CdS Crystals Research Articles

Study of Half Metallic Ferromagnetism and Optical Properties of Mn-Doped CdS

The spin-polarized electronic band structures, density of states and optical and magnetic properties of dilute magnetic semiconductors (DMSs) Cd1−xMnxS with 6.25%, 12.5% and 25% concentrations of Mn have been studied by using ab initio calculations. The electronic band structures show half metallic ferromagnetic (HMF) behaviour with direct band gap at Γ symmetry point. The calculated values of band gaps are 0.8 eV, 0.99 eV, 1.3 eV and 1.5 eV for CdS, Cd0.9375Mn0.0625S, Cd0.875Mn0.1250S and Cd0.75Mn0.25S, respectively. The energy gap of CdS was found to increase by doping with transition metal impurity. The addition of the dopant atoms in CdS turns it into a p-type semiconductor. This half metallic character makes these compounds a potential candidate for spintronics applications. In optical properties, the role of Mn concentration on the absorption coefficient, optical conductivity, refractive index, extinction coefficient and dielectric function has been investigated. The total magnetic moment is found approximately 5.000 μB per dopant atom for Cd1−xMnxS (x = 6.25%, 12.5% and 25%). This value indicates that every Mn impurity adds no hole carriers to the perfect CdS crystal.

A novel quadripartite Cu2O-CdS-BiVO4-WO3 visible-light driven photocatalyst: Brief characterization and study the kinetic of the photodegradation and mineralization of sulfasalazine

A novel quadripartite Cu2O-CdS-BiVO4-WO3 nanocomposite (NC) was prepared by mechanical mixing of the individual semiconductor nanoparticles (NPs). The work focused on the kinetic study of the photodegradation and photo mineralization processes of sulfasalazine (SZ) by the quadripartite NC. XRD patterns showed the cubic phase of CdS and WO3 crystals, the monoclinic BiVO4, and the hexagonal CdS crystals in the composite, which relatively also confirmed by SEM and TEM images. The average crystallite sizes of about 28 nm and 22.5 nm were obtained for the NC by the Scherrer and Williamson-Hall equations, respectively. Photoluminescence (PL) spectra showed the lowest intensity for the composite. Both the lowest PL intensity and the highest photocatalytic activity were achieved when the moles of Cu2O in the composite was 3 times greater than the other components. Diffuse reflectance spectroscopy (DRS) results also showed a relative enhancement in the band gap energy of the composite especially for WO3 NPs alone. The photodegraded SZ solutions were subjected to the COD experiment to estimate the mineralization extent of SZ molecules or its degradation intermediates. Kinetic of both processes obeyed the Hinshelwood kinetic model and the rate constants of 0.0265 min−1 (t1/2 of 26.2 min) and 0.0323 min−1 (t1/2 of 21.5 min) were respectively obtained for the photodegradation and mineralization processes of SZ molecules, confirming that the mineralization of SZ is about 1.23 times faster than its photodegradation extent.

Synthesis and Photoluminescence of Cd1 –x(Ca,Sr)xS:Eu3+ Nanostructures in a Polyacrylate Matrix

Colloidal Cd1 –x(Ca,Sr)xS and Cd1 –xCaxS:Eu3+ (0 < x < 0.20) quantum dots (QDs) have been synthesized by an emerging reagent method in a methylmethacrylate (MMA) medium. The mole fraction of Eu3+ in the starting reaction mixtures was varied from 0 to 0.80 relative to the Ca2+ concentration. Using radical block polymerization of MMA, we have obtained transparent luminescent polymethylmethacrylate (PMMA) based composites: PMMA/Cd1 –x(Ca,Sr)xS and PMMA/Cd1 –xCaxS:Eu3+. Luminescence excitation in the composites is due to interband electron transitions in the CdS and electron transitions from the ground state to excited states of the Eu3+ ions. The observed broadband luminescence is due to structural defects in the CdS crystals, and narrow-band luminescence originates from 5D0 → 7Fj electron transitions of the Eu3+ ions in the bulk of the CdS crystals, in complexes on their surface, and in the bulk of the polymer matrix, independent of the semiconductor particles. The position and intensity of the observed spectral bands depend on the composition and concentration of the components, excitation wavelength, and other factors.

Propagation of linearly polarized light in a heated uniaxial CdS crystal

Propagation of linearly polarized light in a heated uniaxial CdS crystal

Propagation of linearly polarized light in a heated uniaxial CdS crystal

Propagation of linearly polarized light in a heated uniaxial CdS crystal

Determination of picric acid using micro CdS crystal-modified glassy carbon electrode

ABSTRACT Picric acid is a dangerous environmental pollutant due to its high toxicity, and the detection of picric acid in the environment is of great significance. The Cd2+ on the surface of CdS crystals can enrich negative ionic compound to form a complex in water. Therefore, the micro CdS crystals have been synthesised using thioacetamide and cadmium sulfate by means of a simple and cheap hydrothermal method for the detection of picric acid and were characterised by means of X-ray diffractometer, scanning electron microscopy, energy-dispersive spectrometer and AC impedance technique. The electrochemical reduction of picric acid at micro CdS crystal-modified glassy carbon electrode was investigated, revealing that the micro CdS crystals could catalyze picric acid, and the reduction mechanism of picric acid on the surface of micro CdS crystals was also discussed. Based on the reduction of picric acid at the modified electrode, a simple method of detection for picric acid was proposed by applying voltammetry, and a linear regression equation was obtained as I (10−5A) = 6160.53279 c (mol.L−1) + 2.51034 (R = 0.9997) with a recoveries of 96.0–101.0% and relative standard deviations of 1.3–2.9% (n = 6), confirming very high sensitivity and selective detection of picric acid at the micro CdS crystal-modified glassy carbon electrode.

United calculation of the optical and EPR spectral data for Co2+-doped CdS crystal

This article reports a united calculation of the optical band positions and EPR parameters (g factors g//, g⊥ and zero-field splitting D) for Co2+ ion at the trigonal tetrahedral Cd2+ site of CdS crystal by using the complete diagonalization (of energy matrix) method built on the cluster approach. In the approach, the one-electron basis functions are the molecular orbitals composed of the d orbitals of central dn ion and p orbitals of ligands (rather than only the pure d orbitals in the conventional crystal-field theory), and so the contributions from not only the spin-orbit parameter of dn ion, but also that of ligand ion are contained. The calculated results are in rational agreement with the twenty-two (nineteen optical band positions and three EPR parameters) observed spectral values found in the literature. The defect structure (particularly, the angular distortion) of the trigonal Co2+ center in CdS: Co2+ is also acquired by the calculation. The outcomes are discussed.

Model for UV induced growth of semiconductor nanoparticles in polymer films

A theoretical macrokinetic model for photoinduced growth of semiconductor nanoparticles was developed with allowance for specific features of their optical properties in the near ultraviolet region. In [A. A. Smirnov et al., Optical Materials Express, 8 (2018) 1603–1612] the Polymethylmethacrylate (PMMA) film containing good soluble CdS precursors [Cd(N(SCNEt2)2)2] (TEDBCd) was irradiated by an ultraviolet light emitting diode (UV LED) with a central wavelength of 365 nm at different fixed temperatures and at different fixed intensities. The authors in situ followed the evolution of absorbance at a wavelength of 405 nm where the film is initially transparent. The corresponding photon energy is larger than the bandgap of the bulk CdS crystals. The increase in absorbance of the irradiated film at this wavelength was associated with the CdS nanoparticle growth. The main result is that at a given temperature, the effect of UV radiation on the sample is determined by the exposure (dose) rather than the light intensity and the irradiation time separately. The presented paper aims at constructing a model of the semiconductor particle growth initiated by the light-induced destruction of good soluble precursor molecules and fitting this model to the experimental data, making it possible to estimate the most important parameters of the process. The photoinduced formation of CdS nanoparticles is a complicated process that includes photo-mediated destruction of the precursor molecules followed by diffusion-assisted growth of nanoclusters. The feature of the growing semiconductor nanoparticles is that rather small particles do not absorb radiation at a particular wavelength because of the quantum confinement. The theory also takes into account the finite thickness of the sample and the nonlinear effects of radiation shielding.

Enhanced photocatalytic reduction of CO2 using CdS/Mn2O3 nanocomposite photocatalysts on porous anodic alumina support with solar concentrators

Photocatalytic reduction of CO2 has gained interest due to dual benefits of reduction of global warming and production of synthetic fuels. In this work, we report photochemical reduction of CO2 using CdS and CdS/Mn2O3 nanocomposites as photocatalyst supported on porous anodic alumnia (PAA) support. Incomplete anodization of an aluminum film substrate leaves a thin layer of aluminum in the middle that improves mechanical integrity and retain electrical conductivity of the support. The rod shaped crystals of CdS, grown on the support’s pore surface form a crumpled sheet like structure that helps in trapping of light energy incident on the catalyst surface. The photocatalytic reduction of CO2 was performed under the direct sunlight, using reflectors like flat mirrors, compound parabola, and concentrating Fresnel lens to direct solar radiation onto the catalytic surface. The combination of Fresnel lens as concentrator and CdS/Mn2O3 nanocomposite as the catalyst gave exceptional increase in the photocatalytic activity when compared with CdS alone, with a peak formation rate of 52.2 μmol/g.cat/hr of C2H5OH, 1392.3 μmol/g.cat/hr of HCOOH and H2 production at the rate of 2766 μmol/g.cat/hr.

ДОСЛІДЖЕННЯ НЕОДНОРІДНО ЗЧУВСТВЛЕННІХ КРИСТАЛІВ СУЛЬФІДУ КАДМІЮ. ЧАСТИНА II. РЕЛАКСАЦІЙНІ ХАРАКТЕРИСТИКИ

The photoelectric properties of CdS crystals with combined doping has been considered. The relaxation of the photocurrent determined by the long-term (months) redistribution of the sensitive impurity has been found. The possibility of creating of a new type of light sensors with super long memory has been shown. The medium-time (minutes) and fast (seconds) relaxation of the photocurrent under excitation by intrinsic and infrared light has been studied

Two-Photon Absorption and Fluorescence in Micrometer-Sized Single Crystals of a Rhodamine B Coordinated Metal–Organic Framework

A Rhodamine B (RhB) dye coordinated, 2D metal–organic framework (MOF), {[Zn2(L)(RhB)]·5DMF}n (1; DMF = N,N-dimethylformamide), was constructed solvothermally from a −NH2-functionalized ligand and ZnII ions. The MOF features interlayer π···π interaction between the RhB molecules with an overlap of almost 100%. One- and two-photon-excited fluorescence measurements were carried out on micrometer-sized single crystals of varied thickness with continuous-wave and femtosecond pulsed lasers, respectively. The two-photon absorption coefficient was measured relative to the CdS crystal and found to be 7.1 ± 0.7 cm/GW at a wavelength of 1030 nm. Our findings demonstrate a new way of achieving solid-state dye microlasers or microsized light-frequency upconverters.

Spray-assisted vapor deposition of CdS nanoparticles on ZnO nanowires with enhanced photocatalytic performance

ZnO nanowires were synthesized by a hydrothermal method, and CdS nanoparticles were deposited on ZnO nanowires by spray-assisted vapor deposition. The SEM image of ZnO nanowires showed their diameter of ∼100 nm. The TEM image of ZnO/CdS composite showed that the CdS nanoparticles were decorated on the surface of ZnO nanowires. The crystallization of CdS, ZnO and ZnO/CdS was determined by XRD. The photocatalytic performance of CdS, ZnO and ZnO/CdS was investigated by degrading Rhodamine B (RhB) under visible light irradiation. The results showed that the ZnO/CdS composite showed a higher catalytic performance than single phase CdS or ZnO under the same reaction condition. The stability of ZnO/CdS composite was investigated by running RhB degradation reaction in 10 cycles, which showed that ZnO/CdS composite had a high stability over photocorrosion. The mechanism for the enhanced photocatalytic performance in ZnO/CdS composite was also explained.

Surface-Radiative Modes and Longitudinal Excitons in the Spectra of Exciton–Polariton Luminescence

Low-temperature (T = 2 K) spectra of exciton–polariton luminescence in the vicinity of the exciton resonance frequency An = 1 of CdS crystals are studied with allowance for the damping ℏΓ of mechanical excitons. The results of numerical calculations of the partial and interference contributions of bulk and surface-radiative spectral modes in the geometry of the radiation of additional waves into a vacuum with s and p polarizations are analyzed. It is shown that the contributions of purely longitudinal excitons and their interference with polaritons of the upper dispersion branch in luminescence in the vicinity of longitudinal frequency ωL are small (∼10−30%). Nevertheless, these contributions should be taken into account to achieve a quantitative agreement with the experiment; they determine the formation of an additional AL. line under oblique radiation.

The Preparation and Optical Properties of Ni(II) and Mn(II) Doped in ZnTe Nanobelt/Nanorod by Using Chemical Vapor Deposition.

The doping techniques are often used to modify the properties of semiconductors. Transition metal ion doping in semiconductor can lead to dilute magnetic semiconductors (DMSs), which may initiate some novel properties related to spins. In contrast to the wide band semiconductor ZnO, ZnSe and CdS crystal the transition metal (TM) ion aggregate can be the origin of the ferromagnetic behaviors, which influence their optical properties mainly through the exciton-spin interactions due to their high exciton binding energy. For narrow band semiconductor, the carrier-spin coupling is the main cause of magnetism as observed in ZnTe. The ZnTe nanobelt for DMS with the TM ions such as Ni(II) and Mn(II) doping mainly induce the excess carrier effect in the lattice after photo-excitation, whose optical properties are also strongly depended on the fabrication method structure and morphology. Photo-excited carriers and electron-phonon interaction (but less excitons) are responsible for their large redshifts in ZnTe nanostructures. The strong interaction between the doped magnetic ion spins and holes, electron-phonon coupling, p-d hybridization as well as local electron correlation in TM ions determined their optical properties. TM ions incorporation in ZnTe lattice has suppressed the broad defect emission band far from the bandedge and broadened the electron correlations and electron hole plasma band near bandedge when excited by the rising excitation powers. We also identified that the polarized PL of Ni(II) and Mn(II) doped samples to calculate the strain dependence of band splitting near valance band.

Luminescence of CdS:Ag Quantum Dots in a Polymethacrylate Matrix

Semiconductor quantum dots (QDs) exhibit intense luminescence and reproduce optical characteristics. Doping with metal ions has a positive effect on their properties. Introduction of QDs into polymer matrices leads to the formation of a required morphology of composites. There is a problem in synthesis of optically transparent polymer composites containing QDs of the А2В6 group that consists in the extremely low solubility of metal chalcogenides and most of their precursors in monomers. To solve this problem, we used colloidal synthesis. CdS QDs were synthesized by the method of appearing reagents in situ in methylmethacrylate (MMA). Doping with Ag+ ions was performed by adding a silver salt into the reaction mixture during the synthesis of CdS QDs. The PMMA/CdS:Ag luminescent polymer glasses were synthesized by radical block polymerization of MMA. The transparency of the composites at wavelengths exceeding 500 nm reaches 92% (5 mm). The luminescence excitation is related to the interband electron transitions in CdS crystals. Luminescence in the range of 500–600 nm is observed due to electron relaxation via a system of levels in the band gap of doped CdS crystals. The positions and intensities of the spectral bands depend on the Ag+ concentration, particle size, excitation wavelength, and other factors. The formation of Cd(Ag)S/Ag2S structures at Ag+ concentrations higher than 5.0 × 10–3 mol/L quenches the luminescence.

Isoelectronic Oxygen Centers and Conductivity of CdS Crystals Compared with PbS Crystals

The influence of oxygen on the electrical properties of PbS are well known. The goal of this study is to compare and reveal this phenomenon in CdS(O) single crystals, which we have studied in detail previously. The experiments are performed for CdS single crystals with a known oxygen concentration, deviation from stoichiometry, and definite set of intrinsic point defects. They allow us to confirm the results described for PbS and clarify their nature. It is shown that the phenomenon is based on the capture of free charge carriers— electrons—by acceptor-like isoelectronic OS centers with the subsequent formation of associates having a complex structure. Previous conclusions on the dissolution mechanism of oxygen in CdS with deviations from stoichiometry are confirmed. Variations in the electrical properties in oxygen-activated PbS(O), similarly to CdS(O), showed that isoelectronic oxygen centers OS are present in lead sulfide.

Emission from Crystals Irradiated with a Beam of Runaway Electrons

An investigation of the spectral and amplitude-temporal characteristics of emission from different crystals, promising in terms of their application as detectors of runaway electrons, is performed. This emission is excited by subnanosecond electron beams generated in a gas diode. It is found out that at the electron energies of tens–hundreds of kiloelectronvolts, the main contribution into the emission from CsI, ZnS, type IIa artificial and natural diamonds, sapphire, CaF2, ZrO2, Ga2O3, CaCO3, CdS, and ZnSe crystals comes from the cathodoluminescence; the radiation pulse duration depends on the crystal used and sufficiently exceeds the Cherenkov radiation pulse duration. It is demonstrated that the latter radiation exhibits low intensity and can be detected in the short-wave region of the spectrum in the cases where a monochromator and a high-sensitivity photomultiplier tube (PMT) are used.

Anisotropy of acousto-optic figure of merit at the collinear acousto-optic diffraction in hexagonal CdS crystals

Anisotropy of acousto-optic figure of merit at the collinear acousto-optic diffraction in hexagonal CdS crystals

Energy level alignment at the interface of cadmium sulphide single crystal and phthalocyanines: The role of the crystal surface states

Ultraviolet photoelectron spectroscopy was used to study energy levels of (0001) and (0001_) surfaces of bare CdS crystal terminated with Cd and S atoms, respectively, as well as energy level alignment at hybrid interfaces of CdS crystal and donor zinc phthalocyanine (PcZn) or acceptor fluoro-substituted zinc phtalocyanine (F-PcZn) layers, respectively. The data allowed us to distinguish a slight difference between ionization potential of the Cd- and S-terminated facets of the crystal and different contribution of these surfaces to formation of the interfacial dipole at the hybrid interfaces. Ionization potential for the S-terminated surface was slightly higher as compared to the Cd-terminated one for the same crystal, and a more positive dipole was always created on the S-terminated surface independent of whether the donor or acceptor phthalocyanine was used. The results showed that PcZn and F-PcZn render a dual effect at the CdS surface. First, the molecules created a dipole at the interface, however, the sign of this dipole was opposite for PcZn and F-PcZn, respectively. Second, the both molecules contributed to the formation of a depletion layer near the crystal surface. The role of the surface states of the crystal in the above effects has been elucidated. Interaction of PcZn and CdS surface was associated with the pinning of the upper occupied level of the surface states to the positive charge transfer state corresponding to the oxidized HOMO level of the molecule at the interface, whereas interaction of F-PcZn and CdS surface with the pinning of the upper occupied level of the surface states to the negative charge transfer corresponding to the reduced LUMO level of the molecule at the interface, i.e., similar to what is observed for the metal-organic interfaces, where an upper occupied level of semiconductor surface states in our case plays the role of Fermi level in metal.

Synthesis and luminescence spectra of poly(methyl methacrylate)/CdS:Ln(III) composites

Cadmium sulfide was prepared by colloidal synthesis in methyl methacrylate (MMA). Europium and terbium salts were added to the colloidal solutions. Using MMA radical polymerization, we synthesized PMMA/CdS:Eu(III), PMMA/CdS:Tb(III), and PMMA/CdS:Eu(III):Tb(III) luminescent composites. Their luminescence is due to defects in the CdS crystals and the 5Dо → 7Fj and 5D4 → 7Fj electronic transitions of the Eu3+ and Tb3+ ions, respectively. It depends on the composition of the materials, complexation on the surface of the colloidal particles, heat treatment time during synthesis, excitation wavelength, and other factors.