Doped ZnS Samples Research Articles

Optical properties of Silica capped Mn doped ZnS quantum dots

In the present report, silica capped ZnS quantum dots (QDs) have been synthesized using one-step Stober process. The bare Mn doped ZnS samples have been prepared by the co-precipitation method. The samples have then been coated by a SiO2 layer. X ray diffraction have been used to confirm the presence of desired phases and the absence of any impurity phase. The particle size and morphology have been studied through high resolution transmission electron microscopy (HRTEM). The absorption and the emission properties of the bare and the capped samples have been studied through UV-visible and photoluminescence spectroscopy respectively. Fourier-transform infrared (FTIR) spectroscopy was employed to study the band resonances of the samples.

Synthesis and properties of (Fe, Ni)-doped zinc sulfide nanopowders

Pure and (Fe, Ni)-doped ZnS nanopowders have been successfully synthesized by chemical co-precipitation method using Poly Vinyl Pyrrolidone (PVP) as capping agent. Powder X-ray diffraction (XRD) studies reveal that the synthesized powders are in cubic blended structure. The average crystalline size of pure and doped ZnS nanopowder conform around 2–3 nm. In the investigations, Ni is kept constant at 3 mol% and Fe is increased from 1 to 5 mol%. Transition electron microscopy (TEM) is also used to investigate the average size of the nanopowders. TEM results are reasonably in good agreement. SEM micrographs of the (Fe, Ni)-doped nanopowders result in agglomeration with spherical in shape. The EDAX spectra show the chemical composition of dopants is uniform in ZnS. Optical absorption spectra show the absorption edge at 310 nm. Photoluminescence (PL) studies are conducted with excitation wavelength of 306 nm. Pure ZnS exhibits sharp emission peaks at 438 nm, 450 nm and 466 nm. (Fe, Ni)-doped ZnS samples also exhibit the sharp emission peaks at 450 nm and 467 nm with decreasing intensity. The magnetic measurements reveal that 5 mol% Fe- and 3 mol% Ni-doped ZnS nanopowders exhibit a weak ferromagnetic behavior.

(Cu, Ag)-DOPED ZnS WITH WIDE VISIBLE LIGHT RANGE ABSORPTION FOR WATER SPLITTING: A THEORETICAL AND EXPERIMENTAL STUDY

Photocatalytic water splitting using a semiconductor photocatalyst is a promising process for direct solar energy conversion. In this study, the feasibility of the photocatalytic H2 evolution on (Cu, Ag)- doped ZnS catalysts under visible light irradiation has been investigated by using first-principles density functional theory calculations and experimental studies. The present results reveal that (Cu, Ag)-doped ZnS structures have relatively small formation energy, implying that they are more easily obtained in experiment. Moreover, the absorption is enhanced obviously in the visible-light region for (Cu, Ag)-doped ZnS, but their energy levels are still suitable for water splitting to generate H2, which means that (Cu, Ag)-doped ZnS structures are promising candidate photocatalyst materials for H2 production driven by visible light. ZnS and (Cu, Ag)-doped ZnS were prepared using chemical precipitation method. (Cu, Ag)-doped ZnS samples showed an improved photocatalytic activity compared with undoped ZnS. Ag-doped ZnS (0.15 g L[Formula: see text] has the highest hydrogen evolution rate of 794.6 [Formula: see text]mol[Formula: see text] h[Formula: see text] [Formula: see text] g[Formula: see text] at pH 3 (0.1 M Na2S solution as a sacrificing agent).

Effect of Zr doping and aging on optical and photocatalytic properties of ZnS nanopowder

Abstract A facile single step chemical method is reported for the synthesis of Zr doped ZnS nanopowder and its photocatalytic performance has been studied. The average crystallite size of the synthesized powder estimated from X-ray diffraction (XRD) is nearly 1.1 nm. Transmission electron microscopy (TEM) study shows that nanoparticles are agglomerated having a particle size of nearly 10 nm. The optical band gap of ZnS and Zr-doped ZnS, estimated with the help of UV–visible spectroscopy, is 3.7 and 2.9 eV, respectively. Photoluminescence (PL) spectroscopy indicated the role of lattice defects (vacancy, interstitial defects) on optical emission characteristics of doped ZnS samples. The photocatalytic activity of synthesized samples has also been investigated by degrading methylene blue (MB) dye under UV–visible illumination. The degradation quenching has been observed beyond 0.4 mol% doping of Zr in ZnS with maximum efficiency i.e. 80% in 4 h. Thereafter, the effect of aging is monitored for 1.5 months in which the modified emission properties of defect sites modulated the photocatalytic performance of Zr-doped ZnS sample. Further, with the help of various spectroscopic techniques (absorbance, PL and XPS), a mechanism for the photodegradation of MB dye by using Zr-doped ZnS nanopowder has been proposed.

Benchmark Analysis on Magnetic and Photoluminescence Properties of Selective Metal Ions Doped ZnS Nanoparticles

The creation of diluted magnetic semiconductors (DMSs) at lower dimensions that exhibit room temperature ferromagnetism (RTFM) has been given immense significance for the fabrication of a new class of spintronic devices through utilizing spin degrees of freedom besides charge nature of electrons. In this view, nanocrystals of ZnS doped with 4% concentration of Fe, Co, Ni, Cr, Mn, Sr, Cu, and Ce have been synthesized at room temperature (RT) by chemical co-precipitation method. The samples were examined by various characterization techniques like energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and photoluminescence (PL). EDS spectra revealed the existence of parent elements in the prepared samples. XRD characterization disclosed hexagonal structures of nanocrystals, and no secondary phases were observed in all the samples except for Cu and Ni doped ZnS. FTIR data confirmed the proper substitution of dopants in the host lattice as all the graphs have almost same stretchings. The magnetic nature of each sample was evaluated from M-H graphs of VSM, and it corroborated the transition of magnetic properties due to doping. Pristine ZnS showed diamagnetic nature, while Fe and Sr doped ZnS evinced strong ferromagnetic and anti-ferromagnetic properties, respectively. Photoluminescence studies on Ce, Sr and Mn doped ZnS samples revealed strong emission peaks with enhanced luminescence properties compared to bare ZnS. Cu, Cr and Mn doped ZnS exhibited a red shift in emission wavelengths, whereas Co doped ZnS showed emission peak shifted towards the blue region as compared to the host lattice.

Enhancement of third-order nonlinear optical properties of HMTA stabilized pure and doped ZnS nanoparticles and their electronic structures

This study reports the third-order nonlinear optical (NLO) properties of hexamethylenetetramine (HMTA) stabilized pure and transition metals (Cu, Co and Mn) doped ZnS nanoparticles (NPs) and their electronic structures. The third-order NLO properties of pure and transition metals (Cu, Co and Mn) doped ZnS NPs were measured by [Formula: see text]-scan technique. From these measurements, the pure and doped ZnS samples exhibit negative nonlinearity i.e., self-defocusing. The open aperture [Formula: see text]-scan measurement shows saturated absorption within the medium. The prepared pure and doped ZnS samples exhibit nonlinear refractive index of the order of 10[Formula: see text][Formula: see text](cm2/W), nonlinear absorption (NLA) coefficient of the order of 10[Formula: see text][Formula: see text]cm/W and nonlinear optical susceptibility of the order of 10[Formula: see text][Formula: see text]esu. The electronic structures of these ZnS NPs were investigated using near edge X-ray absorption fine structure (NEXAFS) measurements at the C K-, N K- and Co L[Formula: see text]-edges. The C K- and N K-edges XANES spectra reveal the appearance of several spectral features in the range 285–290[Formula: see text]eV and 390–430[Formula: see text]eV respectively. The Co L[Formula: see text]-edge NEXAFS spectrum exhibits multiplet absorption lines similar to those of Co[Formula: see text] ions coordinated in tetrahedral symmetry with four sulfur nearest neighbors. These results clearly demonstrate that divalent Co ions substitute Zn sites. From the Raman spectra, the appearance of multiple resonance Raman peaks indicates that the prepared ZnS samples have good optical quality.

Optical and magnetic properties of diluted magnetic semiconductor Zn0.95M0.05S nanorods prepared by a hydrothermal method

AbstractPure ZnS and doped Zn0.95M0.05S (M = Cr, Ni, Co, Fe and Mn) nanorods were successfully prepared by a hydrothermal method. The effects of the variety of doped elements on the crystal microstructure, morphology, optical and magnetic properties of the samples were investigated by means of X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray energy dispersive spectrometry, photoluminescence spectroscopy, UV–Visible diffuse reflectance spectroscopy and vibrating sample magnetometry. The experimental results show that all samples synthesized by this method possess single phase wurtzite structure with good crystallization, transition metal ions (M = Cr, Ni, Co, Fe and Mn) substitute for the lattice site of Zn2+ and generate single-phase Zn0.95M0.05S nanostructures. The morphologies of the samples are one-dimensional nanorods with good dispersion. The optical band gap of doped Zn0.95M0.05S decreases as the doping ion radius increases, and red shift occurs compared to undoped ZnS nanocrystals. Photoluminescence spectra exhibit clear ultraviolet emission and blue emission. Magnetic measurements indicate that the undoped and doped ZnS samples are ferromagnetic at room temperature.

Characterization of Mn, Cu, and (Mn, Cu) co-doped ZnS nanoparticles

Mn, Cu, and (Mn, Cu) co-doped ZnS nanoparticles were prepared using the hydrothermal method at 180°C. A hexagonal structure of synthesized ZnS nanoparticles was confirmed using X-ray diffraction. Scanning electron microscopy confirmed the morphology and elemental analysis of the ZnS nanoparticle as a spherical shape. Two luminescence peaks appearing in the photoluminescence spectrum of the pure ZnS nanoparticles were shown at 379 and 472 nm, which are attributed to the recombination of the defect states of ZnS. A third peak also appears on the doped ZnS samples. It was identified at about 556 and 580 nm for Cu- and Mn-doped ZnS, respectively, which are commonly attributed to the recombination of charge carriers. With the (Mn, Cu) co-doped ZnS, the emission peak showed a shift to longer wavelengths.

Compositional, morphological, structural, microstructural, optical, and magnetic properties of Fe, Co, and Ni doped ZnS nanoparticles

We present the compositional, morphological, structural, microstructural, optical, and magnetic properties of undoped, Fe, Co, and Ni doped ZnS diluted magnetic semiconductor nanoparticles (NPs) synthesized by chemical refluxing technique at 80 °C using Polyvinylpyrrolidone (PVP) as a stabilizer. EDS spectra confirmed the presence of Zn, Fe, Co, Ni, and S in the samples with expected stoichiometry. XRD and Raman studies revealed that all the samples exhibited cubic structure without any impurity phases. The average diameter of the particles confirmed by HRTEM studies was in the range 5–8 nm. From DRS, the estimated band-gap values were 3.92, 3.70, 3.98, and 3.76 eV for undoped, Ni, Fe, and Co doped ZnS samples, respectively. Photoluminescence studies indicated that the undoped and doped samples exhibited broad and asymmetric PL peaks covering a wide visible range. Room temperature magnetisation studies revealed that the undoped, Fe, Co, and Ni doped samples exhibited diamagnetic, paramagnetic, and ferromagnetic behaviors, respectively. The use of these ions with magnetic properties in systems doped by an innovative method and thus creating a quantum confinement effect.

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.

Structural, morphological and optical properties of Mn doped ZnS nanocrystals

Mn doped ZnS samples with composition formula Zn1-xMn xS where x = 0, 0.02, 0.05 and 0.10 were prepared by chemical method. Samples characterized for its structural, morphological and optical properties by X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and UV-vis spectrometry. XRD patterns confirm cubic zinc blend structure with no secondary phases for pure and Mn doped ZnS. Lattice constant value increases slightly with Mn concentration due to the substitution of Mn in ZnO lattice. TEM images show that the particles have spherical in shape with an average particle size 3-4 nm. The chemical species of the grown crystals are identified by FTIR spectra. Optical absorption spectra show decrement in band gap with increasing Mn concentration.

Structural, morphological and optical properties of Mn doped ZnS nanocrystals

Mn doped ZnS samples with composition formula Zn1-xMn xS where x = 0.00, 0.02, 0.05 and 0.10 were prepared by chemical method. Samples characterized for its structural, morphological and optical properties by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV-vis spectrometer. XRD patterns confirm cubic zinc blend structure with no secondary phases for pure and Mn doped ZnS. Lattice constant value increases slightly with Mn concentration due to the substitution of Mn in ZnS lattice. TEM images show that the particles have spherical in shape with an average particle size between 3-4 nm. The chemical species of the grown crystals are identified by FTIR spectra. Optical absorption spectra show decrement in band gap with increasing Mn concentration.

Optical properties of undoped and cobalt doped ZnS nanophosphor

In the present study, the optical properties of ZnS and cobalt (Co) doped ZnS nanoparticles were investigated at room temperature. ZnS and ZnS:Co nanophosphors were prepared through chemical route, namely the chemical precipitation method and the formation of the nanoparticles were confirmed by X-ray diffraction and field emission scanning electron microscope (FESEM). Band gap energy of the prepared samples is determined by using a UV–vis–NIR spectrophotometer. The photoluminescence property of ZnS and ZnS:Co sample is determined by fluorescence spectroscopy. The sizes of as prepared nanoparticles are found to be in the 8–9nm range. The FESEM morphology shows the formation of nanostructure of ZnS samples. The value of optical band gap has been found to be in the range 4.30–4.03eV. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, Co2+ doped ZnS samples show enhanced visible light emissions under the same UV excitation wavelength of 310nm.

Blue light emission from barium doped zinc sulfide nanoparticles

ZnS nanoparticles with Ba2+doping have been prepared at room temperature through chemical route, namely the chemical precipitation method. The nanostructures of the prepared nanoparticles have been analyzed using X-ray diffraction (XRD) for phase analysis, Field emission scanning electron microscope (FESEM) for the morphological characterization, UV–Vis–NIR spectrophotometer for determining band gap energy and fluorescence spectroscopy for determining the emission wave length. The sizes of as prepared nanoparticles are found to be in 9–10nm range. FESEM morphology shows the formation of nanostructure of ZnS samples. The value of optical band gap has been found to be in range 4.10–4.63eV. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, the Ba2+ doped ZnS samples exhibit visible light emissions under the same UV excitation wavelength of 310nm.

Enhanced photoluminescence properties of ZnS:Cu2+ nanoparticles using PMMA and CTAB surfactants

ZnS nanoparticles with Cu2+ doping have been synthesized at 80°C through a soft chemical route, namely the chemical co-precipitation method at air atmosphere. The water soluble PMMA and CTAB were used as capping agents. The nanostructures of the synthesized nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), UV–vis and fluorescence spectrophotometer. The sizes of as-prepared nanoparticles are found to be below 3.4–5.2nm range. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, in the Cu2+ doped ZnS samples enhanced visible light emissions with emission intensities of ∼2 times larger than that of the undoped sample are observed for CTAB capped sample. The phase changes were observed in different temperatures by TG-DTA.

Enhanced visible light emission from Co2+ doped ZnS nanoparticles

Abstract ZnS nanoparticles with Co 2+ doping have been prepared at room temperature through a soft chemical route, namely the chemical co-precipitation method. The nanostructures of the prepared nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), selected-area electron diffraction (SAED), and UV-vis spectrophotometer. The sizes of as prepared nanoparticles are found to be in 1–4 nm range. Room-temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, in the Co 2+ doped ZnS samples enhanced visible light emissions with emission intensities of ~35 times larger than that of the undoped sample are observed under the same UV excitation wavelength of 280 nm.

Study of 4the influence of annealing parameters on the optical and compositional properties of ZnS, ZnS:Mn and ZnS:Sm grown by Sol Gel

Samples with 3 layers of ZnS were prepared on glass substrate by the Sol Gel method. The annealing parameters were varied as follows: each of the 3 constituent layers of sample 1 was annealed at 400 °C for 12 hrs. For sample 2, the 1rst and 2nd layers were annealed at 300 °C for 2hrs each and the 3rd one at 400 °C for 12 hrs. For sample 3, the 1rst and 2nd layers were annealed at 200 °C for 2hrs each and the 3rd at 400 °C for 12 hrs. Furthermore, 2 samples: one with 3 layers of ZnS:Mn and the other with 3 layers of ZnS:Sm were prepared and annealed similarly to sample 2. AES depth profiles show a transversal diffusion of S in sample 1, a sulfur deficiency in sample 2, and a non distributed excess of S in sample 3. The absorption spectra of the 3 ZnS samples are very similar but the absorption edges shift to smaller energy values for the Mn and Sm doped ZnS samples. Sample 1 presents a PL spectrum with 2 bands at 441 and 537 nm while sample 2 presents a similar spectrum but the bands are 16 and 11 nm blue shifted.

Space charge and excitation efficiency in ZnS thin film electroluminescent devices

Measurements under continuous UV illumination permit one to investigate the influence of a bulk space charge on the excitation efficiency η exc in ZnS thin film electroluminescent devices. Depending on the irradiation intensity, the addition of UV reduces or even erases the space charge which is responsible for the inhomogeneous excitation efficiency. When the space charge is reduced η exc is higher in the region near the anodic insulator-semiconductor interface. In another experiment, neodymium doped ZnS samples are used to determine the variation of the space charge during the charge transfer. Under our driving conditions, the space charge increases during the charge transport in the steady state regime.