ZnS Coatings Research Articles

Prospects of ZnS and ZnO as smart semiconductor materials in light-activated antimicrobial coatings for mitigation of severe acute respiratory syndrome coronavirus-2 infection.

We carried out theoretical and experimental analyses of ZnO and ZnS nanoparticles as smart semiconductor materials in light-activated antimicrobial coating for application in masks. We used low-cost hydrothermally processable precursors to direct the growth of the coatings on cotton fabric. Both ZnO and ZnS coatings had high reactivities as disinfection agents in photocatalysis reactions for the degradation of a methylene blue dye solution. Also, these coatings showed excellent UV protection properties. For understanding at the molecular level, the broad-spectrum biological activities of the ZnO and ZnS coatings against Fusarium Oxysporum fungi, Escherichia coli bacteria, and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus and their variants, were investigated computationally. Hexagonal Zn6O6 and Zn6S6 clusters were used as models for the simulations through excited- and ground-state calculations. The theoretical findings show that changes in the local chemical environment in these excited systems have a profound impact on their physical and chemical properties and thus, can provide a better understanding to engineer new functional materials in light-activated antimicrobial coatings for the mitigation of SARS-CoV-2 infection.

Simulating the spectral characteristics of reflection in planar porous structures with antireflection coatings ZnS/DyF3

This paper presents the results of modeling a planar multilayer structure with layers of porous silicon, ZnS and DyF3 coatings by the optical matrix method. It was shown that the optical matrix method, taking into account the model of porous silicon with a variable band gap, which takes into account the porosity gradient, allows us to approximate the course of the curve of the real experiment

Fabrication of the hierarchical CdS flowers assembled from flakes with (0001) facets exposed as efficient photocatalyst for H2 production

The photocatalysts with more reactive crystal facets exposed usually exhibit enhanced photocatalytic ability. Herein, the hierarchical CdS flowers assemble from flakes with reactive (0001) facets exposed were prepared through a facile solvothermal process by employing novel WCl6 as structure-directing agent. The enhanced crystallinity, smaller band gap and extended spectra absorption range were achieved. The formation mechanism of hierarchical CdS flowers was analysis. The optimal samples exhibited the much higher photocatalytic H2-production activity and photostability compared with normal CdS spheres prepared without WCl6 addition. The result of photostability study employing MoS2 and ZnS coatings indicated that the photostability of hierarchical CdS flowers was mainly affected by the degree of self corrosion.

Cu-doped ZnS coatings for optoelectronics with enhanced protection for UV radiations

Molecular dopants are of great importance in nano-chemical compounds by improving the function of inorganic electronic devices. In this article, Cu:ZnS (CZS) powders were made using the chemical method. Thin films were deposited by the physical method. The CZS films showed cubic crystal structures with a single hexagonal peak. The impact of an increase in Cu2+ dopants was investigated not only in reducing the grain size but also in reducing the optical energy gap and deviation parameters of the lattice constants. The estimated energy gaps of CZS nanostructures (NSs) were (3.70, 3.66, 3.0, and 3.76 eV) for Cu dopant (0, 1.5, 3.0, and 4.5 at.%); an indication of a blueshift. Redshift was also noticed for Cu dopant 4.5% due to interstitial sites. Moreover, the transmittance for all specimens was (70–95%) in the visible and near IR-region and reduced in the UV range (< 400 nm). The decrease in light transmittance occurred in the UV range when the Cu2+ concentration increased. Besides, the study revealed a reduction in the power loss of the thin film indicating high quality and a highly optimized electrical and electronic system. The Neural Network was utilized to obtain validation of results by the theoretical study.

Luminescence enhancement mechanisms of AgInS2/ZnS core/shell nanoparticles fabricated by suppressing quaternary alloying

Nanoparticles of chalcopyrite semiconductors with I–III–VI2 compositions have attracted attention as potential non-toxic alternatives to highly luminescent Cd–chalcogenide semiconductor nanoparticles. Numerous studies have reported that chalcopyrite nanoparticles capped with ZnS shells exhibit enhanced luminescence efficiencies; however, neither the actual core/shell structure nor the origin of the enhanced emission has been explained. Moreover, luminescence enhancement in I–III–VI2 nanoparticles alloyed with Zn (e.g. Zn–Ag–In–S) complicates our understanding of the origin of enhanced luminescence efficiencies in core/shell nanoparticles. In this study, we found the optimal heating condition for fabricating ZnS shells around AgInS2 nanoparticles by suppressing the alloying of the core and shell components. For AgInS2 nanoparticles with an average diameter of 3.4 nm, maximum luminescence enhancement was achieved when ZnS shells were formed at 393 K. Analyses of the carrier recombination mechanisms indicate that the luminescence improvement was due to both passivation of the non-radiative recombination centres on the nanoparticle surfaces by the ZnS shells and the formation of additional radiative recombination centres induced by a slight inclusion of Zn2+ ions in the core/shell interface region. When ZnS coatings were applied at higher temperatures, AgInS2–ZnS alloy nanoparticles formed because of the penetration and diffusion of Zn2+ ions into the nanoparticle bodies followed by the heat-accelerated cation exchange reaction between the Zn2+, Ag+ and In3+ ions. The boundary fabrication temperature between the formation of core/shell nanoparticles and that of alloy nanoparticles was estimated to be 420–430 K.

Role of ZnS shell on stability, cytotoxicity, and photocytotoxicity of water-soluble CdSe semiconductor quantum dots surface modified with glutathione

The present study examines the stability and cytotoxicity of two quantum dots (QDs) systems in cell culture medium in the presence and absence of a thin layer of a ZnS shell. The two systems were built from a core, CdSe, and surface modified with glutathione (GSH), named CdSe∼GSH and CdSe/ZnS∼GSH. CdSe/ZnS∼GSH QDs exhibited a high photostability with a pronounced enhancement in photoluminescence in cell culture medium. Both systems showed insignificant reduction in cell viability of HFB-4 and MCF-7 cell lines in the dark. Following 60 min of low laser power exposure (irradiance of 10 mW cm−2), CdSe∼GSH QDs showed a remarkable decrease in cell viability, which may result from the detachment of GSH molecules, whereas CdSe/ZnS∼GSH QDs showed an insignificant decrease either immediately after irradiation or even 2 h post-exposure, which can be attributed to the high affinity between ZnS and GSH coatings. This study demonstrated that a thin layer of ZnS shell played a crucial role in the stability of CdSe/ZnS∼GSH QDs in cell culture medium with an improvement in luminescence efficiency, whereas surface modification with GSH molecules in the presence of ZnS showed no significant cytotoxic effects before or after photoirradiation, which makes this system attractive for several biomedical applications.

Chemical composition, morphology and optical properties of zinc sulfide coatings deposited by low-energy electron beam evaporation

The research determines the features of formation, morphology, chemical composition and optical properties of the coatings deposited by the method, proposed for the first time, of the exposure of mechanical mixture of zinc and sulfur powders to low-energy electron beam evaporation. The findings show that the deposited coatings are characterized by high chemical and structural homogeneity in thickness. The study considers the influence of substrate temperature and thickness of the deposited layer on the morphology and the width of the formed ZnS thin layers band gap. Also was shown the possibility to form ZnS coatings with this method using the mixture of zinc and copper sulfide powders.

The Influence on Cell Cycle and Cell Division by Various Cadmium‐Containing Quantum Dots

Quantum dots (QDs) have attracted great attention because of their favorable optical properties and have been widely applied in biomedical fields. However, in recent years, there have been an increasing number of reports about the cytotoxicity of QDs, especially cadmium-containing QDs, which may release cadmium ions to induce cytotoxicity. Importantly, the chemical composition and surface modifications of cadmium-based QDs determine the amount of Cd(2+) released inside the cell. Thus, there is an urgent need for more systematic work to study the relationship between cytotoxicity and the surface properties of QDs. In this article, the cytotoxicity of seven cadmium-containing QDs with different constituent elements and surface chemistries are compared. The results show that the cytotoxicity of QDs is closely related to their constituent elements and surface properties: First, CdTe@ZnS core-shell QDs show much lower cytotoxicity than naked ones when they have similar surface modifications; second, the positively charged QDs are more toxic than the negatively charged ones. Moreover, both positively and negatively charged QDs without ZnS coatings lead to multipolar spindles, misaligned chromosomes, and G2/M checkpoint failures. Interestingly, although CdSe QDs with a PEG coating cause no apparent cytotoxicity in any of the cell lines studied, they can localize near the contractile ring during cytokinesis and then block contractile ring disassembly. The cellular effect of CdTe QDs comes not only from the release of cadmium ions but also the intracellular distribution of QD nanoparticles in cells and the associated nanoscale effects. It is also found that QD-caused cytokinesis failure is closely related to the decreased expression of Cyclin A and Cyclin B. Taken together, the above findings provide new insight into the dynamic fate of QDs during cell mitosis, and are important for understanding the intracellular effects of QDs on the mitotic spindle and chromosomes during cell division. Furthermore, this kind of cytotoxicity evaluation method should be applicable to studies of the biological effects and health impacts of other nanomaterials.

Effects of passivation treatment on performance of CdS/CdSe quantum-dot co-sensitized solar cells

Carrier recombination can greatly reduce the efficiencies of quantum-dot sensitized solar cells (QDSSCs). This work aims to find a general preparation route to reduce carrier recombination in QDSSCs. The effects of a series of passivation treatments on CdS/CdSe quantum-dot (QD) co-sensitized solar cells are investigated. The QDs were synthesized on a nanoporous TiO2 electrode by the successive ionic layer adsorption and reaction processes. The different types of treatment included a blocking layer, a fluoride-ion coating, a ZnS coating, annealing, a TiO2 scattering layer and an Au counterelectrode. The power conversion efficiency was observed to become three times larger after treatment. The effectiveness of each treatment method is as follows in descending order: blocking layer≅TiO2 scattering layer>Au counterelectrode>F− ions and ZnS coatings>annealing. The best cell yields a current density of 14.6mA/cm2 and a respectable power conversion efficiency of η=3.11% under AM 1.5 sun. The passivation procedure makes a useful general guide for researchers for the preparation of QDSSCs.

Effect of ZnS coatings on the enhancement of the photovoltaic properties of PbS quantum dot-sensitized solar cells

We have studied the effect of ZnS coatings on the photovoltaic properties of PbS quantum dot-sensitized solar cells (QDSSCs). PbS QDs are suitable materials for QDSSCs because of their wide light absorption range; however, their high photochemical reactivity is a problem that needs to be overcome for solar cell applications. In this paper, a ZnS passivation layer was applied to PbS QDs adsorbed onto electrodes using a successive ionic layer adsorption and reaction (SILAR) method for different numbers of cycles in both aqueous and methanol solutions. It was demonstrated that, as a consequence of the low viscosity of methanol, the performance of the PbS QDSSCs was greatly enhanced when a methanol, rather than aqueous, solution was used in the SILAR method. The optical absorption properties of PbS QDs adsorbed on TiO2 electrodes with or without ZnS surface passivation were studied. An increase in size of the PbS QDs after coating with ZnS was confirmed by a red shift in the optical absorption spectra measured using photoacoustic spectroscopy. The photovoltaic properties of a sandwich structure of PbS QDSSCs were studied under “one sun” illumination using a polysulfide (S/S2−) redox system as the electrolyte and Cu2S on brass as the counter electrode. The short-circuit current density dramatically increased from 0.50 mA/cm2 to 11.2 mA/cm2 after the electrodes were modified with the ZnS coating. The maximum conversion efficiency that was achieved for PbS QDSSCs with a ZnS coating under one sun illumination was 1.92%.

Linear ion source with magnetron hollow cathode discharge

A linear ion source with magnetron hollow cathode discharge is described in this paper. The linear ion source is based on an anode layer thruster with closed-drift electrons that move in a closed path in the E×B fields. An open slit configuration is designed at the end of the ion source for the extraction of the linear ion beam produced by the magnetron hollow cathode discharge. The special configurations enable uninterrupted and expanded operation with oxygen as well as other reactive gases because of the absence of an electron source in the ion source. The ion current density and uniformity were experimentally evaluated. Using the ion source, surface modification was conducted on polyethylene terephthalate polymer films to improve the adhesion strength with ZnS coatings.

The cathodoluminescence generated in ZnS phosphor powder with non‐luminescent ZnS coatings: a comparison of experimental data with Monte Carlo calculations

AbstractField emission displays (FEDs) are a possible alternative to other display technologies. They work similarly to CRTs, but instead of an electron gun they have an array of tiny metallic tips acting as electron emitters. This array is situated in close proximity to the phosphor screen and produces light by a process of cathodoluminescence (CL). During prolonged electron beam irradiation a non‐luminescent ZnO layer forms on the irradiated surface of the ZnS phosphor powder according to the electron‐stimulated surface chemical reactions (ESSCR) mechanism. The low‐energy electrons used in FEDs have a shallow penetration depth and since the CL is dependent upon the energy loss in the ZnS bulk itself, growth of the ZnO layer significantly degrades the CL intensity. Monte Carlo techniques may be used to simulate the electron trajectories and energy loss in many different types of materials. Energy loss profiles in the ZnS for different non‐luminescent ZnS coatings of known thickness were determined using the Monte Carlo electron trajectory simulations. Since only energy loss in the ZnS powder results in CL an increase in the thickness of the ZnS coating decreases the CL intensity accordingly. Simulations were performed for electron energies varying from 2 to 10 keV and at incident angles accommodating for the morphology of the phosphor powder. These results compared very well with the experimental results measured by other authors. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Study of interaction of ZnS coatings with Cu(I) and Cu(II) by cyclic voltammetry

Electrochemical behaviour of electroless ZnS coatings on glass carbon and their interaction with Cu+ and Cu2+ ions were investigated by cyclic voltammetry in 0.1 M NaOH, 0.1 KClO4 and 1.0 M CH3COOH solutions. Independently of the medium pH cathodic reduction of ZnS was found to be preceded by hydrogen evolution. When ZnS interacts with Cu2+ ions, non-stoichiometric copper sulphide (Cu2−xS, where 1.4 ≤ 2 − x ≤ 2) and elementary sulphur are formed according to the reaction 2 − x)ZnS+ (2 − x)Cu2+ → Cu2−xS + (2 − x)Zn2+ + (1 − x)S0. The interaction of ZnS with Cu+ proceeds with the formation of stoichiometric copper sulphide (Cu2S).

Infrared thin-film totally reflecting quarter-wave retarders

Double-layer ThF(4)-ZnS coatings on a prism of KCl, KBr, and KI are optimized to give totally reflecting quarter-wave retarders at a wavelength of 10.6 microm. The influence on the design parameters of the light absorption occurring at high temperatures is described.

Study on antireflective coatings of PbTe/PbSnTe heterojunction infrared detectors

ZnS antireflective coatings and passivation layer are developed on self-made PbTe/PbSnTe heterojunction infrared detectors and following experiments have been finished: WaterProof properties of ZnS coatings; Anti-reflective properties of PbSnTe materials and their detectors with ZnS coatings, respectively; ageing and stability tests of the PbSnTe detectors with ZnS coatings.

Study on antireflective coatings of PbTe/PbSnTe heterojunction infrared detectors

ZnS antireflective coatings and passivation layer are developed on self-made PbTe/PbSnTe heterojunction infrared detectors and following experiments have been finished: WaterProof properties of ZnS coatings; Anti-reflective properties of PbSnTe materials and their detectors with ZnS coatings, respectively; ageing and stability tests of the PbSnTe detectors with ZnS coatings.

Interface properties of various passivations of HgCdTe

The effects of different surface treatments of the p-type Hg(x-1)Cd(x)Te (x about 0.2) alloy, including anodic-sulfide, anodic-oxide, and ZnS coatings, on the surface charge density and surface mobility were investigated. Measurements of surface recombination velocities in samples passivated by either a ZnS coating on a freshly etched surface or by anodic native sulfide combined with deposited ZnS showed essentially the same temperature dependence down to 50 K. For the same original material, both the surface state density and the activation energy were found to be similar. It is suggested that, for both passivations, the surface is controlled by traps that can be related to lattice defects, such as vacancies.

Exact expressions for calculating thin-film absorption coefficients from laser calorimetric data

Analytic expressions for the optical absorptance of a single-layer thin film of arbitrary thickness on a substrate are derived. Multireflections are considered to be coherent within the thin film and incoherent within the substrate; absorptance is assumed to be small. Substrate and thin-film absorptance can be separated by means of two measurements: in one case light enters the coating–substrate system from the coated side, in the other case from the uncoated side. With this technique, optical absorption coefficients of ZnS and hard carbon coatings have been determined using a CO2 laser calorimeter.

Observation and morphology of small-scale laser induced damage

Laser-induced damage of lambda/4 ThF(4)/ZnS coatings for 10.6 microm is studied. Extended areas of the coated surfaces are recorded on high resolution film both before and after irradiation using Twyman-Green and knife-edge techniques, the latter method proving to be superior and quite useful. Comparisons are made to establish a possible correlation between the location of damage sites and previous defects. The morphology of the damage is also studied using Nomarski microscopy to determine possible causes of damage. Damage on coated silicon substrates resembles melts and burns with cracking and/or annealing around some burned areas, while damage to the coated silica substrates resembles bubbles that are arranged along scratches or in clusters. The high correlation between damage sites and previous defects suggests that clean defect-free coatings have greatly increased damage thresholds.

Investigation of microdamage to dielectric coatings by laser radiation

An experimental investigation was made of the behavior of microdefects in refractory oxide and sulfide-fluoride dielectric coatings in the prethreshold range of exposure to laser radiation. The results obtained demonstrated clearly that the centers of optical breakdown in ZnS and SrF2 (or MgF2) coatings were strongly absorbing microinhomogeneities, whereas in coatings made of ZrO2 and SiO2 neither the concentration of microinhomogeneities (of > 1 μ size) nor their dimensions were affected by the action of a pulse (or a series of pulses) of power density just below the threshold.