Influence of wide band gap oxide substrates on the photoelectrochemical properties and structural disorder of CdS nanoparticles grown by the successive ionic layer adsorption and reaction (SILAR) method

The photoelectrochemical properties of nanoheterostructures based on the wide band gap oxide substrates (ZnO, TiO2, In2O3) and CdS nanoparticles deposited by the successive ionic layer adsorption and reaction (SILAR) method have been studied as a function of the CdS deposition cycle number (N). The incident photon-to-current conversion efficiency (IPCE) passes through a maximum with the increase of N, which is ascribed to the competition between the increase in optical absorption and photocarrier recombination. The maximal IPCE values for the In2O3/CdS and ZnO/CdS heterostructures are attained at N ≈ 20, whereas for TiO2/CdS, the appropriate N value is an order of magnitude higher. The photocurrent and Raman spectroscopy studies of CdS nanoparticles revealed the occurrence of the quantum confinement effect, demonstrating the most rapid weakening with the increase of N in ZnO/CdS heterostructures. The structural disorder of CdS nanoparticles was characterized by the Urbach energy (EU), spectral width of the CdS longitudinal optical (LO) phonon band and the relative intensity of the surface optical (SO) phonon band in the Raman spectra. Maximal values of EU (100–120 meV) correspond to СdS nanoparticles on a In2O3 surface, correlating with the fact that the CdS LO band spectral width and intensity ratio for the CdS SO and LO bands are maximal for In2O3/CdS films. A notable variation in the degree of disorder of CdS nanoparticles is observed only in the initial stages of CdS growth (several tens of deposition cycles), indicating the preservation of the nanocrystalline state of CdS over a wide range of SILAR cycles

Raman study of light-emitting SiNx films grown on Si by low-pressure chemical vapor deposition

Si-rich silicon nitride (SRSN) films were deposited on Si wafers by low pressure chemical vapor deposition (LPCVD) technique and, subsequently, annealed at (800–1200) °C to form Si precipitates. The composition of SiNx films was measured by Rutherford backscattering spectrometry (RBS). Two sets of samples differed by the amount of excessive Si (Siexc) in silicon nitride were studied. Evolution of Si nanoclusters from amorphous to crystalline ones during high temperature treatment was examined by Raman scattering (RS) spectroscopy. The amorphous Si clusters were already revealed in as-deposited SiNx while the annealing results in their crystallization. The crystalline nanoprecipitates are only registered in nitride films after annealing at 1200 °C. A dependence of Raman scattering intensity from the Si wafer on the temperature of annealing of SiNx/Si structures was revealed. This information was used to explain the phase transformations in SRSNs during high temperature treatments. The peculiarities of photoluminescence (PL) spectra for two sets of Si-rich SiNx films are explained taking into account the contribution from the quantum confinement effect of Si nanocrystals and from the native defects in silicon nitride matrix, such as N- and K-centers

Raman Study of CVD Graphene Irradiated by Swift Heavy Ions

CVD-graphene on silicon was irradiated by accelerated heavy ions (Xe, 160 MeV, fluence of 1011 cm-2) and characterized by Raman spectroscopy. The defectiveness of pristine graphene was found to be dominated by grain boundaries while after irradiation it was determined by both grain boundaries and vacancies. Respectively, average inter-defect distance decreased from ~ 24 to ~ 13 nm. Calculations showed that the ion irradiation resulted in a decrease in charge carrier mobility from ~ 4.0 × 103 to ~ 1.3·103 cm2/V s. The results of the present study can be used to control graphene structure, especially vacancies concentration, and charge carrier mobility

The Opportunity of Using Diode Laser with the Length of 1940 nm in the Treatment of Hemorrhoids

Aim: to improve the results of treatment of patients with hemorrhoidal disease of the 2nd and 3rd stages by using a diode laser with a wavelength of 1940 nm.Materials and methods. The study included 28 patients with hemorrhoids of the second or third stage. A new treatment method based on the use of a diode laser with a wavelength of 1940 nm was applied to all patients. This technique (laser hemorrhoidoplasty) provides for the thermal effect of laser radiation on the cavernous tissue of the internal hemorrhoid node and the terminal branches of the upper rectal artery. The intensity of postoperative pain syndrome was assessed and the clinical symptoms of hemorrhoidal disease manifestations were studied before and after surgery. To study the effectiveness of the proposed method and to assess the depth of thermal exposure to laser radiation, transrectal ultrasound with Dopplerography and pathomorphological examination were performed. The functional state of the rectal locking apparatus before surgery and in the postoperative period was assessed using sphincterometry. The quality of life of patients who underwent laser hemorrhoidoplasty was studied according to the SF 36 questionnaire.Results. Surgical intervention was performed under both local and spinal anesthesia. Intraoperative complications in the form of hemorrhoidal node bleeding were noted in 3 patients. In the early postoperative period, inflammatory edema of external hemorrhoids was diagnosed in 4 patients. The intensity of the pain syndrome was assessed on the VAS scale and by day 7 in 93 % of patients it did not exceed 1 point. All 28 patients were followed up within 1 to 6 months after the operation. All had no complaints characteristic of hemorrhoidal disease, no relapse of the disease was detected in any observation. Transrectal ultrasound with Dopplerography was performed, which made it possible to diagnose a 2–3-fold decrease in blood flow along the terminal branches of the upper rectal artery, and internal hemorrhoids determined earlier, before surgery, were not visualized already 1 month after surgery. According to sphincterometry, no violations of anal retention function were detected in all 28 patients.Conclusion. Surgical treatment of hemorrhoids of the 2nd and 3rd stages with the use of a diode laser with a wavelength of 1940 nm. with proper technical performance and the choice of optimal energy, it allows to achieve a good clinical effect. The proposed method of intervention ensures the absence of a pronounced pain syndrome, which does not lead to a significant decrease in the quality of life already in the early postoperative period and allows to shorten the period of labor rehabilitation. Laser hemorrhoidoplasty is a highly effective method of treating hemorrhoids at stages 2 and 3 of the disease and opens up the possibility of treatment on an outpatient basis

Micro Raman investigation of graphene synthesized by atmospheric pressure CVD on copper foil from decane

In this article we present the results of micro-Raman studies of graphene grown on copper foil surface by atmospheric pressure CVD using decane as precursor, nitrogen as carrier gas with zero flow of hydrogen. Analysis of Raman spectroscopy data showed that film contains spots with single layer thick graphene. We observed significant blue shift of 2D and G bands positions for mono-atomically thick graphene on copper foil. Following literature we relate this shift to the strain induced by the presence of copper substrate. Moreover, we observed changes in the defectiveness of graphene layers after the transfer, which was related to the appearance of chemically-induced defects and defects induced by changes in the mechanical strain

Differential Carbohydrate Recognition by Campylobacter jejuni Strain 11168: Influences of Temperature and Growth Conditions

The pathogenic clinical strain NCTC11168 was the first Campylobacter jejuni strain to be sequenced and has been a widely used laboratory model for studying C. jejuni pathogenesis. However, continuous passaging of C. jejuni NCTC11168 has been shown to dramatically affect its colonisation potential. Glycan array analysis was performed on C. jejuni NCTC11168 using the frequently passaged, non-colonising, genome sequenced (11168-GS) and the infrequently passaged, original, virulent (11168-O) isolates grown or maintained under various conditions. Glycan structures recognised and bound by C. jejuni included terminal mannose, N-acetylneuraminic acid, galactose and fucose. Significantly, it was found that only when challenged with normal oxygen at room temperature did 11168-O consistently bind to sialic acid or terminal mannose structures, while 11168-GS bound these structures regardless of growth/maintenance conditions. Further, binding of un-capped galactose and fucosylated structures was significantly reduced when C. jejuni was maintained at 25°C under atmospheric oxygen conditions. These binding differences identified through glycan array analysis were confirmed by the ability of specific lectins to competitively inhibit the adherence of C. jejuni to a Caco-2 intestinal cell line. Our data suggests that the binding of mannose and/or N-acetylneuraminic acid may provide the initial interactions important for colonisation following environmental exposure

Confocal spectrometer for study of organic-inorganic perovskites

Organic-inorganic perovskites (OIPs) are promising photovoltaic materials due to the simplicity of synthesis technique and attractive physical properties. It is known that the power conversion efficiency of solar cells with an OIP photoabsorbing layer has recently reached approximately 23%. Unfortunately, OIPs easily degrade under influence of heat, moisture, oxygen and light soaking. Encapsulation of OIP layers to protect them against moisture and oxygen is necessary, which hampers to use traditional methods of analysis such as electron and probe microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, X-ray diffraction, etc. As a result, significant difficulties in determination of photodegradation mechanisms arise, so, we are forced to look for other techniques of highly informative nondestructive analysis of such structures. For studying photoinduced processes in OIP layers, we applied confocal spectrometer, which allowed to use a laser beam (i) as a source of optical radiation causing photodegradation; (ii) for the local analysis of changes in the structure of the area exposed to optical radiation using Raman and photoluminescence (PL) spectra; (iii) for local measurement of solar cell parameters (short circuit current, open circuit voltage). The presence of a 3D piezoelectric scanner enables one to do the mapping of spectral and photoelectric parameters, which is important for establishing the homogeneity of the objects under study. The proposed approach allows obtaining information on the phase composition and spectrum of electronic states (from the Raman and PL spectra), as well as on the dynamics of charge carriers. By recording PL and Raman spectra, short circuit current and open circuit voltage under laser beam illumination, one can observe the evolution of the system in th

Confocal spectrometer for study of organic-inorganic perovskites

Organic-inorganic perovskites (OIPs) are promising photovoltaic materials due to the simplicity of synthesis technique and attractive physical properties. It is known that the power conversion efficiency of solar cells with an OIP photoabsorbing layer has recently reached approximately 23%. Unfortunately, OIPs easily degrade under influence of heat, moisture, oxygen and light soaking. Encapsulation of OIP layers to protect them against moisture and oxygen is necessary, which hampers to use traditional methods of analysis such as electron and probe microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, X-ray diffraction, etc. As a result, significant difficulties in determination of photodegradation mechanisms arise, so, we are forced to look for other techniques of highly informative nondestructive analysis of such structures. For studying photoinduced processes in OIP layers, we applied confocal spectrometer, which allowed to use a laser beam (i) as a source of optical radiation causing photodegradation; (ii) for the local analysis of changes in the structure of the area exposed to optical radiation using Raman and photoluminescence (PL) spectra; (iii) for local measurement of solar cell parameters (short circuit current, open circuit voltage). The presence of a 3D piezoelectric scanner enables one to do the mapping of spectral and photoelectric parameters, which is important for establishing the homogeneity of the objects under study. The proposed approach allows obtaining information on the phase composition and spectrum of electronic states (from the Raman and PL spectra), as well as on the dynamics of charge carriers. By recording PL and Raman spectra, short circuit current and open circuit voltage under laser beam illumination, one can observe the evolution of the system in th

Carrier dynamics in highly-excited TlInS2: Evidence of 2D electron-hole charge separation at parallel layers

We report a comprehensive study of the time-resolved photoluminescence (PL), carrier recombination, and carrier diffusion under diverse laser pulse excitations in TlInS2. The 2Dlayered crystals were grown by Bridgman method without or by a small Erbium presence in the melt. The investigation expose large differences in two crystal types, although, a linear nonradiative lifetime and carrier diffusivity attain close values at high excitation with no contribution of the Auger recombination and absence of the band gap narrowing effect. Moreover, at high pulse power, we detect imprinted transient grating fringes which are attributed to new crystal phase formed by 2D electron-hole charge separation on local layers. The versatile model of the spontaneously polarized 2D-crystal has been developed to explain observed features and ergodicity of charge dynamic processes. The model embraces the planar stacking faults (PSFs) as a distortion which edge is acting as sink of strong recombination. The reduced occurrence of the PSFs in the Erbium doped TlInS2 is the main attribute which determines enhancement of PL by a factor of 50, and improves carrier diffusion along 2D-layers. The simulation permits to evaluate the PSFs sizes of about 0.7 m. Presented results allow improving 2D-crystal growth technology for novel sensor devices with separated excess charges

Carrier dynamics in highly-excited TlInS2: Evidence of 2D electron-hole charge separation at parallel layers

We report a comprehensive study of the time-resolved photoluminescence (PL), carrier recombination, and carrier diffusion under diverse laser pulse excitations in TlInS2. The 2Dlayered crystals were grown by Bridgman method without or by a small Erbium presence in the melt. The investigation expose large differences in two crystal types, although, a linear nonradiative lifetime and carrier diffusivity attain close values at high excitation with no contribution of the Auger recombination and absence of the band gap narrowing effect. Moreover, at high pulse power, we detect imprinted transient grating fringes which are attributed to new crystal phase formed by 2D electron-hole charge separation on local layers. The versatile model of the spontaneously polarized 2D-crystal has been developed to explain observed features and ergodicity of charge dynamic processes. The model embraces the planar stacking faults (PSFs) as a distortion which edge is acting as sink of strong recombination. The reduced occurrence of the PSFs in the Erbium doped TlInS2 is the main attribute which determines enhancement of PL by a factor of 50, and improves carrier diffusion along 2D-layers. The simulation permits to evaluate the PSFs sizes of about 0.7 m. Presented results allow improving 2D-crystal growth technology for novel sensor devices with separated excess charges