Investigation of Structural, Optical and Antibacterial Activity of ZnS Nanoparticles

The implementation of ZnS-SnS BM NPs for phenanthrene degradation: An adsorptive photocatalyst approach and its toxicity studies in adult zebrafish

Phenanthrene is a persistent organic pollutant released by numerous industries. The purpose of the study is to construct a batch reactor for phenanthrene degradation using a bimetallic (BM) ZnS-SnS nanoparticle as a photocatalyst. ZnS-SnS BM NPs were used as a photocatalyst, employed from precursors Zinc acetate dihydrate and tin (II) chloride dihydrate, with crystalline cubic-shaped particle sizes. ZnS-SnS BM NPs were utilized in batch adsorption assays to assess the impact of phenanthrene degradation parameters on various PAHs (Polycyclic aromatic hydrocarbons) concentrations, pH levels, and irradiation sources. Adsorption kinetic and isotherm tests revealed that the pseudo-first order kinetic model, pseudo-second order kinetic model, and Langmuir isotherm model all fit effectively with the effective phenanthrene degradation using ZnS-SnS BM NPs. The degraded product were analyzed for GC-MS, revealing that organic pollutant phenanthrene was converted into harmless by-products like n-hexadecenoic acid, oleic acid, and octadecanoic acid. The toxicity of phenanthrene was observed to decrease with an increase in ZnS-SnS BM NPs concentration. ZnS-SnS BM NP concentration of 150 μg/mL, the zone of inhibition values was recorded highest zone of inhibition (19 ± 1.2 mm) against the strains S. epidermis followed by B. cereus and Clostridium spp. Further adult zebrafish were found to be less toxic to ZnS-SnS BM NPs after 96 h of exposure, with an LD50 of 100 μg/L. The toxicity escalated as concentrations increased. Behavior test showed normal swimming, learning, and memory in open tank and T-maze tests, while 100 μg/L showed pausing/frozen time in zebra fish therefore low doses are considered safe. Hence by employing ZnS-SnS BM NPs can be engaged in waste water treatment for PAH degradation.

Microwave-assisted synthesis of praseodymium (Pr)-doped ZnS QDs such as nanoparticles for optoelectronic applications

Praseodymium (Pr)-doped ZnS nanoparticles were synthesized using a low-cost microwave-assisted technique and investigations on their structure, morphology, optical properties, Raman resonance, dielectric properties, and luminescence were conducted. Broad X-ray diffraction peaks suggested the formation of low-dimensional Pr-doped ZnS nanoparticles with a cubic structure that was validated using transmission electron microscopy (TEM)/high-resolution TEM analysis. The energy gaps were identified using diffuse reflectance spectroscopy and it was found that the values varied between 3.54eV and 3.61eV for different samples. Vibrational experiments on Pr-doped ZnS nanoparticles revealed significant Raman modes at ~270 and ~350 cm-1 that were associated with optical phonon modes that are shifted to lower wavenumbers, indicating phonon confinement in the synthesized products. The photoluminescence (PL) spectra of all samples demonstrated that the pure and Pr-doped ZnS nanoparticles were three-level laser active materials. Energy-dispersive X-ray spectroscopy and mapping study confirmed the homogeneous presence of Pr in ZnS. TEM studies showed that the particles were of very small size and in the cubic phase. The samples had high dielectric constant values between 13 and 24 and low loss values, according to the dielectric analysis. With an increase in frequency and a change in the Pr content of ZnS, an intense peak could be seen in the PL spectra at a wavelength of 360 nm, and some other peaks observed corresponded to the transition of Pr3+ . The produced nanoparticles were appropriate for optoelectronic applications due to their short dimension, high energy gap, high dielectric constant, and low loss values.

Defect engineering for enhanced optical and photocatalytic properties of ZnS nanoparticles synthesized by hydrothermal method

Defect engineering is a promising method for improving light harvesting in photocatalytic materials like Zinc sulphide (ZnS). By altering the S/Zn molar ratio during hydrothermal processes, Zn and S defects are successfully introduced into the ZnS crystal. The band structures can be modified by adding defects to the crystal structure of ZnS samples. During the treatment process, defects are formed on the surface. XRD and Raman studies are used for the confirmation of the crystallinity and phase formation of the samples. Using an X-ray peak pattern assessment based on the Debye Scherer model, the Williamson-Hall model, and the size strain plot, it was possible to study the influence of crystal defect on the structural characteristics of ZnS nanoparticles. The band gap (Eg) values were estimated using UV-Vis diffuse spectroscopy (UV-Vis DRS) and found that the Eg is reduced from 3.28 to 3.49 eV by altering the S/Zn molar ratio. Photoluminescence study (PL) shows these ZnS nanoparticles emit violet and blue radiations. In keeping with the results of XRD, TEM demonstrated the nanoscale of the prepared samples and exhibited a small agglomeration of homogenous nanoparticles. Scanning electron microscopy (SEM) was used to examine the surface morphology of the ZnS particles. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS) were used to evaluate and validate the elemental composition. XPS results indicate the presence of defects on the prepared ZnS nanoparticles. For the investigation of vacancy-dependent catalytic activity under exposure to visible light, defective ZnS with different quantities of Zn and S voids are used as catalysts. The lowest S/Zn sample, ZnS0.67 and the highest S/Zn sample, ZnS3, show superior photocatalytic activity.

Sulfidogenic Bioreactor-Mediated Formation of ZnS Nanoparticles with Antimicrobial and Photocatalytic Activity

The use of sulfidogenic bioreactors is a biotechnology trend to recover valuable metals such as copper and zinc as sulfide biominerals from mine-impacted waters. In the present work, ZnS nanoparticles were produced using "green" H₂S gas generated by a sulfidogenic bioreactor. ZnS nanoparticles were physico-chemically characterized by UV-vis and fluorescence spectroscopy, TEM, XRD and XPS. The experimental results showed spherical-like shape nanoparticles with principal zinc-blende crystalline structure, a semiconductor character with an optical band gap around 3.73 eV, and fluorescence emission in the UV-visible range. In addition, the photocatalytic activity on the degradation of organic dyes in water, as well as bactericidal properties against several bacterial strains, were studied. ZnS nanoparticles were able to degrade methylene blue and rhodamine in water under UV radiation, and also showed high antibacterial activity against different bacterial strains including Escherichia coli and Staphylococcus aureus. The results open the way to obtain valorous ZnS nanoparticles from the use of dissimilatory reduction of sulfate using a sulfidogenic bioreactor.

Recent advances in metal sulfide nanoparticle-added bionanocomposite films for food packaging applications

Metal sulfide nanoparticles have recently attracted much attention due to their unique physical and functional properties. Metal sulfide nanoparticles used as optoelectronic and biomedical materials in the past decades are promising for making functional nanocomposite films due to their low toxicity and strong antibacterial activity. Recently, copper sulfide and zinc sulfide nanomaterials have been used to produce food packaging films for active packaging. Metal sulfide nanoparticles added as nanofillers are attracting attention in packaging applications due to their excellent potential to improve mechanical, barrier properties, and antibacterial activity. This review covers the fabrication process and important applications of metal sulfide nanoparticles. The development of metal sulfides reinforcing mainly copper sulfide and zinc sulfide nanomaterials as multifunctional nanofillers in bio-based films for active packaging applications has been comprehensively reviewed. As the recognition of metal sulfide nanoparticles as a functional filler increases, the development and application potential of active packaging films using them is expected to increase.

Enhanced photodegradation of methylene blue from aqueous solution using Al-doped ZnS nanoparticles

The post-transition semiconducting material of pure zinc sulfide (ZnS) and various concentrations of aluminum (Al) (2.5 wt%, 5.0% wt, 7.5 wt%, and 10% calcined at 200 °C) doped ZnS nanoparticles (NPs) were synthesized by sol-gel procedure. The crystal-like nature and phase structure of the product were examined by powder XRD analysis. This analysis shows that the pure ZnS nanoparticle does not form any secondary phase. The functional group of synthesized materials was analyzed by FTIR examination. The energy gap of the materials is calculated using electro-optic analysis and the Kubelka-Munk equation varies from 3.04 nm to 3.63 nm. The photoluminescence studies show the wide emissions (blue to green) for pure ZnS and Al-doped ZnS nanomaterials. The SEM images show the spherical structure and the agglomerated nanostructures. The presence of Zn, S, and Al are confirmed by EDAX spectra. From HR-TEM studies, pure ZnS and Al-doped ZnS nanoparticles exhibit uniform particle sizes. The rate of degradation was observed using MB dye. MB dye has maximum wavelength (λ_max) of 664 nm. The dye degradation efficiency was improved as the dye ratio increased. Photocatalytic activities studies show the intensity of photocatalytic activities decreased for the maximum time interval. Doping of Al in ZnS boosts the photocatalytic activity. Hence, Al-doped ZnS appears to be better decomposing MB dye when exposed to visible light.

Highly biocompatible formulations based on Arabic gum Nano composite hydrogels: Fabrication, characterization, and biological investigation

In the study, fabrication of Arabic gum (AG) hydrogels via reverse micellization method is reported. AG hydrogels were utilized as capping agents to encapsulate zinc sulphide (ZnS), and cadmium sulphide (CdS) nanoparticles via in-situ reduction. Pristine and nanocomposite hydrogels (AG-ZnS and AG-CdS) were characterized through SEM, EDX, TEM, XRD, FTIR, TGA, UV/Visible, and photoluminescence spectroscopy. The hydrogels were subjected to multiple biological assays including antimicrobial, antioxidant, and anti-diabetic formulation, in addition to biocompatibility test. The hydrogels were found to be more effective against bacterial and fungal strains. For instance, AG-ZnS exhibited excellent growth inhibition activity against Escherichia coli (ZoI: 12 ± 1.04 mm) and Candida albicans (35 ± 0.94 mm). Likewise, the nanocomposites hydrogel also displayed excellent DPPH and ABTS free radical scavenging capacity, total antioxidant capacity (TAC), and total reducing power (TRP) ability. Among the hydrogels, AG-ZnS demonstrated considerable α-amylase, and α-glucosidase inhibition potential. Above all, the hydrogels were found highly compatible with human red blood cells (hRBCs). Owing to remarkable antioxidant, antibacterial, antifungal, and bio-compatible nature, the fabricated nanocomposites hydrogels have the potential to be explored in tissue engineering, wound healing, drug delivery, and in environmentally friendly hygiene products.

Preparation of pectin/agar-based functional films integrated with zinc sulfide nano petals for active packaging applications

Here we report on the robust synthesis of zinc sulfide nanoparticles (ZnSNP) using a simple one-pot reaction. The prepared ZnSNP was characterized and confirmed to be a petal-shaped nanoparticle. The ZnSNP was added to fabricate the pectin/agar-based functional composite film. The integration of ZnSNP has greatly improved the physical properties of the film, such as mechanical and UV protection properties, without significantly changing the transparency of the film. The addition of the nanofillers did not affect the film's hydrophobicity, water vapor barrier, and thermal properties. Moreover, the composite film showed intense antibacterial activity against foodborne pathogenic bacteria, E. coli and L. monocytogenes. The functional bio-nanocomposite films based on pectin/agar have high potential in active packaging applications.