Spectra Of ZnS Research Articles

SYNTHESIS AND CHARACTERISTICS OF ZnS NANOWIRES

The creation of a nanoporous silicon dioxide layer in the a-SiO2/Si-n structure was accomplished by irradiation with xenon ions at a cyclotron and then chemical etching with an aqueous solution of hydrogen fluoride with the addition of palladium. The truncated cone-shaped nanopores had diameters ranging from 486 to 509 nm. Then ZnS nanowires synthesized by electrochemical deposition (ECD) method, depending on the voltage at the electrodes of the electrolytic cell and as a result zinc sulfide nanowires with cubic structure and spatial symmetry group F-43m (216) were obtained. The sample is characterized by (111), (200), (220), (331) (311) planes, respectively, which is in good agreement with the cubic phase of ZnS. The charge-voltage characteristics (CVC) of ZnS showed that an n-type conductivity semiconductor was formed. Measurements of the photoluminescence (PL) spectra of ZnS were recorded on a CM 2203 spectrofluorimeter. The PL spectra were recorded in the range of 250 nm to 450 nm at room temperature. The PL spectra of the precipitated precipitates reveals emission in a wide UV-visible spectral range. It can be seen that the luminescence spectra have quite complex components and can be divided into five Gaussian curves. As can be seen the FL spectrum of the deposited ZnS consists of bands at 3.15 eV, 3.3 eV, 3.4 eV, 3.55 eV and 3.73 eV. Also analyzing the spectra energy dispersive analysis showed that the ZnS nanoproofs consist of Zn – 42.5% and S – 57.5%.

Shungite Carbon Nanoparticles as Modifiers of Zns:Cu Phosphor, Based on Analysis of the EPR Spectral Lines of Mn<sup>+2</sup>

Water dispersions of shungite carbon (ShC) nanoparticles were used for modifying the particle surface of ZnS:Cu, commercial electrophosphor. The EPR spectrum of ZnS:Cu powder has parameters consistent with the paramagnetic centers of Mn+2. Modifying the phodphor surface with ShC nanoparticles results in a non-monotonic change in line width, amplitude and integral intensity caused by nanoparticle concentration, which correlates with variations in the brightness of electroluminescence. Variations in the parameters of spectral lines with nanoparticle concentration and UHF saturation power are interpreted in terms of modification and creation of additional dislocations in the subsurface layer of phosphor with new physico-chemical properties.

Nonstationary Stimulated Raman Scattering by Polaritons in Cubic Crystals

The purpose of this article is to consider two aspects of the nonstationary stimulated Raman scattering by polaritons in cubic crystals. The first feature is related to the pump field, which, by deforming the permittivity of the medium, changes its symmetry. As a result, for example, the cubic crystal becomes anisotropic. The second one results from the possibility of exciting anomalous longitudinal waves at the frequency of the mechanical phonons which is the fundamental difference between scattering by dipole-active (polar) phonons and that of by dipole-inactive (nonpolar) ones. When the phonon frequency is approached, the amplitude of the transverse polariton wave decreases due to increased absorption and the wave mismatch. The polariton wave becomes practically longitudinal. Such a wave is maintained by the pump field and exists only in a pumped medium. The system of four shortened nonstationary equations (two for the Stokes waves with perpendicular polarizations and two for both transverse and longitudinal polariton waves) is obtained. The analysis is carried out for a given stationary pump field which is assumed to be a linearly polarized plane electromagnetic wave. Principal attention was paid to the calculation and analysis of the gain factor which defines the intensities of both stimulated (SRS) and spontaneous Raman scattering. The expressions for two proper gain factors gμ are obtained for Stokes waves in nonstationary case. It was shown that the pumped cubic crystal becomes anisotropic. It is also shown that the values of intensities calculated by using the expression for gμ are consistent with the experimental results for spectra of ZnS.

Fracto-mechanoluminescence in Mn/Cu doped ZnS induced by steel ball and cylindrical piston

Herein, we present a comparison of fracto-mechanoluminescence (FML) from ZnS: Mn/Cu phosphor trigerred by steel ball and cylindrical piston and prepared by solid state reaction (SSR) route. The FML was observed with different manner of impact on these two phosphors in terms of its dependence on time and impact velocity. The results show the linear and quadratic nature of peak FML intensity of these phosphors on the impact of cylinder piston and steel ball respectively. It was found that in both the manner of impact, the FML intensity initially increases with time attains a peak value followed by decrease at still longer times. The total ML intensity also linearly increases with increasing mass of the phosphor samples. The Mechanoluminescence (ML) and Photoluminescence (PL) spectra of ZnS:Mn and ZnS:Cu phosphors are recorded, which lie at 540 nm and 580 nm, respectively.

A fluorescent sensor based on one-step fabrication of chitosan/ZnS: Mn2+ composite film for iodine ion detection

Biocompatible chitosan-coated ZnS:Mn2+ composite films were successfully fabricated via a one-step in situ route. The present paper reports the synthesis, characterization and fluorescence studies of Mn doped ZnS nanoparticles films. These are characterized using SEM, DSC, UV–vis Spectroscopy and fluorescence studies. The fluorescence spectra of ZnS:Mn2+ nanoparticles were measured for different concentrations of I− used. The fluorescence emission of the films was sensitive to the presence of I−. The effect of its concentration on the emission of the film decreased significantly with the increasing of I− concentration from 0~3.6 × 10−5 mol/L. The fluorescence dependent on the concentration could be described by correlation equation. The response of the film to the same concentrations of I− was fully reversible. The composite films should potentially be applied to detect I− in biological system and environment.

Growth and Characterization of ZnS Films by Chemical Bath Deposition

ZnS films are formed by chemical bath deposition using variety zinc sources such as zinc acetate (Zn (CH3COO)2), zinc sulfate (ZnSO4), zinc nitrate (Zn (NO3)2), iodide zinc (ZnI2), zinc chloride (ZnCl2) and zinc acetyl (Zn (acac)2). X-ray diffraction results show all broad spectra of ZnS. It is considered that amorphous ZnS can be grown. All samples show high transmittance. It is deduced that the decrease of transmittance around 3.7 eV is due to the ZnS band gap. Scanning electron microscopy shows that grain size becomes large with decreasing the instability constants of the zinc sources. It is assumed that zinc becomes ionization with decreasing the instability constants. All samples show a signal of O-H bond from fourier transform infrared spectra. It is assumed that the Zn (OH)2exists in each sample.

Study of the Photo-oxidation and Photolysis of Unsaturated and Cross-linked Polyesters (UP) in the Presence of Photoactive or not Inorganic Fillers

Abstract Disturbances of the photochemical evolution involved in the photolysis and in the photo-oxidation at long wavelengths (e?300 nm) of poly(propylene glycol-maleatophtalate cross-linked by the styrene (UP),caused by the addition of photo-active pigment such as zinc sulphide or black iron oxides,and no photoactive inorganic fillers such as calcium carbonate have been analysed by means of FTIR and U.V. spectrophotometry. The photo-oxidation observed by FTIR of the polymer UP in the presence of inorganic fillers leads to the same photoproducts such as ones of the photo-oxidation of the virgin polymer, but the oxidation rate is greatly affected by the nature and the percentage of the inorganic filler. Zinc sulfide and black iron are incorporated in the film of polymers, the absorption spectra of ZnS reveals that this pigment is not as absorbent as titanium oxide in a more limited field. On the other hand, with a very low inner filter effect, black iron oxides promote the formation of absorbing photoproducts. The addition of Calcium carbonate non- absorbing filler to the UP, causes a slight decrease in the evolution of the I.R

Absence of photocatalytic activity in the presence of the photoluminescence property of Mn–ZnS nanoparticles prepared by a facile wet chemical method at room temperature

Mn-doped ZnS nanoparticles (NPs) were prepared with dopants at various concentrations using a facile, simple and inexpensive wet chemical method at room temperature. The physicochemical properties of NPs were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV–vis) and photoluminescence (PL). XRD analysis confirmed formation of ZnS with zinc blende structure and average crystallite size of about 2nm. TEM analysis revealed formation of hyperfine NPs with rather good uniformity. The room temperature photoluminescence (PL) spectrum of ZnS:Mn2+ exhibited an orange-red emission around 600nm. The maximum PL intensity was observed for 7.5% Mn doped ZnS. The photocatalytic performance of ZnS:Mn2+ was successfully demonstrated for degradation of three different model dyes (i.e. Rhodimine B (Rh. B), Bromocresol Green (BCG) and Bromochlorophenol Blue (BCB)). The results revealed that not only was there a remarkable difference in photocatalytic performance of Mn doped ZnS for all three different dyes at different dopant concentrations but also photocatalytic activity was decreased by Mn doping.

Synthesis and Study of Optical and Photocatalytic Properties of Mn and Sm Doped ZnS Grown by Sol-Gel

Optical and photocatalytic properties of ZnS, ZnS:Mn2+ (20 and 30 wt%) and ZnS:Sm3+ (20 and 30 wt%) samples formed by three coatings, were studied. The layers were deposited on glass substrate by the sol-gel dip coating process. The catalytic activity of the samples was determined by means of the photodecomposition of methylene blue under Ultra Violet and visible light irradiations. The Fourier Transform Infrared (FTIR) spectrum of ZnS shows the presence of OH, N–H, N–C and S–H groups. The last two groups suggest the formation of a thiocyanuric group (NCS−) on the surface of the sample which enables the photocatalytic activity of undoped ZnS and doped ZnS under visible light irradiation.

A study on the defects structure of colloidal ZnS using Ag surface plasmons

The effects of Ag surface plasmons (SPs) on the defects of ZnS are investigated. The photoluminescence (PL) spectra of ZnS on an Ag film show well resolved, enhanced, and red-shifted emissions compared to reference samples. The enhancement of the PL by the Ag layer is attributed to an enhanced energy transfer between overlapping band energies of ZnS by Ag SP. Based on the results, it is suggested that the PL emissions from defects can be enhanced and distinguished by SPs, which provide a direction for the application of SPs to characterize inorganic materials.

Luminescence Properties of ZnS:Cu,Tm Semiconductor Nanocrystals Synthesize by a Hydrothermal Process

ZnS:Cu,Tm nanocrystal with 15nm cubic structures have been synthesized by hydrothermal approach at 200°C. The photoluminescence (PL) properties and the effect of hydrothermal treatment time on the structure, morphology and PL spectra of ZnS:Cu,Tm samples have been studied. The as-obtained samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectra.The result indicated that the PL emission spectrum of codoped with Cu and Tm sample compares with undoped ZnS and doped with Cu alone samples has a significant changes, while the PL emission peak has red shift and PL emission intensity increased. The samples size and crystallization are increase with extending of the treatment time. However, when the hydrothermal treatment time is too long(>12h), the PL emission intensity of sample instead of decreased. Demonstrated changes in surface state of nanomaterials have a greater impact on its luminescence properties.

Synthesis and Characterization of ZnS: Fe/ZnS Core-Shell Nanocrystals

ZnS:Fe and ZnS:Fe/ZnS core-shell nanocrystals were synthesized by chemical precipitation method. It was found that the ZnS: Fe based nanocrystals possess zinc blende structure. Compared to ZnS: Fe nanocrystals, the intensity of the X-ray diffraction peaks of ZnS: Fe/ZnS nanocrystals reduced and these peaks moved to lower angles. TEM images show that ZnS: Fe based nanocrystals are spheroidal and the average particles size is about 3~4 nm. PL spectra of ZnS: Fe nanocrystals revealed several mission bands, ~406nm, ~444nm, ~416nm, However, PL spectra of ZnS: Fe/ZnS nanocrystals showed several mission bands, ~420nm, ~432nm, ~449nm.

Synthesis and photoluminescent and nonlinear optical properties of manganese doped ZnS nanoparticles

In this work we synthesized ZnS:Mn 2+ nanoparticles by chemical method using PVP (polyvinylpyrrolidone) as a capping agent in aqueous solution. The structure and optical properties of the resultant product were characterized using UV–vis optical spectroscopy, X-ray diffraction (XRD), photoluminescence (PL) and z-scan techniques. UV–vis spectra for all samples showed an excitonic peak at around 292 nm, indicating that concentration of Mn 2+ ions does not alter the band gap of nanoparticles. XRD patterns showed that the ZnS:Mn 2+ nanoparticles have zinc blende structure with the average crystalline sizes of about 2 nm. The room temperature photoluminescence (PL) spectrum of ZnS:Mn 2+ exhibited an orange-red emission at 594 nm due to the 4T 1– 6A 1 transition in Mn 2+. The PL intensity increased with increase in the Mn 2+ ion concentration. The second-order nonlinear optical properties of nanoparticles were studied using a continuous-wave (CW) He–Ne laser by z-scan technique. The nonlinear refractive indices of nanoparticles were in the order of 10 −8 cm 2/W with negative sign and the nonlinear absorption indices of these nanoparticles were obtained to be about 10 −3 cm/W with positive sign.

Solvothermal Synthesis and Photoluminescence Properties of ZnS:Mn2+/ZnO Core–Shell Nanocrystals

High-quality ZnS:Mn2+ and ZnS:Mn2+/ZnO core-shell nanocrystals (NCs) were synthesized via a solvothermal method, and characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) and photoluminescence (PL) spectra. Compared with the bare ZnS:Mn2+ NCs (10 nm), the obtained ZnS:Mn2+/ZnO core-shell NCs have a smaller size (4 nm) and better dispersion, which could be attributed to the added ammonia that adsorbed on the surface of ZnS nuclei and hindered their further growth. From the PL spectrum of ZnS:Mn2+NCs, orange luminescence at about 595 nm is observed, which is attributed to the 4T1-6A1 transition of the Mn2+. Meanwhile, the PL intensity of the ZnS:Mn2+/ZnO core-shell NCs is enhanced, and the emission peak is shifted from 595 to 581 nm. The enhancement of the PL intensity is due to the elimination of the surface defects after the growth of the ZnO shell on ZnS:Mn2+ NCs, while the peak blue shift is mainly ascribed to the stress from the mismatch of lattice constants between ZnS and ZnO NCs.

Absorption, luminescence excitation, and infrared transmittance spectra of ZnS(O)-ZnSe(O) crystals in the context of the band anticrossing theory

The paper reports the results of optical studies of the absorption, luminescence excitation, and infrared transmittance spectra for the set of ZnS(O)-ZnSe(O) alloys with highly inconsistent properties of anions. It is shown that the band anticrossing theory applied to the alloys provides a general interpretation of their specific optical properties not properly understood previously. A band model of transitions with absorption in a complex multiband formed due to oxygen is presented. The specific features of the absorption and luminescence excitation spectra are interpreted to gain an insight into the distribution and states of oxygen in the crystals. The effect of oxygen on the transmittance band of the ZnS-ZnSe alloys in the near-infrared spectral region is considered. A new approach to the interpretation of the infrared absorption bands associated with oxygen is developed. The calculation algorithms that provide a means for determining the spectral position of the bands in relation to the dissolved oxygen content are suggested.

Transformation of luminescence centers in CVD ZnS films subjected to a high hydrostatic pressure

The cathodoluminescence and optical-transmission spectra of ZnS were analyzed to study the effect of a high hydrostatic gas pressure (1500 atm at 1000°C) on the equilibrium between intrinsic point defects in zinc sulfide grown by chemical vapor deposition (CVD) with an excess of zinc. The cathodoluminescence spectra were measured at 80–300 K and excitation levels of 1022 and 1026 cm−3 s−1; the optical-transmission spectra were measured at 300 K in the wavelength range 4–12 µm. It is found that exposure to a high hydrostatic gas pressure transforms the self-activated emission in the cathodoluminescence spectrum: (i) a new short-wave-length band appears at 415 nm with its intensity increasing by one to three orders of magnitude; and (ii) the long-wavelength band that peaks at 445 nm and is observed in as-grown crystals becomes quenched. Simultaneously, the cathodoluminescence band peaked at 850 nm and related to vacancies VS is no longer observed after high-pressure treatment. These effects are attributed to a partial escape of excess zinc (Zni) from crystals and additional incorporation of oxygen into lattice sites (OS). A doublet band I1, which peaked at ∼331–332 nm at 80 K and at ∼342–343 nm at 300 K and is related to excitons bound to acceptor levels of oxygen centers, was observed. This band is found to be dominant in the cathodoluminescence spectrum at an excitation level of 1026 cm−3 s−1. Traces of the ZnO phase are apparent after the high-pressure treatment in both the cathodolumi-nescence spectra (the bands at 730 and 370 nm) and the transmission spectra (narrow bands in the region of 6–7 µm).

Defect Structure and Luminescence Behavior of ZnS:Mn2+ Crystals

The photo-, electro-, and cathodoluminescence spectra of ZnS:Mn2+ crystals are studied, and the defect density in the crystals is evaluated by decorating freshly cleaved surfaces with anthraquinone. The results are used to assess the site symmetry around the Mn centers responsible for the emissions at 557, 578, and 600 nm.

Electroluminescence behavior of ZnS :Mn2+ crystals

The electroluminescence spectra of ZnS and ZnS:Mn2+ crystals were studied under excitation in ac and dc electric fields from 103 to 104 V/cm. The relative intensities of the 465-, 510-, and 530-nm emissions in the ZnS crystals are found to depend on excitation conditions. The frequency-dependent brightness–voltage behavior of the ZnS:Mn2+ crystals is interpreted in terms of prebreakdown electroluminescence.

Variation of the electroluminescence spectra of ZnZ:Mn thin-film emitters depending on the excitation level

The electroluminescence (EL) spectra of ZnS:Mn thin-film emitters measured in various regions of the luminance wave exhibit, besides the bands characteristic of the intracenter emission from Mn2+ ions, additional EL bands peaked at ∼530 and ∼655 nm, which are probably related to the trapping of free electrons on deep centers formed by the sulfur vacancies VS2+ and VS+. These traps may lead to the formation of a negative bulk charge in a near-cathode region, inducing a decrease in the growth rate (or even a drop) of current through the phosphor, as well as a decay of instantaneous luminance.

Recent developments in the MOVPE growth of low H content ZnSe-based compounds and heterostructures

The origin of unintentional hydrogen (H) incorporation during metalorganic vapour phase epitaxy (MOVPE) of ZnSe-based compounds is reviewed and discussed. Hydrogen enters in MOVPE-grown ZnSe as a result of alkyls surface reactions, effectively passivating intentional nitrogen (N) acceptors in p-doped ZnSe during the fabrication of blue-light emitting diodes and laser diodes. The existence of a marked trade-off between the proclivity of common Se alkyls to incorporate H and their thermal stability is pointed out. Current strategies to overcome this process limitation are then described along with results achieved and technological drawbacks. The use of a novel class of VI-group alkyl precursors of the form R 2X 2 [where X=Se, S and R is an ethyl (Et) or methyl (Me) radical] is proposed as an alternative solution. These alkyls allow a reduction of H incorporation in ZnSe-based materials, whilst retaining the low temperatures required for the growth of device quality wide band-gap II–VI compounds. Dimethyldiselenide (Me 2Se 2) and diethyldisulphide (Et 2S 2) allow the pyrolytic MOVPE growth of Zn(S)Se compounds below 400 °C. Mass spectrometry fragmentation experiments performed on the alkyl molecular ions allowed to investigate their relative bond strengths and likely decomposition paths. The reduced thermal stability of these alkyls is attributed to a weakening of the XC bonds in the R 2X 2 molecule induced by the stronger XX bond. Secondary ion mass spectrometry (SIMS) analysis showed that as-grown ZnSe have [H]≈(1–3)×10 17 cm −3, i.e. among the lowest ever reported for MOVPE-grown layers. The functional validation of the new S and Se alkyls is completed by the structural and optical characterisation of Zn(S)Se-based heterostructures grown on (100)GaAs. High-resolution X-ray diffraction studies are presented along with cathodoluminescence (CL) measurements and compared to what reported in the literature. The epilayer structural properties compare well with that of molecular beam epitaxy and MOVPE grown Zn(S)Se heterostructures. CL spectra of ZnSe epilayers appear of good quality, with pronounced band-edge emissions and reduced deep level contributions. Specific emissions in the spectra of ZnS and ZnSe confirm the occurrence of several impurities in the layers, whose origin can be in part attributed to the yet insufficient purity of the novel alkyls.