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Tuning optical properties of cadmium thiourea acetate nonlinear optical crystal exploiting organic ligand of L-proline
摘要： Modifying optical properties of crystal is very fundamental need for designing various photonic devices, hence in the current investigation, the L-proline (LP) has been firstly doped in cadmium thiourea acetate (CTA) crystal with the aim to optimize the UV–Visible, second harmonic generation (SHG) efficiency, luminescence and third-order nonlinear optical (TONLO) properties of CTA crystal. The pure and doped CTA crystals have been grown by slow solvent evaporation technique at 35°C. The structural parameters of grown crystals have been determined using the single crystal X-ray diffraction technique. The incorporation of LP in CTA crystal matrix has been confirmed by Fourier transforms infrared analysis. The UV–Visible studies have been employed within the wavelength range of 200–900 nm to explore the enhancing impact of LP on CTA crystal. The LP doped CTA crystals were subjected to Kurtz–Perry test and Z-scan analysis to identify the nonlinear nature of studied crystals. The SHG efficiency of LP-CTA crystal shows significant increase owing to enhanced charge transfer over the organic ligand of LP. The laser-induced TONLO properties of LP-doped CTA crystal have been determined at 632.8 nm. The nature of nonlinear refraction and absorption has been explored by close and open aperture Z-scan configuration. The magnitude of nonlinear refraction (n2), absorption coefficient (β), cubic susceptibility (χ3) and figure of merit has been determined using the transmittance data. The color-centered luminescence studies have been carried out which established the prominent redshift in peak maxima of emission wavelength of CTA crystal due to doping of LP. Comparative analysis of pure and doped crystal confirmed the dominance of LP doping.
关键词： optical studies,TONLO parameters,Crystal growth,Z-scan analysis
更新于2025-09-23 15:22:29
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CuI Film Produced by Chemical Extraction Method in Different Media
摘要： CuI crystalline thin films were produced on substrates (commercial glass) using chemical extraction method in different chemical bath media. In this study, their structural, optical and electrical properties were analyzed. Transmittance, absorption, optical band gap and refractive index of the films were examined by UV/VIS spectrum. XRD data showed that the film has a hexagonal structure for CuI. Surface and elemental (in terms of ratio) analysis of the films were performed via SEM and EDX analysis. The highest average grain size of CuI was observed for the film produced in aqueous media whereas the lowest average grain size was seen in chloroform bath. The curve formed by the number of crystallites per unit area (N) is different than the curves of dislocation density and average grain size. Number of crystallites per unit area has reached its maximum value in CCl4 bath, but it has been decreased in chloroform bath. In addition, film thickness has varied between 1232 nm and 3624 nm according to the solvent of bath.
关键词： CuI films,Thin film,Chrystal growth,Optical properties
更新于2025-09-23 15:22:29
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Microstructural Aspects of Infiltration Growth YBCO Bulks with Chemical Pinning
摘要： Single grain YBa2Cu3O7-x (YBCO, Y123) bulk superconductors were prepared by infiltration growth (IG) process. The solid phase precursor was prepared by solid state synthesis from Y2O3+BaCuO2 powders. The influence of the composition of the source of melt for infiltration and the CeO2 addition on the transition temperature and critical current density was studied. It is shown that the studied samples are doped by Yb from the Yb2O3 substrate. The dependences of Yb concentration on the distance from the bottom of the samples were measured by EDS microanalysis at SEM. Correlation between the fabrication technology, level of Yb doping, microstructure and superconducting properties is discussed.
关键词： infiltration growth,chemical pinning,microstructure,YBCO bulk superconductor
更新于2025-09-23 15:22:29
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Morphology Controllable Synthesis of Hierarchical WO3 Nanostructures and C2H2 Sensing Properties
摘要： In this paper, we reported the morphology controllable synthesis of hierarchical WO3 nanostructures, i.e. nanorods, nanospheres and nanoflowers, via a facile hydrothermal route. All the obtained WO3 nanostructures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET), respectively. A possible growth mechanism for the three various nanomaterials was proposed in detail. WO3 based gas sensors were fabricated with the synthesized nanomaterials and the gas sensing performances to acetylene (C2H2), one of the fault characteristic gases dissolved in power transformer oil, were systematically measured. It was found that the sensor based on nanosheet-assembled nanoflowers with largest surface (56.74 m2g-1) exhibits the highest sensing performance including gas response (32.31) and response-recovery time (12 s, 17 s) to 200 ppm C2H2. The results indicate that WO3 sensing materials could be a promising choice for synthesizing high-performance C2H2 sensors for the judgement of the early latent faults of the oil immersed transformer.
关键词： Hierarchical WO3,Gas sensors,Growth mechanism,C2H2 sensing performances
更新于2025-09-23 15:22:29
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Growth of high quality AlN/sapphire templates with high growth rate using a medium-temperature layer
摘要： In this work, crack-free 3.3-μm-thick AlN ?lms with high crystalline quality and atomic smooth surfaces were achieved on sapphire substrates at a high growth rate of 2.9 μm/h. Double-axis x-ray rocking curves showed a full width at half maximum of 315 and 419 arc sec for (0002) and (101ˉ2) re?ections, respectively, corresponding to a total threading dislocation (TD) density of 9.79 × 10^8 cm^-2. Cracks were suppressed and crystalline quality was improved by introducing a medium-temperature (MT) layer. It was found that the density of both screw- and edge-type TDs could be signi?cantly reduced by introducing the MT-AlN layer under appropriate temperature. The crystalline improvement is attributed to the delayed coalescence of the AlN islands and higher probability for the annihilations of TDs by the MT-AlN layer under appropriate temperature. This method provides a promising way in growing practical thick AlN templates suitable for large-scale industrial production.
关键词： High growth rate,MOCVD,Crack-free,Medium-temperature layer,AlN
更新于2025-09-23 15:22:29
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Catalytic synthesis of SiC nanowires in an open system
摘要： SiC nanowires (NWs) are usually synthesized in a closed vacuum reaction system which limits the yield of SiC NWs. In this work, SiC NWs and carbon nanotubes were synthesized in an open tube furnace at 1550 ℃ with Si powder as silicon sources, ethanol as carbon sources and ferrocene as catalyst. The as-synthesized products were ultralong β-SiC NWs with the diameter about 80-100 nm and the length up to several tens micrometers. The diameter of the carbon nanotubes was about 20-30 nm. The carbon nanotube yarns about 20 cm in length were obtained at the end of the tube furnace. The growth mechanism of SiC NWs and carbon nanotubes were proposed. Compared with the traditional synthetic techniques in the high vacuum closed system, the novel synthesis method in the open system provided a new approach to the synthesis of SiC NWs.
关键词： Carbon nanotubes,SiC nanowires,Open reaction system,Growth mechanism
更新于2025-09-23 15:22:29
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DWARF4 accumulation in root tips is enhanced via blue light perception by cryptochromes
摘要： Brassinosteroid (BR) signalling is known to be coordinated with light signalling in aboveground tissue. Many studies focusing on the shade avoidance response in aboveground tissue or hypocotyl elongation in darkness have revealed the contribution of the BR signalling pathway to these processes. We previously analysed the expression of DWARF 4 (DWF4), a key BR biosynthesis enzyme, and revealed that light perception in aboveground tissues triggered DWF4 accumulation in root tips. To determine the required wavelength of light and photoreceptors responsible for this regulation, we studied DWF4-GUS marker plants grown in several monochromatic light conditions. We revealed that monochromatic blue LED light could induce DWF4 accumulation in primary root tips and root growth as much as white light, while monochromatic red LED could not. Consistent with this, a cryptochrome1/2 double mutant showed retarded root growth under white light while a phytochromeA/B double mutant did not. Taken together, our data strongly indicated that blue light signalling was important for DWF4 accumulation in root tips and root growth. Furthermore, DWF4 accumulation patterns in primary root tips were not altered by auxin or sugar treatment. Therefore, we hypothesize that blue light signalling from the shoot tissue is different from auxin and sugar signalling.
关键词： light signalling,brassinosteroid,DWF4,phytochromes,cryptochromes,hypocotyl elongation,photoreceptor,root growth,BR biosynthesis
更新于2025-09-23 15:22:29
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The role of carbon in the formation mechanism of F-type centers in α-Al2O3:C,Mg single crystals
摘要： In this study, an α-Al2O3:C,Mg single crystal was grown using the Czochralski method with graphite resistance heating, Al2O3, MgO, and graphite powder as raw materials. Both the graphite heating unit and the shield served as the carbon source during the growth process. The structure and the optical properties of the crystal were investigated. The as-grown crystal shows a prominent absorption band at 206 nm, 230 nm, and 256 nm. The excitation-emission (EE) spectrum reveals a weak luminescence center (435/510 nm) that is attributed to the F2t (2 Mg). We calculate the concentration of the F-type centers using Smakula’s equation. Using the first principles simulation method, we studied the relation between the C atoms and the absorption properties of the crystal, and we discuss the role of carbon in the formation mechanism of the F-type luminescence centers for a α-Al2O3:C,Mg crystal.
关键词： Color centers,Al2O3:C,Crystals growth,Mg
更新于2025-09-23 15:22:29
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Effect of Anti-vascular Endothelial Growth Factor Antibody on the Survival of Cultured Retinal Ganglion Cells
摘要： Purpose: To investigate the effects of anti-vascular endothelial growth factor (VEGF) antibody on the survival of retinal ganglion cell (RGC)-5 cells differentiated with staurosporine under oxidative stress. Methods: We used real-time polymerase chain reaction and Western blot to confirm the expression of VEGF, VEGF receptor (VEGFR)-1 and VEGFR-2 in RGC-5 cells differentiated with staurosporine for 6 hours. The differentiated RGC-5 cells were treated with 800 μM hydrogen peroxide (H2O2) for 24 hours to induce oxidative stress. Then, the survival rate of RGC-5 was confirmed by lactate dehydrogenase assay at each concentration (0, 0.01, 0.1, and 1 mg) using bevacizumab as the anti-VEGF antibody. The expression of VEGF, VEGFR-1, and VEGFR-2 was confirmed using real-time polymerase chain reaction. Results: VEGF, VEGFR-1, and VEGFR-2 were all expressed in differentiated RGC-5 cells. When RGC-5 cells were simultaneously treated with bevacizumab and 800 μM H2O2, survival of RGC-5 decreased with bevacizumab concentration. VEGF expression in RGC-5 cells increased with increasing concentration of bevacizumab. Similar patterns were observed for VEGFR-1 and VEGFR-2, but the degree of increase was smaller than that for VEGF. Conclusions: When bevacizumab was administered to differentiated RGC-5 cells, the cell damage caused by oxidative stress increased. Therefore, given these in vitro study results, caution should be exercised with bevacizumab treatment.
关键词： Oxidative stress,RGC-5,Retinal ganglion cell,Anti-vascular endothelial growth factor,Bevacizumab
更新于2025-09-23 15:22:29
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Fabrication and Optical Properties of 2at.%Yb:LuYAG Mixed Crystal through Nanocrystalline Powders
摘要： Ytterbium doped Lu1.5Y1.5Al5O12 (LuYAG) nanocrystalline powders were synthesized by a wet chemical mixed precipitant co-precipitation (MPP) method, and then the mixed crystal of Yb:LuYAG was grown in an optical floating zone (OFZ) furnace at the speed of 6–10 mm/h, using a [111] oriented YAG seed crystal. The transmittance of the polished LuYAG crystal is close to the ideal value of LuAG or YAG. The X-ray rocking curve shows complete symmetry and the full width at half maximum (FWHM) is 10 arc-second, indicating the good quality of as grown Yb:LuYAG multicomponent garnet crystal. The thermal luminescent spectrum at room temperature shows four deep energy traps at around 1–1.3 eV. X-ray excited luminesce (XEL) spectra is measured to characterize the existence of LuAl or YAl shadow defects in the bulk single crystal. The emission peak at around 320 nm indicates that the LuYAG crystal prepared by OFZ have lower concentrations of antisite defects (AD) with respect to its Czochralski counterpart.
关键词： crystal growth,optical floating zone,LuYAG,optical properties
更新于2025-09-23 15:22:29