2021, Sanchez-Iglesias, A., Grzelczak, M., Rakovich, Y., Krivenkov, V., Samokhvalov, P., Nabiev, I., Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

© 2021 The Royal Society of Chemistry.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.

2024, Granizo, E., Kriukova, I., Escudero-Villa, P., Samokhvalov, P., Nabiev, I., Гранисо Роман, Эвелин Алехандра, Крюкова, Ирина Сергеевна, Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

The combination of micro- or nanofluidics and strong light-matter coupling has gained much interest in the past decade, which has led to the development of advanced systems and devices with numerous potential applications in different fields, such as chemistry, biosensing, and material science. Strong light-matter coupling is achieved by placing a dipole (e.g., an atom or a molecule) into a confined electromagnetic field, with molecular transitions being in resonance with the field and the coupling strength exceeding the average dissipation rate. Despite intense research and encouraging results in this field, some challenges still need to be overcome, related to the fabrication of nano- and microscale optical cavities, stability, scaling up and production, sensitivity, signal-to-noise ratio, and real-time control and monitoring. The goal of this paper is to summarize recent developments in micro- and nanofluidic systems employing strong light-matter coupling. An overview of various methods and techniques used to achieve strong light-matter coupling in micro- or nanofluidic systems is presented, preceded by a brief outline of the fundamentals of strong light-matter coupling and optofluidics operating in the strong coupling regime. The potential applications of these integrated systems in sensing, optofluidics, and quantum technologies are explored. The challenges and prospects in this rapidly developing field are discussed.

2020, Krivenkov, V., Dyagileva, D., Samokhvalov, P., Nabiev, I., Rakovich, Y., Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimEfficient 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.

2020, Efimov, A. E., Agapova, O. I., Agapov, I. I., Korostylev, E., Nifontova, G., Krivenkov, V., Zvaigzne, M., Samokhvalov, P., Nabiev, I., Нифонтова, Галина Олеговна, Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

The layer-by-layer (LbL) deposition approach allows combined incorporation of fluorescent, magnetic, and plasmonic nanoparticles into the shell of polyelectrolyte microcapsules to obtain stimulus-responsive systems whose imaging and drug release functions can be triggered by external stimuli. The combined use of fluorescent quantum dots (QDs) and magnetic nanoparticles (MNPs) yields magnetic-field-driven imaging tools that can be tracked and imaged even deep in tissue when the appropriate type of QDs and wavelength of their excitation are used. QDs are excellent photonic labels for microcapsule encoding due to their close-to-unity photoluminescence (PL) quantum yields, narrow PL emission bands, and tremendous one- and two-photon extinction coefficients. However, the presence of MNPs and electrically charged polyelectrolyte molecules used for the LbL fabrication of magneto-optical microcapsules provokes alterations of the QD optical properties because of the photoinduced charge and energy transfer resulting in QD photodarkening or photobrightening. These lead to variation of the microcapsule PL signal under illumination, which hampers their tracking and quantitative analysis in cells and tissues. Here, we have studied the effects of the structure and spatial arrangement of the nanoparticles within the microcapsule polyelectrolyte shell, the total shell thickness, and the shell surface charge on their PL properties under continuous illumination. The roles of the charge transfer and its main driving forces in the stability of the microcapsules PL signal have been established, and the design of the microcapsules dually encoded with QDs and MNPs providing the strongest and most stable PL has been determined. Controlling the energy transfer from the QDs and MNPs and the charge transfer from QDs to polyelectrolyte layers in the engineering of magneto-optical microcapsules with a bright and stable PL signal extends their applications to long-lasting quantitative fluorescence imaging.

2020, Rakovich, Y. P., Krivenkov, V., Samokhvalov, P., Nabiev, I., Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

Reliable control of spontaneous radiation from quantum emitters, such as quantum dots (QDs), is an extremely important problem in quantum science, nanophotonics, and engineering. The QD photoluminescence (PL) may be enhanced near plasmon nanoparticles because of excitation field enhancement or the Purcell effect. However, both of these effects have their specific limitations. The excitation enhancement is usually accompanied by a decrease in the PL quantum yield (QY) due to the plasmon-induced energy transfer, and the Purcell effect cannot significantly enhance the PL of QDs with an initially high QY because of the obvious limitation of the QY by the value of 100%. Here, we have shown that the synergistic combination of excitation enhancement caused by silver nanospheres and the Purcell effect caused by silver nanoplates in the same QD-in-polymer hybrid thin-film nanostructure permits simultaneous increases in the radiative and excitation rates to be obtained. This overcomes the limitations of each individual effect and yields a synergistic PL increase (+1320%) greater than the sum of the PL enhancements determined by each effect alone (+70% and +360%).

2020, Il'gach, D., Yakimansky, A., Zvaigzne, M., Domanina, I., Nabiev, I., Samokhvalov, P., Набиев, Игорь Руфаилович, Самохвалов, Павел Сергеевич

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Colloidal quantum dots (QDs) are a promising luminescent material for the development of next generation hybrid light-emitting diodes (QDLEDs). In particular, QDs are of great interest in terms of the development of solid-state light sources with an emission spectrum that mimics daylight. In this study, we used CdSe(core)/ZnS/CdS/ZnS(shell) QDs with organic ligands mimicking polyfluorene and its modified derivatives to obtain QD–polymer composites emitting white light. We found that the emission of the composites obtained by spin-coating, being strongly dependent on the chemical structure of the polymer matrix and the QD-to-polymer mass ratio, can be accurately controlled and adjusted to bring its emission spectrum close to the spectrum of daylight (CIE coordinates: 1931 0.307; 0.376). Moreover, the light emission of these composites has been found to be temporally stable, which is due to the minimal structural instability and volume-uniform charge and energy transfer properties. Thus, the use of the synthesized polyfluorene-based organic ligands with controllable chemical structures adaptable to the structure of the polymer matrix can significantly increase the stability of white light emission from QD composites, which can be considered promising electroluminescent materials for fabrication of white QDLEDs.

2020, Dovzhenko, D., Martynov, I., Samokhvalov, P., Osipov, E., Lednev, M., Chistyakov, A., Nabiev, I., Мартынов, Игорь Леонидович, Самохвалов, Павел Сергеевич, Осипов, Евгений Валерьевич, Чистяков, Александр Александрович, Набиев, Игорь Руфаилович

Controlling spontaneous emission by modifying the local electromagnetic environment is of great interest for applications in optoelectronics, biosensing and energy harvesting. Although the development of devices based on one-dimensional porous silicon photonic crystals with embedded luminophores is a promising approach for applications, the efficiency of the embedded luminophores remains a key challenge because of the strong quenching of the emission due to the contact of the luminophores with the surface of porous silicon preventing the observation of interesting light-matter coupling effects. Here, we experimentally demonstrate an increase in the quantum dot (QD) spontaneous emission rate inside a porous silicon microcavity and almost an order of magnitude enhancement of QD photoluminescence intensity in the weak light-matter coupling regime. Furthermore, we have demonstrated drastic alteration of the QD spontaneous emission at the edge of the photonic band gap in porous silicon distributed Bragg reflectors and proved its dependence on the change in the density of photonic states. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

2020, Alexandrov, A., Zvaigzne, M. A., Lypenko, D., Nabiev, I., Samokhvalov, P., Лыпенко, Дмитрий Александрович, Набиев, Игорь Руфаилович, Самохвалов, Павел Сергеевич

© 2020, The Author(s).Colloidal quantum dots and other semiconductor nanocrystals are essential components of next-generation lighting and display devices. Due to their easily tunable and narrow emission band and near-unity fluorescence quantum yield, they allow cost-efficient fabrication of bright, pure-color and wide-gamut light emitting diodes (LEDs) and displays. A critical improvement in the quantum dot LED (QLED) technology was achieved when zinc oxide nanoparticles (NPs) were first introduced as an electron transport layer (ETL) material, which tremendously enhanced the device brightness and current efficiency due to the high mobility of electrons in ZnO and favorable alignment of its energy bands. During the next decade, the strategy of ZnO NP doping allowed the fabrication of QLEDs with a brightness of about 200 000 cd/m2 and current efficiency over 60 cd/A. On the other hand, the known ZnO doping approaches rely on a very fine tuning of the energy levels of the ZnO NP conduction band minimum; hence, selection of the appropriate dopant that would ensure the best device characteristics is often ambiguous. Here we address this problem via detailed comparison of QLEDs whose ETLs are formed by a set of ZnO NPs doped with Al, Ga, Mg, or Li. Although magnesium-doped ZnO NPs are the most common ETL material used in recently designed QLEDs, our experiments have shown that their aluminum-doped counterparts ensure better device performance in terms of brightness, current efficiency and turn-on voltage. These findings allow us to suggest ZnO NPs doped with Al as the best ETL material to be used in future QLEDs.

2020, Karaulov, A., Krivenkov, V., Samokhvalov, P., Dyagileva, D., Nabiev, I., Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

© 2020 American Chemical Society.Conventional approaches to the determination of the two-photon absorption cross-section (TPACS) of fluorescent semiconductor nanocrystals, including quantum dots (QDs) and nanoplatelets (NPLs), cannot be applied to samples with unknown concentrations and low optical densities and may be inaccurate in the case of multiexciton nanocrystal excitation. Here, we have studied the two-photon-excited photoluminescence saturation in QD and NPL samples and propose a novel technique for determining of their TPACS from the parameters of this process. The technique allows the measurement of the TPACSs of single exciton states in the samples of unknown concentration, as well as in thin films with ultralow optical densities. The calculated values agreed with the results obtained by conventional methods. The new technique paves new ways to studying small amounts of fluorescent nanocrystals of unknown quantity under two-photon excitation.

2020, Dovzhenko, D., Krivenkov, V., Kriukova, I., Samokhvalov, P., Nabiev, I., Крюкова, Ирина Сергеевна, Самохвалов, Павел Сергеевич, Набиев, Игорь Руфаилович

Photoluminescence (PL)-based sensing techniques have been significantly developed in practice due to their key advantages in terms of sensitivity and versatility of the approach. Recently, various nanostructured and hybrid materials have been used to improve the PL quantum yield and the spectral resolution. The near-infrared (NIR) fluorescence excitation has attracted much attention because it offers deep tissue penetration and it avoids the autofluorescence of the biological samples. In our study, we have shown both spectral and temporal PL modifications under two-photon excitation of quantum dots (QDs) placed in one-dimensional porous silicon photonic crystal (PhC) microcavities. We have demonstrated an up-to-4.3-fold Purcell enhancement of the radiative relaxation rate under two-photon excitation. The data show that the use of porous silicon PhC microcavities operating in the weak coupling regime permits the enhancement of the PL quantum yield of QDs under two-photon excitation, thus extending the limits of their biosensing applications in the NIR region of the optical spectrum. (C) 2020 Optical Society of America