Nanoscale zinc oxide based heterojunctions as visible light active photocatalysts for hydrogen energy and environmental remediation

Built-In Electric Field Boost Photocatalytic Degradation of Pollutants in Wastewater

The photocatalysis technique shows significant potential for wastewater degradation; however, the rapid recombination of photogenerated holes and electrons severely limits its photocatalytic efficiency. This situation necessitates the development of effective strategies to tackle these challenges. One well-documented approach is built-in electric field engineering in heterojunctions or composites, which has been shown to enhance electron transfer and thereby reduce the recombination of electrons and holes. This strategy has proven highly effective in significantly improving photocatalytic activity for the degradation of pollutants in wastewater. In this context, we summarize recent advancements in built-in electric field engineering in photocatalysts, highlighting the fundamentals and modifications of this approach, as well as its positive impact on photocatalytic performance in the degradation of wastewater pollutants.

Improved photocatalytic performance of cobalt doped ZnS decorated with graphene nanostructures under ultraviolet and visible light for efficient hydrogen production

Highly dispersed Cobalt doped ZnS nanostructures were successfully fabricated on the surfaces of graphene sheets via a simple hydrothermal method. X-ray diffraction (XRD), X-ray photocurrent spectroscopy (XPS), Raman spectroscopy (RS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) were utilized to analyze the structural characteristics of the cobalt doped ZnS decorated with grapheneCo x Zn 1 - x S rGO nanostructures (NSs). UV-visible optical absorption (UV-vis) studies were conducted to investigate their optical properties. In laboratory studies utilizing water and visible light, the photocatalytic activity ofCo x Zn 1 - x S rGO NSs at (x = 0, 1, 2, 4 and 6 atm.%) were evaluated. Graphite Oxide (GO) was successfully transformed into sheets of graphene andCo x Zn 1 - x S rGO NSs possessed a crystalline structure according to the findings of XRD, RS and FTIR analysis. SEM investigation showed graphene sheets enhanced with ZnS NSs possessed cuboidal, spheroidal form of structure and displayed a paper like appearance. UV-vis confirmed a noticeable rapid increase in transmittance along the UV wavelength area and confirmed a highly transparent NSs in the wavelength range of (180-800 nm). Calculations using density functional theory (DFT) revealed that the Co NSs have more negative conduction bands than ZnS, allowing for effective electron transfer from cobalt to ZnS and exhibiting a band gap decrease as Co content increased. TheCo 0.04 Zn 0.96 S rGO NSs sample had the highest photocatalytic activity, measured at 7648.9 μ mol h - 1 . A combination of improved dispersion properties, greater surface area, increased absorption and enhanced transfer of photogenerated electrons,Co x Zn 1 - x S rGO NSs increased the photocatalytic hydrogen generation activity.

Elucidating the Role of Electron Transfer in the Photoluminescence of MoS2 Quantum Dots Synthesized by fs-Pulse Ablation

Herein, MoS2 quantum dots (QDs) with controlled optical, structural, and electronic properties are synthesized using the femtosecond pulsed laser ablation in liquid (fs-PLAL) technique by varying the pulse width, ablation power, and ablation time to harness the potential for next-generation optoelectronics and quantum technology. Furthermore, this work elucidates key aspects of the mechanisms underlying the near-UV and blue emissions the accompanying large Stokes shift, and the consequent change in sample color with laser exposure parameters pertaining to MoS2 QDs. Through spectroscopic analysis, including UV-visible absorption, photoluminescence, and Raman spectroscopy, we successfully unraveled the mechanisms for the change in optoelectronic properties of MoS2 QDs with laser parameters. We realize that the occurrence of a secondary phase, specifically MoO3-x, is responsible for the significant Stokes shift and blue emission observed in this QD system. The primary factor influencing these activities is the electron transfer observed between these two phases, as validated by excitation-dependent photoluminescence and XPS and Raman spectroscopies.

Investigation of Photoluminescence and Optoelectronics Properties of Transition Metal-Doped ZnO Thin Films

Thin films of zinc oxide (ZnO) doped with transition metals have recently gained significant attention due to their potential applications in a wide range of optoelectronic devices. This study focuses on ZnO thin films doped with the transition metals Co, Fe, and Zr, exploring various aspects of their structural, morphological, optical, electrical, and photoluminescence properties. The thin films were produced using RF and DC co-sputtering techniques. The X-ray diffraction (XRD) analysis revealed that all the doped ZnO thin films exhibited a stable wurtzite crystal structure, showcasing a higher structural stability compared to the undoped ZnO, while the atomic force microscopy (AFM) imaging highlighted a distinctive granular arrangement. Energy-dispersive X-ray spectroscopy was employed to confirm the presence of transition metals in the thin films, and Fourier-transform infrared spectroscopy (FTIR) was utilized to investigate the presence of chemical bonding. The optical characterizations indicated that doping induced changes in the optical properties of the thin films. Specifically, the doped ZnO thin film's bandgap experienced a significant reduction, decreasing from 3.34 to 3.30 eV. The photoluminescence (PL) analysis revealed distinguishable emission peaks within the optical spectrum, attributed to electronic transitions occurring between different bands or between a band and an impurity. Furthermore, the introduction of these transition metals resulted in decreased resistivity and increased conductivity, indicating their positive influence on the electrical conductivity of the thin films. This suggests potential applications in solar cells and light-emitting devices.

Polythiophene as a Double-Electrostatic Template for Zinc Oxide and Gold: Multicomponent Nano-Objects for Enhanced Photocatalysis

Using electrostatic self-assembly and electrostatic nanotemplating, a quaternary nanostructured system consisting of zinc oxide nanoparticles, gold nanoparticles, poly[3-(potassium-4-butanoate)thiophene-2,5-diyl] (PT), and methyltrioctylammonium chloride (MTOA) (PT-MTOA-ZnO-Au) was designed for aqueous photocatalysis. The PT-MTOA hollow sphere aggregates served as an electrostatic template for both individual inorganic nanoparticles controlling their morphology, stabilizing the nanoparticles, and acting as a photosensitizer. The hybrid structures included spherical ZnO nanoparticles with a diameter of d = 2.6 nm and spherical Au nanoparticles with d = 6.0 nm embedded in PT-MTOA hollow spheres with a hydrodynamic radius of R_H = 100 nm. The ZnO nanoparticles acted as the main catalyst, while the Au nanoparticles acted as the cocatalyst. As a photocatalytic model reaction, the dye degradation of methylene blue in aqueous solution using the full spectral range from UV to visible light was tested. The photocatalytic activity was optimized by varying the Zn and Au loading ratios and was substantially enhanced regarding the components; for example, it was increased by about 61% using PT-MTOA-ZnO-Au compared to the composite without gold particles. A photocatalytic mechanism of the methylene blue degradation was proposed when catalyzed by these multicomponent nano-objects. Thus, a simple procedure of templating two different nanoparticle species within the same cocatalytically active template has been demonstrated, which can be extended to other inorganic particles, making a variety of task-specific catalysts accessible.

MoS2-Based Nanocomposites for Photocatalytic Hydrogen Evolution and Carbon Dioxide Reduction

Photocatalysis is a facile and sustainable approach for energy conversion and environmental remediation by generating solar fuels from water splitting. Due to their two-dimensional (2D) layered structure and excellent physicochemical properties, molybdenum disulfide (MoS₂) has been effectively utilized in photocatalytic H₂ evolution reaction (HER) and CO₂ reduction. The photocatalytic efficiency of MoS₂ greatly depends on the active edge sites present in their layered structure. Modifications like reducing the layer numbers, creating defective structures, and adopting different morphologies produce more unsaturated S atoms as active edge sites. Hence, MoS₂ acts as a cocatalyst in nanocomposites/heterojunctions to facilitate the photogenerated electron transfer. This review highlights the role of MoS₂ as a cocatalyst for nanocomposites in H₂ evolution reaction and CO₂ reduction. The H₂ evolution activity has been described comprehensively as binary (with metal oxide, carbonaceous materials, metal sulfides, and metal-organic frameworks) and ternary composites of MoS₂. Photocatalytic CO₂ reduction is a more complex and challenging process that demands an efficient light-responsive semiconductor catalyst to tackle the thermodynamic and kinetic factors. Photocatalytic reduction of CO₂ using MoS₂ is an emerging topic and would be a cost-effective substitute for noble catalysts. Herein, we also exclusively envisioned the possibility of layered MoS₂ and its composites in this area. This review is expected to furnish an understanding of the diverse roles of MoS₂ in solar fuel generation, thus endorsing an interest in utilizing this unique layered structure to create nanostructures for future energy applications.

Synthesis of Platinum Nanoparticles Supported on Fused Nanosized Carbon Spheres Derived from Sustainable Source for Application in a Hydrogen Generation Reaction

The dwindling supply of fossil fuels has prompted the search for an alternative energy source that could effectively replace them. Potential renewable energy sources such as solar, wind, tidal, and geothermal are all promising but each has its own drawbacks. Hydrogen gas on the other hand can be combusted to produce energy with only water as a byproduct and can be steadily generated via the aqueous media hydrolysis reaction of Sodium Borohydride (NaBH₄). This study successfully synthesized fused carbon spheres derived from sugar and decorated them with platinum nanoparticles to form a novel composite material (PtFCS) for catalyzing this reaction. The platinum nanoparticles were produced by reducing chloroplatinic acid in a solution with sodium borohydride and using sodium citrate as a capping agent for the nanoparticles. Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were used to characterize and determine the size and shape of the Pt nanoparticles (PtNPs) and fused carbon spheres. TEM was able to determine the average size of the fused carbon spheres to be 200 nm and the average size for the PtNPs to be 2-3 nm. The PtFCS composite was tested for its ability to catalyze the hydrolysis of NaBH₄ under various reaction conditions including various solution pH, various temperatures, and various dosages of sodium borohydride. The catalyst was found to perform the best under acidic solution conditions (pH 6), producing hydrogen at a rate of 0.0438 mL/mg_cat·min. The catalyst was determined to have an activation energy of 53.0 kJ/mol and could be used multiple times in succession with no loss in the volume of hydrogen produced. This sugar-derived composite catalyst shows promise and could be implemented as a sustainable catalyst for the generation of hydrogen fuel.

Enhanced Monitoring of Photocatalytic Reactive Oxygen Species: Using Electrochemistry for Rapid Sensing of Hydroxyl Radicals Formed during the Degradation of Coumarin

Many recent research studies have reported indirect methods for the detection and quantification of OH radicals generated during photocatalysis. The short lifespan and high reactivity of these radicals make indirect detection using probes such as coumarin a more viable quantification method. Hydroxyl radical production is commonly monitored using fluorescence spectroscopy to determine the concentration of the compound 7-hydroxycoumarin, which is formed from hydroxyl radical attack on coumarin. There are, however, a number of additional hydroxylated coumarins generated during this process, which are less amenable to detection by fluorescence spectroscopy. Consequently, limitations and inaccuracies of this method have previously been reported in the literature. As an alternative approach to those previously reported, this work has developed an electrochemical screening method using coumarin as a OH radical trap, that is capable of in situ monitoring of not only 7-hydroxycoumarin, but all the main mono-hydroxylated products formed. As a result, this technique is a more representative and comprehensive method for the quantification of OH radicals produced by photocatalysts using coumarin as a probe molecule. Moreover, the electroanalytical method provides a portable, rapid, sensitive, and accurate in situ method for the monitoring of OH radical formation without the need for sample preparation.

Concurrent fabrication of ZnO-ZnFe2O4 hybrid nanocomposite for enhancing photocatalytic degradation of organic pollutants and its bacterial inactivation

In this research, we looked at how heterostructure fabrication, phase ratio, and crystalline nature affect the photocatalytic activity of ZnO/ZnFe₂O₄ nanocomposite for the degradation of Rhodamine B (RhB) dye when exposed to sunlight irradiation. Magnetic ZnO/ZnFe₂O₄ hybrid nanocomposites were made using a co-precipitation technique. The synthesized hybrid nanocomposite were analyzed using a variety of characterization techniques to understand more about their chemical, crystallinity, and photoactive characteristics. Using UV-Visible spectra, the absorption and photocatalytic efficiency of photocatalysts were investigated. By using XPS and FTIR measurements, the surface composition and functionalization of the produced nanocomposite were observed. The synthesized ZnO/ZnFe₂O₄ nanocomposites exhibit irregular morphologies, and the average crystallite size is about 30 nm, by the findings of the transmission electron microscope. When exposed to solar light for 90 min, the prepared photocatalysts exceed ZnO nanoparticles in terms of photocatalytic performance by more than 45%. Pseudo-first-order kinetics governs the adsorption of RhB onto nanocomposite surfaces. Finally, the ZnO/ZnFe₂O₄ nanocomposites were employed for antibacterial treatments against the waterborne pathogens Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus). The outcomes demonstrated that the optimal disinfection efficiency against E. coli and S. aureus germs were 98.6 and 97.4%, respectively, associated with superior cycling durability. Therefore, this work offers a simple and rapid approach to the development of hybrid nanocomposites that could be used to create various photocatalytic and optical materials.

Removal of PFASs from water by carbon-based composite photocatalysis with adsorption and catalytic properties: A review

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent organic pollutants widely distributed in aquatic environments. The adsorption and photocatalytic methods have been widely used to remove PFASs in water because of their respective advantages. Still, they have apparent defects when used alone. Therefore, the adsorption and photocatalytic technologies are combined through suitable preparation methods, and the excellent properties of the two are used to synergize the treatment of organic pollutants. This strategy of "concentrating" pollutants and then degrading them in a centralized manner plays an essential role in removing trace PFASs. Nevertheless, a review focusing on this kind of adsorption photocatalyst system is lacking. This review will fill this gap and provide a reference for developing a carbon-based composite photocatalyst. Firstly, different carbon-based composite photocatalysts are reviewed in detail, focusing on the differences in various composite materials' excellent adsorption and catalytic properties. Secondly, the factors influencing the removal effect of carbon-based composite photocatalysts are discussed. Thirdly, the removal mechanism of carbon-based composite photocatalysts is summarized in detail. The removal process involves two steps: adsorption and photodegradation. The adsorption process involves multiple cooperative adsorption mechanisms, and photocatalytic degradation includes oxidative and reductive degradation. Fourthly, the comparison of adsorption-photocatalysis with common treatment techniques (including removal rate, range of adaptation, cost, and the possibility of expanding application) is summarized. Finally, the prospects of carbon-based composite photocatalysts for repairing PFASs are given by evaluating the performance of different composites.

Spectral tuning of biotemplated ZnO photonic nanoarchitectures for photocatalytic applications

The photocatalytic activity of a flat surface can be increased by micro- and nanostructuring the interface to increase the area of the contact surface between the photocatalyst and the solute, and moreover, to optimize charge carrier transfer. Further enhancement can be achieved by using photonic nanostructures, which exhibit photonic band gap (PBG). Structurally coloured butterfly wings offer a rich 'library' of PBGs in the visible spectral range which can be used as naturally tuned sample sets for biotemplating. We used conformal atomic layer deposition of ZnO on the wings of various butterfly species (Arhopala asopia, Hypochrysops polycletus, Morpho sulkowskyi, Polyommatus icarus) possessing structural colour extending from the near UV to the blue wavelength range, to test the effects arising from the nanostructured surfaces and from the presence of different types of PBGs. Aqueous solutions of rhodamine B were used to test the enhancement of photocatalytic activity that was found for all ZnO-coated butterfly wings. The best reaction rate of decomposing rhodamine B when illuminated with visible light was found in 15 nm ZnO coated M. sulkowskyi wing, the reflectance of which had the highest overlap with the absorption band of the dye and had the highest reflectance intensity.

Spectral tuning of biotemplated ZnO photonic nanoarchitectures for photocatalytic applications

The photocatalytic activity of a flat surface can be increased by micro- and nanostructuring the interface to increase the area of the contact surface between the photocatalyst and the solute, and moreover, to optimize charge carrier transfer. Further enhancement can be achieved by using photonic nanostructures, which exhibit photonic band gap (PBG). Structurally coloured butterfly wings offer a rich 'library' of PBGs in the visible spectral range which can be used as naturally tuned sample sets for biotemplating. We used conformal atomic layer deposition of ZnO on the wings of various butterfly species (Arhopala asopia, Hypochrysops polycletus, Morpho sulkowskyi, Polyommatus icarus) possessing structural colour extending from the near UV to the blue wavelength range, to test the effects arising from the nanostructured surfaces and from the presence of different types of PBGs. Aqueous solutions of rhodamine B were used to test the enhancement of photocatalytic activity that was found for all ZnO-coated butterfly wings. The best reaction rate of decomposing rhodamine B when illuminated with visible light was found in 15 nm ZnO coated M. sulkowskyi wing, the reflectance of which had the highest overlap with the absorption band of the dye and had the highest reflectance intensity.

Spectral tuning of biotemplated ZnO photonic nanoarchitectures for photocatalytic applications

The photocatalytic activity of a flat surface can be increased by micro- and nanostructuring the interface to increase the area of the contact surface between the photocatalyst and the solute, and moreover, to optimize charge carrier transfer. Further enhancement can be achieved by using photonic nanostructures, which exhibit photonic band gap (PBG). Structurally coloured butterfly wings offer a rich 'library' of PBGs in the visible spectral range which can be used as naturally tuned sample sets for biotemplating. We used conformal atomic layer deposition of ZnO on the wings of various butterfly species (Arhopala asopia, Hypochrysops polycletus, Morpho sulkowskyi, Polyommatus icarus) possessing structural colour extending from the near UV to the blue wavelength range, to test the effects arising from the nanostructured surfaces and from the presence of different types of PBGs. Aqueous solutions of rhodamine B were used to test the enhancement of photocatalytic activity that was found for all ZnO-coated butterfly wings. The best reaction rate of decomposing rhodamine B when illuminated with visible light was found in 15 nm ZnO coated M. sulkowskyi wing, the reflectance of which had the highest overlap with the absorption band of the dye and had the highest reflectance intensity.

Tin bisulfide nanoplates anchored onto flower-like bismuth tungstate nanosheets for enhancement in the photocatalytic degradation of organic pollutant

The development of efficient heterojunctions through a simple and facile method is an effective way to enhance the photocatalytic performance of bismuth-based oxide semiconductors for industrial applications. Here, the novel flower-like type II SnS₂/Bi₂WO₆ heterostructure consisting of bismuth tungstate (Bi₂WO₆) nanosheets and tin bisulfide (SnS₂) nanoplates was successfully designed and synthesized. The crystal structure, composition, morphology, and photoelectric properties of the heterostructure were systematically characterized. In addition, the photocatalytic activity of SnS₂/Bi₂WO₆ was analyzed and compared with Bi₂WO₆ or SnS₂ alone or physical mixture of SnS₂ and Bi₂WO₆. 2%SnS₂/Bi₂WO₆ presents a 3.1 times greater degradation rate constant (0.0065 min^-1) than that of Bi₂WO₆ (0.0021 min^-1) under low visible light irradiation (5.3 mW·cm^-2, a 44 W LED), while SnS₂ alone exhibits no photocatalytic effect toward glyphosate. Furthermore, 2%SnS₂/Bi₂WO₆ maintains 93% of its original photocatalytic activity even after four cycles. The possible photocatalytic degradation pathway of glyphosate and photocatalytic mechanism are also proposed. The excellent photocatalytic performance of SnS₂/Bi₂WO₆ is attributed to the decoration of SnS₂ nanoplates on the surface of Bi₂WO₆, appropriate (113)/(020) ratio, increased visible-light absorption, and effective separation of photoinduced carriers. This paper reports a new methodology that can act as a reference basis to design and develop visible-light responsive photocatalysts with outstanding photocatalytic performance for carbon dioxide reduction, water splitting, and pollutant degradation.

Synthesis of the Porous ZnO Nanosheets and TiO2/ZnO/FTO Composite Films by a Low-Temperature Hydrothermal Method and Their Applications in Photocatalysis and Electrochromism

In this paper, porous zinc oxide (ZnO) nanosheets were successfully prepared by a simple low-temperature hydrothermal method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) tests showed that the synthesized product was ZnO with porous sheet structure. The diameter of porous nanosheets was about 100 nm and the thickness was about 8 nm. As a photocatalyst, the degradation efficiencies of porous ZnO nanosheets for methyl orange (MO), methylene blue (MB) and Rhodamine B (RhB) were 97.5%, 99% and 96.8%, respectively. In addition, the degradation efficiency of ZnO for mixed dyes (Mo, MB and RhB) was satisfactory, reaching 97.7%. The photocatalytic stability of MB was further tested and remained at 99% after 20 cycles. In the experiment, ZnO/FTO (fluorine-doped tin oxide) composites were prepared by using ZnO as the conductive layer. Titanium dioxide (TiO2) was deposited on the surface of ZnO/FTO by electrodeposition, so as to obtain a TiO2/ZnO/FTO composite. By studying the electrochromic properties of this composite, it was found that the TiO2/ZnO/FTO composite shows a large light modulation range (55% at 1000 nm) and excellent cycle stability (96.6% at 200 cycles). The main reason for the excellent electrochromic properties may be the synergistic effect between the porous structure and the polymetallic oxides. This study is helpful to improve the photocatalytic efficiency and cycling stability of metal oxides, improve the transmittance of thin films and provide a new strategy for the preparation of ZnO composite materials with excellent photocatalytic and electrochromic properties.

Current advancements on the fabrication, modification, and industrial application of zinc oxide as photocatalyst in the removal of organic and inorganic contaminants in aquatic systems

Industrial wastewaters contain hazardous contaminants that pollute the environment and cause socioeconomic problems, thus demanding the employment of effective remediation procedures such as photocatalysis. Zinc oxide (ZnO) nanomaterials have emerged to be a promising photocatalyst for the removal of pollutants in wastewater owing to their excellent and attractive characteristics. The dynamic tunable features of ZnO allow a wide range of functionalization for enhanced photocatalytic efficiency. The current review summarizes the recent advances in the fabrication, modification, and industrial application of ZnO photocatalyst based on the analysis of the latest studies, including the following aspects: (1) overview on the properties, structures, and features of ZnO, (2) employment of dopants, heterojunction, and immobilization techniques for improved photodegradation performance, (3) applicability of suspended and immobilized photocatalytic systems, (4) application of ZnO hybrids for the removal of various types of hazardous pollutants from different wastewater sources in industries, and (5) potential of bio-inspired ZnO hybrid nanomaterials for photocatalytic applications using renewable and biodegradable resources for greener photocatalytic technologies. In addition, the knowledge gap in this field of work is also highlighted.

The role of size-controlled CeO2 nanoparticles in enhancing the stability and photocatalytic performance of ZnO in natural sunlight exposure

In order to enhance the photocatalytic performance and stability, the various proportions of the size controlled cerium oxide (CeO₂) nanoparticles were dispersed at the pre-synthesized ZnO. Although, the expected dual absorption onsets, probably due to the diminutive difference between the bandgaps of CeO₂ (∼2.9 eV) and ZnO (∼3.1 eV), were not observed however, a blue shift in the bandgap energy of ZnO was witnessed with the increasing surface density of CeO₂ particles. The delayed excitons recombination process with the increasing concentration of CeO₂ nanoparticles was verified by the PL spectra. The structural investigation by Raman and XRD analysis revealed the surface attachment of CeO₂ particles without altering the rock-salt lattice of ZnO. The morphological and fine microstructural analysis established the uniform distribution of evenly sized CeO₂ particles at the surface of ZnO with the discrete fringe patterns of both the entities whereas the XPS analysis confirmed the majority of Ce⁴⁺ in dispersed CeO₂. In comparison to pure ZnO, cyclic voltammetric (CV) analysis, under illumination, exposed the supportive role of surface residing CeO₂ particles in eradicating the photo-corrosion of ZnO whereas the chronopotentiometry (CP) predicted the prolonged life-span of the excitons. Compared to pure ZnO, an appreciably high activity was revealed for 10% CeO₂ loading as compared to pure ZnO for the removal of mono and di-nitrophenol derivatives and their mixtures under natural sunlight exposure. The variations in the removal rates in the mixture as compared to individual nitrophenol exposed the structure-based priority of ROS for the respective phenol. The significantly enhanced photocatalytic activity of the composite catalysts revealed the incremental role of surface-mounted CeO₂ entities in boosting the generation of ROS under sunlight irradiation. The experimental observations were correlated and compiled to establish the mechanism of the removal process.

Effect of calcination temperature on the morphology and catalytic properties of ZnO nanostructures fabricated from a chiral precursor for photodegradation of both cationic and anionic dyes

A chiral Zn MOF is fabricated into ZnO microflowers, polyhedrons and nanorods at three different temperatures and these are utilized for the photodegradation of methylene blue and Congo red.

Silver-doped SnO2 nanostructures for photocatalytic water splitting and catalytic nitrophenol reduction

Driven by the quest of renewable and clean energy sources, researchers around the globe are seeking solutions to replace non-renewable fossil fuels to meet the ever-increasing energy supply requirements and solve the relevant environment concerns.

Facile preparation of BiOI/T-ZnOw p–n heterojunction photocatalysts with enhanced removal efficiency for rhodamine B and oxytetracycline

A BiOI/T-ZnOw p–n heterojunction photocatalyst exhibits excellent degradation activities for rhodamine B and oxytetracycline under visible light irradiation.

The photocatalytic performance and mechanism of magnetically retrievable Z-scheme Cr2O3–Fe3O4/C hetero-nanostructure polyhedra

Magnetically retrievable Cr2O3–Fe3O4/C hetero-nanostructure polyhedra have been fabricated. The formation of Z-scheme Cr2O3–Fe3O4/C obviously improves the visible light absorption and promotes the separation of photogenerated charge carriers.

Facile and Robust Construction of 3D-Hierarchical NaNbO3-Nanorod/ZnIn2S4 Heterojunction toward Ultra-high Photocatalytic H2 Production

It is quite imperative yet remained challenging to develop the heterojunction photocatalysts for efficient interfacial charge carriers separation on photocatalytic hydrogen evolution (PHE) reactions. Encouragingly, in this work, we constructed...

Amin M, Kaneti Y, Suendo V. Role of Urea on Structural, Textural, and Optical Properties of Macroemulsion-assisted Synthesized Holey ZnO Nanosheets for Photocatalytic Applications

Using a macroemulsion-assisted solvothermal method, the present study produces holey ZnO nanosheets exhibiting the hexagonal wurtzite crystal structure. In the synthetic process, urea is employed as a hydrolyzing agent. Its...

Recent insights into SnO2-based engineered nanoparticles for sustainable H2 generation and remediation of pesticides

Due to the ongoing industrial revolution and global health pandemics, solar-driven water splitting and pesticide degradation are highly sought to cope with catastrophes such as depleting fossil reservoirs, global warming, and environmental degradation.

Recent Advances in Plasmonic Photocatalysis Based on TiO2 and Noble Metal Nanoparticles for Energy Conversion, Environmental Remediation, and Organic Synthesis

Plasmonic photocatalysis has emerged as a prominent and growing field. It enables the efficient use of sunlight as an abundant and renewable energy source to drive a myriad of chemical reactions. For instance, plasmonic photocatalysis in materials comprising TiO₂ and plasmonic nanoparticles (NPs) enables effective charge carrier separation and the tuning of optical response to longer wavelength regions (visible and near infrared). In fact, TiO₂ -based materials and plasmonic effects are at the forefront of heterogeneous photocatalysis, having applications in energy conversion, production of liquid fuels, wastewater treatment, nitrogen fixation, and organic synthesis. This review aims to comprehensively summarize the fundamentals and to provide the guidelines for future work in the field of TiO₂ -based plasmonic photocatalysis comprising the above-mentioned applications. The concepts and state-of-the-art description of important parameters including the formation of Schottky junctions, hot electron generation and transfer, near field electromagnetic enhancement, plasmon resonance energy transfer, scattering, and photothermal heating effects have been covered in this review. Synthetic approaches and the effect of various physicochemical parameters in plasmon-mediated TiO₂ -based materials on performances are discussed. It is envisioned that this review may inspire and provide insights into the rational development of the next generation of TiO₂ -based plasmonic photocatalysts with target performances and enhanced selectivities.

Preparation and performance of Novel Ni-doped Iron oxychloride with High singlet oxygen generation

Singlet oxygen with lower oxide electrode potential but higher selective oxidation ability towards specific organic contaminants had been paid great attention. An efficient system with high singlet oxygen generation (over...

Differentiated Oxygen Evolution Behavior in MOF-Derived Oxide Nanomaterials Induced by Phase Transition

Oxygen evolution reaction (OER) on the anode has become one of the most widely studied electrochemical processes, which poses an important role in several energy generation technologies. In this work, we have designed and synthesized a series of metal-organic framework (MOF)-derived oxides pyrolyzed at different temperatures for efficient water oxidation in alkaline solutions. First, the barrel-shaped BMM-10 microcrystals can be conveniently synthesized under solvothermal conditions, and the hollow morphology of BMM-10-Fe with low crystallinity can be obtained through the fierce hydrolysis of Fe(III) ions. After being oxidized in air, there are only two typical phases of oxides including BMM-10-Fe-L and BMM-10-Fe-H. During electrolysis, BMM-10-Fe-L turns out to be immediately degraded into active Ni/FeOOH nanosheets with improved OER performance, while there is almost no structural and morphological change in BMM-10-Fe-H due to the structural rigidity and robust stability. Furthermore, the optimal BMM-10-Fe-H exhibits a promising electrocatalytic OER performance with a low Tafel slope of 137.4 mV dec^-1, a small overpotential of 260 mV at 10 mA cm^-2, and a high current retention of 93.8% after the stability test. The present work would motivate the scientific community to construct various MOF-derived nanomaterials for efficient energy storage and conversion applications.

Nonchemical integration of Au/Ag-based reduced graphene nanohybrid combined with 5-Fluorouracil drug to treat cancer cells

The perpetual lack of advanced strategies to prevent aggressive breast cancer with multiple categories represents challenging scientific society problems. Reduced graphene oxide- can treat disease, which was recently investigated due to its ability to induce apoptosis-based death. This research tested the chemotherapeutics in vitro efficacy of reduced graphene oxide embedded with gold and silver nanoparticles toward drug-sensitive breast cancer cells (MCF-7) and their cytotoxicity. Synthesis of the Au-Ag/rGO-5FU nanocomposites has been conducted using a wet chemical approach with chitosan aid as a pore directing and capping agent. The particle structure and morphology well characterized using different systems. HR-TEM shows a narrow-sized distribution of less than 100 nm, which is proper for cell membranes and medical use. The physical combination of the nanocomposite and 5-FU drug has been conducted mechanically using wet chemistry. The Au/Ag/rGO-5FU material's high activity enables it to produce reactive oxygen radicals, which display a potential against MCF-7 cell lines. All the results, including those obtained via cytometry, use the combination of Au/Ag/rGO-5FU to show a more substantial anticancer influence and more drug stability than pure 5-FU.

Facile Fabrication of a ZnO/Eu2O3/NiO-Based Ternary Heterostructure Nanophotocatalyst and Its Application for the Degradation of Methylene Blue

The ZnO-based ternary heterostructure ZnO/Eu2O3/NiO nanoparticles are synthesized using waste curd as fuel by a simple one-pot combustion method. The as-synthesized heterostructure is characterized by using various spectroscopic and microscopic techniques including X-ray diffraction, UV-vis, FTIR, SEM, and TEM analyses. The photocatalytic activity of the ternary nanocomposite was tested for the photodegradation of methylene blue (MB) under solar light irradiation. The results have revealed that the ternary ZnO/Eu2O3/NiO photocatalyst exhibits excellent performance toward the photocatalytic degradation of the studied dye. Optimization studies revealed that the synthesized heterostructure exhibited a pH-dependent photocatalytic activity, and better results are obtained for specific concentrations of dye and catalysts. Among the different light sources employed during the study, the catalyst was found to possess the best degradation efficiency in visible light.

Synthesis, Characterization, and Photocatalytic Performance of ZnO–Graphene Nanocomposites: A Review

ZnO is an exciting material for photocatalysis applications due to its high activity, easy accessibility of raw materials, low production costs, and nontoxic. Several ZnO nano and microstructures can be obtained, such as nanoparticles, nanorods, micro flowers, microspheres, among others, depending on the preparation method and conditions. ZnO is a wide bandgap semiconductor presenting massive recombination of the generated charge carriers, limiting its photocatalytic efficiency and stability. It is common to mix it with metal, metal oxide, sulfides, polymers, and nanocarbon-based materials to improve its photocatalytic behavior. Therefore, ZnO–nanocarbon composites formation has been a viable alternative that leads to new, more active, and stable photocatalytic systems. Mainly, graphene is a well-known two-dimensional material, which could be an excellent candidate to hybridize with ZnO due to its excellent physical and chemical properties (e.g., high specific surface area, optical transmittance, and thermal conductivity, among others). This review analyses ZnO–graphene nanocomposites’ recent advances, addressing the synthesis methods and the resulting structural, morphological, optical, and electronic properties. Moreover, we examine the ZnO–graphene composites’ role in the photocatalytic degradation of organic/inorganic pollutants.

Manganese-Doped Zinc Oxide Nanostructures as Potential Scaffold for Photocatalytic and Fluorescence Sensing Applications

Herein, we report the photocatalytic and fluorescence sensing applications of manganese-doped zinc oxide nanostructures synthesized by a solution combustion technique, using zinc nitrate as an oxidizer and urea as a fuel. The synthesized Mn-doped ZnO nanostructures have been analyzed in terms of their surface morphology, phase composition, elemental analysis, and optical properties with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and UV-Visible (UV-Vis) spectroscopy. A careful observation of the SEM micrograph reveals that the synthesized material was porous and grown in very high density. Due to a well-defined porous structure, the Mn-doped ZnO nanostructures can be used for the detection of ciprofloxacin, which was found to exhibit a significantly low limit of detection (LOD) value i.e., 10.05 µM. The synthesized Mn-doped ZnO nanostructures have been further analyzed for interfering studies, which reveals that the synthesized sensor material possesses very good selectivity toward ciprofloxacin, as it detects selectively even in the presence of other molecules. The synthesized Mn-doped ZnO nanostructures have been further analyzed for the photodegradation of methyl orange (MO) dye. The experimental results reveal that Mn-doped ZnO behaves as an efficient photocatalyst. The 85% degradation of MO has been achieved in 75 min using 0.15 g of Mn-doped ZnO nanostructures. The observed results clearly confirmed that the synthesized Mn-dopedZnO nanostructures are a potential scaffold for the fabrication of sensitive and robust chemical sensors as well as an efficient photocatalyst.