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Photobleaching is one of the basic chemical processes that occur naturally in organic molecules. In this work, we investigate the quantum dynamics of Cy 7.5 dye molecules optically coupled to Au nanorod particles and experimentally demonstrate the decrease of the photobleaching rate in this hybrid system. We discover the effect of a resonance-like behavior not observed before for any type of emitter─the photobleaching rate of the dye molecules reaches a minimum for a suitable number of molecules coupled to the nanoparticle. The manifestation of the effect is the consequence of shifts in the energy levels in the hybrid system caused by the change in the number of molecules coupled to a nanoparticle. The energy shifts are the prerequisite for the effective depopulation of the triplet level, which is responsible for the photodegradation mechanism. The discovered effect paves the way for increasing the efficiency of optoelectronic and photovoltaic devices.

In the present work, based on the density functional theory and crystal structure prediction algorithms, we found novel structures of alkali metal orthocarbonates Li4CO4-C2/c, Na4CO4-C2/c, and K4CO...

Based on ab initio calculations within the density functional theory and crystal structure prediction algorithms, the structure and stability of iron–nitrogen compounds in the pressure range of 100...

The applicability of stationary liquid phases for gas–liquid chromatography was evaluated. The scale for quantitative one-parameter estimation of their polarity was chosen. Absorption and luminescence spectra of the five indicators coumarin 153, coumarin 314, coronene, 4-dicyanomethylene-2-methyl-6-[4-(dimethylamino)styryl]-4H-pyran (DCM), and 3-aminophthalimide in solvents of different polarity were obtained at room temperature. The dependence of the fluorescence and absorption maxima wavelengths on the medium polarity was evaluated. Various spectroscopic polarity scales were compared to show that the coronene fluorescence scale was most appropriate. This scale was used to assess the polarity of some widespread phases (squalane, polydimethylsiloxane PMS-100, 3,3′-oxydipropionitrile, 2-ethylhexylsebacate, etc.) for gas-liquid chromatography. This approach was shown to be promising for preliminary selection of chromatographic stationary phases.

In modern economic infrastructure, Al cables of overhead power transmission lines are used both without and with a steel core (respectively, all aluminum alloy conductor (AAAC) and aluminum conductor steel reinforced (ACSR) cables). In this article, the changes in structural, microstructural, and elastic-microplastic properties have been analyzed for the outer wires of the AAAC (A50) and ACSR cables (AC50/8 cables with a steel core of ~8 mm2 cross-section, hereinafter referred to as AC50) with the cross-section of the stranded conductor of ~50 mm2, which were in operation for 0–20 years in the Volgograd region of Russia. Using the techniques of X-ray diffraction, electron backscattered diffraction, densitometry, and the acoustic method, the structural and microstructural features of the wires have been compared and found to be correlated with their elastic-microplastic properties. It has been ascertained that the presence of a steel core in AC50 leads to a decrease in the defectiveness of the near-surface layer of their aluminum wires. Compared with A50 cables, the development of void defects in the near-surface layer of Al-wires of AC50 cables slows down (by ~1 year with a service life of ~10 years and by ~3 years with a service life of ~20 years).

Orthocarbonates of alkaline earth metals are the newly discovered class of compounds stabilized at high pressures. Mg-orthocarbonates are the potential carbon host phases, transferring oxidized car...

The phase and group velocities of propagation of the electric and magnetic fields along the axis of metal carbon nanotubes have been calculated. In the model used, the electron distribution in nanotubes is described by a cylindrical layer of an almost free electron gas disturbed by an external electric field and electron–electron interaction. For a transverse magnetic field (of the TM type) and transverse electric field (of the TE type), the dependences of the field frequency and phase and group velocities on the wavenumber kz have been determined. It has been found that the frequencies of all TE modes increase monotonically with increasing kz, the group velocities are positive, and the directions of propagation of the phase and group waves coincide. For TM-type modes at low kz values, the group velocity is negative and the directions of propagation of the phase wave and the group wave are opposite, which can be of practical importance for creating on their basis tools for controlling the transmission of signals and energy between nanoelectronic elements.

The molecular-dynamics simulation of the formation of dimers for the case of the low-temperature (001) reconstruction of a GaAs surface terminated in Ga or As atoms is employed using the analytical potential, which takes into account σ- and π-bonds between atoms. The values of the decrease in the potential energy of atoms during the formation of the surface of an isolated dimer are found, and it is discovered that the potential energy of an atom in the As dimer is lower by several tenths of eV than that in the Ga dimer. In the temperature range of 25–40 K, the kinetics of the initial stages of the formation of Ga dimers is studied, and it is obtained that the characteristic energy of thermal activation of the formation of single isolated Ga dimers is ~29 meV and lower than the same value for As dimers (~38 meV). In the temperature range of 28–37 K, the time constants characterizing the average rate of the conversion of a single dimer into a chain of two dimers are estimated. For double Ga and As dimers, the reciprocal values of these times turn out to be in the ranges of 1011–1012 and 109–1010 s–1, while similar parameters for the formation of single dimers lie in the range of 4 × 106–108 and 1.4 × 106–7.4 × 107 s–1.

Using molecular dynamics simulation and evolutionary metadynamic calculations, a series of structures were revealed that possessed enthalpies and Gibbs energies lower than those of aragonite but hi...

In chiral gold nanotubes, alternating electric current generates an electromagnetic field; under these conditions, the nanotubes become emitting solenoid nanoantennas. With the use of the Maxwell equations and taking into account the geometry of nanotubes, their band structure, and the ballistic model of electron transfer, we have calculated the alternating axial magnetic and azimuthal electric fields generated by helical currents in chiral gold nanotubes. The calculations demonstrate that large alternating magnetic and electric fields can be generated in nanoscale volumes of gold nanotubes and that the eigenfrequencies of the field components are in the X-ray range.

A set of structures of homomolecular organic crystals with information on the solvent utilized for crystallization was extracted from the Cambridge Structural Database in order to identify possible...

The results of experiments aimed at fabricating and studying the properties of photodetector structures based on single-layer graphene produced by chemical vapor deposition are presented. The configuration of a Ta2O5 vertical microcavity with a resonance wavelength of about 850 nm and a lower dielectric SiO2/Ta2O5 distributed Bragg reflector is taken as the base structure. The conditions for the transfer and fabrication of mesas in the graphene layer on the microcavity surface are optimized. The diagnostics by Raman spectroscopy of the structural quality of graphene after fabrication of the mesas in the graphene layer and contact pads are indicative of the single-layer structure of graphene with a low intensity of features in its spectrum, responsible for imperfection of the structure. The photocurrent is measured under local optical pumping.

Magnetic fields generated by nanosolenoids based on gold nanotubes have been calculated. The electron energy levels in nanotubes have been calculated by the linearized augmented cylindrical wave method with cyclic Born–Von Karman boundary conditions and with taking into account helical symmetry of the tubes. The numbers of conducting channels, low-temperature ballistic electron currents, and magnetic fields in nanosolenoids based on gold nanotubes of various length and structure have been determined. The data obtained demonstrate that chiral gold nanotubes are promising materials for creation of nanosolenoids with strong magnetic fields and can be used for more realistic design of nanosolenoids.

The effect of gamma irradiation and doping with silicon dioxide on the first-order solid-state phase transition in polytetrafluoroethylene is studied by the differential scanning calorimetry method. A quantitative analysis of the profiles of the heat capacity peaks is carried out on the basis of the theory of diffuse phase transitions. It is shown that the elementary volume of the phase transformation depends on the γ irradiation and the concentration of silicon dioxide.

Based on the first-principles calculations within the density functional theory and crystal structure prediction algorithms iron phosphide phases stable under pressure of the Earth’s core and tempe...

This study considers some aspects of electrolytic plasma in the process of anodic carburising of steel, including the nature of the glow in a vapour gaseous envelope, its thickness under various hydrodynamic conditions; it also examines the formation patterns of a hardened layer after carburising along with quenching in the same electrolyte. The glow in a vapour gaseous envelope was examined with a spectrometer; its profile and thickness were determined by solving energy and mass balance equations in a pre-anode area. The structure of the carburised layer and hardness distribution were explored with an optical microscope and a microhardness tester. Carbon concentration in the carburised layer was determined by means of optical emission spectroscopy. The investigation has revealed that the glow in a vapour gaseous envelope under carburising is a continuous emission from heated bodies—vapour gaseous phase and the sample without any electric discharges. It has been theoretically derived, that in laminar approximation the layer has maximal thickness under certain hydrodynamic conditions. This conclusion has been confirmed by homogeneous distribution of current density throughout the surface of the sample during its carburising under condition of force hydrodynamics, i.e. the sample being flowed round with cooled electrolyte. Aerated stirring in electrolyte does not provide homogeneous current density distribution, which falls in vertical direction. Anodic carburising of steel in a glycerol electrolyte followed by quenching results in the formation of a martensitic layer up to 200 μm in thickness, within 5-min treatment, with maximal microhardness 1000 HV.

The emergence of spin-orbit torques as a promising approach to energy-efficient magnetic switching has generated large interest in material systems with easily and fully tunable spin-orbit torques. Here, current-induced spin-orbit torques in VO$_2$/NiFe heterostructures were investigated using spin-torque ferromagnetic resonance, where the VO$_2$ layer undergoes a prominent insulator-metal transition. A roughly two-fold increase in the Gilbert damping parameter, $\alpha$, with temperature was attributed to the change in the VO$_2$/NiFe interface spin absorption across the VO$_2$ phase transition. More remarkably, a large modulation ($\pm$100%) and a sign change of the current-induced spin-orbit torque across the VO$_2$ phase transition suggest two competing spin-orbit torque generating mechanisms. The bulk spin Hall effect in metallic VO$_2$, corroborated by our first-principles calculation of spin Hall conductivity, $\sigma_{SH} \approx 10^4 \frac{\hbar}{e} \Omega^{-1} m^{-1}$, is verified as the main source of the spin-orbit torque in the metallic phase. The self-induced/anomalous torque in NiFe, of the opposite sign and a similar magnitude to the bulk spin Hall effect in metallic VO$_2$, could be the other competing mechanism that dominates as temperature decreases. For applications, the strong tunability of the torque strength and direction opens a new route to tailor spin-orbit torques of materials which undergo phase transitions for new device functionalities., Comment: 16 pages, 5 figures

It was shown that the nanoindentation treatment of the atomically flat GaAs surface with the tip of atomic-force microscope in contact mode allows to produce small size pits with the depth in the range from a few tenths of nm up to a 1.5 nm. The experimental data can be qualitatively described on the base of kinetic concept of fracture of solid state developed by Zhurkov, which suppose the generation of defects and subsequent destruction of the GaAs surface. The molecular dynamics modelling confirmed thermally activated destruction of a few top atomic layers under indentation. The presented technology could be used to form the shape of solid state surfaces with subnanometer resolution in depth without wet etching processes.

In a spintronic resonator a radio-frequency signal excites spin dynamics that can be detected by the spin-diode effect. Such resonators are generally based on ferromagnetic metals and their responses to spin torques. New and richer functionalities can potentially be achieved with quantum materials, specifically with transition metal oxides that have phase transitions that can endow a spintronic resonator with hysteresis and memory. Here we present the spin torque ferromagnetic resonance characteristics of a hybrid metal-insulator-transition oxide/ ferromagnetic metal nanoconstriction. Our samples incorporate $${\mathrm {V}}_2{\mathrm {O}}_3$$ V 2 O 3 , with Ni, Permalloy ($${\hbox {Ni}}_{80}{\hbox {Fe}}_{20}$$ Ni 80 Fe 20 ) and Pt layers patterned into a nanoconstriction geometry. The first order phase transition in $${\mathrm {V}}_2{\mathrm {O}}_3$$ V 2 O 3 is shown to lead to systematic changes in the resonance response and hysteretic current control of the ferromagnetic resonance frequency. Further, the output signal can be systematically varied by locally changing the state of the $${\mathrm {V}}_2{\mathrm {O}}_3$$ V 2 O 3 with a dc current. These results demonstrate new spintronic resonator functionalities of interest for neuromorphic computing.

It is important to be able to control the physical and chemical integrity of carbon-based porous monolith structures while being tailored for targeted analytical, energy and catalytic based applications. A set up using a CO2 laser in continuous mode (CW CO2 laser) was implemented to cut fragile and porous carbon monolithic (CM) and nanotemplated carbon monolithic (NTCM) rods into discs with a prescribed thickness and dimensional integrity (denoted as LCM and LNTCM, or LCMs). Changes in structure, porosity and composition of LCMs were induced by the efficient thermal energy afforded by the CW CO2 laser irradiation under tightly controlled process conditions. The main effects observed before and after laser cutting were studied in comparison with traditional scalpel blade cutting of carbon monolithic (SCM). FE-SEM images confirmed that the resulting LCMs exhibited a more open, interconnected macroporous structure and smoothed mesopores to a depth of approximately 5 μm, while the structure of the bulk section remained intact. Minimal changes in chemical compositions were confirmed by XPS. Raman spectroscopy revealed a modest increase in the graphitic content on the cross sections of LCM discs. Phenol and Bisphenol A (BPA) was used as a model analyte for demonstration of resulting discs adsorption performance.

We report the results of systematic Raman spectroscopy studies of AlxGa1 –xN (x ~ 0.75) layers grown using plasma-assisted molecular beam epitaxy at various stoichiometric conditions and growth fluxes. The high-intensity asymmetric low-frequency peak obeying Bose statistics is discovered in Raman spectra of the layers grown by temperature-modulated epitaxy at strongly Ga-enriched conditions. Theoretical model is developed to explain the origin and the high intensity of the observed low-frequency peak, which is attributed to the presence of excessive metallic gallium in AlGaN layers and can be explained by vibrations of gallium clusters with a diameter of ~1 nm. The nature of the low-frequency peak is similar to that of the boson peak in glasses, which occupies the same frequency range in Raman spectra. We demonstrate the capabilities of Raman spectroscopy as an express and non-destructive technique for optimization of growth conditions of AlGaN layers to achieve simultaneously the atomically-smooth droplet-free surface morphology and the high structural quality.

Spin-dependent band structures, the electron and spin transport, and the formation of magnetic field in the single-walled chiral gold nanotubes (n1, n2) are calculated using a relativistic lineariz...

The heterocyclic polymer network nanocomposites obtained from bisphtalonitrile and various (from 0.03 to 5 wt %) modified silicate montmorillonite (MMT) nanolayers are studied. The nanostructure together with thermal, relaxation, and elastic properties of the composites are characterized with transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). DMA and TGA measurements were performed in air and nitrogen mediums in the temperature range from 20 to 600–900°C. There was a various degree of exfoliation of MMT in the matrix to form single nanolayers, as well as thin and “thick” packs of MMT nanolayers, depending on its amount. We showed that there are strong constraining dynamics effects of the matrix by nanoparticles and sharp dynamic heterogeneity in the glass transition. We found that there are possibilities of complete suppression of the latter and of preservation of elastic characteristics of the composites unchanged at the temperatures from 20 to 600°C. The nanocomposites exhibit uniquely high thermal properties. A glass transition temperature of 570°C and satisfactory thermal stability are achieved with preservation of integrity of the material up to ~500°C in air and up to ∼900°C in nitrogen.

We perform a comparative study of melting of polytetrafluoroethylene (PTFE) in its unmodified form, after irradiation, and after adding plant-derived silicon dioxide as an additive (content, 1%). Calculation of peak shapes on thermal capacity profiles within the theory of smeared phase transitions enable us to identify the structural changes and their features resulting from irradiation of PTFE and incorporation of the additive in it. α-relaxation at the glass transition in our samples is studied by dynamic mechanical analysis.

The paper presents an attempt to use the Hall–Petch relationship to relate the yield strength of copper and titanium in three different states (initial, annealed, and after equal-channel angular pressing) to the sizes of nano- and micrometer deformation jumps measured using a precision interferometric technique. It is shown that, upon a compression strain near the yield point, one can observe six levels of deformation with three nano- and three micrometer sizes of deformation jumps from 1–2 nm to 20–35 μm. Each of the six structural states of metals is characterized by its own set of deformation jump sizes. Dependences of the yield strengths of copper and titanium on the jump sizes L–1/2 are constructed, and the general regularities and features of deformation jumps for each of the metals in different structural states are discussed.

The spin- and deformation-dependent electron structures of the single-walled chiral and achiral Pt nanotubes are investigated using a relativistic linear augmented cylindrical wave method. It is shown that the Fermi level separates the valence and conduction band curves. The nanotubes are semimetallic. The spin-orbit coupling results in a splitting of dispersion curves equal up to 0.5 eV. The torsional, uniaxial, and uniform strain results in a drastic change of the electronic states at the Fermi level. The mechanical deformation of some Pt nanotubes can induce a formation minigaps in a terahertz region that can be used in electronic devices.

High-efficiency semiconductor lasers and light-emitting diodes operating in the 3–5 μm mid-infrared (mid-IR) spectral range are currently of great demand for a wide variety of applications, in particular, gas sensing, noninvasive medical tests, IR spectroscopy etc. III-V compounds with a lattice constant of about 6.1 A are traditionally used for this spectral range. The attractive idea to fabricate such emitters on GaAs substrates by using In(Ga,Al)As compounds is restricted by either the minimum operating wavelength of ∼8 μm in case of pseudomorphic AlGaAs-based quantum cascade lasers or requires utilization of thick metamorphic InxAl1-xAs buffer layers (MBLs) playing a key role in reducing the density of threading dislocations (TDs) in an active region, which otherwise result in a strong decay of the quantum efficiency of such mid-IR emitters. In this review we present the results of careful investigations of employing the convex-graded InxAl1-xAs MBLs for fabrication by molecular beam epitaxy on GaAs (001) substrates of In(Ga,Al)As heterostructures with a combined type-II/type-I InSb/InAs/InGaAs quantum well (QW) for efficient mid-IR emitters (3–3.6 μm). The issues of strain relaxation, elastic stress balance, efficiency of radiative and non-radiative recombination at T = 10–300 K are discussed in relation to molecular beam epitaxy (MBE) growth conditions and designs of the structures. A wide complex of techniques including in-situ reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning and transmission electron microscopies, X-ray diffractometry, reciprocal space mapping, selective area electron diffraction, as well as photoluminescence (PL) and Fourier-transformed infrared spectroscopy was used to study in detail structural and optical properties of the metamorphic QW structures. Optimization of the growth conditions (the substrate temperature, the As4/III ratio) and elastic strain profiles governed by variation of an inverse step in the In content profile between the MBL and the InAlAs virtual substrate results in decrease in the TD density (down to 3 × 107 cm−2), increase of the thickness of the low-TD-density near-surface MBL region to 250–300 nm, the extremely low surface roughness with the RMS value of 1.6–2.4 nm, measured by AFM, as well as rather high 3.5 μm-PL intensity at temperatures up to 300 K in such structures. The obtained results indicate that the metamorphic InSb/In(Ga,Al)As QW heterostructures of proper design, grown under the optimum MBE conditions, are very promising for fabricating the efficient mid-IR emitters on a GaAs platform.

The tribological experiment applied to the gallium oxide wafer led to changes in its structure which can reduce the single crystal perfection. The effect of mechanical wear on the subsurface layers of the β-Ga2O3 single crystal wafers applied to the plane is studied. A decrease in crystallinity within a mosaic structure appearing in the worn samples is revealed with a help of ω-scan analysis, performed by XRD. SEM analysis of the wear track relief of the worn samples showed an emergence of the lamellas framed by domain walls as a result of single crystal splitting.

The growth features of GaN nanorods on patterned c-sapphire substrates with a regular microcone array having a different density and base diameter in the ranges of (1–5) × 107 cm–2 and 2.5–3.5 μm, respectively, are investigated. The kinetics is studied and the selective-growth regimes are determined for single GaN nanorods with a diameter of 30–100 nm at the vertices of microcones under radically lower growth rates on their slopes. The effect of the configuration of microcones, the substrate temperature, the roughness of the initial surface, and the presence of indium as a surfactant on the degree of growth selectivity is investigated.

We investigated the growth of III-N/graphene heterostructures as a single process in a MOVPE reactor. Raman spectra revealed that graphene can be successfully deposited on sapphire substrate by propane pyrolysis if temperature exceeds 1060 °C and hydrogen is used as a carrier gas. GaN epitaxial layers and heterostructures on such graphene using both high-temperature AlN buffer layer and low-temperature GaN nucleation layer was demonstrated. Analysis of surface morphology and X-Ray diffraction curves indicate that GaN quality depends on graphene thickness. Use of copper electroplated Ni-based contact layer combined with thermal shock allows exfoliation of large-area III-N LED structures from sapphire.

We have probed directly the temperature and magnetic field dependence of pinned uncompensated magnetization at the interface of antiferromagnetic ${\mathrm{FeF}}_{2}$ with Cu, using ${\mathrm{FeF}}_{2}\text{\ensuremath{-}}\mathrm{Cu}\text{\ensuremath{-}}\mathrm{Co}$ spin valves. Electrons polarized by the Co layer are scattered by the pinned uncompensated moments at the ${\mathrm{FeF}}_{2}\text{\ensuremath{-}}\mathrm{Cu}$ interface giving rise to giant magnetoresistance. We determined the direction and magnitude of the pinned uncompensated magnetization at different magnetic fields and temperatures using the angular dependencies of resistance. The strong ${\mathrm{FeF}}_{2}$ anisotropy pins the uncompensated magnetization along the easy axis independent of the cooling field orientation. Most interestingly, magnetic fields as high as 90 kOe cannot break the pinning at the ${\mathrm{FeF}}_{2}\text{\ensuremath{-}}\mathrm{Cu}$ interface. This proves that the pinned interfacial magnetization is strongly coupled to the antiferromagnetic order inside the bulk ${\mathrm{FeF}}_{2}$ layer. Studies as a function of ${\mathrm{FeF}}_{2}$ crystalline orientation show that uncompensated spins are only detected in a spin valve with (110) crystal orientation, but not in valves containing ${\mathrm{FeF}}_{2}(100)$ and ${\mathrm{FeF}}_{2}(001)$. This observation is in agreement with symmetry-related considerations which predict the equilibrium boundary magnetization for the ${\mathrm{FeF}}_{2}(110)$ layer.

Overhead power-transmission lines are one of the most important components of modern infrastructure. Their service life is determined by the state of the near-surface defect layers (NSDLs) of wires constituting these lines. Both the structure and microstructure of the NSDLs of wires of the AAAC type (All Aluminum Alloy Conductor), which were in operation during 0 (new) to 62 years, were investigated by methods of the X-ray (XRD) and electron back-scattering diffraction, optical microscopy, and resistivity measurements, as well as by means of densitometric and acoustic measurements with layer-by-layer removal of the near-surface material by etching. Two characteristic thicknesses of the NSDLs were obtained, different methods providing close results, namely, ~30–50 μm and ~56–140 μm. According to the mass-density distribution (XRD), these characteristic thicknesses correspond to the depths from the surface where they occur, respectively, ~70% and ~99% of the density drop in comparison with the bulk density value. The rate of increase in NSDL thickness is ~4 μm/year in the interval from 0 to 18 years. Results of investigation of elastic and microplastic properties of wires after removal of ~35 μm of the upper layer are also presented.

The microstructure of aragonite, one of the main bio-mineral and component of bio-inspired materials, was described in numerous investigations. Using transmission electron microscopy (TEM), for the first time we show the effect of temperature on aragonite microstructure. The local increase of (0.5 0.5 0) reflections intensities and appearance of satellite reflections in [11̅0] zone axis were observed above 350°C. We explain the appearance of satellite reflections by the generation and ordering of {110} twin boundaries and suggest new thermal mechanism of the twin boundaries generation. We check the viability of this mechanism by ab initio molecular dynamics (AIMD) simulations and generalized solid state nudge elastic band (g-SSNEB) calculations.

Comparative analysis of phase and relaxation transitions in poly(tetrafluoroethylene) by differential scanning calorimetry and dynamic mechanical analysis has been carried out. Elimination of procedural errors in the first case has allowed us to obtain true values of thermodynamic parameters for phase transitions and reveal their nature. Quantitative analysis of heat capacity peak profile was performed on the basis of smeared first-order phase transition theory and relaxation glass transition has been characterized.

The effect of additives of 1 and 3 wt % of halloysite on the rate and small jumps of deformation under uniaxial compression of ultrahigh-molecular-weight polyethylene was investigated. A procedure for precision interference measurement with a resolution of 325 nm for displacement and 1 kHz for frequency enabled the detection of several levels of deformation in the micro- and nanometer ranges. The addition of halloysite results in a decrease in the strain rate under the same loading conditions and a change in the characteristics of the strain jumps. Calorimetric measurements showed that melting of polyethylene with a different concentration of halloysite causes a change in the transition energy and the degree of crystallinity.

Milligram-per-second production of selenium nanoparticles in water sols was realized through 7-W, 2 MHz-rate femtosecond laser ablation of a crystalline trigonal selenium pellet. High-yield particle formation mechanism and ultimate mass-removal yield were elucidated by optical profilometry and scanning electron microscopy characterization of the corresponding crater depths and topographies. Deposited selenium particles were inspected by scanning and transmission electron microscopy, while their hydrosols (nanoinks) were characterized by optical transmission, Raman and dynamic light scattering spectroscopy. 2D patterns and coatings were ink-jet printed on thin supported silver films and their bare silica glass substrates, as well as on IR-transparent CaF2 substrates, and characterized by electron microscopy, energy-dispersive x-ray spectroscopy, and broadband (vis-mid IR) transmission spectroscopy, exhibiting crystalline selenium nanoparticles with high refractive index as promising all-dielectric sensing building nanoblocks in nanophotonics.

We investigated structural and emission properties of self-organized InP/GaInP quantum dots (QD) grown by metal organic chemical vapor deposition using an amount of deposited In from 7 to 2 monolayers (ML). In the uncapped samples, using atomic force microscopy (AFM), we observed lateral sizes of 100–200 nm, together with a bimodal height distribution having maxima at ∼5 and ∼15 nm, which we denoted as QDs of type A and B, respectively; and reduction of the density of the type-B dots from 4.4 to 1.6 μm–2. The reduction of the density of B-type dots were observed also using transmission electron microscopy of the capped samples. Using single dot low-temperature photoluminescence (PL) spectroscopy we demonstrated effects of Wigner localization for the electrons accumulated in these dots.

Optical detection systems for portable analytical instrument require commercially available, miniaturized, robust and well performing light sources. Light emitting diodes (LEDs) have been extensively used in portable analytical devices as they are exceptionally stable light sources offering a number of advantages over traditional light sources including robustness, small size and low-cost. In the analytically more significant deep UV spectral range, LEDs suffer from low optical power and parasitic emissions in the visible wavelength range. Recently, newly developed deep UV-LEDs based on aluminium nitride (AlN) substrates have been introduced claiming improved performance, however there is little in terms of systematic evaluation of their performance parameters when used as light sources in chemical sciences. The aim of this work was to investigate the performance of these new generation deep UV‐LEDs, and assess their analytical applicability. Three AlN substrate based LEDs (OPTAN255H, OPTAN255J and OPTAN280J) were selected based on their maximum emission wavelength and maximum optical power. Their emission spectra, optical output power values and energy conversion efficiency (electrical/optical) were investigated. This work shows effects of forward current and voltages on the ratio of intensities of the visible parasitic emission to the desirable deep UV emission. Experimental results show that while the parasitic emission still exists with the new generation deep UV-LEDs, with increasing forward current the ratio of undesirable parasitic emission to the main deep UV emission rapidly decreased to values as low as 0.1% at the maximum forward current (100 mA). The new generation deep UV-LED (255 nm) was then applied as a light source for a photometric on-capillary detection, showing excellent linearity with stray light down to 0.8%, and effective pathlength above 92% of the used capillary inner diameter, and finally the performance was demonstrated by detection of four parabens separated by miniaturised capillary liquid chromatography.

The results of optimization of the design and growth conditions of an In x Al1–xAs metamorphic buffer layer with a high In content (x = 0.05–0.83) grown via MBE on GaAs(001) substrates with the purpose of optimizing its surface morphological characteristics and structural properties and lowering the surface density of threading dislocations. The lowest surface-pattern roughness RMS = 2.3 nm (on an area of 10 × 10 μm) and density of threading dislocations of 5 × 107 cm–2 are found in the samples with a convex-graded metamorphic buffer layer.

Nanoindentation to a depth of 1 nm in (001) GaAs surfaces terminated by As simulated in the temperature range from 1 to 15 K using the molecular-dynamics method is simulated. It is shown that this is accompanied by surface reconstruction with the formation of stable dimers As (1 × 2), which do not disappear after indenter withdrawal from the surface.

The structure of Ti6Al4 V alloy, its microhardness, surface roughness and corrosion resistance after anodic plasma electrolytic nitrocarburising (PEN/C) in an electrolyte containing carbamide and ammonium chloride were investigated. An X-ray diffractometer and a scanning electron microscopy were used to characterise the phase composition and structure of the modified surface. The effect of processing temperature on the corrosion resistance of the PEN/C samples was examined by means of potentiodynamic polarisation in Ringer’s solution. It was found that the PEN/C provides the formation of the external oxide layer (rutile) and a solid solution of carbon and nitrogen in titanium with martensite structure after quenching in the electrolyte. The microhardness of the layer is 740 HV; the surface roughness decreases from 1 to 0.63 μm. Corrosion resistance in Ringer’s solution does not deteriorate after anodic PEN/C at low temperature.

Steel surface can be polished after its plasma electrolytic nitriding using the same electrolyser. Medium carbon steel is nitrided in the aqueous solution containing ammonium chloride and ammonium ...

The effect of solid-state phase transitions on the kinetic parameters of creep deformation in polytetrafluoroethylene has been studied by differential scanning calorimetry and a laser-interferometric creep rate meter. It has been shown that the deformation activation volumes and the elementary phase transition volume differ from each other by more than an order of magnitude. The crystalline component of this polymer becomes a liquid-crystal phase coexisting with an amorphous phase.

A number of carbonates with promising optical properties were synthesized during the past decade, proving the potential of carbonate systems as a source of novel optical materials. Here we report a new noncentrosymmetric Na2Ca4(CO3)5 carbonate (P63mc; a = 10.37402(14) A, c = 6.25935(9) A) with “M13M23XY3Z” structural type. This structural type, built upon an M13M23 cationic array with three types of anion-filled voids (X, Y, and Z), can accommodate a variety of cations (alkali, alkaline earth, and rare earth) and anions (carbonate, borate, and halide), as we show by extensive analysis of structures of known compounds, and appears to be very promising for the search of new optical materials.