resonance interaction between matter and localized electromagnetic field in a cavity have recently attracted much interest because they offer the possibility of controllably modifying some of the fundamental material properties. However, despite the large number of such studies, these is no universal approach that would allow investigation of sets of different samples with wide variation of the main experimental parameters of the optical modes. In this work, the main optical parameters of a previously developed universal tunable microcavity cell, i.e., the Q factor and mode volume, as well as their dependence on the characteristics of cavity mirrors and spacing between them, are analyzed. The results obtained will significantly expand the scope of applications of resonance interaction between light and matter, including such effects as the enhancement of Raman scattering, long-range resonance nonradiative energy transfer, and modification of chemical reaction rates., This work was supported by the Ministry of Science and Higher Education of the Russian Federation,contract no. 4.Y26.31.0011.

Semiconductor quantum dots (QDs) are known for their ability to exhibit multiphoton emission caused by recombination of biexcitons (BX). However, the quantum yield (QY) of BX emission is low due to the fast Auger process. Plasmonic nanoparticles (PNPs) provide an attractive opportunity to accelerate BX radiative recombination. Here, we demonstrate the PNPs induced distance-controlled enhancement of BX emission of single QDs. Studying the same single QD before and after its integration with the PNPs, we observed a plasmon-mediated increase in the QY of BX emission. Remarkably, the enhancement of BX emission remains pronounced even at distances of 170 nm. We attribute this effect to efficient coupling, which results in the trade-off between resonance energy transfer from QD to gold nanorods and the Purcell effect at small QD-PNP separations and the predominant influence of the Purcell effect at longer distances. Our findings constitute a reliable approach to managing the efficiency of multiexciton emission over a wide span of distances, thus paving the way for new applications., The authors acknowledge the financial support from the Ministry of Education and Science of the Russian Federation (Grant 14.Y26.31.0011). Y.R. acknowledges support from MINECO (Ministerio de Economiá y Competitividad, Spain), Project Fis2016.80174-P (PLASMOQUANTA).

Light-matter coupling between the molecular dipole transitions and a confined electromagnetic field provides the ability to control the fundamental properties of coupled matter. The use of tunable optical microcavities for electromagnetic field confinement allows one to affect the coupled state properties in a controllable manner, whereas the coupling strength in this system strongly depends on the transition dipole moment and a mode volume of the cavity. In this study we have demonstrated controllable emission of Rhodamine 6G organic molecules with relatively low and unoriented dipole moments in a strong coupling regime by placing them into a tunable Fabry-Perot microcavity.

Resonance interaction between a localized electromagnetic field and excited states in molecules paves the way to control fundamental properties of a matter. In this study, we encapsulated organic molecules with relatively low unoriented dipole moments in the polymer matrix, placed them in tunable optical microcavity and realized, for the first time, controllable modification of the broad photoluminescence (PL) emission of these molecules in strong coupling regime at room temperature. Notably, while in most previous studies it was reported that the single mode dominates in the PL signal (radiation of the so-called branch of the lower polariton), here we report on the observation of two distinct PL peaks, evolution of which has been followed as the microcavity mode is detuned from the excitonic resonance. A significant Rabi splitting estimated from the modified PL spectra was as large as 225 meV. The developed approach can be used both in fundamental research of resonant light-mater coupling and its practical applications in sensing and development of coherent spontaneous emission sources using a combination of carefully designed microcavity with a wide variety of organic molecules., Ministry of Education and Science of the Russian Federation (14.Y26.31.0011); Ministerio de Economiá y Competitividad (FIS2016.80174-P, PLASMOQUANTA).

Semiconductor quantum dots (QDs) are known for their unique photophysical properties and, in particular, their ability to multiphoton emission caused by recombination of biexcitons. However, the luminescence quantum yield of biexciton states is relatively low due to the fast Auger non-radiative process. Plasmonic nanoparticles can significantly accelerate the radiative rate of QDs. In this study we demonstrate the distance-controlled enhancement of the biexciton emission of single CdSe/ZnS/CdS/ZnS QDs due to their coupling with gold nanorods. We explain this enhancement as the distancedependent trade-off between the energy transfer and the Purcell effect. Our findings constitute a reliable approach to managing the efficiency of multiphoton emission over a wide span of distances.

Semiconductor quantum dots (QDs) have been demonstrated to be a promising material for developing innovative optoelectronic systems and lasers. The strong and weak coupling effects between localized plasmons in noble metal nanoparticles and excitons in QDs can modulate photoluminescence properties of the latter, scaling up their applications. In particular, these effects can strongly affect the photoluminescence (PL) lifetime of QDs, opening prospects for significantly increasing the quantum yield of the biexciton emission in single QD. Here, we provide а convincing proof of the formation of many-exciton states in hybrid material based on CdSe/ZnS/CdS/ZnS core/multishell QDs and gold nanorods (NRs) embedded in thin films of PMMA. The presence of NRs causes at least an order-of-magnitude decrease in the PL lifetimes of single QD. The obtained results have demonstrated the possibility of detecting biexciton states in QDs as the main component of emission of the hybrid QD-NR material., We acknowledge the support of grant no. 14.Y26.31.0011 of the Ministry of Education and Science of the Russian Federation. Y.R. acknowledges support from project Fis2016.80174-P (PLAS-MOQUANTA) from MINECO (Ministerio de Economiá y Competitividad), Spain.

Semiconductor quantum dots (QDs) are widely used as components of hybrid materials for development of efficient light emitters and convertors. Their unique nonlinear optical properties, such as two-photon absorption and two-photon photoluminescence from biexcitons, make them promising materials for photovoltaic and optoelectronic applications. In this study, thin-film hybrid materials based on the CdSe(core)/ZnS/CdS/ZnS(multishell) QDs have been fabricated, and the two-photon photoluminescence (PL) from the generated biexcitons have been studied. The results show that fabricated thin-film hybrid materials based on the QDs are efficient fluorophores in the one- and two-photon PL regimes for applications in optoelectronics and biosensing.

The light-matter interaction between a molecule and confined electromagnetic field is of great interest because it allows tuning the energy states and the spectral properties of the coupled matter. This effect offers a great number of applications in many areas, such as nonlinear physics, biosensing and lasing. The most widely used approach to achieve light-matter coupling is to place an ensemble of molecules inside an optical cavity. In order to maximize the effects of interaction, it is necessary to model the spectral properties of the cavity in order to find the optimal parameters for the experiments. In this study, the model for the numerical calculation of the spectral and spatial properties of electromagnetic modes of a tunable microcavity was developed and a mode analysis has been performed. The cavity transmission spectra and the electromagnetic field distribution were investigated. The results showed a good agreement with the experimental data obtained earlier.

An understanding of the mechanisms of energy transfer and conversion on the nanoscale is one of the key requirements for an implementation of highly efficient photonic nanodevices based on hybrid organic/inorganic nanomaterials. In this work we conduct steady-state and time resolved optical studies of the emission properties of an ensembles and single semiconductor quantum dots and attached organic dye molecules. We revealed that the luminescence intensity of a hybrid structure does not follow the blinking behavior of quantum dots. We also demonstrated an efficient single photon generation from single hybrid nanostructures which involves an energy transfer from donor to acceptor as main excitation source., This work was supported by the Ministry of Education and Science of the Russian Federation under grant no. 14.Y26.31.0011. Y. R. and T. H. acknowledges support from Project Fis2016.80174-P (PLASMOQUANTA) from MINECO (Ministerio de Economiá y Competitividad), Spain.

Single crystal needle-like diamonds shaped as rectangular pyramids were produced by combination of chemical vapor deposition and selective oxidation with dimensions and geometrical characteristics depending on the deposition process parameters. Photoluminescence spectra and their dependencies on wavelength of excitation radiation reveal presence of nitrogen- and silicon-vacancy color centers in the diamond crystallites. Photoluminescence spectra, intensity mapping, and fluorescence lifetime imaging microscopy indicate that silicon-vacancy centers are concentrated at the crystallites apex while nitrogen-vacancy centers are distributed over the whole crystallite. Dependence of the photoluminescence on excitation radiation intensity demonstrates saturation and allows estimation of the color centers density. The combination of structural parameters, geometry and photoluminescent characteristics are prospective for advantageous applications of these diamond crystallites in quantum information processing and optical sensing., Authors are grateful for financial support from Russian Federation President Program for young scientist: Grant# МК-9230.2016.2 (for EAO and FTT) and Grant# MK-5860.2016.2 (for KGK).

Based on analogy between quantum mechanics and the classical electrodynamics, we sorted dielectric microspheres with almost identical positions of their whispering gallery mode (WGM) resonances as photonic atoms. Such microspheres were assembled in a wide range of structures including linear chains and planar photonic molecules. We studied WGM hybridization effects in such structures using side coupling by tapered microfibers as well as finite difference time domain modeling. We demonstrated that the patterns of WGM spectral splitting are representative of the symmetry, number of constituting atoms and topology of the photonic molecules. Such splitting patterns can be viewed as “spectral signatures” of corresponding molecules. Excellent agreement was found between measured and calculated fiber-transmission spectra for different molecules.

Based on analogy between quantum mechanics and the classical electrodynamics, we sorted dielectric microspheres with almost identical positions of their whispering gallery mode (WGM) resonances as photonic atoms. Such microspheres were assembled in a wide range of structures including linear chains and planar photonic molecules. We studied WGM hybridization effects in such structures using side coupling by tapered microfibers as well as finite difference time domain modeling. We demonstrated potential sensing functionality as well as new ways of controlling WGM coupling constants in such molecules. Excellent agreement was found between measured and calculated fiber-transmission spectra for different molecules.

Microfluidic devices present the basis of modern life sciences and chemical information processing. To control the flow and to allow optical readout, a reliable sensor material that can be easily utilized for microfluidic systems is in demand. Here, we present a new optical readout system for pH sensing based on pH sensitive, photoluminescent glutathione capped cadmium telluride quantum dots that are covalently immobilized in a poly(acrylate) hydrogel. For an applicable pH sensing the generated hybrid material is integrated in a microfluidic sensor chip setup. The hybrid material not only allows in situ readout, but also possesses valve properties due to the swelling behavior of the poly(acrylate) hydrogel. In this work, the swelling property of the hybrid material is utilized in a microfluidic valve seat, where a valve opening process is demonstrated by a fluid flow change and in situ monitored by photoluminescence quenching. This discrete photoluminescence detection (ON/OFF) of the fluid flow change (OFF/ON) enables upcoming chemical information processing., MF and SL gratefully acknowledge the cluster of Excellence “Center for Advancing Electronics Dresden (CfAED) for financial and assistant support. AD thanks the Government of the Russian Federation (Grant 074-U01) through ITMO Post-Doctoral Fellowship and the European Social Fund (ESF) for financing within the project “ChemIT”.

Mixed aerogels from semiconductor and metal nanoparticles represent an outstanding hybrid material with exceptional properties due to two striking advantages: the creation of a huge quantity of semiconductor-metal interfaces combined with a highly porous three-dimensional nanostructured network. We present a versatile synthetic pathway towards hybrid aerogels built up by joint gelation of CdTe and noble metal nanoparticles (Au, Pd and bimetallic Au/Pd). A straightforward HO treatment inducing gel formation is developed as a more elegant alternative compared to the established photooxidation approach. The use of HO allows a reproducible, simple and mild gel formation which can be easily upscaled. The tremendous influence of the HO concentration on gelation mechanism and gelation kinetics is revealed by photoluminescence quantum yield (PLQY) determinations. Resulting gels are extensively characterized via transmission electron microscopy (TEM), scanning TEM (STEM), energy dispersive X-ray analysis (EDX) as well as photoluminescence (PL) spectroscopy and PL lifetime measurements. By varying the composition of the herein presented noble metal nanoparticles in a controlled fashion the range of semiconductor-metal hybrid aerogels is widened, which demonstrates the versatility and consistency of our approach. This synthetic flexibility grants access to a variety of different mixed hybrid aerogels which are of high significance for catalytic, sensing and photonic applications., Parts of TEM investigations have been carried out at the Leibniz-Institut für Polymerforschung Dresden e.V. Access to their TEM facility is gratefully acknowledged. AD thanks the Government of the Russian Federation (Grant 074-U01) through ITMO Post-Doctoral Fellowship.

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.

This work takes inspiration from chemistry where the spectral characteristics of the molecules are determined by hybridization of electronic states evolving from the individual atomic orbitals. Based on analogy between quantum mechanics and the classical electrodynamics, we sorted dielectric microspheres with almost identical positions of their whispering gallery mode (WGM) resonances. Using these microspheres as classical photonic atoms, we assembled them in a wide range of structures including linear chains and planar photonic molecules. We studied WGM hybridization effects in such structures using side coupling by tapered microfibers as well as finite difference time domain modeling. We demonstrated that the patterns of WGM spectral splitting are representative of the symmetry, number of constituting atoms and topology of the photonic molecules which in principle can be viewed as “spectral signatures” of various molecules. We also show new ways of controlling WGM coupling constants in such molecules. Excellent agreement was found between measured transmission spectra and spectral signatures of photonic molecules predicted by simulation., The authors gratefully acknowledge support from U.S. Army Research Office through Dr. J. T. Prater under Contract No. W911NF‐09‐1‐0450 and DURIP W911NF‐11‐1‐0406 and W911NF‐12‐1‐0538. This work was also supported by Center for Metamaterials, an NSF I/U CRC, Award No. 1068050. Also, this work was sponsored by the Air Force Research Laboratory (AFRL/RYD, AFRL/RXC) through the AMMTIAC contract with Alion Science and Technology and the MCF II contract with UES, Inc.

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.

Strong coupling of plasmons and excitons can form hybrid states, the so called “plexcitons”. Especially with molecular J-aggregated dye molecules strong interaction becomes observable even under ambient conditions. In our work we investigate the nature of plexcitonic states formed in gold nanorods coated with a cyanine dye by transient absorption spectroscopy. We demonstrate that plexcitons show tunable plasmonic and excitonic non-linear optical behaviour. Our experimental data can be explained on the basis of a simple Lorentz oscillator model. We find that both the quality factor and the coupling strength between plasmons and excitons can be optically manipulated on an ultrashort time scale. T. Simon, D. Melnikau, A. Sanchez-Iglesias, M. Grzelczak, L. Liz-Marzan, Y. Rakovich, J. Feldmann and A. Urban, Exploring the optical non-linearities of plasmon-exciton hybrid resonances in coupled colloidal nanostructures, submitted (2016)

The effect of induced transparency, which is related to photoinduced bleaching of photoabsorbers, is being intensely studied and has many applications in the field of sensing. Along with this classical effect, numerous studies on induced transparency in coupled plasmon–exciton systems, which is accompanied by the formation of hybrid states, have been recently published. The formation of a new coupled system results in various spectral modifications. For example, induced transparency manifests itself as a narrow dip in the absorption spectrum of a coupled system. This effect can be used in sensing, the feasibility of which is the main objective here, where a variety of materials and methods for obtaining the induced transparency are considered. Various morphologies and geometries of plasmonic nanoparticles are discussed as well as types of molecular absorbers to assess the most favorable combinations for the evolvement of induced transparency. The potential applications of the induced transparency effect in sensing and molecular diagnostics are summarized., The Ministry of Education and Science of the Russian Federation, grant no. 14.Y26.31.0011, supported this study. Support from the project Fis2016.80174-P (PLASMOQUANTA) from MINECO (Ministerio de Economiá y Competitividad), Spain, is also acknowledged.

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].

Strong coupling of plasmons and excitons can form hybrid states, the so-called “plexcitons”. Although plasmons have a low quality factor, the exceptionally high coupling strength with molecular aggregates, in particular J-aggregates, allows the realization of strong interaction. Despite several studies in recent years showing the formation of plexcitonic states, their nature, especially at very short times, is still insufficiently investigated. In this article, we identify the nonlinear optical behavior of plexcitons formed on gold nanorods coated with J-aggregated cyanine molecules at short times by transient absorption spectroscopy and a simple Lorentz oscillator model. We control the spectral overlap of the two resonances and analyze the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states. We demonstrate that at ultrashort time scales plexcitons show tunable plasmonic and excitonic nonlinear performance according to the hybridization model. In a first approach, we discover a way to optically manipulate the quality factor and study the effects on the coupled hybrid states. As a second approach, we find that the coupling strength can also be influenced on an ultrashort time scale in the strong coupling regime when plexcitons are excited., This work has been financially supported by the ERC Advanced Grant HYMEM and the Bavarian State Ministry of Science, Research, and Arts through “Solar Technologies Go Hybrid” (SolTech) as well as through Projects FIS2013-41184-P and MAT2013-46101-R of the Spanish Ministry of Economy and Competitiveness (MINECO).

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.

Physikalische Chemie/Elektrochemie, TU Dresden, Bergstr. 66b, 01062 Dresden, GermanyIn this work we report on the development of novel hybrid material with enhanced photodynamicproperties based on methylene blue and CdTe nanocrystals. Absorption spectroscopy, visible photo-luminescence spectroscopy and ”uorescence lifetime imaging of this system reveal ef“cient chargetransfer between nanocrystals and the methylene blue dye. Near infra-red photoluminescencemeasurements provide evidence for an increased ef“ciency of singlet oxygen production by themethylene blue dye. In vitro studies on the growth of HepG2 and HeLa cancerous cells were alsoperformed, they point towards an improvement in the cell kill ef“ciency for the methylene blue-semiconductor nanocrystals hybrid system.

In recent years the studies of electromagnetic modes in solid spherical microcavities have been of great interest both for their potential applications and fundamental optical properties. A system of coherently coupled microcavities may be called a “photonic molecule” and can be employed in the tight-binding device in order to manipulate photons in micrometer length scale. In this work we demonstrate the possibility of mode manipulation in systems of symmetric photonic molecules formed by placing several high-Q micro-spheres in contact. We observe photonic nanojets that reflect the symmetry of the photonic molecule, with 3 jets located at 120 degrees with respect to each other for the triangular photonic molecule. A benzene molecule-like structure consisting of a 7-microspheres cyclic photonic molecule shows a field emission pattern similar to the spatial distribution of the orbitals of the benzene molecule. We also present some results showing the coexistence of whispering gallery modes and photonic nanojets in the same structure.

The development of artificial photosynthetic systems that utilize solar energy is one of the most challenging goals of chemistry and material sciences. The straightforward way to construct an artificial photosynthetic device for practical solar fuel production for the practical use of solar energy is to mimic the structural and functional organization of the natural photosynthetic machinery. In photosynthetic organisms, light is initially absorbed by antenna protein–pigment complexes in which it induces an excited electronic state (exciton), and then excitons (or electron–hole pairs) are transferred by means of F rster resonance energy transfer (FRET) to specialist chlorophyll cofactors in specialized reaction centers (RCs); here, excitons dissociate into their constituent carriers which are used in chemical transformations for the synthesis of high-energy molecules that fuel the organism. An artificial device that mimics this process for solar energy conversion should include, among other components, an efficient light-harvesting antenna capable of transferring the excitation energy to the RC. Based on the principle of photosynthesis, a variety of artificial antenna systems have been developed using supramolecular chemistry in which dendrimers incorporate porphyrins or other organic fluorophores or organometallic complexes. Although efficient excitation-energy transfer was obtained in such systems, the use of organic fluorophores in light-harvesting systems is rather limited because of their narrow spectral windows for light-collecting and lack of photostability. Recently it was suggested that inorganic nanocrystals, which are able to collect light over a wide spectral window, may achieve significantly greater absorption than natural photosystems, thus enhancing and could thus be used to enhance the light-harvesting process. Simultaneously, these nanocrystals may also be very efficient in excitationenergy transfer. This has led us to contemplate the development of hybrid materials in which light energy harvested by the nanocrystals in the optical region may be transferred to the RC in order to enhance the efficiency of the photosynthetic process. The simplest and best understood photosynthetic RC is that found in purple bacteria (Rhodobacter sphaeroides, for example). Although RCs from different photosynthetic organisms vary in their structure and composition, they are always composed of complexes of pigments and proteins, and RC fromRb. sphaeroides is known to be a good model of all the photosynthetic RCs. Here, we demonstrate that photoluminescent quantum dots (QDs) of these selected photoluminescence (PL) wavelengths may be tagged with the RC of Rh. sphaeroides in such a way that FRET from the QD to the RC is realized (Figure 1). A nearly threefold increase in the rate of generation of excitons in the RC is demonstrated, and theoretical estimates predict even stronger enhancements, thus indicating that further optimization is possible. Advances in inorganic synthesis have resulted in the production of monodispersed QDs such as highly photoluminescent CdSe/ZnS core/shell and CdTe nanocrystals. The light absorption by these QDs appears as a quasicontinuous superposition of peaks with extinction coefficients orders of magnitude higher than those of organic molecules. QDs are ultrastable against photobleaching, and the quantum [*] Prof. I. Nabiev CIC NanoGUNE Consolider, 20018 San Sebastian (Spain) and EA n83798, Universit de Reims Champagne-Ardenne 51100 Reims (France) and Ikerbasque, Basque Foundation for Science 48011 Bilbao (Spain) Fax: (+34)943-574-001 E-mail: i.nabiev@nanogune.eu

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.

International audience; The occurrence of metastases is one of the main causes of death in many cancers and themain cause of death for breast cancer patients. Micrometastases of disseminated tumour cellsand circulating tumour cells are present in more than 30% of breast cancer patients withoutany clinical or even histopathological signs of metastasis. Low abundance of these cell typesin clinical diagnostic material dictates the necessity of their enrichment prior to reliabledetection. Current micrometastases detection techniques are based on immunocytochemicaland molecular methods suffering from low efficiency of tumour cells enrichment andobserver-dependent interpretation. The use of highly fluorescent semiconductor nanocrystals,also known as ‘‘quantum dots’’ and nanocrystal-encoded microbeads tagged with a widepanel of antibodies against specific tumour markers offers unique possibilities for ultra-sensitive micrometastases detection in patients’ serum and tissues. The nanoparticle-baseddiagnostics provides an opportunity for highly sensitive parallel quantification of specificproteins in a rapid and low-cost method, thereby providing a link between the primarytumour and the micrometastases for early diagnosis.

In this review, we discuss the feasibility of laser cooling of semiconductor nanocrystal quantum dots by phonon-assisted anti-Stokes photoluminescence. Taking into account recent experimental advances, in particular, the development of semiconductor nanocrystals with very high quantum yield, we analyze in detail how the various physical processes in nanocrystals might help or hinder the cooling process. Possible experimental approaches to achieve efficient optical cooling are also discussed.

We will review recent advances in the investigation of optical modes in single three-dimensional whispering-gallery microcavities and coupled microresonators. Due to the small size and high quality factor these resonators have the potential for development of single-photon emitters, nanojets, sensors and low-threshold lasers and for fundamental studies of optical matter interactions.