Recently, photoluminescence tomography based on the confocal laser scanning microscopy with two-photon excitation has been developed to study the distribution of point and extended defects in the bulk of ZnSe laser crystals. This article presents the use of the tomography to investigate luminescent micro inclusions in transparent amorphous media such as silicate glass. Studies of CdZnSSe crystals synthesized in a silicate glass melt have been carried out using the tomography with both two-photon and single-photon excitation of luminescence. Zn-rich glass manufactured in the 19th century has been found to contain micron-sized crystals of CdZnSSe of hexagonal crystal system exhibiting intense photoluminescence. The photoluminescence band of these crystals has been found to peak at about 2.1 eV (∼ 590 nm) at 300 K. Minor shifts in the maximum of bands and changes in their shape in individual crystals or at tomogram points within the crystal are associated with variations in their composition. Changes in the photoluminescence band shape and maximum due to the excitation of luminescence in CdZnSSe crystallites by laser radiation of different energies have also been observed in this study.

Nanoparticles (NPs) exhibiting X-ray-excited UV-C luminescence can be used in radiation therapy to deactivate cancer cells through photochemical reactions of DNA with UV-C quanta. Colloidal solutions of monoclinic La1−xPrxPO4 NPs (x = 0.01–0.3), luminescent in the UV-C range (220–280 nm), with different morphologies, from nanofiber (diameter and length not larger than 15 and 600 nm, respectively) to short nanorod (diameter and length not larger than 8 and 35 nm, respectively), were obtained by a microwave-assisted hydrothermal method. For possible biomedical use, the synthesis parameters (pH = 8, anion excess coefficient = 2) were determined, at which nanorods of suitable sizes (diameter and length not larger than 10 and 80 nm, respectively) with the brightest UV-C luminescence among all synthesized nanorods were obtained. A gradual increase in the optimal concentration of Pr3+ ions with maximum luminescence brightness from 4 mol-

Introduction: The process of laser-induced breakdown of amorphous and crystalline selenium nanoparticles (Se NPs) of various shapes during nanosecond laser fragmentation of aqueous colloidal solutions of nanoparticles with different concentrations has been studied.Methods: The methods of studying the characteristics of plasma and acoustic oscillations induced by optical breakdown are applied. The methods of assessing the concentration of hydrogen peroxide and hydroxyl radicals, the amount of long-lived reactive species of protein and 8-oxoguanine are applied.Results: It has been established that in the process of laser fragmentation of selenium nanoparticles at a wavelength of 532 nm, corresponding to the maximum absorption of selenium, the highest probability of breakdown, the number of plasma flashes, their luminosity and the amplitude of acoustic signals are achieved at concentrations of the order of 109 NPs/mL. It has been shown that the use of selenium nanoparticles of various shapes and structures leads to a change in the photoacoustic signal during laser-induced breakdown. When crystalline selenium nanoparticles are irradiated, the intensity of the photoacoustic response during breakdown turns out to be greater (1.5 times for flash luminosity and 3 times for acoustics) than when amorphous particles are irradiated at the same concentration. It has been shown that selenium nanoparticles exhibit significant antioxidant properties. Selenium nanoparticles effectively prevent the formation of reactive oxygen species (ROS) during water radiolysis, eliminate radiation-induced long-lived reactive species of protein, and reduce the radiation-chemical yield of a key marker of oxidative DNA damage - 8-oxoguanine.Discussion: In general, the intensity of processes occurring during laser fragmentation of amorphous and crystalline selenium nanoparticles differs significantly. The antioxidant properties are more pronounced in amorphous selenium nanoparticles compared to crystalline selenium nanoparticles.

We present Raman spectroscopy of the polycrystalline Si and Ge films deposited by molecular beam deposition on a dielectric substrate. The Raman study has been made using lasers with different wavelengths. Structural properties of the poly-films have been studied by XRD and TEM. The Raman spectra are characterized by appearance of the additional wide peaks around 500 cm^-1 and 290 cm^-1 in the main vibrational bands of TO(c-Si) and TO(c-Ge) phonons, respectively. It is shown that these peaks correspond to scattering in grain boundary area. For the poly-Si films, both a downward shift and an asymmetrical broadening of the vibrational band of TO(c-Si) near 520 cm^-1 are observed, whereas there is only a symmetric broadening in the spectra of poly-Ge. The Raman line shape has been modeled within the framework of the phonon confinement theory taking into account the sizes of coherent scattering domains obtained using XRD. The model includes a symmetrical band broadening observed in polycrystalline films. It is shown that confinement of phonon propagation might be in the poly-Si films. The phonon dispersion and the density of phonon states have been simulated using density functional theory. It has been found that phonon confinement relates to grain boundaries rather than other extended defects such as twins (multiple twins, twin boundaries), the appearance of which does not lead to significant changes in phonon dispersion and density of phonon states.

This paper studies the dynamics of the development of laser breakdown plasma in aqueous colloids of dysprosium nanoparticles by analyzing the time patterns of plasma images obtained using a high-speed streak camera. In addition, the distribution of plasma flashes in space and their luminosity were studied, and the amplitude of acoustic signals and the rate of generation of new chemical products were studied depending on the concentration of dysprosium nanoparticles in the colloid. Laser breakdown was initiated by pulsed radiation from a nanosecond Nd:YAG laser. It is shown that the size of the plasma flash, the speed of motion of the plasma–liquid interface, and the lifetime of the plasma flash decrease with an increasing concentration of nanoparticles in the colloid. In this case, the time delay between the beginning of the laser pulse and the moment the plasma flash reaches its maximum intensity increases with increasing concentrations of nanoparticles. Varying the laser fluence in the range from 67 J/cm2 to 134 J/cm2 does not lead to noticeable changes in these parameters, due to the transition of the breakdown plasma to the critical regime. For dysprosium nanoparticles during laser breakdown of colloids, a decrease in the yield of hydrogen peroxide and an increase in the rate of formation of hydroxyl radicals per water molecule, characteristic of nanoparticles of rare earth metals, are observed, which may be due to the participation of nanoparticles and hydrogen peroxide in reactions similar to the Fenton and Haber–Weiss reactions.

Using two-photon confocal microscopy in the spectral range of 0.44–0.73 μm, the spatial distribution of the luminescent characteristics of CVD-ZnSe doped with chromium using the HIP process was studied. It has been established that as a result of this process, four types of impurity-defect centers are formed in the crystal. It is shown that their formation involves point centers that form in the doping zone and diffuse deep into the crystal. Assumptions are made about the nature of these point centers.

IntroductionThe process of forming selenium nanoparticles with various shapes and structures through laser ablation and fragmentation in various solvents has been explored.MethodsLaser ablation and laser fragmentation techniques were employed using nanosecond Nd:YAG second harmonic laser irradiation in 9 different working fluids, including water. The characteristics of the resulting nanoparticles were assessed using transmission electron microscopy (TEM), dynamic light scattering (DLS), spectroscopy, and X-ray diffraction (XRD) methods.ResultsLaser ablation and subsequent laser fragmentation of some organic solvents, such as ethanol, propanol-2, isobutanol, polyethylene glycol, and diethanolamine, have been found to produce trigonal selenium in the form of elongated nanorods approximately 1 μm long and 200 nm thick, with a well-defined crystal structure. In contrast, the use of deionized water, acetone, glycerol, and benzene as solvents results in the formation of spherical amorphous nanoparticles approximately 100 nm in diameter.DiscussionThe polarity of the solvent molecules has been shown to influence the growth of crystalline selenium nanorods in solution during laser ablation and laser fragmentation. Generally, polar solvents hinder the growth of crystalline nanorods, due to interactions between selenium and solvent molecules. Nonpolar solvents, on the other hand, allow for laser fragmentation to reduce particle size and initiate the epitaxial growth of elongated, crystalline selenium nanorods.

The dependencies of the average exciton luminescence power in ZnSe and ZnSe crystal samples doped with Fe 2+ on the average excitation radiation (ER) power during two-photon absorption of this radiation in the samples were investigated. The experimental dependence of the average luminescence power as a function of the average ER power at each point of this functional dependence was approximated by a power function. The index of power for the ZnSe:Fe 2 + sample was close to 4 over the entire range of ER power, while in the ZnSe crystal without doping this the index of power depended on the ER power and decreased from 4.5 to 2.2 with increasing ER power. The obtained results are explained by the fact that the value of the index of power depends on the density of energy levels in the band gap associated with impurity defect centers (IDC) in the samples, and the difference in the behavior of the index of power with the different power of ER in them is explained by a higher concentration of IDC in sample doped with iron compared to undoped. The simulation to support this point of view are provided. The results point to the possibility of assessing the quality of semiconductor crystals in terms of IDC density by the dependence of exciton two photon luminescence power on the power of the ER upon its two photon absorption.

Foodborne infections are an important global health problem due to their high prevalence and potential for severe complications. Bacterial contamination of meat during processing at the enterprise can be a source of foodborne infections. Polymeric coatings with antibacterial properties can be applied to prevent bacterial contamination. A composite coating based on fluoroplast and Ag2O NPs can serve as such a coating. In present study, we, for the first time, created a composite coating based on fluoroplast and Ag2O NPs. Using laser ablation in water, we obtained spherical Ag2O NPs with an average size of 45 nm and a ζ-potential of −32 mV. The resulting Ag2O NPs at concentrations of 0.001–0.1% were transferred into acetone and mixed with a fluoroplast-based varnish. The developed coating made it possible to completely eliminate damage to a Teflon cutting board. The fluoroplast/Ag2O NP coating was free of defects and inhomogeneities at the nano level. The fluoroplast/Ag2O NP composite increased the production of ROS (H2O2, OH radical), 8-oxogualnine in DNA in vitro, and long-lived active forms of proteins. The effect depended on the mass fraction of the added Ag2O NPs. The 0.01–0.1% fluoroplast/NP Ag2O coating exhibited excellent bacteriostatic and bactericidal properties against both Gram-positive and Gram-negative bacteria but did not affect the viability of eukaryotic cells. The developed PTFE/NP Ag2O 0.01–0.1% coating can be used to protect cutting boards from bacterial contamination in the meat processing industry.

The structure and properties of TiNx electrodes obtained by plasma-enhanced atomic layer deposition in the 20 nm TiNx/10 nm La: HfO2(Hf0.5Zr0.5O)/20 nm TiNx/1 μm SiO2 system have been studied by electron microscopy and electron energy loss spectroscopy. It is shown that the electrode material has a TiNxOy composition, the band gap width varies within 1.7–2.5 eV, the resistivity is 208 μOm cm and the value of the temperature coefficient of resistance (20–100°C) is equal to –31.4 ⋅ 10–6 1/K.

A comparative study of the sizes and spatial structure of single dielectric colloidal nanoparticles of lanthanum fluoride, doped with rare-earth neodymium ions (Nd3+:LaF3), and their conglomerates in an aqueous solution has been performed. Nanoparticles were synthesized by aqueous co-precipitation method with subsequent hydrothermal microwave (HTMW) treatment. Experiments were performed using three methods: transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and dynamic light scattering (DLS). An analysis of the results has shown that a stable colloidal solution of nanoparticles is formed during synthesis. The solution consists of single lanthanum fluoride nanoparticles, having a narrow (10–30 nm) size distribution, and nanoclusters formed on their basis. It is also shown that the spatial structure of nanoclusters cannot be described in terms of the fractal model, which is widely used to describe clusters formed in colloidal solutions of nanoparticles of various nature.

The structure and properties of TiN x electrodes obtained by plasma-assisted atomic layer deposition in the 20 nm TiN x /10 nm La:HfO 2 (Hf 0.5 Zr 0.5 O)/20 nm TiN x /1 μm SiO 2 system have been studied by electron microscopy and electron energy loss spectroscopy. It is found that the material of the electrode has the composition TiN x O y , the bandgap ranges from 1.7 to 2.5 eV, the resistivity is 208 μΩ cm, and the temperature coefficient of resistivity in the range of 20–100°C equals –31.4 × 10 –6 K –1 .

A comparative study of the sizes and spatial structure of single dielectric colloidal nanoparticles of lanthanum fluoride, doped with rare-earth neodymium ions (Nd 3+ :LaF 3 ), and their conglomerates in an aqueous solution has been performed. Nanoparticles were synthesized by aqueous co-precipitation method with subsequent hydrothermal microwave (HTMW) treatment. Experiments were performed using three methods: transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and dynamic light scattering (DLS). An analysis of the results has shown that a stable colloidal solution of nanoparticles is formed during synthesis. The solution consists of single lanthanum fluoride nanoparticles, having a narrow (10–30 nm) size distribution, and nanoclusters formed on their basis. It is also shown that the spatial structure of nanoclusters cannot be described in terms of the fractal model, which is widely used to describe clusters formed in colloidal solutions of nanoparticles of various nature.

An investigation is performed of the photoconductivity in ZnSe crystals doped with iron via thermal diffusion in the 470–5000 nm range of wavelengths at temperatures of 77 and 300 K. Samples display high photoconductivity in the visible region. Effects of the long-term growth and relaxation of the photocurrent are discovered along with the dependence of the periods of photocurrent growth and relaxation on the wavelength of exciting radiation, its power, and the voltage applied to a sample. The effect of the quenching of residual photoconductivity upon irradiation in the range of 850–940 nm is observed.

The structure and properties of TiNx electrodes obtained by plasma-enhanced atomic layer deposition in the 20 nm TiNx/10 nm La: HfO2(Hf0.5Zr0.5O)/20 nm TiNx/1 μm SiO2 system have been studied by electron microscopy and electron energy loss spectroscopy. It is shown that the electrode material has a TiNxOy composition, the band gap width varies within 1.7–2.5 eV, the resistivity is 208 μOm cm and the value of the temperature coefficient of resistance (20–100°C) is equal to –31.4 ⋅ 10–6 1/K.

— Using Raman spectroscopy and transmission electron microscopy, boron nanoparticles synthesized by ablation in target isopropanol from boron by radiation of a pulsed ytterbium fiber laser are studied. The nanoparticle size is 5–50 nm, their composition includes boron and carbon. Nanoparticles have a carbon shell with a structures period of 0.34 nm. The application of produced nanoparticles as additives to hydrocarbon fuels and in boron neutron capture therapy is discussed.

In this paper, iron oxide nanoparticles coated with trisodium citrate were obtained. Nanoparticles self-assembling stable clusters were ~10 and 50–80 nm in size, consisting of NPs 3 nm in size. The stability was controlled by using multi-angle dynamic light scattering and the zeta potential, which was −32 ± 2 mV. Clusters from TSC-IONPs can be destroyed when interacting with a hen egg-white lysozyme. After the destruction of the nanoparticles and proteins, aggregates are formed quickly, within 5–10 min. Their sizes depend on the concentration of the lysozyme and nanoparticles and can reach micron sizes. It is shown that individual protein molecules can be isolated from the formed aggregates under shaking. Such aggregation was observed by several methods: multi-angle dynamic light scattering, optical absorption, fluorescence spectroscopy, TEM, and optical microscopy. It is important to note that the concentrations of NPs at which the protein aggregation took place were also toxic to cells. There was a sharp decrease in the survival of mouse fibroblasts (Fe concentration ~75–100 μM), while the ratio of apoptotic to all dead cells increased. Additionally, at low concentrations of NPs, an increase in cell size was observed.

Development of eco-friendly and biodegradable package materials is an important goal of modern science and international industry. Poly(lactic)-co-glycolic acid (PLGA) is suitable for this purpose. However, biocompatible materials may be contaminated with bacteria. This problem may be solved by the addition of metal oxides nanoparticles (NPs) with antibacterial properties. Although metal oxides NPs often show cytotoxicity against plant and mammalian cells, a new nanocomposite based on PLGA and aluminum oxide (Al2O3) NPs has been developed. The PLGA/Al2O3 NP composite has pronounced antibacterial properties. The addition of Al2O3 NPs 0.01% inhibited growth of E. coli for >50%. The antimicrobial effect of Al2O3 NPs is implemented through the generation of reactive oxygen species and damage of bacterial proteins and DNA. The biocompatibility of the nanocomposite with plant and mammalian cells was studied. The PLGA/Al2O3 NP composite did not influence the growth and development of tomatoes and cucumbers. PLGA and its composite with Al2O3 NPs 0.001–0.1% did not influence viability and proliferation of mammalian cells, on their density or substrate colonization rate. The developed nanocomposite has controlled mechanical properties, high antibacterial activity and high biocompatibility, which makes it an attractive candidate for building and food package material manufacture and agriculture.

The problem of bacterial contamination through surfaces is important for the food industry. In this regard, there is a growing interest in new coatings based on nanoparticles that can provide a long-term antibacterial effect. Aluminum oxide nanoparticles are a good candidate for such coatings due to their availability and good biocompatibility. In this study, a coating containing aluminum oxide nanoparticles was produced using polytetrafluoroethylene as a polymer matrix—a polymer that exhibits excellent mechanical and physicochemical properties and it is not toxic. The obtained coatings based on “liquid Teflon” containing various concentrations of nanoparticles (0.001–0.1 wt%) prevented the bacterial growth, and they did not exhibit a cytotoxicity on animal cells in vitro. Such coatings are designed not only to provide an antibacterial surface effect, but also to eliminate micro damages on surfaces that inevitably occur in the process of food production.

An original method was proposed to reduce the quenching of the NIR fluorescence of colloidal solutions of 0.1 at. % Nd3+: LaF3 nanoparticles (NPs) synthesized by aqueous co-precipitation method followed by hydrothermal microwave treatment. For this, an aqueous colloidal solution of NPs was precipitated by centrifugation and dissolved in the same volume of DMSO. The kinetics of static fluorescence quenching of Nd3+ donors of doped NPs dispersed in two solvents was analyzed to determine and to compare the concentrations of OH- quenching acceptors uniformly distributed throughout the volume of the NPs. The dependences of the relative fluorescence quantum yield φ of colloidal solutions on the concentration of OH- groups in the NPs were calculated and were also used to determine concentration of acceptors in the volume of NPs in different solvents. It was found that the concentration of OH- groups in NPs dispersed in DMSO is almost two times lower than in NPs dispersed in water. This gives an almost two-fold increase in the relative fluorescence quantum yield φ for the former. The sizes of synthesized NPs were monitored by common TEM and by applying a rapid procedure based on optical visualization of the trajectories of the Brownian motion of NPs in solution using a laser ultramicroscope. The use of two different methods made it possible to obtain more detailed information about the studied NPs.