ZnS System Research Articles

Tuning the magnetic properties of doped ZnS using transition metal doping: A multi-scale computational approach

Transition metal (TM)-doped dilute magnetic semiconductors (DMS) have emerged as promising materials for spintronic applications such as spin-polarized transport and information storage. However, achieving robust room-temperature ferromagnetism in DMS remains a key challenge. This work undertakes a comprehensive investigation of the effects of Ti- and Cr-doping and (Ti,Cr)-codoping on the structural, electronic, and magnetic properties of wurtzite ZnS using first-principles pseudopotential plane-wave self-consistent field calculations and Monte Carlo simulations. The first-principles DFT calculations were performed using the spin-polarized GGA+U approach to account for strong electron–electron interactions. Structural relaxations revealed expanded lattice parameters and bond lengths for the doped systems compared to pure ZnS, attributed to the larger ionic radii of the dopants. Formation energy calculations confirmed the thermodynamic stability of doping. The band structure and density of states analysis demonstrated the half-metallic nature of the doped ZnS systems with 100% spin polarization induced by strong hybridization between the TM-3d and S-3p states. This mediates robust ferromagnetic coupling, with total magnetic moments around 4-8 μB/cell depending on dopant type and concentration. To complement the zero-temperature DFT results, temperature-dependent Monte Carlo simulations using the single-spin flip Heat Bath algorithm were implemented. The modeling of magnetization, susceptibility, specific heat, and hysteresis loops enabled extracting Curie temperatures up to 427.6 K for 12.5% Cr-doped ZnS. The synergistic combination of first-principles DFT and Monte Carlo computational techniques provides significant insights into tailoring the magnetic properties of TM-doped ZnS dilute magnetic semiconductors. The tunability of structural, electronic, and magnetic characteristics through control of dopant selection and concentration demonstrates the promising potential of transition metal-doped ZnS for spintronic devices operable at room-temperature.

Tuning the electronic structure and absorption spectrum of ZnTe/ZnS heterojunctions by selective doping with yttrium: A first-principle study

This paper systematically investigates the electronic structure and optical properties of zinc-blende ZnTe, ZnS systems, ZnTe/ZnS heterojunctions, and Y-doped ZnTe/ZnS heterostructions using the generalized gradient approximation (GGA) method under the density functional theory (DFT) framework. The results show that compared to the single-component ZnTe or ZnS systems, the ZnTe/ZnS heterojunction has a smaller bandgap width and undergoes a redshift in the absorption spectrum, which is favorable for more valence band electrons to be excited by light and transition to the conduction band, thereby enhancing the optoelectronic properties of the material. After Y-doping in the ZnTe/ZnS heterojunction system, when the doping concentration is between 1.56[Formula: see text]at% and 4.69[Formula: see text]at%, doping Y in the ZnS layer would result in the lowest energy formation of the system. Therefore, it can be inferred that in experiments, if the doping concentration is increased beyond this range, Y atoms are more likely to be arranged in the ZnS layer. Compared with the pure ZnTe/ZnS heterojunction system, increasing the Y doping concentration results in a wider bandgap and a more prominent blue shift in the absorption spectrum. Therefore, it is possible to adjust the bandgap of the heterojunction by changing the doping concentration to fabricate heterojunction device with different photoelectric effects and luminescence properties.

Structural, dynamical and thermodynamical stability of Cd1-xZnxS ternary systems

Cd1-xZnxS alloys are currently explored as one class of the most promising for producing hydrogen energy under visible-light irradiation. Here, using an ab intio evolutionary algorithm, we reveal that CdS–ZnS systems can form nearly thermodynamically stable crystal phases of Cd3ZnS4 (P-43m), CdZnS2 (P-4m2), and CdZn3S4 (P-43m), with low miscibility temperatures of 130 °C. By decomposing the formation enthalpy of the alloys into multiple contributions, it is found that electronic charge exchange plays a key role in controlling the weak thermodynamic instability of Cd1-xZnxS alloys. Phonon dispersion and elastic constants calculations were carried out to demonstrate the dynamical and mechanical stabilities of these structures. The bandgap in CdZnS alloys is tunable from wide direct bandgaps of 2.54eV (CdS) → 2.70eV (Cd3ZnS4) →2.93eV (CdZnS2) → 3.33eV (CdZn3S4) → 3.86eV (ZnS), with a nonlinear dependence on the composition. We found a medium-sized optical bandgap bowing of ∼1eV and ∼0.7eV; while considering respectively the wurtzite (WZ) and zinc-blend (ZB) crystal phases as reference of the compounds parents CdS and ZnS. The bowing has a remarkable contribution due to the structural volume-deformation effect; whereas charge exchange contribution is found relatively weak.

Surface Properties of Components in the InP–ZnS System

Surface Properties of Components in the InP–ZnS System

Synthesis of diluted magnetic semiconductor ZnS:Cr and ZnS:(Cr+V) nanoparticles for spintronic applications

The design of optimally diluted magnetic semiconductors that exhibit strong ferromagnetism at room temperature is also imperative for developing spintronic devices. In this study, we describe the wet chemical preparation and characterization of ZnS, ZnS:Cr (1 at%), ZnS:Cr (1 at%) + V (1 at%), and ZnS:Cr (1 at%) + V (2 at%) NPs for spin-electronic device applications. Wide-ranging structural analyses suggested the incorporation of both Cr and V ions into the ZnS system. Morphological analysis revealed that the synthesized samples were in the nanoregime with a zero-dimensional alignment. Photoluminescence (PL) spectra displayed diminished luminescence intensity with doing and co-doping. and Electron paramagnetic resonance analysis revealed the presence and augmentation of spins with increasing V co-dopant concentration in the ZnS:Cr (1 at%) host lattice. Vibrating sample magnetometer analysis revealed that the ZnS:Cr (1 at%), ZnS:Cr (1 at%) + V (1 at%), and ZnS:Cr (1 at%) + V (2 at%) NPs exhibited strong ferromagnetism with clear hysteresis loops at room temperature.

Hydrogen evolution properties: Cr doping and V co-doping effect of ZnS nanoparticles

In this study, the effects of Cr doping and V co-doping on the hydrogen (H2) evolution properties of ZnS nanoparticles (NPs) were evaluated. An economical and facile hydrothermal method was used to synthesize ZnS, Zn0.99Cr0.01S, Zn0.98V0.01Cr0.01S, and Zn0.97V0.02Cr0.01S NPs. All the samples exhibited a cubic structure with effective Cr doping and V co-doping in the parent ZnS lattice. The variable bandgap of ZnS was engineered by Cr doping and V co-doping. Therefore, blue emission with a diminished fluorescence efficiency was achieved for the ZnS system by doping and co-doping. The Zn0.97V0.02Cr0.01S system showed the highest H2 evolution potential (12098 µmol h−1g−1) in 5 h under artificial solar illumination. Thus, V co-doping enriched the H2 production capacity of the ZnS:Cr system.

Development and validation of a real-time and non-destructive method for direct measurement of solid mixture based on reflection spectra

The Belt and Road countries are facing low resource exploitation efficiency and environmental pollution problems in the field of industrialization and production. Real-time and accurate determination of solid composition is urgently required. Herein, a new quantitative model and method were developed based on the mass conservation law, the elementary reaction and interaction between light and substance. Charge-coupled Device receiver was used to directly measure the solids and quickly obtain the spectral reflectance. According to the difference of spectral reflectance, partial least squares mathematical iterative fitting is utilized to optimize the model parameters based on the relationship between concentration and reflectance at 380–740 nm. It is applied to three typical mineral systems: I. Fe2O3 and Fe3O4 system with different metal valence states; II. ZnO and ZnS system with different anions; and III. Fe2O3 and ZnS system with different element compositions. The best characteristic wavelengths are 560 nm, 720 nm and 680 nm. The goodness of fit is 0.97–0.99 with root mean square less than 0.04, standard recoveries 98%–108%, and relative error of blind sample less than 5%. Compared with some conventional solid analysis methods, this method has the advantages of real-time, non-destructive, no pretreatment and no secondary pollution.

Adsorption Properties of Novel Materials Based on the InP–ZnS System

Adsorption Properties of Novel Materials Based on the InP–ZnS System

Effect of B2O3 additive on the properties of ZnS-Ge system and the resulting thin-film coatings

The effect of B2O3 additive to ZnS and ZnS-Ge system on their properties and parameters of thin-film coatings obtained from them has been studied. The essence of the additive is the binding of ZnO in Zinc sulfide, which has a negative effect due to the interaction with the evaporator material. According to X-ray diffraction, the introduction of B2O3 additive to ZnS results in the disappearance of the wurtzite phases (β-ZnS and ZnO). There is also a change in the IR spectra, in which reveal the bands at ≈300 cm−1 and 415 cm−1, which correspond to the valence vibrations of the Zn-S and Zn-O bonds, respectively. It is established that the addition of B2O3 noticeable improves the technological mode of evaporation in vacuum of materials due to the increase of their volatility. The reflection spectra of thin films of undoped and doped ZnS indicate a certain increase in the refractive index of the latter, while in the ZnS-Ge system such a difference is not observed. The mechanical durability of coatings increases especially significantly - more than 10 times for ZnS and more than 2 times - for the ZnS-Ge system. Therefore, the use of B2O3 as an additive has proved to be an effective method for minimizing the effects of oxide impurities in chalcogenide materials on the properties of thin-film coatings.

Redox Catalysis Promoted Activation of Sulfur Redox Chemistry for Energy-Dense Flexible Solid-State Zn-S Battery.

In aqueous Zn-ion batteries, the intercalation chemistry often foil attempts at the realization of high energy density. Unlocking the full potential of zinc-sulfur redox chemistry requires the manipulation of the feedbacks between kinetic response and the cathode's composition. The cell degradation mechanism also should be tracked simultaneously. Herein, we design a high-energy Zn-S system where the high-capacity cathode was fabricated by in situ interfacial polymerization of Fe(CN)64--doped polyaniline within the sulfur nanoparticle. Compared with sulfur, the FeII/III(CN)64/3- redox mediators exhibit substantially faster cation (de)insertion kinetics. The higher cathodic potential (FeII(CN)64-/FeIII(CN)63- ∼ 0.8 V vs S/S2- ∼ 0.4 V) spontaneously catalyzes the full reduction of sulfur during battery discharge (S8 + Zn2FeII(CN)6 ↔ ZnS + Zn1.5FeIII(CN)6, ΔG = -24.7 kJ mol-1). The open iron redox species render a lower energy barrier to ZnS activation during the reverse charging process, and the facile Zn2+ intercalative transport facilitates highly reversible conversion between S and ZnS. The yolk-shell structured cathode with 70 wt % sulfur delivers a reversible capacity of 1205 mAh g-1 with a flat operation voltage of 0.58 V, a fade rate over 200 cycles of 0.23%/cycle, and an energy density of 720 Wh kgsulfur-1. A range of ex situ investigations reveal the degradation nature of Zn-S cells: aggregation of inactive ZnS nanocrystals rather than the depletion of Zn anode. Impressively, the flexible solid-state Zn battery employing the composite cathode was assembled, realizing an energy density of 375 Wh kgsulfur-1. The proposed redox electrocatalysis effect provides reliable insights into the tunable Zn-S chemistry.

Comparison of the Bulk and Surface Properties of InBV–ZnS Semiconductor Solid Solutions

The bulk (crystal-chemical and structural) and surface (acid base) properties of InBV–ZnS semiconductor solid solutions with different AIII–BV (InP and InAs) binary components are investigated under identical conditions. The regularities of the variation in the investigated properties with composition, which are generally statistical (smooth) for the InP–ZnS system and have extrema for the InAs–ZnS system, are established. The initial (air-exposed) surfaces of the solid solutions, as the surfaces of the binary components of the systems, are weakly acidic (pHiso < 7), which allows us to state their high activity with respect to the main gases. Considerations concerning the nature of active (acid base) sites are presented and confirmed. The interrelation between the surface and bulk properties of the solid solutions is established, which offers opportunities for the prediction and inexpensive search for advanced high-efficiency materials for the semiconductor-gas analysis without time-consuming investigations of the surface properties.

Study of the photocatalytic activity of CdS–ZnS nano-composite in the photodegradation of rifampin in aqueous solution

The elimination of rifampin (RN) as a pollutant from an aqueous solution was performed via the photodegradation process by the coupled CdS–ZnS system under visible light irradiation. The catalyst was briefly characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and transmission electron microscope (TEM) techniques. The cubic ZnS structure and the hexagonal CdS structure with the crystallite size of 10 nm were detected from the XRD patterns. From the DRS results, the bandgap energies of 2.3, 3.9, and 2.4 eV were obtained for CdS, ZnS, and CdS–ZnS, respectively. The pH-values of 5.2 (5.25), 5.8 (5.8), and 5.9 (5.88) were obtained for the pHpzc of CdS, ZnS, and CdS–ZnS by two methods, respectively. Increased photocatalytic activity of the coupled ZnS–CdS system was achieved compared to the single systems and when the moles of CdS is 6 times higher than the ZnS component, the best activity was obtained. The optimal degradation conditions were the catalyst dose: 0.5 g/L, CRN: 8 mg/L, pH: 2, and irradiation time: 120 min. The rate constants of RN photodegradation and mineralization (from the chemical oxygen demand (COD) results) were 0.028 and 0.019 min−1, respectively. The mechanism pathway was similar to the type (II)-heterojunction system in which the accumulated holes in VB-ZnS, the accumulated electrons in CB-CdS, and hydroxyl radicals are more important reactive species in the photodegradation of RN molecules. Further, this mechanism is useful for hydrogen production by both the photogenerated electrons in CB-CdS and CB-ZnS positions. Another mechanism that can illustrate the photodegradation process is similar to the direct Z-scheme mechanism pathway in which the accumulated electrons in the CB-ZnS, the accumulated holes in the VB-CdS, and the superoxide radicals are more important active centers for the degradation of RN molecules. Also, the accumulated holes in the CB-CdS position are another active center to oxidize RN molecules. Besides, the accumulated holes in the CB-ZnS position are more suitable for hydrogen production. The photogenerated holes in the CB-CdS position are also capable to oxidize water molecules for oxygen evolution.

Visible LED‐Assisted Effective Charge Separation in Ruthenium‐Doped ZnS System for Efficient Photodegradation of Organic Dye

AbstractHarvesting solar light efficiently and effective photo‐induced charge separated photocatalysts becoming an immense demand for environment salvation. Herein, the one‐step solvothermal method has been employed to synthesize Zn1–xRuxS nanoparticles (NPs). A systematic study for the photocatalytic degradation of Methylene blue (MB) for the first time in Ru doped ZnS system has been carried out with visible light (LED) irradiation. Density functional theory has been employed to study the structural, electronic properties and charge transfer mechanism throughout the Ru doped ZnS system. Theoretical results and UV‐Vis spectra suggest a reduction of bandgap as a function of Ru concentration. Bader charge analysis for both the structures as well as photoluminescence quenching has shown Ru acts as a charge center in the charge transfer process. The optimum photodegradation efficiency is achieved in case of 1% Ru doped ZnS NPs. Thus Ru doping in ZnS NPs has a significant role in showing effective photocatalytic behaviour.

Spin polarized first principles calculations on electronic, magnetic and optical properties of Zn(1−x)AxS (A = Cr/Mn/Fe) using mBJ approximation

A systematic investigation on structural, electronic, magnetic and optical properties of Zn(1−x)AxS (A = Cr/Mn/Fe) are performed using first principles calculations within the frame work of spin polarized density functional theory (SP-DFT) as implemented in WIEN2k. The electronic, magnetic and optical properties are performed using the local spin density approximation (LSDA) coupled with modified Becke Johnson (mBJ) potential. The present results show that Zn(1−x)MnxS systems exhibit semiconducting behaviour whereas a half-metallic character is shown by both Zn(1−x)CrxS and Zn(1−x)FexS systems. Although undoped ZnS is a non-magnetic semiconductor, the calculated spin polarized density of states of Cr2+:ZnS and Fe2+:ZnS show 100% spin polarization at Fermi energy, EF. The optical properties, including the real and imaginary part of dielectric function, reflectivity, refractive index, absorption co-efficient, electron energy loss function and optical conductivity of undoped ZnS and Zn(1−x)AxS (A = Cr/Mn/Fe) systems are calculated using mBJ potential. The substitution of Cr and Fe in ZnS not only influences the position of absorption peaks of parent semiconductor in the UV region, but also leads to the formation of new narrow peaks in the visible and IR regions. A considerable red shift in the absorption peak due to the substitution of Fe and Cr shows a good agreement with the previous theoretical results. These outcomes imply that Zn(1−x)AxS (A = Cr/Fe) systems cover the spectral range from IR to near UV and seem to be the promising candidates for optoelectronic and spintronic applications.

Effect of cobalt doping on the structural, optical and magnetic properties of sol-gel derived ZnS nanocrystalline thin films and ab initio studies

The effect of Co doping on the structural, optical and magnetic properties of sol-gel derived ZnS films was investigated for their dilute magnetic semiconducting behaviour. X-ray diffraction pattern shows nanocrystalline nature of the films. Raman spectroscopy was used to study the vibrational properties of the films and also to identify any kind of secondary phases. The surface morphology and roughness of the films was analysed through scanning electron microscopy and atomic force microscopy. The chemical binding state of Co in ZnS lattice was confirmed from the X-ray photoelectron spectroscopy. The optical band gap is found to be decreasing with the incorporation of Co in ZnS. The red emission ~1.7 eV ensures tetrahedral occupation of Co atoms in ZnS lattice. The observed room temperature ferromagnetism in Co:ZnS films is attributed to carrier induced magnetization as well as to the intrinsic defects. The origin of magnetism in Co:ZnS system was studied in terms of the spin-polarized electronic density of states obtained through the density functional theory.

Comparative Physical-Chemical Properties of Binary and Multicomponent Semiconductors in CdS–ZnSe and CdS–ZnS Systems

Solid substitution solutions in CdS–ZnSe and CdS–ZnS systems have been fabricated and certified. Bulk (crystal chemistry, structural, and optical) and surface (acid–base) properties of these solutions have been examined as compared to each other and their binary components. Regularities of changes in the investigated properties upon changes in the systems’ compositions and in a series of analogs have been established: these regularities have predominantly exhibited an extremal nature. Interrelations between the established regularities have been validated, which allows predicting, based only on bulk properties, the surface activity of advanced materials (fabricated solid solutions) toward gases of varied electronic nature—components of natural and technological media. Practical guidelines on application of these materials to produce appropriate sensors have been provided.

Carrier-induced ferromagnetism in half-metallic Co-doped ZnS-diluted magnetic semiconductor: a DFT study

Systematic experimental and theoretical calculations have been performed to investigate the origin of the carrier-induced ferromagnetism in the Co-doped ZnS-diluted magnetic semiconductors. The crystalline structure, morphology of the chemically synthesized Co-doped ZnS nanoparticles are evaluated using X-ray diffraction (XRD) and transmission electron microscopy (TEM) and obtained the average crystallite size in the range 5–8 nm. Fourier transform-infrared spectra reveal the characteristic Zn–S vibrations of cubic ZnS and also show the splitting of peaks with increasing Co concentration which indicates that the Co-doping level beyond 3% affects the structure of ZnS. The room temperature ferromagnetic behavior analyzed by M–H curve exhibited up to the doping level 5%, achieving due to the indirect ‘p–d’ exchange interactions between the localized ‘d’ spins of Co2+ ion and the free-delocalized carriers in the host lattice. The existence of the antiferromagnetic coupling is discernable beyond the 5% doping level, owing to the short-range super-exchange interactions between the characteristic ‘d’ spins of the Co2+ ions which minimize the ferromagnetic ordering. Band structure and density of states (DOS) calculations demonstrate the p–d hybridization mechanism in Co-doped ZnS system which is the main cause of realizing ferromagnetic ordering in the system and also shows the half-metallic characteristics with the combination of semiconducting and metallic nature in the spin-up and spin-down states, respectively.

Thermodynamic modeling of phase equilibria and defect chemistry in the Zn-S system

Though important and fundamental, a satisfactory theoretical framework of modeling multiple point defects in the context of phase equilibria is still lacking. In this work, a methodology that models point defects, electrons, holes and the underlying phase equilibria simultaneously is developed and applied to the Zn-S system. It overcomes some issues in previous works, such as inconsistency in the reference state for electrons. The model parameters are directly related to the Gibbs energy of formation of point defects computed from first-principles phonon calculations. A double exponential function is proposed to parameterize the entropy of formation of point defects as a function of temperature. Using this approach, phase diagrams, concentrations of point defects and free carriers, the majority carrier, and defect-related properties exemplified by the electrical conductivity are obtained under various conditions, in agreement with experimental data. The present methodology provides a way to integrate first-principles calculations and experimental data into the CALPHAD model, enabling description of multi-component semiconductor systems.

Ferromagnetic ordering in chemically synthesized ZnS:Mn diluted magnetic semiconductor: A density functional theory explanation

We have carried out DFT calculations to investigate the origin of room temperature ferromagnetism in experimentally obtained Mn doped ZnS magnetic semiconductor. For experimental investigations, the formation of the cubic ZnS structure of ∼4 nm in size is confirmed by XRD and TEM results. Theoretical calculations reveal that Mn doped ZnS system possesses half metallic characteristics in addition to strong p–d hybridization between the d-states of Mn atom and the p-states of surrounding S atoms, which leads to the strong ferromagnetic coupling and is experimentally realized in the M–H curves of Mn doped ZnS nanoparticles. The ferromagnetic coupling between Mn–Mn atoms are studied by using two dopant model, replacing two Zn atoms by two Mn atoms in ZnS supercell, which depicts that ferromagnetic state is always ground state. In calculating formation energies for single and two Mn dopant ZnS systems, negative values of formation energy are obtained indicating of higher stability of the system.

Histological analysis of anti-cancer drug loaded, targeted Mn:ZnS quantum dots in metastatic lesions of 4T1 challenged mice.

5-Fluororaucil (5-FU) as anti-cancer drug was reported to induce thymidine synthase (TS) overexpression and cancer cell resistance. To improve its therapeutic efficacy and selective targeting, here we developed a targeted delivery system mediated by the active ligand-folate receptor chemistry to deliver the 5-FU drug selectively into the tumor microenvironment. The preparation was achieved by exploring chitosan (CS)-biopolymer based system with folic acid (FA)-conjugation. The 5-FU@FACS-Mn:ZnS quantum dots (QDs) based on the histological assessment conducted in the 4T1 challenged mice showed an improved tumor remission in the liver, spleen and lungs. The 5-FU@FACS-Mn:ZnS composite induced anti-proliferative properties in these organs as compared to the free 5-FU drug. Unlike the 5-FU@FACS-Mn:ZnS treated groups which showed some specific morphological changes such as cell shrinkage without obvious presence of adipocytes, the excised section of the tumor in the untreated control group and the free 5-FU drug treated group showed necrotic and degenerated cells; these cells are multifocally distributed in the tumor mass with evidence of widely distributed adipocytes within the tumor mass. These findings suggest that the 5-FU@FACS-Mn:ZnS composite has a superior role during the induction of apoptosis in the 4T1 cells as compared to the free 5-FU drug treated groups. The results of the study therefore suggest that the impregnation of 5-FU anti-cancer drug within the FACS-Mn:ZnS system significantly improves its selective targeting efficacy, in addition to improving the anti-proliferative properties and attenuate possible tumor resistances to the 5-FU drug. The work discusses about the anti-metastatic effects of folic acid-bound 5-Fluororacil loaded Mn:ZnS quantum dots towards 4T1 cell line proliferation in mice based on the histological analysis.