Fabrication of Z-scheme magnetic MoS2/CoFe2O4 nanocomposites with highly efficient photocatalytic activity

Activation of peroxymonosulfate by novel magnetically recyclable CoFe2O4/MXene quantum dots composites for rapid degradation of tetracycline: Synergistic performance and mechanisms

Tetracycline (TC), a commonly used antibiotic in wastewater, poses environmental and health risks, thus demanding advanced catalysts for its effective removal. In this work, for the first time, we integrated cobalt ferrite (CoFe2O4) and MXene quantum dots (MQDs) to form magnetic heterojunctions for rapid degradation of TC in the presence of peroxymonosulfate (PMS). Anchoring MQDs on the CoFe2O4 nanoparticles remarkably promoted the overall degradation rate of TC to 98.2% within 20 min via both radical and non-radical pathways. The first-order kinetic constant was 0.170 min-1, 3.5 and 15.5 times higher than that of CoFe2O4 and MQDs alone, respectively. Quenching experiments revealed that the addition of p-benzoquinone (p-BQ) and furfuryl alcohol (FFA) reduced the degradation of TC within 20 min to 56.2% and 28.4%, respectively, indicating that the primary reactive oxygen species for TC degradation in the CoFe2O4/MQDs + PMS system are •O2- and 1O2. CoFe2O4/MQDs also exhibited superparamagnetic property, which enabled their effective recovery by external magnetic field. Their reusability was verified by retaining 81.4% of catalytic efficacy in the consecutive 8th cycle. The CoFe2O4/MQDs + PMS system also exhibited excellent practicability in natural water samples as the degradation rates in both tap water and lake water environments exceeded 90%. Three potential pathways for TC degradation were proposed based on the liquid chromatography-mass spectrometry (LC-MS) characterizations and TC progressively transformed into 13 intermediates. This work may contribute to the ongoing efforts to develop advanced catalysts and strategies for mitigating the environmental impact of antibiotic pollution, offering a pathway toward sustainable and efficient water treatment technologies.

Co-based Nanozymatic Profiling: Advances Spanning Chemistry, Biomedical, and Environmental Sciences

Nanozymes, next-generation enzyme-mimicking nanomaterials, have entered an era of rational design; among them, Co-based nanozymes have emerged as captivating players over times. Co-based nanozymes have been developed and have garnered significant attention over the past five years. Their extraordinary properties, including regulatable enzymatic activity, stability, and multifunctionality stemming from magnetic properties, photothermal conversion effects, cavitation effects, and relaxation efficiency, have made Co-based nanozymes a rising star. This review presents the first comprehensive profiling of the Co-based nanozymes in the chemistry, biology, and environmental sciences. The review begins by scrutinizing the various synthetic methods employed for Co-based nanozyme fabrication, such as template and sol-gel methods, highlighting their distinctive merits from a chemical standpoint. Furthermore, a detailed exploration of their wide-ranging applications in biosensing and biomedical therapeutics, as well as their contributions to environmental monitoring and remediation is provided. Notably, drawing inspiration from state-of-the-art techniques such as omics, a comprehensive analysis of Co-based nanozymes is undertaken, employing analogous statistical methodologies to provide valuable guidance. To conclude, a comprehensive outlook on the challenges and prospects for Co-based nanozymes is presented, spanning from microscopic physicochemical mechanisms to macroscopic clinical translational applications.

Photodegradation of rhodamine-B in aqueous environment using visible-active gC3N4@CS-MoS2 nanocomposite

Rapid industrial expansion leads to environmental pollution especially in an aqueous environment. Photocatalytic degradation is one of the most efficient and environmentally friendly techniques used to treat industrial pollution due to its complete degradation capability of a variety of water contaminants to their non-toxic state. Graphitic carbon nitride (gC3N4) and molybdenum disulfide (MoS2) provide efficient dye degradation, but MoS2 has few disadvantages. Hence, chitosan (CS) supported gC3N4-MoS2 hybrid nanocomposite was developed in this study to reduce these issues by accelerating the degradation of dye molecules such as rhodamine-B under visible light. The prepared gC3N4@CS-MoS2 hybrid nanocomposite was thoroughly characterized using various analytical tools including FTIR, XRD, SEM, EDX, XPS, UV-Visible, and PL spectra. Several influencing parameters such as irradiation time, initial pH, dosage, and initial dye concentration were optimized by batch mode. The photodegradation of rhodamine-B could be induced by the heterogeneous gC3N4@CS-MoS2-water hybrid nanocomposite. The narrow band gap of gC3N4@CS-MoS2 (1.80 eV) makes it suitable for effective degradation of rhodamine-B due to more active in the visible region and attained its highest degradation efficiency of 99% after 40 min at pH 8 with minimum dosage of 60 mg. The possible degradation mechanism was tentatively proposed for rhodamine-B dye molecules from aqueous environment. The present work shows a novel photocatalyst for the purification and detoxification of dye molecules as well as other water contaminants found in polluted wastewater.

Deep mineralization of VOCs in an embedded hybrid structure CoFe2O4/MoS2/PMS wet scrubber system

Peroxymonosulfate (PMS)-based advanced oxidation processes in liquid phase systems can actively degrade toluene. In this work, the catechol structural surfactant was introduced to synthesize the dispersed and homogeneous CoFe2O4 nanospheres and embedded into MoS2 nanoflowers to form magnetically separable heterojunction catalysts. The innovative approach effectively mitigated the traditionally low reduction efficiency of transition metal ions during the heterogeneous activation process. In CoFe2O4/MoS2/PMS system, the toluene removal efficiency remained 95% within 2 h. The contribution of SO4⋅-, ·O2-, ·OH, and 1O2 was revealed by radical quenching experiment and electron paramagnetic resonance spectroscopy. The results illustrated that MoS2 offers ample reduction sites for facilitating PMS activation via Fe3+/Fe2+ redox interactions. Furthermore, an investigation into the toluene degradation pathway within the CoFe2O4/MoS2/PMS system revealed its capability to suppress the formation of toxic byproducts. This ambient-temperature liquid-phase method presented promising route for the removal of industrial volatile organic pollutants.

Highly efficient flower-like ZnIn2S4/CoFe2O4 photocatalyst with p-n type heterojunction for enhanced hydrogen evolution under visible light irradiation

The construction of a p-n heterojunction structure is considered to be an effective method to improve the separation of electron-hole pairs in photocatalysts. A series of ZnIn₂S₄/CoFe₂O₄ (ZIS/CFO) photocatalysts with p-n heterojunctions were prepared via a method involving ultrasonication and calcination. The synthesized photocatalysts were tested and analyzed via various testing techniques, and their hydrogen evolution rates were evaluated. Compared with pure ZIS, ZIS/CFO with different mass ratios of CFO to ZIS showed improved photocatalytic hydrogen production performance, and the optimal photoactivity showed a nearly 12-fold increase, which can be attributed to the formation of p-n junctions and the formed internal electric field, accelerating the separation of electron-hole pairs and effectively improving the photocatalytic hydrogen evolution rate. The excellent stability of the ZIS/CFO composite was proven by three cycle experiments. In addition, the ZIS/CFO composite also possessed excellent magnetic properties to realize facial magnetic recoverability. This work paves the way for the design and preparation of magnetically recoverable p-n heterojunction photocatalysts.

In-situ construction of Zr-based metal-organic framework core-shell heterostructure for photocatalytic degradation of organic pollutants

Photocatalysis is an eco-friendly promising approach to the degradation of textile dyes. The majority of reported studies involved remediation of dyes with an initial concentration ≤50 mg/L, which was away from the existing values in textile wastewater. Herein, a simple solvothermal route was utilized to synthesize CoFe2O4@UiO-66 core-shell heterojunction photocatalyst for the first time. The photocatalytic performance of the as-synthesized catalysts was assessed through the photodegradation of methylene blue (MB) and methyl orange (MO) dyes at an initial concentration (100 mg/L). Under simulated solar irradiation, improved photocatalytic performance was accomplished by as-obtained CoFe2O4@UiO-66 heterojunction compared to bare UiO-66 and CoFe2O4. The overall removal efficiency of dyes (100 mg/L) over CoFe2O4@UiO-66 (50 mg/L) reached >60% within 180 min. The optical and photoelectrochemical measurements showed an enhanced visible light absorption capacity as well as effective interfacial charge separation and transfer over CoFe2O4@UiO-66, emphasizing the successful construction of heterojunction. The degradation mechanism was further explored, which revealed the contribution of holes (h+), superoxide (•O2 -), and hydroxyl (•OH) radicals in the degradation process, however, h+ were the predominant reactive species. This work might open up new insights for designing MOF-based core-shell heterostructured photocatalysts for the remediation of industrial organic pollutants.

Enhanced synchronous photocatalytic 4-chlorophenol degradation and Cr(VI) reduction by novel magnetic separable visible-light-driven Z-scheme CoFe2O4/P-doped BiOBr heterojunction nanocomposites

The co-existence of organic contaminants and heavy metals including 4-chlorophenol (4-CP) and Cr(VI) in aquatic system have become a challenging task in the wastewater treatment. Herein, the synchronous photocatalytic decomposition of 4-CP and Cr(VI) over new Z-scheme CoFe₂O₄/P-BiOBr heterojunction nanocomposites were revealed. In this work, the nanocomposites were successfully developed via a surfactant-free hydrothermal method. The heterojunction interface was created by decorating magnetic CoFe₂O₄ nanoparticles onto P-BiOBr nanosheets. The as-fabricated CoFe₂O₄/P-BiOBr nanocomposites substantially improved the synchronous decomposition of 4-CP and Cr(VI) compared to the single-phase component samples under visible light irradiation. Particularly, the 30-CoFe₂O₄/P-BiOBr nanocomposite displayed the best photocatalytic performance, which decomposed 95.6% 4-CP and 100% Cr(VI) within 75 min. The photocatalytic improvement was assigned to the Z-scheme heterojunction assisted charge migration between CoFe₂O₄ and P-BiOBr, and the acceleration of charge carrier separation was validated by the findings of charge dynamics measurements. The harmful 4-CP was photodegraded into smaller organics whereas the Cr(VI) was photoreduced into Cr(III) after 30-CoFe₂O₄/P-BiOBr photocatalysis, and the good recyclability of fabricated nanocomposite in photocatalytic reaction also showed promising potential for practical applications in environmental remediation. Finally, the radical quenching tests confirmed that there existed the Z-scheme path of charge migration in CoFe₂O₄/P-BiOBr nanocomposite, which was the mechanism responsible for its high photoactivity.

Immobilization of bismuth oxychloride on cellulose nanocrystal for sunlight-driven superior photosensitized degradation

Semiconductor photocatalysis is considered to be an important green technology for sewage treatment. However, most of the pollutant degradation studies used simulated sunlight in a laboratory, which has great energy cost with limited applications in industry. Herein, cellulose nanocrystal (CNC) with rich hydroxyl groups and high specific surface area are used as the matrix to construct composites with BiOCl, which improves the dispersibility with an increased number of oxygen vacancies on BiOCl. The obtained composite photocatalyst, i.e., BiOCl/CNC, showed an excellent performance with good recyclability. Within 30 min, 99% of RhB (20 mg/L) was degraded under simulated visible light and 94% under natural sunlight. The reaction system maintains excellent catalytic performance after being scaled up by 10×. Compared with reported BiOCl-based composites in literature, BiOCl/CNC had excellent photocatalytic activity for the RhB degradation with good recyclability. Subsequently, by identifying the active species, a reasonable photocatalytic mechanism was proposed for RhB degradation. This work developed an economical and effective visible light sensitive photocatalyst for the treatment of organic dyes in water.

A comprehensive study on the heterogeneous electro-Fenton degradation of tartrazine in water using CoFe2O4/carbon felt cathode

In this study, cobalt ferrite coated carbon felt (CoFe₂O₄/CF) was synthesized by solvothermal method and applied as cathode for electro-Fenton (EF) treatment of tartrazine (TTZ) in water. The materials were characterized by SEM, XRD, FTIR, CV, and EIS to explore their physical, chemical, and electrical properties. The effects of solvothermal temperature and metal content on the TTZ removal were examined, showing that 220 °C with 2 mM of Co and 4 mM of Fe precursors were the best synthesis condition. Various influencing factors such as applied current density, pH, TTZ concentration, and electrolytes were investigated, and the optimal condition was found at 8.33 mA cm^-2, pH 3, 50 mgTTZ L^-1, and 50 mM of Na₂SO₄, respectively. By radical quenching test, , ¹O₂, and HO were recognized as the key reactive oxygen species and the reaction mechanism was proposed for the EF decolorization of TTZ using CoFe₂O₄/CF cathode. The reusability and stability test showed that the highly efficient CoFe₂O₄/CF cathode is very promising for practical application in wastewater treatment, especially for dyes and other recalcitrant organic compounds to improve its biodegradability.

Highly improved supercapacitance properties of MnFe2O4 nanoparticles by MoS2 nanosheets

Manganese ferrite (MnFe₂O₄) nanoparticles were synthesized via a hydrothermal method and combined with exfoliated MoS₂ nanosheets, and the nanocomposite was studied as a supercapacitor. X-ray diffractometry and Raman spectroscopy confirmed the crystalline structures and structural characteristics of the nanocomposite. Transmission electron microscopy images showed the uniform size distribution of MnFe₂O₄ nanoparticles (~ 13 nm) on few-layer MoS₂ nanosheets. UV-visible absorption photospectrometry indicated a decrease in the bandgap of MnFe₂O₄ by MoS₂, resulting in a higher conductivity that is suitable for capacitance. Electrochemical tests showed that the incorporation of MoS₂ nanosheets largely increased the specific capacitance of MnFe₂O₄ from 600 to 2093 F/g (with the corresponding energy density and power density of 46.51 Wh/kg and 213.64 W/kg, respectively) at 1 A/g, and led to better charge-discharge cycling stability. We also demonstrated a real-world application of the MnFe₂O₄/MoS₂ nanocomposite in a two-cell asymmetric supercapacitor setup. A density functional theory study was also performed on the MnFe₂O₄/MoS₂ interface to analyze how a MoS₂ monolayer can enhance the electronic properties of MnFe₂O₄ towards a higher specific capacitance.

Nanozyme based on CoFe2O4 modified with MoS2 for colorimetric determination of cysteine and glutathione

A nanozyme based on CoFe₂O₄ modified with MoS₂ was constructed for colorimetric determination of cysteine (Cys) and glutathione (GSH). Firstly, ferrite CoFe₂O₄ is synthesized, and it is then modified by MoS₂ to form a flower-like polymer (MoS₂@CoFe₂O₄). In the presence of H₂O₂, a redox interaction takes place, and the resulting hydroxyl promoted a colorimetric conversion from colorless to blue in the presence of 3,3',5,5'-tetramethylbenzidine (TMB). However, once Cys or GSH is added, they are capable to compete with the interaction of the hydroxyl with TMB, resulting in an inhibition of the colorimetric conversion. The colorimetric distinction is sensitive to the amount of target. The results obtained proved that the catalytic efficiency of MoS₂@CoFe₂O₄ is 4.4-fold and 1.8-fold to that of MoS₂ and CoFe₂O₄. Meanwhile, the K_m values to TMB and H₂O₂ are 0.067 and 0.048 mM, respectively, which are 6.5-fold and 77-fold, respectively smaller than those of natural peroxidase such as HPR. This indicates that the MoS₂@CoFe₂O₄ possesses a favorable interaction affinity. Additionally, the colorimetric distinction caused by the competition between TMB and cysteine or glutathione is obvious. The signal responses to cysteine and glutathione are linear in the range 0.5~15 μM and 0.5~35 μM, and the LODs are 0.10 and 0.21 μM, respectively. In practical assay of Cys in serum, the RSD of the sample tests is 4.6%, and the recoveries for the spiked assays are 95.3% and 96.0% with the RSD of 2.1% and 4.2%, respectively.

Hybridized 2D Nanomaterials Toward Highly Efficient Photocatalysis for Degrading Pollutants: Current Status and Future Perspectives

Organic pollutants including industrial dyes and chemicals and agricultural waste have become a major environmental issue in recent years. As an alternative to simple adsorption, photocatalytic decontamination is an efficient and energy-saving technology to eliminate these pollutants from water environment, utilizing the energy of external light, and unique function of photocatalysts. Having a large specific surface area, numerous active sites, and varied band structures, 2D nanosheets have exhibited promising applications as an efficient photocatalyst for degrading organic pollutants, particularly hybridization with other functional components. The novel hybridization of 2D nanomaterials with various functional species is summarized systematically with emphasis on their enhanced photocatalytic activities and outstanding performances in environmental remediation. First, the mechanism of photocatalytic degradation is given for discussing the advantages/shortcomings of regular 2D materials and identifying the importance of constructing hybrid 2D photocatalysts. An overview of several types of intensively investigated 2D nanomaterials (i.e., graphene, g-C₃ N₄ , MoS₂ , WO₃ , Bi₂ O₃ , and BiOX) is then given to indicate their hybridized methodologies, synergistic effect, and improved applications in decontamination of organic dyes and other pollutants. Finally, future research directions are rationally suggested based on the current challenges.

Bifunctional reusable Co0.5Ni0.5Fe2O4 nanoparticle-grafted carbon nanotubes for aqueous dye removal from contaminated water

Highly stable and reusable CNF-grafted CNTs for efficient and effective aqueous dye removal from contaminated waters.

Selective oxidation of alcohols by using CoFe2O4/Ag2MoO4 as a visible-light-driven heterogeneous photocatalyst

Using a CoFe₂O₄/Ag₂MoO₄ heterostructure as a novel, stable, inexpensive, and reusable photocatalyst with high-performance for the oxidation of alcohols.

Spinel ferrite (AFe2O4)-based heterostructured designs for lithium-ion battery, environmental monitoring, and biomedical applications

The development of spinel ferrite nanomaterial (SFN)-based hybrid architectures has become more popular owing to the fascinating physicochemical properties of SFNs, such as their good electro-optical and catalytic properties, high chemothermal stability, ease of functionalization, and superparamagnetic behaviour. Furthermore, achieving the perfect combination of SFNs and different nanomaterials has promised to open up many unique synergistic effects and advantages. Inspired by the above-mentioned noteworthy properties, numerous and varied applications have been recently developed, such as energy storage in lithium-ion batteries, environmental pollutant monitoring, and, especially, biomedical applications. In this review, recent development efforts relating to SFN-based hybrid designs are described in detail and logically, classified according to 4 major hybrid structures: SFNs/carbonaceous nanomaterials; SFNs/metal–metal oxides; SFNs/MS₂; and SFNs/other materials. The underlying advantages of the additional interactions and combinations of effects, compared to the standalone components, and the potential uses have been analyzed and assessed for each hybrid structure in relation to lithium-ion battery, environmental, and biomedical applications.

We have summarized recent developments in SFN-based hybrid designs. The additional interactions, combination effects, and important changes have been analyzed and assessed for LIB, environmental monitoring, and biomedical applications.

Trace Amount CoFe2O4 Anchored on a TiO2 Photocatalyst Efficiently Catalyzing O2 Reduction and Phenol Oxidation

Semiconducting TiO₂ is the most studied photocatalyst for organic oxidation by O₂. To accelerate the reaction, a cocatalyst for O₂ reduction or for organic oxidation is often used, but the bifunctional one is rare. Herein we report a spinel CoFe₂O₄ (CF) efficiently catalyzing O₂ reduction and phenol oxidation on TiO₂ in aqueous suspensions at pH 3-11. The composite materials (CF/TiO₂) were made by depositing 0-5 wt % CF onto TiO₂ through a hydrothermal method. Solid characterization showed that CF nanoparticles (5 nm) homogeneously distributed in CF/TiO₂, whereas the TiO₂ phase remained unchanged in crystal structure and crystallite size. For phenol oxidation under UV light, CF was nearly not active, but 0.01 wt % CF/TiO₂ was more active than TiO₂, by approximately a factor of 3.6. Such trend in activity among the catalysts was also observed from the photocatalytic reduction of O₂ to H₂O₂, from the electrochemical reduction of O₂, and from the photoelectrochemical oxidation of phenol and H₂O. An open-circuit potential and photoluminescence measurement suggest that there is an interfacial electron transfer from TiO₂ to CF, followed by O₂ reduction. Accordingly, a possible mechanism is proposed, involving CF catalysis for O₂ reduction and phenol oxidation. Then the mutual promotion between electron and hole transfer results in great enhancement in the efficiency of charge separation and hence in the rate of chemical reaction. Because spinel compounds have rich composition and unique structures, they are worthy of being further investigated as cocatalysts of a semiconductor photocatalysis.

Degradation of bisphenol a using peroxymonosulfate activated by WO3@MoS2/Ag hollow nanotubes photocatalyst

WO₃@MoS₂/Ag (HW@MA) hollow tubes were successfully engineered to photodegrade bisphenol A (BPA) combined with peroxymonosulfate (PMS) for the first time. XRD, XPS, TEM and SEM were conducted. The HW@MA tubes present excellent photocatalytic performance on the removal of BPA. The intermediate products of BPA were investigated by GC-MS analysis and the degradation pathway was proposed. To explore the transferred mechanism of photoproduced carriers, the electron paramagnetic resonance (EPR) technique was carried out. The results revealed that the superoxide radical (O₂^-), hydroxyl radical (OH), sulfate radical (SO₄^-) were the main active radicals. Moreover, the formed schottky junctions enhanced the separation efficiency of photoinduced electron-hole pairs. Besides, the effect of the photocatalysts' dosage, PMS concentration, pH of the initial solution and co-existing anions on the BPA degradation were investigated.

Enhanced Photocatalytic Activities of RhB Degradation and H2 Evolution from in Situ Formation of the Electrostatic Heterostructure MoS2/NiFe LDH Nanocomposite through the Z-Scheme Mechanism via p-n Heterojunctions

Designing of an efficient heterostructure photocatalyst for photocatalytic organic pollutant removal and H₂ production has been a subject of rigorous research intended to solve the related environmental aggravation and enormous energy crises. Z-scheme-based charge-transfer dynamics in a p-n heterostructure could significantly replicate the inherent power of natural photosynthesis, which is the key point to affect the transportation of photoinduced exciton pairs. In this finding, a series of p-type MoS₂ loaded with n-type NiFe-layered double hydroxide (LDH) forming a heterostructure MoS₂/NiFe LDH were designed by electrostatic self-assembled chemistry and an in situ hydrothermal strategy for photocatalytic rhodamine B (RhB) dye degradation and H₂ production. The creation of p-n heterojunctions of type-II and Z-scheme mode of charge transfer modified the optical and electronic property of the as-synthesized MSLDH3, thereafter promoting the generation, separation, and migration of photoinduced electron-hole pairs. The as-synthesized MSLDH3 showed superior photocatalytic activities in degradation of RhB with H₂ evolution, which was enhanced by 3- and 4.5-fold and 10.9 and 19.2 times higher than that of NiFe LDH and MoS₂, respectively. Last but not the least, heterostructure MSLDH3 possesses practical stability for its resultant enhanced photocatalytic activity with recyclability for everyday life.

Research on the sustainable efficacy of g-MoS2 decorated biochar nanocomposites for removing tetracycline hydrochloride from antibiotic-polluted aqueous solution

Antibiotic concentrations in surface waters far exceed the pollution limit due to the abuse of pharmaceuticals, resulting in an urgent need for an approach with potential efficiency, sustainability and eco-friendliness to remove antibiotic pollutants. A novel biochar-based nanomaterial was synthesized by hydrothermal synthesis and was investigated for its removal potential for tetracycline hydrochloride (TC) from both artificial and real wastewater. The associative facilitation between biochar and g-MoS₂ nanosheets was proposed, revealing the favorable surface structures and adsorption properties of the composite. The related adsorption kinetics, isotherms and thermodynamics were studied by several models with adsorption experimental data, turning out that biochar decorated by g-MoS₂ exhibited optimum TC removal with adsorption capacity up to 249.45 mg/g at 298 K. The adsorption behavior of TC molecules on g-MoS₂-BC can be interpreted well by three-step process, and it is dominated by several mechanisms containing pore-filling, electrostatic force, hydrogen bond and π-π interaction. In addition, the cost-effective g-MoS₂-BC nanocomposites demonstrated excellent adsorption and recycling performance in TC-contaminated river water, which might provide the underlying insights needed to guide the design of promising approach for contaminant removal on a large scale in practical application.

Two-dimensional MoS2 modified using CoFe2O4 nanoparticles with enhanced microwave response in the X and Ku band

A novel MoS₂/CoFe₂O₄ two-dimensional composite was designed, which showed ideal impedance matching and enhanced interface polarization.

Fabrication of MoS2/TiO2 heterostructures with enhanced photocatalytic activity

Two-dimensional nanophotocatalysts MoS₂/TiO₂ with a tunable decoration amount of MoS₂ nanosheets were fabricated through a hydrothermal route.