Effect of CdS loading on the properties and photocatalytic activity of MoS2 nanosheets.

Molybdenum sulfide (MoS2) and modified MoS2 with different percentages of CdS (10%, 30%, and 50% CdS@MoS2) were successfully synthesized and characterized. The photocatalytic performance of the MoS2 and CdS@MoS2 was evaluated by degrading brilliant green (BG), methylene blue (MB), and rhodamine B (RhB) dyes under visible light irradiation. Amongst the synthesized photocatalysts, 50% CdS@MoS2 exhibited the highest photocatalytic activity, degrading 97.6%, 90.3%, and 75.5% of BG, MB, and RhB dyes, respectively within 5 h. The active species involved in the degradation processes were investigated. All trapping agents inhibited BG and MB degradation to a similar extent, indicating that all of the probed active species play an important role in the degradation of BG and MB. In contrast, h+ and O2•- were found to be the main reactive species in the photocatalytic RhB degradation. A potential mechanism for the photocatalytic degradation of dyes using CdS@MoS2 has been proposed. This work highlights the potential of CdS@MoS2 as a photocatalyst for more efficient water remediation applications.

Microwave-assisted synthesis of ZnS@CuInxSy for photocatalytic degradation of coloured and non-coloured pollutants.

Copper indium sulfide (CuInS2) exhibits strong visible light absorption and thus has the potential for good photocatalytic activity; however, rapid charge recombination limits its practical usage. An intriguing strategy to overcome this issue is to couple CuInS2 with another semiconductor to form a heterojunction, which can improve the charge carrier separation and, hence, enhance the photocatalytic activity. In this study, photocatalysts comprising CuInS2 with a secondary CuS phase (termed CuInxSy) and CuInxSy loaded with ZnS (termed ZnS@CuInxSy) were synthesized via a microwave-assisted method. Structural and morphological characterization revealed that the ZnS@CuInxSy photocatalyst comprised tetragonal CuInS2 containing a secondary phase of hexagonal CuS, coupled with hexagonal ZnS. The effective band gap energy of CuInxSy was widened from 2.23 to 2.71 as the ZnS loading increased from 0 to 30%. The coupling of CuInxSy with ZnS leads to long-lived charge carriers and efficient visible-light harvesting properties, which in turn lead to a remarkably high activity for the photocatalytic degradation of brilliant green (95.6% in 5 h) and conversion of 4-nitrophenol to 4-nitrophenolate ions (95.4% in 5 h). The active species involved in these photocatalytic processes were evaluated using suitable trapping agents. Based on the obtained results, photocatalytic mechanisms are proposed that emphasize the importance of h+, O2•-, and OH- in photocatalytic processes using ZnS@CuInxSy.

Recent development of metal oxides and chalcogenides as antimicrobial agents.

Pathogenic microbes are a major concern in hospitals and other healthcare facilities because they affect the proper performance of medical devices, surgical devices, etc. Due to the antimicrobial resistance or multidrug resistance, combatting these microbial infections has grown to be a significant research area in science and medicine as well as a critical health concern. Antibiotic resistance is where microbes acquire and innately exhibit resistance to antimicrobial agents. Therefore, the development of materials with promising antimicrobial strategy is a necessity. Amongst other available antimicrobial agents, metal oxide and chalcogenide-based materials have shown to be promising antimicrobial agents due to their inherent antimicrobial activity as well as their ability to kill and inhibit the growth of microbes effectively. Moreover, other features including the superior efficacy, low toxicity, tunable structure, and band gap energy has makes metal oxides (i.e. TiO2, ZnO, SnO2 and CeO2 in particular) and chalcogenides (Ag2S, MoS2, and CuS) promising candidates for antimicrobial applications as illustrated by examples discussed in this review.

Recent Progress of Metal-Organic Frameworks and Metal-Organic Frameworks-Based Heterostructures as Photocatalysts.

In the field of photocatalysis, metal-organic frameworks (MOFs) have drawn a lot of attention. MOFs have a number of advantages over conventional semiconductors, including high specific surface area, large number of active sites, and an easily tunable porous structure. In this perspective review, different synthesis methods used to prepare MOFs and MOFs-based heterostructures have been discussed. Apart from this, the application of MOFs and MOFs-based heterostructures as photocatalysts for photocatalytic degradation of different types of pollutants have been compiled. This paper also highlights the different strategies that have been developed to modify and regulate pristine MOFs for improved photocatalytic performance. The MOFs modifications may result in better visible light absorption, effective photo-generated charge carriers (e-/h+), separation and transfer as well as improved recyclability. Despite that, there are still many obstacles and challenges that need to be addressed. In order to meet the requirements of using MOFs and MOFs-based heterostructures in photocatalysis for low-cost practical applications, future development and prospects have also been discussed.

Molybdenum Disulfide-Based Nanomaterials for Visible-Light-Induced Photocatalysis.

Visible-light-responsive photocatalytic materials have a multitude of important applications, ranging from energy conversion and storage to industrial waste treatment. Molybdenum disulfide (MoS2) and its variants exhibit high photocatalytic activity under irradiation by visible light as well as good stability and recyclability, which are desirable for all photocatalytic applications. MoS2-based materials have been widely applied in various fields such as wastewater treatment, environmental remediation, and organic transformation reactions because of their excellent physicochemical properties. The present review focuses on the fundamental properties of MoS2, recent developments and remaining challenges, and key strategies for tackling issues related to the utilization of MoS2 in photocatalysis. The application of MoS2-based materials in visible-light-induced catalytic reactions for the treatment of diverse kinds of pollutants including industrial, environmental, pharmaceutical, and agricultural waste are also critically discussed. The review concludes by highlighting the prospects of MoS2 for use in various established and emerging areas of photocatalysis.

Role of Anions in the Synthesis and Crystal Growth of Selected Semiconductors.

The ideal methods for the preparation of semiconductors should be reproducible and possess the ability to control the morphology of the particles with monodispersity yields. Apart from that, it is also crucial to synthesize a large quantity of desired materials with good control of size, shape, morphology, crystallinity, composition, and surface chemistry at a reasonably low production cost. Metal oxides and chalcogenides with various morphologies and crystal structures have been obtained using different anion metal precursors (and/or different sulfur sources for chalcogenides in particular) through typical synthesis methods. Generally, spherical particles are obtained as it is thermodynamically favorable. However, by changing the anion precursor salts, the morphology of a semiconductor is influenced. Therefore, precursors having different anions show some effects on the final forms of a semiconductor. This review compiled and discussed the effects of anions (NO3 -, Cl-, SO4 2-, CH3COO-, CH(CH3)O-, etc.) and different sources of S2- on the morphology and crystal structure of selected metal oxides and chalcogenides respectively.

Recent progress of phytogenic synthesis of ZnO, SnO2, and CeO2 nanomaterials.

A critical investigation on the fabrication of metal oxide nanoparticles (NPs) such as ZnO, SnO2, and CeO2 NPs synthesized from green and phytogenic method using plants and various plant parts have been compiled. In this review, different plant extraction methods, synthesis methods, characterization techniques, effects of plant extract on the physical, chemical, and optical properties of green synthesized ZnO, SnO2, and CeO2 NPs also have been compiled and discussed. Effect of several parameters on the size, morphology, and optical band gap energy of metal oxide have been explored. Moreover, the role of solvents has been found important and discussed. Extract composition i.e. phytochemicals also found to affect the morphology and size of the synthesized ZnO, SnO2, and CeO2 NPs. It was found that, there is no universal extraction method that is ideal and extraction techniques is unique to the plant type, plant parts, and solvent used.

Zinc oxide and zinc oxide-based nanostructures: biogenic and phytogenic synthesis, properties and applications.

Zinc oxide nanoparticles (ZnO NPs) are considered as very significant and essential material due to its multifunctional properties, stability, low cost and wide usage. Many green and biogenic approaches for ZnO NPs synthesis have been reported using various sources such as plants and microorganisms. Plants contain biomolecules that can act as capping, oxidizing and reducing agents that increase the rate of reaction and stabilizes the NPs. This review emphasizes and compiles different types of plants and parts of plant used for the synthesis of ZnO and its potential applications at one place. The influence of biogenic and phytogenic synthesized ZnO on its properties and possible mechanisms for its fabrication has been discussed. This review also highlights the potential applications and future prospects of phytogenic synthesized ZnO in the field of energy production and storage, sun light harvesting, environmental remediation, and biological applications.

Effect of Mg doping on ZnO fabricated using aqueous leaf extract of Ziziphus mauritiana Lam. for antioxidant and antibacterial studies.

Aqueous leaf extract of Ziziphus mauritiana Lam. was successfully used to synthesize zinc oxide (ZnO) and magnesium-doped ZnO (Mg-doped ZnO) particles and acted as capping and stabilizing agent. UV-Vis diffuse reflectance spectra showed that optical band gap energy of ZnO has narrowed from 3.11 to 3.08 eV and 3.03 eV when doped with 1% Mg and 5% Mg, respectively. Powder X-ray diffraction and X-ray photoelectron spectroscopy studies confirmed the purity and crystalline nature of the synthesized materials. FT-IR spectroscopy revealed the presence of phytochemicals coated on the surface of synthesized materials. The synthesized materials were found to effectively scavenge DPPH radicals in the presence of visible light in comparison to the dark. The antibacterial properties of the synthesized materials were evaluated against Staphylococcus aureus and Escherichia coli. The obtained results revealed that Staphylococcus aureus seemed to be more sensitive to the green synthesized ZnO and Mg-doped ZnO than Escherichia coli.