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Metal-organic frameworks (MOFs) are promising sacrificial templates for synthesis of carbon functional materials with a relatively high concentration of stabilized metallic species. In this work coordination polymers based on trans,trans-muconic acid and transition metals (Cu, Zn, Ni, Co) were prepared and selected as the precursors for supramolecular organization of nanocomposites. The coordination polymers and metal-containing thermolysis products obtained were characterized using a number of analytical techniques including powder X-ray diffraction, elemental analysis, thermal gravimetric analysis, scanning electron microscopy and volumetric nitrogen adsorption/desorption. This study extends the application of coordination polymers as precursors for designing of carbon materials incorporating metal nanoparticles. It is shown that appropriate choice of metal-organic precursors in solid-phase thermolysis allowed to get materials with determined morphologies.

A new experimental method for panoramic contactless determination of the laminar-turbulent transition position in a three-dimensional boundary layer is described. It is demonstrated that this method allows accurate determination of the transition region boundaries at both low and enhanced levels of free-stream turbulence.

High-contrast optical imaging is achievable using phosphorescent labels to suppress the short-lived background due to the optical backscatter and autofluorescence. However, the long-lived phosphorescence is generally incompatible with high-speed laser-scanning imaging modalities. Here, we show that upconversion nanoparticles of structure NaYF4:Yb co-doped with 8% Tm (8T-UCNP) in combination with a commercial laser-scanning multiphoton microscopy are uniquely suited for labeling biological systems to acquire high-resolution images with the enhanced contrast. In comparison with many phosphorescent labels, the 8T-UCNP emission lifetime of ∼ 15 µs affords rapid image acquisition. The high-order optical nonlinearity of the 8T-UCNP (n ≈ 4, as confirmed experimentally and theoretically) afforded pushing the resolution limit attainable with UCNPs to the diffraction-limit. The contrast enhancement was achieved by suppressing the background using (i) bandpass spectral filtering of the narrow emission peak of 8T-UCNP at 455-nm, and (ii) time-gating implemented with a time-correlated single-photon counting system that demonstrated the contrast enhancement of > 2.5-fold of polyethyleneimine-coated 8T-UCNPs taken up by human breast adenocarcinoma cells SK-BR-3. As a result, discrete 8T-UCNP nanoparticles became clearly observable in the freshly excised spleen tissue of laboratory mice 15-min post intravenous injection of an 8T-UCNP solution. The demonstrated approach paves the way for high-contrast, high-resolution, and high-speed multiphoton microscopy in challenging environments of intense autofluorescence, exogenous staining, and turbidity, as typically occur in intravital imaging.

Here we report a systematic study of all-inorganic perovskite-inspired systems based on CsxPbI2Brx alloys with x ranging from 0.95 to 4. The identified optimal non-stoichiometric composition Cs1.2PbI2Br1.2 delivered the best optoelectronic, structural and photovoltaic characteristics in combination with the improved stability. The elucidated remarkable effect of the Cs4PbI2Br4 impurity phase, serving as a reservoir of CsBr, on the photothermal stability and photovoltaic performance of CsPbI2Br perovskite films offers a new paradigm in the development of more efficient and stable all-inorganic perovskite solar cells.

This paper is devoted to an experimental investigation of the distributed receptivity of a laminar swept-wing boundary layer to unsteady freestream vortices with streamwise orientation of the vorticity vector. The experiments were performed on a model of a swept wing with a sweep angle of at fully controlled disturbance conditions with freestream vortices generated by a special disturbance source. It is found that the unsteady streamwise vortices are able to provide very efficient excitation of cross-flow instability modes without requiring the presence of any surface non-uniformities. The developed experimental approach is shown to allow us to perform a detailed quantitative investigation of the mechanism of distributed excitation of unsteady boundary-layer disturbances due to scattering of freestream vortices on natural base-flow non-uniformity. This mechanism has been studied experimentally in detail. Part 1 of the present investigation (Borodulin et al., J. Fluid Mech., vol. 908, 2021, A14) was devoted to the description of the experimental approach and the base-flow structure, the method of excitation of fully controlled streamwise-elongated freestream vortices, the results of measurements of structure of these vortices and the experimental evidence of high efficiency of the distributed vortex receptivity mechanism under study. Meanwhile, the present paper (Part 2) is devoted to: (a) theoretical background and definition of the distributed receptivity coefficients and (b) obtaining experimental quantitative characteristics of the distributed vortex receptivity including values of the corresponding receptivity coefficients for their three different definitions as functions of the disturbance frequency, spanwise wavenumber and wave propagation angle.

We studied HCl uptake by MgCl2 and sea salt over a relative humidity (RH) range from 0% to 34% at 278-313 K using a differential bead-filled flow tube coupled to a high-pressure chemical ionization mass spectrometer. The results showed that dry MgCl2 and sea salt are essentially inert to gaseous HCl with a probability of less than 10-6 . However, under humid conditions, HCl was found to be efficiently taken up by wet inorganic surfaces. The HCl uptake coefficient for MgCl2 and sea salt increased squarely with RH, reaching a value of 0.00123 and 0.00171, respectively, at 29% RH and 298 K. Such wetting behavior is even enhanced at elevated temperatures, with the coefficient reaching 0.00208 and 0.00239, respectively, at 313 K. Based on the study of the dependence of γHCl on the initial HCl concentration, we estimate γHCl as 0.012 at 24% RH at a typical HCl concentration in the troposphere. In addition, the observation of the remarkable enhancement in the OH uptake by the HCl-treated salts agrees with the results of our previous investigation, which suggested that water absorption on salts enhances γOH by lowering the surface pH. The proposed mechanism of HCl uptake by sea salt aerosol has implications for ozone production in the marine boundary layer.

Local overheating of biotissue is a critical step for biomedical applications, such as photothermal therapy, enhancement of vascular permeability, remote control of drug release, and so on. Overheating of biological tissue when exposed to light is usually realized by utilizing the materials with a high-absorption cross section (gold, silica, carbon nanoparticles, etc.). Here, we demonstrate core/shell NaYF4:Yb3+, Tm3+/NaYF4 upconversion nanoparticles (UCNPs) commonly used for bioimaging as promising near-infrared (NIR) absorbers for local overheating of biotissue. We assume that achievable temperature of tissue labeled with nanoparticles is high enough because of Yb3+ resonance absorption of NIR radiation, whereas the use of auxiliary light-absorbing materials or shells is optional for photothermal therapy. For this purpose, a computational model of tissue heating based on the energy balance equations was developed and verified with the experimentally obtained thermal-graphic maps of a mouse in response to the 975-nm laser irradiation. Labeling of biotissue with UCNPs was found to increase the local temperature up to 2°C compared to that of the non-labeled area under the laser intensity lower than 1 W/cm2. The cellular response to the UCNP-initiated hyperthermia at subcritical ablation temperatures (lower than 42°C) was demonstrated by measuring the heat shock protein overexpression. This indicates that the absorption cross section of Yb3+ in UCNPs is relatively large, and microscopic temperature of nanoparticles exceeds the integral tissue temperature. In summary, a new approach based on the use of UCNP without any additional NIR absorbers was used to demonstrate a simple approach in the development of photoluminescent probes for simultaneous bioimaging and local hyperthermia.

The addition of Lewis acids changes the path of the reaction of N-vinylpyrroles with 3,4-dihydroisoquinoline-N-oxides: formal (3 + 3)-cycloaddition proceeds instead of (3 + 2)-cycloaddition. In the case of benzoyl(3,4-dihydroisoquinolin-2-ium-2-yl)amides, reaction path does not change in the same conditions, but changing of the diastereoselectivity occurs and other diastereomer of (3 + 2)-cycloaddition became predominant.

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (C H⋯O) and moderate (N H⋯N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.

The paper is devoted to experimental investigation of an efficient mechanism of distributed excitation of nonstationary Gortler vortices in a boundary layer on concave wall due to scattering of three-dimensional, streamwise oriented freestream vortices on natural two-dimensional base-flow nonuniformity associated with the boundary layer growth. The investigations are performed in a broad range of disturbance frequencies and spanwise wavenumbers. The measurements have shown that the distributed receptivity mechanism is able to modify significantly the disturbance growth rates. This mechanism is found to be able to compete successfully with the linear instability mechanism. It is found that at relatively low frequencies and not too large freestream disturbance amplitudes, the Gortler modes’ development is dominated basically by the corresponding linear instability mechanism. Meanwhile, this mechanism becomes weaker with growth of frequency and, simultaneously, the distributed receptivity mechanism gets stronger. This leads to enhancement of role of the latter in amplification of Gortler instability modes, and at high frequencies the role of the distributed receptivity mechanism becomes very important and often even decisive one. Based on deep processing of the experimental data, quantitative values of the distributed linear receptivity coefficients are obtained for the case of excitation of unsteady Gortler modes and estimated for the case of steady Gortler vortices by means of extrapolation to the zero frequency. A complementary experiment devoted to investigation of the problem of linear unsteady Gortler instability is performed for the particular conditions of the distributed receptivity experiments. All main stability characteristics are obtained and compared with calculated ones. In general, the experimental information presented in this paper can be used for verification of various instability and vortex receptivitytheories.

The 1,3-dipolar cycloaddition of nitrones to N-propadienyl indoles and pyrroles proceeds predominantly via the C1-C2 bond to form 4-methyleneisoxazolidines. In the case of aldonitrones, the cis-isomers are predominantly formed.

Metal–organic polyhedra (MOPs) have attracted great interest in the past decade. As a new series of nano-material, MOPs have high outer and inner specific surface areas and are able to be applied in different areas such as catalysis, gas sequestration, drug delivery, molecule sensing, etc. In this review, the focus is made on the design and synthetic strategies approaching edge-bridged tetrahedra MnL6 and face-capped tetrahedra MnL4. Besides the synthesis, structure, and properties of tetrahedral self-assemblies are also considered, while tetrahedra will be compared with other complicated multinuclear constructions. The discussion of how the properties of tetrahedral cages can be altered by varying employed subcomponents is made. Moreover, the multifarious host–guest system and behavior of metal–organic tetrahedral self-assemblies for catalytic applications are addressed in details.

Acylethynylpyrroles, available via the transition metal-free coupling of pyrroles with acylhaloacetylenes are readily annelated with propargylamine in a one-pot step-wise procedure: catalyst-free heating (60–65 °C, 6–16 h) in DMSO and then keeping for 2.5 h with CuI at the same temperature. The products are pyrrolyl-pyridines isolated in good to excellent yields (56–94%). It is experimentally shown that dehydrogenation of intermediate dihydropyridine moiety is not resulted from the oxidation with DMSO (Me2S was not detected) or air (argon blanket) and is likely associated with the CuI catalysis.

The addition of Lewis acids change the reaction mechanism of the cycloaddition of N-vinylpyrroles with azomethine imine and C,N-diarylnitrones. The formal (3+3)-cycloaddition is observed instead of (3+2)-dipolar cycloaddition, which take place in the absence of catalysts. This unusual (3+3)-cycloaddition leads to heterocyclic compounds with pyrazolo[1,2-a]pyrrolo[1,2-d][1,2,4]triazine- and pyrrolo[2,1-d][1,2,5]oxadiazine cores, which are difficultly achievable by other methods.

Original multiscale flaked silver SERS-substrate (MFSS substrate) was applied for glycated albumin (GA) biosensing. The substrate is composed from silver flakes that have three orders of magnitude size dispersion: from 50 nm to 2 μm. The multiscale silver structure refracts the incident light and various surface plasmons are excited. Some of the internal plasmons are localized and give rise of the large local electric field. It was demonstrated that Raman scattering signal strongly depends: a) on “hot spots” formation at the edges and points of contact of silver plates, and b) on the angle of incidence. As a result the silver structure operates as an effective SERS substrate. To achieve the selectivity to glycated part, the surface of SERS-substrate was modified with 4-mercaptophenylboronic acid (4-mPBA). Various saccharides (Fru, Glc, Suc, Dex) were taken as model compounds for the glycated proteins determination. The saccharides contain cis-diol groups that form five- or six-membered ethers with boronic acid. Spectrum of SERS-substrate changes after sugar/glycated albumin treatment. Main differences in the SERS-spectra of sugar/glycated albumin treated SERS-substrate and control are referred to phenylboronic acid vibrations (999, 1021, 1072 and 1589 cm−1). Principal component analysis (PCA) and Partial Least Squares Regression (PLS-R) were used to discriminate spectra and to construct calibration curve, as well as to measure GA values in real samples of human plasma. Multiscale flaked silver SERS-substrate modified with 4-mPBA allows quantitative one-step biosensing of glycated albumin in 15 μl of human plasma.

The paper is based on results obtained within an international project ‘RECEPT’ of the European Framework Program FP7. The experiments were carried out in a three-dimensional boundary layer developing on an experimental model of a long-laminar-run swept airfoil (sweep angle of 35°). The model was mounted in a test section of the lowturbulence wind-tunnel MTL (KTH, Stockholm) at an angle of attack of −5° and equipped with sidewalls provided satisfaction of infinite-span conditions. The cross-flow (CF) instability modes were predominant in this case, while the Tollmien–Schlichting (TS) waves were suppressed by a favorable pressure gradient. The main measurements were carried out by means of hot-wire anemometry at conditions of excitation of fully controlled, unsteady surface and flow perturbations. These perturbations were excited by special sources: (1) a row of oscillating membranes and (2) a vibrating wire, at frequencies of fs and fv, respectively. A very good, quantitative agreement between the measured and calculated (by linear stability theory based on PSE approach) amplification curves was found at surface frequency fs. However, the evolution of the CF-modes excited at difference combination frequency fsv– = fs – fv turned out to be very much different from the theoretical one. Thorough analysis of the obtained results has shown that the only explanation of these discrepancies can be associated with presence of a distributed receptivity mechanism due to scattering of freestream vortices on the CF-instability waves excited by surface vibrations. Another unusual and unexpected phenomenon found in the present experiments is associated with anomalous amplification of difference combination modes with the zero spanwise wavenumbers E′. This phenomenon was observed in the flow, which is stable with respect to both CF- and TSwaves having E′ = 0 for all frequencies. There is no explanation of this finding at present.

There are several kinds of velocity disturbances, which may affect the transition to turbulence in a swept wing boundary layer. Tollmien-Schlichting (TS) waves are among most important of them. The properties of TS waves and their potential competition with cross-flow waves on a swept wing are poorly studied in theoretical works and were not studied experimentally at all. This paper presents the method of excitation of fully controlled 3D TS waves via interaction of free-stream vortices and surface vibrations. The experimental approach developed here will be used for investigation of the corresponding receptivity problem.

Hitherto unknown N-allenylpyrrole-2-carbaldehydes were synthesized via the formylation of readily available N-allenylpyrroles under the action of the mild formylating complex DMF/(COCl)2. The reaction selectively proceeds in the case of pyrroles with electron-withdrawing substituents to afford the products in good to excellent yields. For pyrroles bearing electron-donating substituents, the reaction proceeds in a cascade manner to deliver unusual complex products, the structure of which was confirmed by X-ray diffraction analysis. The target N-allenylpyrrole-2-carbaldehydes represent promising synthons for organic synthesis.

A combined theoretical and numerical analysis of an experiment devoted to the excitation of Gortler vortices by localized stationary or vibrating surface nonuniformities in a boundary layer over a concave surface is performed. A numerical model of generation of small-amplitude disturbances and their downstream propagation based on parabolic equations is developed. In the framework of this model, the optimal and the modal parts of excited disturbance are defined as solutions of initial-value problems with initial values being, respectively, the optimal disturbance and the leading local mode at the location of the source. It is shown that a representation of excited disturbance as a sum of the optimal part and a remainder makes it possible to describe its generation and downstream propagation, as well as to predict satisfactorily the corresponding receptivity coefficient. In contrast, the representation based on the modal part provides only coarse information about excitation and propagation of disturbance in the range of parameters under investigation. However, it is found that the receptivity coefficients estimated using the modal parts can be reinterpreted to preserve their practical significance. A corresponding procedure was developed. The theoretical and experimental receptivity coefficients are estimated and compared. It is found that the receptivity magnitudes grow significantly with the disturbance frequency. Variation of the span-wise scale of the nonuniformities affects weakly the receptivity characteristics at zero frequency. However, at high frequencies, the efficiency of excitation of Gortler vortices depends substantially on the span-wise scale.

This paper is devoted to an experimental investigation of receptivity of a laminar swept-wing boundary layer due to scattering of free-stream vortices on localized (in the streamwise direction) surface vibrations. The experiments were conducted under completely controlled disturbance conditions by means of a hot-wire anemometer on a model of a swept wing with a sweep angle of 25°. Both the free-stream vortices and the surface vibrations were generated by disturbance sources; their frequency–wavenumber spectra were measured thoroughly. The free-stream vorticity vectors were directed perpendicular to the incident-flow velocity vector and parallel to the swept-wing-model surface. The linearity of the receptivity mechanism under investigation (in a sense that the corresponding receptivity coefficients are independent of the disturbances amplitudes) has been checked carefully. The main goal of this experiment was to estimate the vibration-vortex receptivity coefficients as functions of the disturbance frequency, spanwise wavenumber and vortex offset parameter. This goal has been attained. Being defined in Fourier space, the obtained receptivity coefficients are independent of the specific surface vibration shape and can be used for verification of various receptivity theories.

Asymmetric meso-CF3-dipyrromethanes with amino- and nitrogen heterocyclic functions, a new family of the BODIPY dye precursors, have been synthesized in 70–90 % yield by condensation of trifluoro(pyrrolyl)ethanols with pyrroles in the presence of AlCl3. This catalyst, for the first time, was shown to be more efficient than commonly used P2O5, which was entirely inactive in the condensation of pyrroles having basic substituents (amino group and pyrazole moiety).

Extensive combined experimental and theoretical investigations of the linear evolution of three-dimensional (3D) Tollmien-Schlichting (TS) instability modes of 3D boundary layers developing on a swept airfoil section have been carried out. The flow under consideration is the boundary layer over an airfoil at 35 degrees sweep and an angle of attack of +1.5 degree. At these conditions, TS instability is found to be the predominant one. Perturbations with different frequencies and spanwise wavenumbers are generated in a controlled way using a row of elastic membranes. All experimental results are deeply processed and compared with results of calculations based on theoretical approaches. Very good quantitative agreement of all measured and calculated stability characteristics of swept-wing boundary layers is achieved.

Observation of the wanted Raman signal from SERS substrates is hampered by the background luminescence. We investigate the metasurface made of periodic silicon micro bars with thin silver layer on the top. The computer simulations as well as real experiment reveal the anomalous optical response of the metasurface is due to the excitation of the metal-dielectric surface resonances. We demonstrate the enhanced Raman signal from the organic molecules of 5,5-dithio-bis[2-nitrobenzoic] acid deposited on the microbar metasurface. The microbar metasurface exhibits large Raman/luminescence (signal/noise) ratio. As result it operates as an efficient SERS substrate.

The paper is devoted to some results of a EC project RECEPT (FP7). The experiments were carried out in a three-dimensional boundary layer developing on an experimental model of a long-laminar-run airfoil (sweep angle of 35°, chord of 0.8 m). The model was mounted in a test section of a low-turbulence wind tunnel MTL (KTH, Stockholm) at an angle of attack of -5 degrees. The cross-flow instability modes (CF) were the most amplified ones, while the Tollmien–Schlichting instability modes were suppressed by a favorable pressure gradient. The main measurements were performed by means of a single-wire hot-wire probe at conditions of excitation of fully controlled, unsteady surface and flow perturbations. These perturbations were excited by special sources: (i) a surface membrane and (ii) a vibrating wire. The two sources oscillated at frequencies fs and fv, respectively. The membrane had a diameter of 6 mm. It was mounted into the model surface and located at a chordwise coordinate of 120 mm downstream the leading edge. The vibrating wire was mounted at a tension upstream the leading edge and parallel to it and adjusted in a way to provide location of one of the amplitude maxima of the excited quasi-2D vortex street near the boundary layer edge. The incident flow velocity was of about 10 m/s and varied in the chordwise direction. A rather efficient excitation of packets of three-dimensional CF-modes was found at frequency fs (due to action of a mechanism of the boundary-layer receptivity to surface vibrations) as well as at two combinational frequencies fsv+ = fs + fv and fsv- = fs - fv (due to action of a receptivity mechanism associated with scattering of the controlled freestream vortices on the controlled surface vibrations). The amplification curves (amplitudes and phases) of CF-modes were obtained in a broad range of problem parameters (spanwise wavenumbers and frequencies fs and fv), as well as the amplitudes and phases of the corresponding receptivity coefficients of 'vibrational' and 'vortex-vibration' receptivity mechanisms. Comparison with calculations carried out by means of linear (locally-parallel) stability theory (LST) was performed. A very good, quantitative agreement between results of measurements and calculations was found at surface frequency fs. It is found that the CF-modes excited at the combinational frequencies fsv evolve downstream in a way that is different from the LST. A thorough analysis of disturbance spanwise profiles of amplitudes and phases, their spectra, and the disturbance amplification curves showed that the features of downstream evolution of the CF-modes observed at frequency fsv can be explained by action of a distributed receptivity mechanism. This mechanism is associated with scattering of the controlled freestream vortices with frequency fv on the CF-instability modes excited by surface vibrations at frequency fs. Nowadays such distributed receptivity mechanism is remained completely unexplored. Therefore, the obtained experimental data seems to be of great basic and practical importance.

Optical properties of two-dimensional periodic systems of the dielectric micro bars and micro cones are investigated. Computer simulations as well as real experiment reveal anomalous optical response of the dielectric metasurface due to excitation of the dielectric and metal-dielectric resonances, which are excited in-between metal nanoparticles and dielectric cones and bars. In the metal-dielectric resonance local electric field can be orders on magnitude larger than the field in the plasmon resonance only. To investigate local electric field the signal molecules were deposited on the metal nanoparticles. We demonstrate the enhancement of the electro- magnetic field by detecting the Raman signal from the of organic acid molecules deposited on the investigated metasurface.

This experimental work is devoted to a parametric study of characteristics of the laminar-turbulent transition occurred in a model of a crossflow-dominated swept-wing boundary layer. The experiments are performed in 39 different regimes with low and elevated freestream turbulence levels both in the absence and in the presence of steady freestream vortices of various spanwise scales. The measurements are performed at several values of freestream velocity for two types of distributed surface roughness. Transition scenarios and criteria of turbulence onset are investigated and the problem of transition prediction is examined. It is shown that in all studied cases, the turbulence onset starts with the appearance of local high-frequency secondary instability of the base flow perturbed by primary instability modes. It is found that the 30% level of the threshold zero-to-peak amplitude of combined boundary-layer disturbances (i.e., the steady ones plus unsteady ones) can be used in all studied cases as a simplif...

The present work is a continuation of previous experiments (carried out in the Blasius boundary layer) and devoted to quantitative investigation of influence of an adverse pressure gradient on two efficient mechanisms of excitation of 3D TS instability waves due to a distributed boundary layer receptivity to free-stream vortices. These mechanisms are associated with distributed scattering of 3D amplified free-stream vortices both on the natural boundary-layer nonuniformity (on smooth surface) and on 2D surface nonuniformities (waviness). The corresponding detailed hotwire measurements were carried out in a self-similar boundary layer with Hartree parameter βH = –0.115 in a wide range of the problem parameters. Complex values of quantitative characteristics of the physical phenomenon under study (the distributed receptivity coefficients) are evaluated by based on the obtained experimental data. It is found that the adverse pressure gradient leads to reduction of efficiency of the investigated vortexroughness receptivity mechanism.