Comparison between solar cell heterostructures based on poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate) (PEDOT:PSS) organic complex thin film and semiconductors (Si, GaAs) with flat and microrelief interfaces have been performed. PEDOT:PSS film thicknesses and optical parameters were ascertained using spectroscopic ellipsometry, while electrical dc-conductivity was determined using the four-point probe method. A method of increasing the conductivity of PEDOT:PSS films by forming a multilayer film with a decreased content of PSS component is proposed. Plasmon-active metal nanoparticles (Au, Ag) have been grown on the active interface region to increase photoconversion efficiency. They reduce the structure series resistance and increase the I–V characteristic fill factor as well as the incident light absorption. The post-processing treatment method of fabricated structures to obtain a tunnel-thin intermediate layer of SiO2 of optimal thickness has been proposed. The photoelectric properties of the fabricated solar cells have shown that GaAs-based structures have more stable long-term characteristics and higher open-circuit voltage than Si-based ones.

The impact of femtosecond (fs) laser radiation on semiconductors with direct (ZnSe, GaAs, CdZnTe) band gap, with the structurally induced direct-to-indirect band gap transition (PbI2, GaSe) and indirect band gap (Si) has been studied. The fs-laser treatment of semiconductors has been performed in the multi-pulse regime in air environment. The influence of fs-laser radiation parameters on surface morphology of the semiconductors has been analyzed by scanning electron microscopy (SEM) and 2D Fourier transform of SEM images, optical photoluminescence spectroscopy. Under the treatment with the fundamental fs-laser radiation (800 nm, about 130–150 fs), both low spatial frequency LIPSS and high spatial frequency LIPSS have been observed. Specific features of LIPSS of two types (low spatial frequency LIPSS and high spatial frequency LIPSS) and other structure peculiarities (grooves, grains, different defects in periodic structure, i.e., loops, strip breaks, and ablation products) have been also analyzed. The formation mechanisms of LIPSS are also considered within the scope of two approaches, namely an electromagnetic approach and matter reorganization processes.

Plasmonic cavity metasurfaces based on metal laser-induced periodic surface structures (LIPSSs) and non-spherical metal nanoparticles (NPs) were shown to provide the highly sensitive detection and imaging of biomolecules at room temperature without their special labelling. We studied the enhancement of Raman scattering of 5’-deoxyadenosine monophosphate (dAMP) deposited on two types of fabricated cavity metasurfaces: 1) Ag LIPSSs and Ag triangular nanoprisms, 2) crystalline Si LIPSSs and a pre-deposited thin gold film modified during laser treatment. Both types of the metasurfaces contain metal or metal-semiconductor substrates processed with femtosecond laser radiation in a single step. An enhancement of more than 100 times for some Raman peaks of dAMP at Ag nanoprisms/Ag LIPSSs was achieved. In the case of Au NPs/Si LIPSS metasurface a slight increase of Raman spectrum of dAMP was revealed. This effect additionally emphasizes the crucial role of the near-field coupling of the localized surface plasmon modes of Ag nanoprisms and the propagating surface plasmon polaritons of Ag surfaces and consequent formation of collective plasmonic gap modes of the entire plasmonic cavity that determine the appearance of hot spots at such metasurfaces.

In this work femtosecond laser treatment of crystalline silicon was performed with the aim of producing laser-induced periodic surface structures (LIPSSs), and emission from the processing area was measured. Broad photoluminescence (PL) of the oxidized silicon, second-harmonic generation (SHG) of the laser radiation on the structured surface and sharp emission lines (ELs) of the ablated silicon atoms were detected. The ratio of intensities of SHG to PL (or SHG to EL) is suggested as a real-time figure of merit for LIPSS formation. Diffraction patterns of white light on the produced LIPSS confirm this suggestion.

Small clusters of cesium-lead-iodide perovskites (CLIPs) have been prepared in the Na-X zeolite matrix and studied by means of spectroscopy and quantum chemical modeling. Regularity of pores in single crystals of zeolite assures the formation of clusters of a certain size. By the first-principles quantum chemical calculations, we have determined that clusters Cs4PbI6, Cs5Pb2I9, and probably Cs7Pb5I16 with a size of 0.74, 1.29, and 1.36 nm, respectively, have elevated stability compared to other species, and they fit into the pores of Na-X zeolite. Electronic energy spectra of these clusters have been calculated and compared with experimentally measured ones.

Au-GaAs metal-semiconductor composite microstructures have been prepared by an anisotropic etching of n-GaAs (100) wafers doped with Te (1016 to 1017 cm-3) with subsequent photostimulated chemical deposition of noble metal (Au) on formed semiconductor quasigratings. The microrelief topology of GaAs surface is controlled by the anisotropic etching conditions. Au metal was deposited on the structured GaAs surface as randomly placed nanoparticles of various shape and size and/or nanowires on the top of the hills of formed semiconductor microstructure. As the number of Au nanoparticles increases, they tend to localize on the ledges of the GaAs microrelief forming a system of approximately parallel nanowires. Obtained periodic structures with submicron to microns periods without Au nanoparticles and with deposited nanoparticles have been studied by means of scanning electron microscopy, optical spectroscopy (photoluminescence spectroscopy at room temperature), and photoelectric measurements. The decrease of the relative intensity of main photoluminescence band for samples with Au nanostructures compared to ones without nanoparticles deposition and simultaniously changes of the shape of photocurrent spectra of Au-GaAs microstructures have been observed. Such correlation in behaviour of measured spectra make formed Au-GaA metal-semiconductor microstructures perspective for the application in plasmonic photovoltaics.

The ZnSe single crystal treatment in air environment with linearly polarized Ti/sapphire femtosecond (fs)laser pulses of the energy density of around 0.04-0.05 J/cm2 with central wavelength of 800 nm and the pulse duration of 140 fs at a repetition rate of 1 kHz generates the laser-induced periodic surface structures (LIPSSs). The setup with a cylindrical quartz lens at normal incidence allowed processing a relatively large area of the ZnSe sample in one pass of the laser beam. Morphology analysis of LIPSS by scanning electron microscopy (SEM) and image processing reveals the existence of two periods of around 200.0 nm and 630.0 nm simultaneously. All LIPSSs demonstrate the orientation perpendicular to the laser beam polarization. The possible nature of LIPSS formation on ZnSe single crystal is caused by the synergetic influence of the interference mechanism involving surface plasmon polaritons and hydrodynamic effects of surface morphology modification. The fs-laser-induced changes of carrier concentrations in ZnSe specify obtained periods of high spatial frequency LIPSS. The influence of femtosecond laser processing on luminescent properties of ZnSe single crystal has been studied by an analysis of the photoluminescence (PL) and X-ray luminescence (XRL) spectra of laser-treated and untreated areas in the visible region of spectrum at room and low temperatures. The PL spectra and XRL spectra, as well as temperature dependencies of XRL spectra or thermally stimulated luminescence curves, demonstrate a good correlation for untreated and fs-laser-treated ZnSe surfaces. Specific PL bands related to the extended structural defects do not appear for LIPSS at the ZnSe sample under an excitation of 337 nm (3.68 eV). The Relative intensities and position of separate components of observed luminescence bands after ultrashort laser treatment do not change significantly. Thus, the structural perfection of the ZnSe single crystal surface is preserved.

The features of laser structuring of the n-doped crystalline silicon surface achieved by femtosecond laser irradiation with different wavelengths, namely fundamental wavelength of 800 nm, the second (400 nm) and the third (266 nm) laser harmonics, have been studied. Morphology analysis of the processed Si surface reveals laser-induced periodic surface structures (LIPSS) perpendicular to the laser beam polarization for all the applied laser wavelengths. The laser-processed Si surfaces also contain nanoparticles and defects in periodic structure (strip breaks, bifurcations, nodes, etc.). In the case of circularly polarized laser irradiation, the irregular granular structure with the short-range order distance of about 600 nm has been observed. The 2D-FFT analysis of SEM images of LIPSS generated by the fundamental laser wavelength detects structures with two periods simultaneously: near-subwavelength ripples and weaker deep-subwavelength ripples. The latter are attributed to the second harmonic generation of the laser radiation at the surface. For 400 nm laser irradiation the ripple period is observed in the range of 290–310 nm, for 266 nm – 240–250 nm. The effect of the pulse irradiation energy density on the LIPSS morphology has been investigated for linearly polarized femtosecond laser radiation with the wavelength of 800 nm. The main period of LIPSS has been observed to decrease slightly with the decrease of laser pulse energy density that is in agreement with theoretical model of LIPSS formation.

The simultaneous quantum-chemical and spectral investigations of the possible relaxation pathways in the excited state for the two α,ω-di-substituted polyenes were performed. Lengthening of the polymethine chain is accompanied by the considerable decreasing of the first electron transition and hence is manifested as the bathochromic shift of both absorption and fluorescence spectra; however, the nature of transition does not change. It is established that the considerable changes of the bond lengths in polymethine chain for both vinylogs in the excited state cause firstly the appearance of the fast component in short wavelengths spectral region; after relaxation, the intensity of the fast component decreases, and it disappears, but then the spectral band, shifted bathochromically, appears, so that its maximum coincide with the band maximum in the steady-state fluorescence maximum, what corresponds to the final symmetrical relaxation of bond lengths. The parallel quantum-chemical calculation shows that two highest levels are mainly formed by the donor levels of both terminal groups and hence twice occupied splitting levels. Upon excitation, one of the splitting MO (HOMO) becomes single occupied; this causes the molecule in the excited state to be unstable and could transform it to the unsymmetrical form. Such relaxation path is confirmed by the time-resolved spectra: the spectral band in both molecules, with the different polymethine chains, undergoes the subsequent bathochromical shifting.

Experimental and computational studies of resonant Raman spectra of truly monosized (CdSe)33 and (CdSe)34 nanoclusters have been performed. First-principles calculations of vibrations are performed to account for the peculiarity of the spectrum and resonant Raman selection rules. The calculation method is based on the analysis of the spatial distribution of the electron density in the ground and excited states and the corresponding displacement of atoms after the electronic transition. The calculated vibrational density of states and resonant Raman spectra of CdSe nanoclusters in a core-cage arrangement are distinctively different from those of small nanocrystals in the bulk fragment model and reasonably agree with the experimentally observed spectral features. The agreement can be considered as experimental evidence for the shell structure of "magic" CdSe nanoclusters. The resonant conditions for the Raman measurements and two different kinds of samples stabilized with decylamine in toluene and with cysteine in water ensure the reliability of our measurements and the minor influence of the stabilizer.

The label-free detection of biomolecules by means of fluorescence spectroscopy and imaging is topical. The developed surface-enhanced fluorescence technique has been applied to achieve progress in the label-free detection of biomolecules including deoxyribonucleic acid (DNA) bases. In this study, the effect of a strong enhancement of photoluminescence of 5'-deoxyadenosine-monophosphate (dAMP) by the plasmonic nanocavity metasurface composed of the silver femtosecond laser-induced periodic surface structure (LIPSS) and gold nanorods or nanospheres has been realized at room temperature. The highest value of 1220 for dAMP on the Ag-LIPSS/Au nanorod metasurface has been explained to be a result of the synergetic effect of the generation of hot spots near the sharp edges of LIPSS and Au nanorod tips together with the excitation of collective gap mode of the cavity due to strong near-field plasmonic coupling. A stronger plasmonic enhancement of the phosphorescence compared to the fluorescence is achieved due to a greater overlap of the phosphorescence spectrum with the surface plasmon spectral region. The photoluminescence imaging of dAMP on the metasurfaces shows a high intensity in the blue range. The comparison of Ag-LIPSS/Au nanorod and Ag-LIPSS/Au-nanosphere metasurfaces shows a considerably higher enhancement for the metasurface containing Au nanorods. Thus, the hybrid cavity metasurfaces containing metal LIPSS and nonspherical metal nanoparticles with sharp edges are promising for high-sensitive label-free detection and imaging of biomolecules at room temperature.

Direct surface modification of dental implants based on zirconium (Zr), Ti–Zr alloys, and zirconia ceramics has been achieved by the irradiation of their surfaces with Ti:sapphire femtosecond laser. Fundamental (800 nm) and third (266 nm) harmonics of femtosecond laser have been used for the surface treatment. Laser treatment is one of the effective techniques of micro- and nanotexturing of the dental implant surfaces that can improve the adhesion of living tissues. The peculiarities of morphology of laser-treated surfaces have been studied using scanning electron microscopy. It has been revealed that efficient structuring of implant specimens has been observed at a higher irradiation power density at a higher scanning speed. An increase of the laser power density also contributes to the uniformity of the structure within the laser beam spot on the surface, which minimizes the inhomogeneity at the junctures of strips of consecutive laser beam passes. The wettability of laser-treated specimens is essentially dependent on preliminary treatment before femtosecond laser processing.

A quantum-chemical study of the atomic charges and bond orders in the cations of the linear conjugated systems was performed. It is shown that total charge in the collective system of the π-electrons generates the soliton-like wave of the alternated partial charges along the conjugated chain not only in ground state but also in the excited state. The excitation is accompanied by the change of the soliton phase and the wave dimension. Additionally, it is established that the electron density redistribution at the atoms and bonds also forms the soliton-like wave. In paper, the dependence of the solitonic wave shape on the dimension and section of the polymethine is studied; established regularities in the charge distribution in excited state could be used for the molecular design of organic semiconducting materials.

A reliable photoluminescence (PL) spectroscopy and imaging of biomolecules at room temperature is a challenging and important problem of biophysics, biochemistry, and molecular genetics. A unique effect of strong plasmonic enhancement of the PL by metal nanostructures is one of the most effective approaches for this purpose. The highest enhancement is provided by metal nanostructures with densely packed sharp tips, periodically arranged metal nanostructures, and plasmonic cavities. All of these features have been realized in the plasmonic cavity metasurface based on the silver (Ag) laser-induced periodic surface structure and Ag triangular nanoprisms studied in the present work. The strong plasmon-enhanced PL of 5'-deoxyadenosine monophosphate deposited on such metasurfaces has been revealed at room temperature. The observed enhancement of more than 1000-fold has been interpreted as a result of synergetic action of the generation of a high concentration of hot spots near the sharp edges of the laser-induced surface structure and nanoprisms together with excitation of the collective gap mode of the cavity due to strong near-field plasmonic coupling. Correspondingly, the plasmonic cavity metasurfaces consisting of metal laser-induced periodic surface structures and nonspherical metal nanoparticles with sharp edges have been shown to be crucial for the highly sensitive detection and imaging of biomolecules at room temperature without consuming any dye labels.

Surface texturing of metals and alloys with Ti: Sapphire femtosecond laser has been carried out in air.The peculiarities of surface patterns formed on the surface of noble metals (silver, gold, copper), refractory metal (tungsten) and metal-semiconductor alloy under ultrashort laser pulses have been studied by means of the surface morphology analysis.The influence of the laser ablation process on the formation of nanoscale features on the laser treated surfaces has been discussed.In the experiments, the low fluence multi-pulse regime near the ablation threshold for studied materials has been realized.The average sizes of nanoscale features formed under ultrashort laser processing on the surface structures have been determined for silver, gold, copper and tungsten.Observed enhancement of Raman signal for some vibrations of Methylene Blue dye adsorbed on laser-induced Ag surface structures demonstrates the possibility of an application of the laser-textured substrates as surface enhanced Raman scattering (SERS) substrates used for biosensing.

The present report concentrates on little known peculiarities of laser-induced periodic surface structures (LIPSS) on metals and alloys formed upon irradiation by linearly polarized Ti/sapphire femtosecond laser pulses with the energy density of 0.17–1.0 J/cm2 in air environment. The peculiarities discussed are spontaneous twofold reduction in period and appearance of dislocations in the quasi-grating LIPSS. The twofold reduction in period is interpreted as a result of the second harmonic generation (SHG) of the laser light on the surface, stimulated and enhanced by surface roughness. LIPSS with two times shorter period stimulate SHG, and in this way a positive feedback mechanism works. The dislocations in the LIPSS are explained as the interference of scattered wave, which may contain optical vortices, with the incident plane wave. The quasi-grating with the dislocations works as a spatial phase modulator for the scattered wave and provides a positive feedback for enhancement of the dislocations. A successful example of application of LIPSS on noble metals as a SERS substrate and a discussion of their features important for such application is presented.

The paper analyzes the experience of people’s, infected by HIV, loneliness as an existential category and as a part of all their spectrum of feelings and experiences. The central existential problem for people with HIV-positive status is social and interpersonal isolation, which brings to loneliness. There are no publications that highlight the loneliness of people, who lives with HIV, through the prism of an existential approach. The article also considers the problem of stigmatization, self-stigmatization and isolation of HIV-infected individuals. The situation is aggravated by the fact that terminally ill people not only experience negative emotions, but also realize their own guilt for infecting their illness, feel shame because of the negative social status of the "sinful" disease. People with HIV are a special subculture in our society; they often consider themselves as outcasts. Thanks to this research, the subjective meanings that have people with HIV put into the concept of loneliness are revealed. The author did her own semantic differential, which was helped in finding differences in the experience and understanding of loneliness by hypochondriacal people who are afraid of infecting HIV, as well as persons with a positive HIV status. The results of two groups were statistically handled by using factor analysis. As a result the components of the loneliness category for the control (hypochondriac) and experimental (people infected by HIV) groups were picked out. Eventually, hypochondriacal people actualize loneliness through the following factors: "anxiety-depression", "hopelessness" and "vulnerability". In turn, people with HIV-positive status, see loneliness through: "despair", "disgust" (directed both at oneself and at the outside world), and "rejection". The results can be explained by the fact that persons with HIV infection have already felt the consequences of social isolation and loneliness, therefore they describe themselves as outcasts, despair and disgust both to themselves and to others. While people who only afraid of contracting HIV predict this can lead to anxiety, hopelessness and vulnerability. However, the selected components are rather situational than a priori, so the picture may change somewhat upon repeated investigation.

Peculiarities of the laser treatment of a composite consisting of a thin film of a metal (gold) on the surface of a semiconductor substrate [silicon (100)] have been studied. Micro- and nanostructurings of the metal-semiconductor composite sample have been achieved by the irradiation of its initial surface with a Ti : sapphire femtosecond laser. Laser ablation leads to the patterning of the surface of the composite with laser-induced periodic surface structures (LIPSS) and the formation of semiconductor nanohills, metal nanoparticles, and/or nanowires on the top of hills. The presence of some nanoscale surface features is confirmed by a low-frequency shift of the silicon phonon band in Raman spectra. Prepared microstructured surface barrier solar cells are characterized by means of scanning electron microscopy, optical spectroscopy, and photoelectric measurements.