Emission In Ultraviolet Region Research Articles

Highly Efficient Ultraviolet Third-Harmonic Generation in an Isolated Thin Si Meta-Structure.

Nonlinear nanophotonic devices have shown great potential for on-chip information processing, quantum source, 3D microfabrication, greatly promoting the developments of integrated optics, quantum science, nanoscience and technologies, etc. To promote the applications of nonlinear nanodevices, improving the nonlinear efficiency, expanding the spectra region of nonlinear response and reducing device thickness are three key issues. Herein, this study focuses on the nonlinear effect of third-harmonic generation (THG), and present a thin Si meta-sructure to improve the THG efficiency in the ultraviolet (UV)region. The measured THG efficiency is up to 10-5 at an emission wavelength of 309nm. Also, the THG nanosystem is only 100nm in thickness, which is two-five times thinner than previous all-dielectric nanosystems applied in THG studies. These findings not only present a powerful thin meta-structure with highly efficient THG emission in UV region, but also provide a constructive avenue for further understanding the light-matter interactions at subwavelength scales, guiding the design and fabricating of advanced photonic devices in future.

Synthesis and Characterization of a NLO crystal - bis (thiourea) zinc sulphate doped with L-malic acid

The nonlinear optical (NLO) material L-malic acid bis(thiourea) zinc sulphate (LMBTZS) was grown by slow evaporation method. The effect of L-malic acid doping on the morphology of the LMBTZS single crystal has been studied. The unit cell parameters were determined by single crystal XRD. The functional groups and force constant of LMBTZS was identified by FTIR analysis. The photoluminescence spectrum of LMBTZS shows the strong emission in ultraviolet region. The thermal behaviours were identified by TG/DTA analyses. Dielectric studies of the grown crystal was carried out. The SHG efficiency was confirmed by powder technique of Kurtz and Perry. LMBTZS is found to be an excellent NLO and piezo-electric material.

Luminescence properties and energy transfer of Ce3+/Dy3+co-activated LaAl2.03B4O10.54 phosphors for wLEDs

Dy3+ ions doped inorganic materials have attracted extensive attentions for their peculiar white emission and simple preparing process. However, Dy3+ ions in these materials have low emission intensity due to the weak absorption in ultraviolet spectral region. Ce3+ ions in most of inorganic compounds show a broad emission in ultra-violet region. Thus, Ce3+ is an effective sensitizer for Dy3+. In this work, a sequence of novel white light-emitting phosphors LaAl2.03B4O10.54: Ce3+/Dy3+ was synthesized by high-temperature solid-state reaction method. Under the excitation at 310 nm, the luminescence properties and energy transfer behavior were investigated in detail for Ce3+/Dy3+ co-doped LaAl2.03B4O10.54 phosphors. The energy transfer efficiency from Ce3+ to Dy3+ was calculated to be 56% with the quadrupole–quadrupole interaction mode. The emitting color of the samples can be modulated from (0.210, 0.123) to white region (0.263, 0.237) by properly changing the doping concentration of Dy3+. The results in this work indicate that the color tunable LaAl2.03B4O10.54: Ce3+/Dy3+ phosphors may be a potential single component phosphor in the field of wLEDs.

Defect-assisted symmetric cleavage of naphthalene sulphonic acid group in azo dyes using β-In2S3 quantum dots as visible light photocatalyst

Naphthalene sulfonic acid, which is used in the synthesis of azo dye pigments, rubber processing chemicals and pharmaceuticals, is a carcinogenic substance that pollutes water bodies. In this work, we report on the visible light-driven symmetric cleavage of naphthalene sulfonic acid group, present in methyl orange dye and its conversion into the intermediate compounds. These compounds further degrade to inorganic ions such as carbon-di-oxide, nitrates, sulfates, water, and chlorine. Complete degradation of the dye, under visible light irradiation, is attained using β-In2S3 quantum dots as photocatalyst. During homogenous precipitation process, the β-In2S3 quantum dots (~ 9 nm) self-assemble to form microflowers (~ 50 nm) with high surface-to-volume ratio. These quantum dots exhibit size-dependent, active F2g, Eg and Ag1 Raman modes with peaks at ~ 150 cm−1 (In–In stretching mode), 219 cm−1 (In–S bending mode) and 300 cm−1, corresponding to the vibrational modes of cubic phase β-In2S3. The cubic phase β-In2S3 quantum dots are photoactive under visible light exposure and releases highly oxidizing OH· radicals. They have strong band-to-band emission in ultraviolet region (~ 380 nm) and exhibit broad band defect emission with maxima at blue (~ 484 nm), green (~ 580 nm) and red (~ 600 nm) region of electromagnetic spectrum. The emission intensity from these defect energy bands, which are due to sulfur vacancy, indium interstitials and oxygen incorporation, are tuned by varying the In-to-S ratio in the sample. These defects enhance their visible light absorption coefficient and assist in improving the photocatalytic efficiency of the cubic phase β-In2S3 quantum dots. Thus, defect-assisted complete (100%) photodegradation of the azo dye is achieved using cubic β-In2S3 quantum dots with low In-to-S ratio (1:1), low mass of 20 mg and minimum irradiation time (30 min). These photocatalysts can be reused 4 times under 30-min visible light irradiation. Cubic β-In2S3 quantum dots-microflowers is a highly efficient, ecofriendly photocatalyst, which even in very low concentration can remove toxicity from the dye-contaminated water, by exposure to direct sunlight for 30 min.

Changes in the growth orientation, morphological and optical properties of sol-gel nanocrystalline ZnO thin films coated with different thickness

ABSTRACTNanocrystalline ZnO thin films with the varied thickness were deposited on glass substrate using sol-gel spin coating method, and the different thickness of samples was achieved via changing the number of layers. X-ray diffraction patterns of samples showed the preferential orientation at (002) planeupon coating with 2 layers and the gradual increase in random orientation with coating up to 6 layers. Scanning electron microscopeimages appeared a few layer interfaces for 4 and 6 layers sample, and atomic force microscope images revealed the larger particle size and rougher surfacewith increasing thickness, which showed the obvious effects on optical properties of samples too. The increased absorption and reduced energy gap were found through deducing transmittance curves of samples. Further, photoluminescence characteristic was measured and revealed that there are the best intrinsic emission in ultraviolet region and lowest defect emissions in visible region for the sample coated with 4 layers.

Effects of three seeding methods on optimization of temperature, concentration and reaction time on optical properties during growth ZnO nanorods

Today, use of zinc oxide nanorods is necessary in optoelectronic industry. Therefore, control of growth parameters are affected on zinc oxide nanostructures. In this paper, the effect of different seed methods such as spin coating, vapour liquid solid and spray coating on morphology of surface-crystal plates of zinc oxide nanorods has been investigated. Also, growth of zinc oxide nanorods has been done using new method by use of different concentrations of zinc chloride and ammonia at75, 97 and 110 °C. Finally, morphology of surface, crystal plates, structure purity and optical properties of zinc oxide nano rods have been examined by changes of reagent concentration, growth solution temperature and reaction time through SEM, XRD, EDAX and photoluminescence analyses. The different optical properties and surface morphology of zinc oxide nanorods were generated differ by change in concentration. By changes of concentration, pH of growth solution has been changed. Therefor influences defects of crystal structure in the visible and ultraviolet region were obtained. Finally, the ideal thermal annealing is 430 °C. Thermal annealing in vacuum for growth the zinc oxide nano rods at the range of 400–450 °C were showed that, the defects are decreased and or increased due this method for growth in the visible and ultraviolet region. The samples prepared by VLS, have visible and ultraviolet region emission. So there are useful for LED application. It is suitable for UV-laser diodes.

One-dimensional cube-shape CoxZn1−xO nanostructures and their optical properties

One-dimensional cube-shape CoxZn1−xO nanowires have been fabricated through vapor-solid deposition process. Scanning electron microscopy observations reveal that the products consist of a large quantity of cube-shape nanostructures with typical lengths in the range of several tens to several hundreds of micrometers. The room-temperature Raman spectra of CoxZn1−xO exhibited the presence of lattice defects in the system. The photoluminescence properties of CoxZn1−xO nanowires under 10 K–110 K were investigated. The results show that there is an intensive ultraviolet multi-peaks emission under low temperature. The multi-peak emissions are mainly attributed to longitudinal optical phonon replicas of free exciton. The multi-peaks emission in ultraviolet region will exhibit redshift with the increasing temperature. A U-shaped behavior of the full width at half maximum (FWHM) value of the FX-1LO emission peaks at 10 K–110 K was shown.

Wet chemical synthesis of Ce3+ activated fluoro-elpasolite and related fluoro-aluminate phosphors

New results on synthesis and luminescence of Ce3+ activated fluoro-elpasolites and some related fluoroaluminates are presented. Wet chemical synthesis of fluoroaluminates with elpasolite (K2NaAlF6) structure and related fluorides such as simmonsite Na2LiAlF6 and pyrochlore derived rhombohedral phases Cs2NaAl3F12 is described. Ce3+ activation also could be achieved using the simple procedure. Intense Ce3+ emission in ultraviolet region could be observed in the fluoro-aluminates prepared by wet chemical method, without resorting to any thermal treatment except for that required for drying. The method will provide a simple route for preparing this important class of materials.

Crystal Growth, Morphology, Spectral and Optical Studies of Tris (Thiourea) Zinc Sulphate-Nonlinear Optical Material

The Nonlinear Optical (NLO) material Tris (thiourea) zinc sulphate (ZTS) was grown by slow evaporation method. The unit cell parameter and morphology were determined by single crystal XRD. The molecular structure of ZTS was identified by FTIR analysis. The optical properties of ZTS were determined by UV-Vis spectral studies. The photoluminescence spectrum of ZTS shows the strong emission in ultraviolet region at 360 nm. The thermal behaviors were identified by TG/DTA analyzes and the melting point is 240°C. The hardness of the material is measured by micro hardness test. The SHG efficiency was confirmed by powder technique. The Laser damage threshold value of ZTS single crystal was found to be 20.15 MW/Cm 2 . The effect of L-histidine doping on the morphology of the ZTS single crystal has been studied.

Hydrothermal synthesis, crystal structure and physical properties of {[Gd(H2O)4(μ2-C6NO2H5)2Gd(H2O)4](μ3-C6NO2H4)2(ZnCl3)2}·2H2O·2Cl

Abstract A bimetallic 4f–3d tetranuclear complex {[Gd(H2O)4(μ2-C6NO2H5)2Gd(H2O)4](μ3-C6NO2H4)2(ZnCl3)2} · 2H2O · 2Cl (1) has been synthesized via hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. Complex 1 is characterized by a tetranuclear Gd2Zn2 structure with the gadolinium and zinc atoms interconnected by isonicotinic acid ligands. The tetranuclear species of {[Gd(H2O)4(μ2-C6NO2H5)2Gd(H2O)4](μ3-C6NO2H4)2(ZnCl3)2} link to isolated chlorine ions and water molecules via π⋯π interactions and hydrogen bonds to yield a 3-D supramolecular framework. Photoluminescent investigation reveals that the title complex displays an emission in ultraviolet region. The solid-state diffuse reflectance spectra of 1 reveal the presence of a sharp optical gap of 3.66 eV.

Simple approach to NiS 2/Ag 2S composites and their optical properties

NiS 2/Ag 2S composites have been successfully prepared through a simple approach by using nickel disulfide hollow microspheres as precursors under normal temperature and pressure. The morphologies and microstructures of NiS 2 and NiS 2/Ag 2S composites were illustrated by SEM and TEM images. SEM images indicate the average diameter of the silver sulfide nanospheres is 100 nm. And the NiS 2/Ag 2S composites display strong luminescent emission in ultraviolet region. This approach provides a facile route for the synthesis of the NiS 2/Ag 2S composites with interesting optical property. Furthermore, this simple method could be applied to synthesize other composites.

Preparation, structure and photoluminescence properties of SiO 2/ZnO nanocables via electrospinning and vapor transport deposition

SiO 2/ZnO nanocables were prepared by the combination of electrospinning technology and vapor transport deposition procedure. X-ray diffraction patterns indicated that ZnO with wurtzite structure was deposited on SiO 2 nanofibers templates successfully. Field emission scanning electron microscopy and transmission electron microscopy showed that the products were core/shell nanocables with a narrow distribution of the core/shell diameters. The nanocables showed a strong near band edge emission in ultraviolet region and a weak deep level emission at room temperature in their photoluminescence (PL) spectra. The anomalous temperature characteristic of integrated PL intensity in temperature-dependent PL spectra was discussed by considering carrier injection across the interface of SiO 2/ZnO nanocables.