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 developments, advances and strategies in heterogeneous photocatalysts for water splitting

Photocatalytic water splitting (PWS) is an up-and-coming technology for generating sustainable fuel using light energy. Significant progress has been made in the developing of PWS innovations over recent years. In addition to various water-splitting (WS) systems, the focus has primarily been on one- and two-steps-excitation WS systems. These systems utilize singular or composite photocatalysts for WS, which is a simple, feasible, and cost-effective method for efficiently converting prevalent green energy into sustainable H2 energy on a large commercial scale. The proposed principle of charge confinement and transformation should be implemented dynamically by conjugating and stimulating the photocatalytic process while ensuring no unintentional connection at the interface. This study focuses on overall water splitting (OWS) using one/two-steps excitation and various techniques. It also discusses the current advancements in the development of new light-absorbing materials and provides perspectives and approaches for isolating photoinduced charges. This article explores multiple aspects of advancement, encompassing both chemical and physical changes, environmental factors, different photocatalyst types, and distinct parameters affecting PWS. Significant factors for achieving an efficient photocatalytic process under detrimental conditions, (e.g., strong light absorption, and synthesis of structures with a nanometer scale. Future research will focus on developing novel materials, investigating potential synthesis techniques, and improving existing high-energy raw materials. The endeavors aim is to enhance the efficiency of energy conversion, the absorption of radiation, and the coherence of physiochemical processes.

Molybdenum disulfide, exfoliation methods and applications to photocatalysis: a review

This review provides a deep analysis of the mechanical and optoelectronic characteristics of MoS2. It offers a comprehensive assessment of diverse exfoliation methods, encompassing chemical, liquid-phase, mechanical, and microwave-driven techniques. The review also explores MoS2's versatile applications across various domains and meticulously examines its significance as a photocatalyst. Notably, it highlights key factors influencing the photocatalytic process. Indeed, the enhanced visible light responsiveness of materials like MoS2 holds immense potential across a wide range of applications. MoS2's remarkable photocatalytic response to visible light, coupled with its notable stability, opens up numerous possibilities in various fields. This unique combination makes MoS2 a promising candidate for applications that require efficient and stable photocatalytic processes, such as environmental remediation, water purification, and energy generation. Its attributes contribute significantly to addressing contemporary challenges and advancing sustainable technologies.

Temperature dependent charge carrier dynamics in 2D ternary Cu2MoS4 nanoflakes: An effect of electron-phonon coupling

Two-dimensional transition metal chalcogenides (2D TMCs) like MoS2, WS2 etc., have established significant dominance in the field of nanoscience and nanotechnology, owing to their unique properties like strong light-matter interaction, high carrier mobility, large photo-responsivity etc. Despite the widespread utilization of these binary TMCs, their potential in the advancement of the optoelectronic research is limited due to the constraints in band tuning and charge carrier lifetime. To overcome these limitations, ternary transition metal chalcogenides have emerged as promising alternatives. Although, the optical properties of these materials have never been explored properly. Herein, we have investigated one such promising member of this group, Cu2MoS4 (CMS) using both steady state and time-resolved spectroscopic techniques. The material exhibits a broad range of visible light absorption, peaking at 576 nm. Photoluminescence spectroscopy confirmed the presence of both band gap emission and trap state-mediated emissions. Transient absorption spectroscopy unraveled the excited state charge carrier dynamics of CMS in sub-ps timescale, upon irradiation of visible light. We found significant influence of the trap mediated recombination, while Auger process being dominant at high charge density. We extended our study in a wide temperature range (5-300 K), which reveals the impact of electron-phonon coupling strength on the band gap and charge carrier dynamics of this material. This detailed study would draw more attention toward the unexplored optical properties of ternary 2D chalcogenides and will open new avenues for the construction of 2D material-based optical devices.

Sn-doped BiOCl for photoelectrochemical activities and photocatalytic dye degradation under visible light

In this work, bismuth oxychloride (BiOCl) and Sn-doped BiOCl (SBCl) with improved visible light photocatalytic activity were synthesized via the co-precipitation method. The XRD analysis determined the tetragonal phase of BiOCl, 1 %, 5 %, and 10 % SBCl. The crystallite sizes were in the range of 20-34 nm. These results confirmed that the Sn ion was successfully incorporated into the BiOCl lattice. This was further confirmed by FT-IR and Raman analysis. The optical properties, such as the band gap energy, were studied using UV-vis DRS. It was found that doping BiOCl with Sn has a minor effect on the band gap tuning. BET shows that the SBCl samples have acquired a larger specific surface area (14.66-42.20 m2/g) than BiOCl (13.49 m2/g). The photocatalytic performance showed that SBCl samples have higher photocatalytic activity than BiOCl in degrading Rhodamine B (RhB) dye under visible light irradiation. Among the SBCl samples, 5 % SBCl exhibited the highest photocatalytic efficiency which degraded 91.2 % of the RhB dye in 60 min. Moreover, the photoelectrochemical activities of the as-synthesized BiOCl and SBCl were investigated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in the dark and under visible light irradiation. Both studies showed that SBCl exhibits enhanced photoelectrochemical activities than BiOCl. Hence, it can be suggested that SBCl possesses visible light active properties and can be potentially used as a photocatalyst and photoelectrode material.

Synthesis of highly efficient novel two-step spatial 2D photocatalyst material WS2/ZnIn2S4 for degradation/reduction of various toxic pollutants

In this article, we report the synthesis, characterization of novel biofriendly 2D/2D heterostructure WS2/ZnIn2S4 material in which 2D WS2 nanosheets are uniformly distributed spatially onto the spherically arranged 2D leaves of ZnIn2S4. We then studied the in-depth photocatalytic degradation activity of this novel nanocomposite and its pristine component materials on cationic dye: malachite green, anionic dye: congo red and reduction of heavy metal: chromium(VI) and the degradation efficiency of composite material was also tested on rhodamine-B, methylene blue, methyl orange dyes and acetaminophen/paracetamol drug. Form factor, structure factor and shape factor analysis has been carried out using X-ray diffractometry (XRD). Bond vibrations, functional groups and phonon vibration mode analysis has been done based on Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. Morphological and compositional analysis has been done using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDAX) and X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM). Surface area and pore size/distribution was characterized using Brunauer-Emmett-Teller (BET) method and Barrett-Joyner-Halenda Model. Degradation pathways and intermediate products are proposed using the high-performance liquid chromatography (HPLC). Photocatalytic activity of the nanocomposite WS2/ZnIn2S4 is compared with pristine ZnIn2S4 and pristine WS2, which shows more than 50% enhancement in both efficiency and rate of degradation/reduction for all the pollutants. A scavenger study was carried out to get insight of primary and secondary reactive oxygen species (ROS) taking part in degradation. Exciton lifetime, surface charge and stability, and flat band positions were studied based on time-correlated single photon counting (TCSPC) also known as time-resolved photoluminescence (TRPL), zeta potential, and Mott-Schottky respectively. Rate kinetics study was performed to analyze the physical and chemical behaviour of the nanocomposite with pollutants in consideration. Results show ∼100%, ∼90%, and ∼95% degradation efficiency by the heterostructure for malachite green (MG), congo red (CR), and reduction of heavy metal chromium (Cr(VI)) respectively within 5 min, which is a huge improvement as compared to pristine WS2 and pristine ZnIn2S4, both of which show the efficiencies of only ∼25% to∼75% in all the cases.

Environmental remediation of hazardous pollutants using MXene-perovskite-based photocatalysts: A review

Photocatalysis utilizing semiconductors offer a cost-effective and promising solution for the removal of pollutants. MXene and perovskites, which possess desirable properties such as a suitable bandgap, stability, and affordability, have emerged as a highly promising material for photocatalytic activity. However, the efficiency of MXene and perovskites is limited by their fast recombination rates and inadequate light harvesting abilities. Nonetheless, several additional modifications have been shown to enhance their performance, thereby warranting further exploration. This study delves into the fundamental principles of reactive species for MXene-perovskites. Various methods of modification of MXene-perovskite-based photocatalysts, including Schottky junction, Z-scheme and S-scheme are analyzed with regard to their operation, differences, identification techniques and reusability. The assemblance of heterojunctions is demonstrated to enhance photocatalytic activity while also suppressing charge carrier recombination. Furthermore, the separation of photocatalysts through magnetic-based methods is also investigated. Consequently, MXene-perovskite-based photocatalysts are seen as an exciting emerging technology that necessitates further research and development.

Highly effective direct decomposition of organic pollutants via Ag-Zn co-doped In2S3/rGO photocatalyst

Currently, novel photocatalysts have attracted increasing attention to effectively utilizing abundant solar energy to meet the energy demands of humans and mitigate environmental burdens. In this work, we developed a novel and highly efficient photocatalyst consisting of In₂S₃ doped with two elements (Ag and Zn) and decorated with reduced graphene oxide (rGO) sheets. The crystal structure, morphology, electrical properties, and optical properties of the prepared materials were studied using various analytical techniques, and their photocatalytic activity was thoroughly investigated. It was confirmed that within 10 min, over 97% decomposition of organic dyes was achieved by using Ag-Zn co-doped In₂S₃/rGO catalyst, while only 50 and 60% decompositions were achieved by conventional pure In₂S₃ and In₂S₃/rGO nanocomposite, respectively. Its photoelectrochemical (PEC) water-splitting performance was also significantly improved (∼120%) compared with pure In₂S₃ nanoparticles. This study provides a new vision of using Ag-Zn:In₂S₃ decorated on rGO sheets as an efficient photocatalyst under solar light irradiation for environmental remediation and hydrogen production.

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.

Synergistic effects of the Rh-S bond and spatially separated dual cocatalysts on photocatalytic overall water splitting activity of ZnIn2S4 nanosheets under visible light irradiation

Photodeposition of dual-cocatalysts Pt-Cr or Rh-Cr on the surface of ZnIn₂S₄ is used to achieve overall water splitting. Compared with the hybrid loading of the Pt element and Cr element, the formation of the Rh-S bond results in space separation of the Rh element and Cr element. The Rh-S bond and space separation of cocatalysts promote the transfer of bulk carriers to the surface and inhibit self-corrosion.

Ni loaded SnS2 hexagonal nanosheets for photocatalytic hydrogen generation via water splitting

Herein we have prepared the Ni-decorated SnS₂ nanosheets with varying concentrations of Ni from 1 to 10 mol% (1, 2.5, 5, and 10 mol%) and studied their various physicochemical and photocatalytic properties. The chemical reduction technique was utilized to load the Ni nanoparticles on SnS₂ nanosheets. The synthesized Ni decorated SnS₂ (denoted as Ni-SnS₂) was characterized using different spectroscopic techniques such as X-ray diffraction, diffuse reflectance UV-vis and photoluminescence spectroscopy, field emission scanning electron microscopy (FESEM), and field emission transmission electron microscopy (FETEM). XRD revealed the formation of the highly crystalline hexagonal phase of SnS₂ but for nickel loading there is no additional peak observed. Further, the as-prepared Ni-SnS₂ nano-photocatalyst shows absorption behaviour in the visible region, and photoluminescence spectra of the Ni-SnS₂ nanostructures show band edge emission centred at 524 nm, and the peak intensity decreases with Ni loading. The FE-SEM and FE-TEM confirm the formation of hexagonal sheets having evenly distributed Ni nanoparticles of size ∼5-10 nm. BET surface area analysis was observed to be enhanced with Ni loading. The photocatalytic performance of the prepared Ni-SnS₂ nanosheets was evaluated for hydrogen generation via water splitting under a 400 W mercury vapour lamp. Among the prepared Ni-SnS₂ nanostructures, the Ni loaded with 2.5 mol% provided the highest hydrogen production i.e., 1429.2 μmol 0.1 g^-1 (% AQE 2.32) in four hours, almost 1.6 times that of pristine SnS₂ i.e., 846 μmol 0.1 g^-1. Furthermore, the photocatalytic performance of the catalyst is also correlated with the photoconductivity by measuring the photocurrent. The photoconductivity of the samples is revealed to be stable and the conductivity of 2.5 mol% Ni-SnS₂ is higher i.e. 20 times that of other Ni-SnS₂ and pristine SnS₂ catalysts.

Chalcogenides and Chalcogenide-Based Heterostructures as Photocatalysts for Water Splitting

Chalcogenides are essential in the conversion of solar energy into hydrogen fuel due to their narrow band gap energy. Hydrogen fuel could resolve future energy crises by substituting carbon fuels owing to zero-emission carbon-free gas and its eco-friendliness. The fabrication of different metal chalcogenide-based photocatalysts with enhanced photocatalytic water splitting have been summarized in this review. Different modifications of these chalcogenides, including coupling with another semiconductor, metal loading, and doping, are fabricated with different synthetic routes that can remarkably improve the photo-exciton separation and have been extensively investigated for photocatalytic hydrogen generation. In this direction, this review is undertaken to provide an overview of the enhanced photocatalytic performance of the binary and ternary chalcogenide heterostructures and their mechanisms for hydrogen production under irradiation of light.

Fe-Doped MoS2 Nanozyme for Antibacterial Activity and Detoxification of Mustard Gas Simulant

The peroxidase-like catalytic activity of various nanozymes was extensively applied in various fields. In this study, we have demonstrated the preparation of Fe-doped MoS₂ (Fe@MoS₂) nanomaterials with enhanced peroxidase-like activity of MoS₂ in a co-catalytic pathway. In view of Fenton reaction, the peroxidase-like Fe@MoS₂ nanozyme prompted the decomposition of hydrogen peroxide (H₂O₂) to a reactive hydroxyl radical (·OH). The efficient decomposition of H₂O₂ in the presence of Fe@MoS₂ has been employed toward the antibacterial activity and detoxification of mustard gas simulant. The combined effect of Fe@MoS₂ and H₂O₂ showed remarkable antibacterial activity against the drug-resistant bacterial strain methicillin-resistant Staphylococcus aureus and Escherichia coli with the use of minimal concentration of H₂O₂. Fe@MoS₂ was further applied for the detoxification of the chemical warfare agent sulfur mustard simulant, 2-chloroethyl ethyl sulfide, by selective conversion to the nontoxic sulfoxide. This work demonstrates the development of a hybrid nanozyme and its environmental remediation from harmful chemicals to microbes.

Photocatalytic Reduction of Hexavalent Chromium Using Cu3.21Bi4.79S9/g-C3N4 Nanocomposite

The photocatalytic reduction of hexavalent chromium, Cr(VI), to the trivalent species, Cr(III), has continued to inspire the synthesis of novel photocatalysts that are capable of achieving the task of converting Cr(VI) to the less toxic and more useful species. In this study, a novel functionalized graphitic carbon nitride (Cu3.21Bi4.79S9/gC3N4) was synthesized and characterized by using X-ray diffraction (XRD), thermogravimetry analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and scanning electron microscope (SEM). The composite was used for the photocatalytic reduction of hexavalent chromium, Cr(VI), under visible light irradiation. A 92.77% efficiency of the reduction was achieved at pH 2, using about 10 mg of the photocatalyst and 10 mg/L of the Cr(VI) solution. A pseudo-first-order kinetic study indicated 0.0076 min−1, 0.0286 min−1, and 0.0393 min−1 rate constants for the nanoparticles, pristine gC3N4, and the nanocomposite, respectively. This indicated an enhancement in the rate of reduction by the functionalized gC3N4 by 1.37- and 5.17-fold compared to the pristine gC3N4 and Cu3.21Bi4.79S9, respectively. A study of how the presence of other contaminants including dye (bisphenol A) and heavy-metal ions (Ag(I) and Pb(II)) in the system affects the photocatalytic process showed a reduction in the rate from 0.0393 min−1 to 0.0019 min−1 and 0.0039 min−1, respectively. Finally, the radical scavenging experiments showed that the main active species for the photocatalytic reduction of Cr(VI) are electrons (e−), hydroxyl radicals (·OH−), and superoxide (·O2−). This study shows the potential of functionalized gC3N4 as sustainable materials in the removal of hexavalent Cr from an aqueous solution.

Visible Light-Mediated Photoactivated Sulfur Quantum Dots as Heightened Antibacterial Agents

The need for antimicrobial or antibacterial fabric has increased exponentially in recent past years, especially after the outbreak of the SARS-CoV-2 pandemic. Several studies have been conducted, and the primary focus is the development of simple, automated, performance efficient and cost-efficient fabric for disposable and frequent-use items such as personal protective materials. In this regard, we have explored the light-driven antibacterial activity of water-soluble Sdots for the first time. Sdots are a new class of non-metallic quantum dots of the nanosulfur family having a polymeric sulfur core. These Sdots exhibited excellent antibacterial activity by generating reactive oxygen species under sunlight or visible light. Under 6 h of sunlight irradiation, it was observed that >90% of the bacterial growth was inhibited in the presence of Sdots. Furthermore, low toxic Sdots were employed to develop antibacterial fabric for efficiently cleaning the bacterial infection. The prominent zone of inhibition of up to 9 mm was observed post 12 h incubation of Sdots treated fabric with E. coli in the presence of visible light. Furthermore, the SEM study confirmed the bactericidal effect of these Sdots-treated fabrics. Moreover, this study might help explore the photocatalytic disinfection application of Sdots in diverse locations of interest, Sdots-based photodynamic antimicrobial chemotherapy application, and provide an opportunity to develop Sdots as a visible light photocatalyst for organic transformations and other promising applications.

ZnO-based antimicrobial coatings for biomedical applications

Rapid transmission of infectious microorganisms such as viruses and bacteria through person-to-person contact has contributed significantly to global health issues. The high survivability of these microorganisms on the material surface enumerates their transmissibility to the susceptible patient. The antimicrobial coating has emerged as one of the most interesting technologies to prevent growth and subsequently kill disease-causing microorganisms. It offers an effective solution a non-invasive, low-cost, easy-in-use, side-effect-free, and environmentally friendly method to prevent nosocomial infection. Among antimicrobial coating, zinc oxide (ZnO) stands as one of the excellent materials owing to zero toxicity, high biocompatibility to human organs, good stability, high abundancy, affordability, and high photocatalytic performance to kill various infectious pathogens. Therefore, this review provides the latest research progress on advanced applications of ZnO nanostructure-based antibacterial coatings for medical devices, biomedical applications, and health care facilities. Finally, future challenges and clinical practices of ZnO-based antibacterial coating are addressed.

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.

Synthesis and Performance Analysis of Photocatalytic Activity of ZnIn2S4 Microspheres Synthesized Using a Low-Temperature Method

In this paper, we report the synthesis of zinc indium sulfide (ZnIn₂S₄) microspheres synthesized via a low-temperature route, and the as-synthesized material was used for photocatalytic degradation of malachite green (MG), methyl orange (MO), and Direct Red 80 (DR-80) dyes. The as-synthesized material was characterized by powder X-ray diffraction and field-emission scanning electron microscopy for studying the crystal structure and surface morphology, respectively. Fourier transform infrared spectroscopy was performed to determine the functional groups attached. UV-Visible absorption spectrometry was done for light absorbance and band gap analysis, and Mott-Schottky analysis was performed to determine the nature and flat band potential of the material. A scavenger study was performed to analyze the active species taking part in the degradation process. The reusability of the material was tested up to four cycles to check the reduction in efficiency after each cycle. A time-correlated single-photon counting study was performed to observe the average lifetime of generated excitons during photocatalysis. It was found that the as-synthesized porous sample is more efficient in degrading the cationic dye than anionic dyes, which is further explained in the article.

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.

Effects of Preparation Conditions on the Efficiency of Visible-Light-Driven Hydrogen Generation Based on Ni(II)-Modified Cd0.25Zn0.75S Photocatalysts

Hydrogen as an environmentally friendly fuel can be produced by photocatalytic procedures from aqueous systems, utilizing H₂S, an industrial side-product, by conversion and storage of renewable solar energy. Although composites of CdS and ZnS prepared by co-precipitation are very efficient in heterogeneous photocatalytic H₂ generation, the optimal conditions for their synthesis and the effects of the various influencing factors are still not fully clarified. In this work, we investigated how the efficiency of Cd₀.₂₅Zn₀.₇₅S composites modified with Ni(II) was affected by the doping method, Ni-content, hydrothermal treatment, and presence of a complexing agent (ammonia) used in the preparation. The composition, optical, and structural properties of the photocatalysts prepared were determined by ICP, DRS, XRD, TEM, and STEM-EDS. Although hydrothermal treatment proved preferable for Ni-free composites, Ni-modification was more efficient for untreated composites precipitated from ammonia-containing media. The best efficiency (14.9% quantum yield at 380 nm irradiation, 109.8 mmol/g/h hydrogen evolution rate) achieved by surface modification with 0.1–0.3% Ni(II) was 15% and 20% better than those for hydrothermally treated catalyst and similarly prepared Pt-modified one, respectively. Structural characterization of the composites clearly confirmed that the Ni²⁺ ions were not embedded into the CdS-ZnS crystal lattice but were enriched on the surface of particles of the original catalyst in the form of NiO or Ni(OH)₂. This co-catalyst increased the efficiency by electron-trapping, but its too high amount caused an opposite effect by diminishing the excitable surface of the CdS-ZnS particles.

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 S^2- 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.

Mixed-Valence Bimetallic Ce/Zr MOF-Based Nanoarchitecture: A Visible-Light-Active Photocatalyst for Ciprofloxacin Degradation and Hydrogen Evolution

A mixed-valency bimetallic Ce/Zr MOF with Ce³⁺/Ce⁴⁺ ions incorporated and an oxygen vacancy-rich single-component photocatalyst have been designed through the one-step solvothermal route to harness photons from the visible-light spectrum for green energy (H₂) generation and ciprofloxacin (CIP) degradation. The one-pot-engineered bimetallic Ce/Zr MOF shows visible-light-active characteristics accompanied by a narrower band gap, along with enhanced exciton separation and superior ligand-to-metal charge transfer (LMCT), due to the presence of an interconvertible Ce³⁺/Ce⁴⁺ ions pair in comparison to its pristine MOF counterpart. The Ce ion insertion led to increase in electron density around the Zr⁴⁺ ion, along with generation of some oxygen vacancies (OV), which cumulatively led to the rise in the photo-reaction output. The synthesized UNH (Ce/Zr 1:1) MOF displayed a boosted photocatalytic H₂ production rate of 468.30 μmol h^-1 (ACE = 3.51%), which is around fourfolds higher than that of pristine MOFs. Moreover, for CIP photodegradation, the UNH (Ce/Zr 1:1) shows an enhanced efficiency of 90.8% and follows pseudo-first-order kinetics with a rate constant of 0.0363. Typically, the active species involved in the photo-redox reaction of the CIP photodegradation follows the order hydroxyl radical (OH^•) < superoxide radical (O₂^•-), as confirmed by the TA and NBT tests. Consequently, the bimetallic Ce/Zr MOF can be readily employed as a robust photocatalyst with enhanced tendencies towards CIP degradation and H₂ evolution.