ZnS Concentration Research Articles

Dual functions of thiourea for solution combustion synthesis of ZnO/ZnS composite powders: fuel and sulphur source

In the present study, ZnO/ZnS composite powders were synthesized by one-step solution combustion method. Thiourea was used both as the combustion fuel and sulphur source. Oxidizer-to-fuel (O:F) ratios between 0.5 and 1 were chosen as the main synthesis parameter. Structure, microstructure, chemical composition, and photoluminescence properties of the powders were also investigated. X-ray diffraction patterns showed simultaneous functions of thiourea as combustion fuel and sulphur source. The relative concentration of ZnS to ZnO increased by O:F ratio. Fourier-transform infra-red spectroscopy spectra demonstrated some bands associated with the unwanted organic compounds in the final product in addition to Zn–O and Zn–S bonds. Furthermore, scanning electron microscope micrographs showed the presence of some gel-like regions located around highly agglomerated particles. Photoluminescence spectra also indicated strong emission peaks for O:F ratio of 0.5 due to significant crystal defects and lower crystallinity.

Scintillator screen development for fast neutron radiography and tomography and its application at the beamline of the 10 MW BNC research reactor

Simple and inexpensive ZnS-based fast neutron imaging screens have been developed and their performance has been tested and compared to a commercially available one using the RAD beamline of the 10 MW research reactor of the Budapest Neutron Centre (BNC), Hungary. ZnS(Ag) and ZnS(Cu) powders have been mixed with optical epoxy, deaerated and casted into sheet form using an aluminum frame. The ZnS concentration and the screen thickness have been optimised using sample screen pieces. The in-house screens have been tested in camera-based neutron imaging detectors in a reactor beamline and compared with a commercially available polypropylene/ZnS(Cu) fast neutron imaging screen and with a BC400 plastic scintillator slab screen. It has been found that the in-house screen produces only about 60% of light intensity of the commercial polypropylene/ZnS screen, which is mainly due to the lower hydrogen density of the optical epoxy compared to polypropylene by the same amount. The BC400 performs inferior compared to any ZnS-based scintillator tested here. Fast neutron tomography has been performed with both the commercial and the in-house screens on the reactor beamline. A spatial resolution of around 1.6 mm has been achieved. Typically 10–15 min exposures were needed to obtain good quality radiographic images, whereas several hours of acquisition were needed to obtain the full tomographic set images. High quality imaging results have been obtained on large (150 mm in diameter) and dense objects (hydraulic couplings) proving the feasibility and utility of fast neutron imaging for such samples.

Physical and electrochemical properties of electrodeposited undoped and Se-doped ZnS thin films

In this paper, we report the effect of various Se-dopant concentrations on the structural, morphological, optical, electrical, and electrochemical properties of ZnS thin films. Undoped ZnS and Se-doped ZnS thin films were prepared using a three-electrode electrochemical cell. The indium doped tin oxide glass substrate (ITO) was used as the cathode. The anode and reference electrodes were a platinum wire and a saturated calomel electrode (SCE), respectively. An aqueous solution containing ZnCl2 and Na2S2O3 was used as the main solution. Different concentration of the SeO2 solution was added to the main solution to obtain Se-doped ZnS thin films. All deposited films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), photoluminescence (PL), UV–Vis spectroscopy, and electrochemical impedance spectroscopy (EIS). The XRD patterns exhibited forming cubic ZnS for all samples. FESEM images showed big grains about 150–450 nm in a background phase for all samples. PL and UV–Vis analysis examined the optical properties of deposited films. The band gap energy (Eg) of undoped ZnS was estimated to be 3.93 eV, which was reduced to 3.16 eV after Se-doping. Mott-Schottky analysis showed that the carrier concentration of undoped ZnS increased from 6.04 × 1019 cm−3 to 60.01 × 1019 cm−3, after Se-doping.

Microbiological synthesis of zinc sulfide nanoparticles using Desulfovibrio desulfuricans

ABSTRACTZinc sulfide (ZnS) nanoparticles were synthesized in a single-step process using Desulfovibrio desulfuricans at room temperature and atmospheric pressure. The kinetics of ZnS biosynthesis and the cellular distribution of Zn were also studied by measuring the Zn2+ and ZnS concentrations. The microstructure of the ZnS nanoparticles was characterized by means of high-resolution transmission electron microscopy and X-ray diffraction. The particles were essentially granular, and the particle size ranged from approximately 5 to 8 nm. The total UV–Vis spectrum of the product migrated toward blue wavelengths compared with the ultraviolet absorption wavelength of the ZnS bulk material. The yield of ZnS nanoparticles was 97.8% after 96 h. A mechanistic experiment showed that ZnS nanoparticles were produced inside the cells and released into the solution. In the cells, Zn was the most highly concentrated in the membrane, followed by the cell wall and cytoplasm.

Blue green fluorescence from freestanding films of PVDF/ZnS:Cu Nanocomposites

The growth of a novel nanocomposite consisting of Poly Vinylidene Di Fluoride (PVDF) and copper doped zinc sulphide (ZnS:Cu), its realization as flexible freestanding films and its application prospects as a bluish green phosphor form the essence of the work presented in this paper. PVDF is a semicrystalline fluoro polymer with the repeat unit of CH2-CF2.The photoluminescence emission characteristics were investigated in detail for various concentrations of ZnS:Cu in the nanocomposite films. The highlight of the present work is the observation that these luminescent films can be easily peeled off to yield free standing films which are quite stable and flexible.

Photovoltaic application of ZnS loaded silicon dioxide rich composites

In the present work, the composites between ZnS nanoparticles and silicon dioxide were prepared by solid state diffusion method. The oxidation of silicic acid to silicon dioxide and simultaneously formation of composites between ZnS and silicic acid were carried out during solid state diffusion process. As-prepared samples were characterized by using X-ray diffractions (XRD), field emission-scanning electron microscopy (FE-SEM), Ultraviolet–visible spectrophotometers (UV–vis), Raman spectroscopy, Photoluminescence (PL) spectroscopy, thermal analysis (TG-DTA) and photovoltaic response measurements respectively. The influence of increasing ZnS concentration in composites was reflected from photovoltaic characteristics. The highest power conversion efficiency was found to be 1.954% associated with 25wt.% ZnS loaded SiO2 composite, whereas the highest value of fill factor for 10wt.% ZnS loaded SiO2 composite in presence of light source of power 0.0104W/m2. These composites may be practically useful in a region where the light intensity is very weak like polar region (South and North pole).

Optical, phonon and efficient visible and infrared photocatalytic activity of Cu doped ZnS micro crystals

We report, the enhanced photocatalytic behaviour of Cu doped ZnS micro crystals. ZnS and different concentrations of Cu doped ZnS microcrystals were prepared. X-ray diffraction confirms the crystalline and phase of the particles. Morphology and sizes were studied using Scanning Electron Microscopy (SEM). Recorded optical absorption spectra show a band for around 365nm for pure ZnS, but there is a broad band in the near infrared regime for the Cu-doped ZnS microcrystals which are attributed to the d-d transitions of Cu2+ ions. Phonon properties of as-prepared samples were investigated using Raman spectroscopy. Present work we investigate the potential of ZnS and Cu doped ZnS as a photocatalyst. For this from the degradation of methylene blue dye in aqueous media the photocatalytic activity of pure and highest doped ZnS samples with the irradiation of white light and infrared, enhanced photocatalytic activity were observed. Mechanism of white light an IR light based photocatalytic activity is explained based on the electron-hole pair production.

Effect of ZnS nanoparticles on the photoluminescence of Sm3+ ions in methanol

ZnS nanoparticles co-doped with Sm3+ ions were prepared in methanol medium for fixed Sm3+ and varying ZnS concentrations. Enhancements in absorption as well as photoluminescence efficiency of the co-doped samples were observed. This enhanced efficiency is attributed to the effective increase in oscillator strengths of the Sm3+ transitions because of the addition of ZnS nanoparticles.

Quantitative characterization of ZnS:Mn embedded polyurethane optical emission in three mechanoluminescent regimes

ZnS:Mn is one of the brightest mechanoluminescent (ML) materials known, which makes it a prime candidate for use in Structural Health Monitoring (SHM) applications. For this work crystalline ZnS:Mn powder was embedded in a clear polyurethane (PU) matrix. The total emitted energy per unit solid angle per unit area, as well as the average radiance values of different samples are measured with a calibrated camera to determine the concentration and thickness of ZnS:Mn/PU for optimal emission. A trend is observed where emission from tensile loading appears stronger than that from compressive loading, and emission from fracture is stronger than that from plastic loading which itself is stronger than that from elastic loading. Also, the ML emissions by elastic and plastic loadings tend to increase with material thickness and ZnS:Mn concentration. Both tensile- and bending-induced fracture modes were tested. While for tensile fracture the emission is approximately independent of thickness and concentration, the emission accompanying an abrupt bending fracture increases with the ZnS:Mn concentration. This work presents a first quantitative absolute measurement of ML emission of ZnS:Mn, while also introducing the use of PU as potential host material, that can benefit many SHM and other applications.

Studies of physical properties of the Al doped ZnS thin films prepared by Spray

Undoped and Al doped ZnS were prepared via an efficient and low cost chemical co-precipitation method using Spray. In the present we study effect of Al concentration on structural, optical and electrical properties is studied using X-ray diffraction (XRD), the UV–visible, Fourier transform infrared spectroscopy and the impedance analyzer. The XRD shows that crystalline sizes which are in the range 22–59 nm which it increases with the highest values of Aluminium concentration. The optical measurements revealed that as the ZnS undoped and Al doping ZnS concentration increases the band gap decreases in the range of 3.72 to 3.61 eV thereby improving the optical properties of the ZnS thin film. Then, the impedance analyzer indicate firstly that the conductivity increase with the increasing of the doping concentration, the temperature and the frequency. On the other hand, the calculated values of the activation energy decrease with increasing of concentration of Al doping.

Antibacterial effect assessment of ZnS: Ag nanoparticles

Objective(s): A large ratio of surface to volume of nanoparticles in comparison with bulk ones, will increase the cell penetration and therefore their toxicity. Materials and Methods: Chemical precipitation method was used in order to synthesis of ZnS:Ag quantum dots. Their Physical properties and characteristics were assessed by X-ray diffraction, Ultra Violet-Visible Spectrophotometer, Transmission Electron Microscope and it was shown that the obtained ZnS:Ag quantum dots are cubic with high-quality. Antibacterial effects of ZnS:Ag nanoparticles against Pseudomonas aeroginosa, Staphylococcus aureus and Salmonella typhi were investigated. Disc bacteriological tests were used in order to assessment of the antibacterial effects of ZnS:Ag nanoparticles. Results: The size of inhibition zone was different according to the type of bacteria and the concentrations of ZnS:Ag QDs. The maximum diameter was happened for S. aureus. The results of MICs obtained fromBroth Dilution for Pseudomonas aeruginosa , Staphylococcus aureus and Salmonella typhi, are 3.05 , 3.05 and 6.1 mg/ml whereas the amounts of obtained MBCs are 12.2 , 6.1 and 12.2 mg/ml respectively. Conclusion: In conclusion, by increasing the nanoparticle concentration in wells and discs, the growth inhibition and diameter of inhibition zone has also been increased.

Investigation of Acidithiobacillus ferrooxidans in pure and mixed-species culture for bioleaching of Theisen sludge from former copper smelting.

The aim of this study was to investigate the potential of bioleaching for the treatment of an environmentally hazardous waste, a blast-furnace flue dust designated Theisen sludge. Bioleaching of Theisen sludge was investigated at acidic conditions with Acidithiobacillus ferrooxidans in pure and mixed-species culture with Acidiphilium. In shaking-flask experiments, bioleaching parameters (pH, redox potential, zinc extraction from ZnS, ferrous- and ferric-iron concentration) were controlled regularly. The analysis of the dissolved metals showed that 70% zinc and 45% copper were extracted. Investigations regarding the arsenic and antimony species were performed. When iron ions were lacking, animonate (Sb(V)) and total arsenic concentration were highest in solution. The bioleaching approach was scaled up in stirred-tank bioreactors resulting in higher leaching efficiency of valuable trace elements. Concentrations of dissolved antimony were approx. 23 times, and of cobalt, germanium, and rhenium three times higher in comparison to shaking-flask experiments, when considering the difference in solid load of Theisen sludge. The extraction of base and trace metals from Theisen sludge, despite of its high content of heavy metals and organic compounds, was feasible with iron-oxidizing acidophilic bacteria. In stirred-tank bioreactors, the mixed-species culture performed better. To the best of our knowledge, this study is the first providing an appropriate biological technology for the treatment of Theisen sludge to win valuable elements.

Preparation and investigation on third-order nonlinear optical properties of ZnS/MWCNTs composite materials

ZnS/MWCNTs composite materials with different concentrations of ZnS were prepared and their third-order nonlinear optical properties were studied through experiments and theoretical analysis. Structure and morphology characterizations of the ZnS/MWCNTs composite materials showed that ZnS quantum dots (QDs) were uniformly attached on the surface of MWCNTs. Third-order nonlinear optical properties of all the MWCNTs samples, ZnS QDs and ZnS/MWCNTs composite materials were measured by using Z-scan technique with a picosecond pulse laser. Experimental results showed that the composite materials always presented saturated absorption properties of MWCNTs and a negative nonlinear refraction effect of ZnS.

Enhanced third-order optical nonlinearity in Ce3+ ion-doped zinc sulfide–polyvinyl alcohol freestanding nanocomposite films

Undoped, 0, 2, and 5 mol% Ce-doped ZnS–PVA nanocomposite films have been prepared using in situ chemical method. X-ray diffraction patterns confirm that the prepared nanocomposite films are in cubic structure of ZnS. UV–Vis optical absorption spectra of Ce3+-doped ZnS–PVA films exhibit the red-shifted phenomenon with the increasing Ce dopant concentration in ZnS. Scanning electron microscope images reveal the morphology changes in the films with Ce doping. The high values of real and imaginary parts of dielectric constant at low frequencies are attributed to the space charge polarization, whereas the loss tangent of Ce-doped ZnS–PVA nanocomposite films at low frequency with the increasing Ce dopant concentration indicates the enhancement of optical quality of the films. The Z-scan technique exhibits a reverse saturable absorption process in nonlinear absorption studies and self-focusing optical nonlinearity in nonlinear refractive studies under the experimental conditions. The highest nonlinear optical parameters such as nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear optical susceptibility are found to be about 9336.6 cm/GW, 1.782 × 10−4 cm2/GW, and 2.103 × 10−5 esu, respectively, for 5 mol% Ce3+-doped films. The estimated third-order nonlinear optical susceptibility is eight orders of magnitude larger than that of bulk ZnS, and four–five orders of magnitude higher than those of the some representative materials reported. Hence, the Ce3+-doped ZnS–PVA nanocomposite films investigated here emerge as promising candidates for the development of nonlinear optical devices.

One-step synthesis of Cu2ZnSnS4 thin films by reactive magnetron co-sputtering

Cu2ZnSnS4 (CZTS) is suitable to replace conventional materials as absorber layer in solar cell applications. CZTS is composed of earth abundant and non-toxic elements, and exhibits an optical bandgap of 1.5eV and a high absorption coefficient in the visible range. CZTS thin films are usually synthesized by “two-step” processes consisting on the deposition of metallic precursors (Cu, Zn and Sn) followed by an annealing in sulfur containing atmosphere. These techniques allow developing efficient solar cells, but present major drawbacks: (i) a low control of the film properties, and (ii) the problems related to the implementation of a two steps process for large scale applications. In this work, we present the successful synthesis of crystallized CZTS using a “one-step” process namely the reactive magnetron co-sputtering of two metallic targets (copper–tin alloy and zinc) in Ar/H2S mixture. Multiwavelength Raman spectroscopy (325, 532 and 785nm) demonstrated the presence of CZTS for specific conditions. Our data reveal that a substrate temperature higher than 300°C is required to grow crystallized CZTS films and that the crystalline structure depends on the power applied to the CuSn target (PCuSn). For low PCuSn, CZTS films containing low concentrations of ZnS and Cu2−xS are obtained (Cu poor and S rich stoichiometry). Increasing PCuSn, CZTS disappears to the profit of SnS, Cu4Zn clusters and ZnS which is explained by the combination of high Cu concentration and low S concentration. Finally, the most promising film for photovoltaic applications exhibits a dense microstructure with large (200–300nm) CZTS grains.

Structural and optical studies of pHEMA encapsulated ZnS:Ni2+ nanoparticles

In this study, ZnS:Ni2+ nanostructures have been synthesized through chemical precipitation method using poly (2-hydroxyethyl methacrylate) (pHEMA) as capping agent. The structural, morphological and optical properties at different pHEMA concentration of ZnS:Ni2+ were studied by using X–ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV–Vis Spectroscopy (UV–Vis), fourier transform infrared spectroscopy (FT-IR), Photoluminescence (PL). The Average crystalline size of the nanoparticles was found to be in the range of ∼3.59–4.36nm. The surface morphological analysis reveals that the pHEMA capped nanoparticles showed homogeneous smooth surface. HR-TEM analysis reminds the original size of pHEMA capped nanoparticles. The band gap investigation revealed the size dependent of quantum confined nanoparticles. The immobilized nanoparticles in pHEMA matrix were verified by FT-IR studies. Novel luminescence properties have been observed for uncapped and pHEMA capped ZnS nanoparticles. The optimal capping concentration was successfully determined and its influence on photoluminescence behavior has been thoroughly analyzed.

Study the efficiency of single crystal CdTe/ZnCdS solar cell at various temperatures and illumination levels

Abstract CdTe is the best suited semiconductor for solar cells due to its band gap value 1.47 eV which is close to solar spectrum, low sublimation temperature and high absorption coefficient in the range of solar spectrum. To improve the photovoltaic performance of CdS/CdTe thin film solar cells, the CdS window layer is alloyed with different concentration of ZnS to reduce the resistivity and increase the band gap values. The single crystal CdTe based solar cell devices were prepared by vacuum evaporation method and have undergone for different temperature at various illumination levels to enhance the cell efficiency. We have achieved 14.37% efficiency and increased short circuit current density and open circuit voltage by reducing series resistance of the cell.

Compositional evolution and surface-related phenomena effects in ZnS–SiO2 nanocomposite films

ZnS–Silica nanocomposite thin films were prepared by the sol–gel method. The effect of ZnS:SiO2 molar ratio on structural, morphological and optical properties of thin films was characterized by XRD, FTIR, SEM, AFM, UV–Vis and PL spectroscopy. XRD patterns indicate the phase structure of ZnS particles embedded in SiO2 composite thin films is hexagonal while hexagonal–cubic mixed phase with dominant hexagonal structure is observable beyond 40:60 ZnS:SiO2 molar ratio. SEM and AFM images revealed that the morphology of the samples was strongly affected by variation in composite ratio. According to fractal and power spectral density analyses, at lower silica mixing compositions in 50:50 molar ratio, the composite films represented superior fractal dimension and roughness parameter. The optical transmittance of the films in visible region decreases with ZnS concentration. The pertinent optical constants and single-oscillator parameters along with Urbach tail were determined and discussed. The optical band gap descended gradually (from 3.98 to 3.94 eV) with increasing ZnS content. PL study showed that with increasing ZnS molar ratio, the emission intensity enhances generally.

ZnS–Ag–ZnO as an Excellent UV-Light-Active Photocatalyst for the Degradation of AV 7, AB 1, RR 120, and RY 84 Dyes: Synthesis, Characterization, and Catalytic Applications

ZnS-loaded Ag–ZnO, synthesized by a precipitation–thermal decomposition method, was used for the degradation of four toxic azo dyes, namely, Acid Violet 7 (AV 7), Acid Black 1 (AB 1), Reactive Red 120 (RR 120), and Reactive Yellow 84 (RY 84), under UV light irradiation. To determine the optimum amount of ZnS for the efficient removal of these dyes, the concentration of ZnS was varied with the optimum concentration of 2 wt % Ag. A concentration of 3 wt % ZnS-loaded Ag–ZnO was found to be most efficient in the degradation of these four azo dyes, and this catalyst was characterized by different techniques. Although XRD did not give a Ag peak, the presence of metallic silver was confirmed by XPS measurements. The photocatalytic activity of optimized ZnS-loaded Ag–ZnO was compared with those of other catalysts for azo dye degradation. ZnS–Ag–ZnO was found to be more efficient than Ag–ZnO, ZnS–ZnO, commercial ZnO, prepared ZnO, TiO2 P25, and TiO2 for the degradation of azo dyes under UV light. The mineralizatio...

Enhanced photoelectrical conductivity of poly (3-hexylthiophene) by incorporation of ZnS nanoparticles

This paper reports an enhanced photoconduction behaviour of organic (poly 3-hexylthiophene)–inorganic (zinc sulphide) hybrid system. Poly (3-hexylthiophene) (P3HT) and ZnS nanoparticles have been synthesized by chemical route at 0°C and 80°C, respectively. The separately prepared organic–inorganic materials were blended in a nanohybrid system and coated over to ITO electrodes to forms different samples with different concentrations (5–15wt%) of ZnS nanoparticles. The UV–visible spectra of these hybrid materials show an increase in the FWHM with ZnS nanoparticles, attributing to the enhanced optical properties. The photoconduction behaviour of the prepared samples has been investigated through current–voltage (I–V) measurements carried out under dark and light with fixed intensity (∼4.0W/m2) of tungsten lamp. It is observed that photocurrent increases with ZnS concentration. Also, quenching has been observed for the samples having higher concentration of ZnS nanoparticles, in P3HT matrix. The temperature dependence of electrical current in dark and light shows that the decrease in the resistivity with the temperature is more pronounced in the presence of light, indicating a photon activated process.