The Zn1-xBixO (0 ≤ x ≤ 0.1) combustion products were synthesized by solution combustion method using Zn(NO3)2·6H2O and Bi(NO3)3·5H2O as oxidizers and glycine as a fuel. To enhance the solubility of Bi in the ZnO hexagonal structure, the different portions of the combustion products were subsequently annealed (600 °C/5 h) and ball-milled under 350 rpm for 10 h. The various multifunctional Zn1-xBixO materials were analyzed by different characterization techniques (XRD, TG–DTA, FT-IR, NIR, Raman, and FESEM-EDX) to explore the physico-chemical properties. In a wide range of composition (x), only the x = 0 and 0.02 revealed a single hexagonal phase with a Zn1-xBixO structure for the combustion products and annealed samples. Remarkably, the multifunctional nanocrystalline Zn1-xBixO (0 ≤ x ≤ 0.1) materials were successfully obtained in phase pure form upon subsequent ball-milling of the combustion products, while the annealing treatment failed to enhance the solubility of Bi for x = 0.04, 0.06, 0.08, and 0.1. As the combustion products and annealed materials show higher NIR reflectance in the NIR region for x = 0, 0.02, maybe used as solar protecting color pigment materials. Though the ball milling of combustion products enhanced the solubility of Bi in the ZnO structure, it heavily affected the NIR reflectance of Zn1-xBixO. Agglomeration of fine particles is observed in the FESEM micro-images of Zn1-xBixO; x = 0.1 (ball-milled) materials. From the present research findings, we conclude that high-energy ball milling has a substantial impact on the phase formation and the properties of the ball-milled Zn1-xBixO samples.

The remarkable enhancement in the solubility of Bi in the ZnO phase, Zn1-xBixO (0 ≤ x ≤ 0.1), by high energy ball milling technique

• ZnS/SG QDs/Ag 2 S nanocomposite show remarkable potential for photocatalytic degradation under visible light irradiation. • Preliminary kinetic studies confer a pseudo first-order kinetic. • Immobilization of the Ag 2 S NPs had a synergic effect on photocatalytic characteristics. Today, contamination of water resources by pesticides and their presence in the food chain is one of the environmental problems. An economical method to eliminate of pesticides is the degradation in the presence of sunlight, which intensifies the need to design and manufacture new generation photocatalysts with short gap bands to accelerate the process of optical degradation. In this study, sulfur-doped graphene quantum dots (SG QDs) were successfully synthesized by the hydrothermal method and stabilized on the surface of ZnS semiconductor nanoparticles. Then, the core–shell structure of ZnS-SG QDs was decorated and reinforced with Ag 2 S nanoparticles. After confirming the structure of the prepared photocatalyst by X-ray diffraction (XRD), fourier transform infrared (FT-IR), scanning, and transmission electron microscopy (SEM & TEM) analyses, the photocatalyst's ability to optically degrade the two organophosphorus toxins diazinon and fenitrothion was evaluated. The results showed that the presence of Ag 2 S improved the photocatalytic activity and increased the degradation efficiencies to amount 40% for diazinon and fenitrothion. Furthermore, kinetic study showed that the photocatalytic degradation is initially followed by first order model and after that the mechanism is possibly changed to the second order model. 

Enhanced visible-light photocatalytic activity of ZnS/S-graphene quantum dots reinforced with Ag2S nanoparticles

The continuous growth of the world population has led to the constant increase of environmental pollution, with serious consequences for human health. Toxic, non-biodegradable, and recalcitrant organic pollutants (e.g., dyes, pharmaceuticals, pesticides) are discharged into water resources from various industries, such as textiles, leather, pharmaceuticals, plastics, etc. Consequently, the treatment of industrial wastewater, via a sustainable technology, represents a great challenge for worldwide research. Photocatalytic technology, an innovative technique based on advanced oxidation process (AOP), is considered a green technology with promising prospects in the remediation of global environmental issues. In photocatalysis, a very important role is attributed to the photocatalyst, usually a semiconductor material with high solar light absorption capacity and conductivity for photogenerated-charge carriers. Zinc sulfide (ZnS), as n-type semiconductor with different morphologies and band gap energies (Eg = 3.2–3.71 eV), is recognized as a promising photocatalyst for the removal of organic pollutants from wastewater, especially under UV light irradiation. This review deals with the recent developments (the last five years) in ZnS nanostructures (0D, 1D, 3D) and ZnS-based heterojunctions (n-n, n-p, Z scheme) used as photocatalysts for organic pollutants’ degradation under simulated (UV, Vis) and sunlight irradiation in wastewater treatment. The effects of different synthesis parameters (precursors’ type and concentration, capping agents’ dosages, reaction time and temperature, metal doping, ZnS concentration in heterostructures, etc.) and properties (particle size, morphology, band gap energy, and surface properties) on the photocatalytic performance of ZnS-based photocatalysts for various organic pollutants’ degradation are extensively discussed.

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Recent Developments in ZnS-Based Nanostructures Photocatalysts for Wastewater Treatment

High-quality optically defect-free 1D ZnS nanostructures by a modified thermal evaporation method

https://link.springer.com/content/pdf/10.1557/s43580-021-00143-9.pdf

Synthesis of CdS and TGA-capped CdS quantum dots from different Cd precursors

Semiconductor quantum dots such as zinc sulfide have interesting potential applications, due to their size-dependent optical properties. These nanostructures can be used for applications in agriculture, environmental chemistry, and fluorescence microscopy. The great rise in nanotechnology has sparked the scientific community’s interest in nanomaterials for the use of photodegradation in aquatic bodies. Quantum Dots (QDs) such as ZnS nanoparticles (NPs) can absorb electromagnetic radiation and generate subsequently reactive oxygen species (ROS) directly in aqueous phase. The presence of ROS in aquatic environments can be used to destroy organic contaminants by photocatalysis. Previous studies had evidenced that the presence of impurities (i.e. copper, manganese, nickel) in the crystalline structures of QDs can enhance their optical properties and consequently their catalytic capacity. Because of this, the present investigation was focused on generating water stable ZnS nanoparticles with catalytic properties. In this work, we have synthesized pure and doped ZnS nanoparticles using a reflux method. The morphology of these QDs was characterized by transmission electron microscopy (TEM). We also studied the photocatalytic properties of these nanostructures. A red shift was observed in the photoluminescence peak of pure ZnS nanoparticles when they were doped with heavy metals. Pure ZnS NPs and Mn-doped ZnS NPs showed luminescent peaks at 444 nm and 596 nm, respectively. Photodegradation studies were evaluated in the presence of organic dyes like Tropaeolin O (TO) and different concentrations of quantum dots (250 ppm and 500 ppm). The photodegradation of TO was dependent on the QDs concentration and exposure time. The destruction of organic dyes in the presence of photo-excited ZnS nanoparticles is envisioned as a fast and clean technology. The destruction of organic dyes in the presence of photo-excited ZnS nanoparticles is envisioned as a fast and clean technology.

Carla I. Quiles-Vélez

Papers

Synthesis, characterization, and photocatalytic activity of ZnS and Mn-doped ZnS nanostructures