Unique Redox Research Articles

FcCe-MOF-NH2-based colorimetric and fluorometric dual-mode detection of sulfide ions

Sulfide ions, commonly present as toxic anions in industrial processes, require the creation of a convenient and reliable detection platform. In this study, we developed a dual-mode colorimetric and fluorometric method to detect sulfide ions using the cerium-ferrocene bimetal-organic framework (MOF), i.e., FcCe-MOF-NH2, which was synthesized by a common solvo-thermal approach. The FcCe-MOF-NH2 promises the peroxidase-like activity and blue emission peaked at 453 nm. In the presence of H2O2, the FcCe-MOF-NH2 catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation, yielding the blue oxidized product (oxTMB), while the fluorescence peak at 453 nm was suppressed due to the inner filter effect (IFE). The Km values of FcCe-MOF-NH2 for TMB and H2O2 were 0.099 mM and 0.179 mM, respectively, showing its good affinity with the substrates. Due to a unique redox reaction between H2O2 and S2−, the peroxidase-like activity of FcCe-MOF-NH2 was markedly suppressed, leading to fluorescence restoration. Hence, the colorimetric and fluorometric dual-mode detection of S2− was realized, exhibiting a linear range of 0.5–100 μM and 0.2–60 μM with a detection limit of 0.43 μM and 0.078 μM, respectively. The developed platform was successfully applied to the detection of S2− in actual water samples.

Protein-Labeling Reagents Selectively Activated by Copper(I).

Copper is an essential trace element that participates in many biological processes through its unique redox cycling between cuprous (Cu+) and cupric (Cu2+) oxidation states. To elucidate the biological functions of copper, chemical biology tools that enable selective visualization and detection of copper ions and proteins in copper-rich environments are required. Herein, we describe the design of Cu+-responsive reagents based on a conditional protein labeling strategy. Upon binding Cu+, the probes generated quinone methide via oxidative bond cleavage, which allowed covalent labeling of surrounding proteins with high Cu+ selectivity. Using gel- and imaging-based analyses, the best-performing probe successfully detected changes in the concentration of labile Cu+ in living cells. Moreover, conditional proteomics analysis suggested intramitochondrial Cu+ accumulation in cells undergoing cuproptosis. Our results highlight the power of Cu+-responsive protein labeling in providing insights into the molecular mechanisms of Cu+ metabolism and homeostasis.

Targeting Trypanothione Metabolism in Trypanosomatids.

Infectious diseases caused by trypanosomatids, including African trypanosomiasis (sleeping sickness), Chagas disease, and different forms of leishmaniasis, are Neglected Tropical Diseases affecting millions of people worldwide, mainly in vulnerable territories of tropical and subtropical areas. In general, current treatments against these diseases are old-fashioned, showing adverse effects and loss of efficacy due to misuse or overuse, thus leading to the emergence of resistance. For these reasons, searching for new antitrypanosomatid drugs has become an urgent necessity, and different metabolic pathways have been studied as potential drug targets against these parasites. Considering that trypanosomatids possess a unique redox pathway based on the trypanothione molecule absent in the mammalian host, the key enzymes involved in trypanothione metabolism, trypanothione reductase and trypanothione synthetase, have been studied in detail as druggable targets. In this review, we summarize some of the recent findings on the molecules inhibiting these two essential enzymes for Trypanosoma and Leishmania viability.

Regulating the Electron Distribution of Metal-Oxygen for Enhanced Oxygen Stability in Li-rich Layered Cathodes.

Li-rich Mn-based layered oxides (LLO) hold great promise as cathode materials for lithium-ion batteries (LIBs) due to their unique oxygen redox (OR)chemistry, which enables additional capacity. However, the LLOs face challenges related to the instability of their ORprocess due to the weak transition metal (TM)-oxygen bond, leading to oxygen loss and irreversible phase transition that results in severe capacity and voltage decay. Herein, a synergistic electronic regulation strategy of surface and interior structures to enhance oxygen stability is proposed. In the interior of the materials, the local electrons around TM and O atoms may be delocalized by surrounding Mo atoms, facilitating the formation of stronger TM─O bonds at high voltages. Besides, on the surface, the highly reactive O atoms with lone pairs of electrons are passivated by additional TM atoms, which provides a more stable TM─O framework. Hence, this strategy stabilizes the oxygen and hinders TM migration, which enhances the reversibility in structural evolution, leading to increased capacity and voltage retention. This work presents an efficient approach to enhance the performance of LLOs through surface-to-interior electronic structure modulation, while also contributing to a deeper understanding of their redox reaction.

Phosphorus-Ligand Redox Cooperative Catalysis: Unraveling Four-Electron Dioxygen Reduction Pathways and Reactive Intermediates.

The reduction of dioxygen to water is crucial in biology and energy technologies, but it is challenging due to the inertness of triplet oxygen and complex mechanisms. Nature leverages high-spin transition metal complexes for this, whereas main-group compounds with their singlet state and limited redox capabilities exhibit subdued reactivity. We present a novel phosphorus complex capable of four-electron dioxygen reduction, facilitated by unique phosphorus-ligand redox cooperativity. Spectroscopic and computational investigations attribute this cooperative reactivity to the unique electronic structure arising from the geometry of the phosphorus complex bestowed by the ligand. Mechanistic study via spectroscopic and kinetic experiments revealed the involvement of elusive phosphorus intermediates resembling those in metalloenzymes. Our result highlights the multielectron reactivity of phosphorus compound emerging from a carefully designed ligand platform with redox cooperativity. We anticipate that the work described expands the strategies in developing main-group catalytic reactions, especially in small molecule fixations demanding multielectron redox processes.

Spontaneous Degradation of the "Forever Chemicals" Perfluoroalkyl and Polyfluoroalkyl Substances (PFASs) on Water Droplet Surfaces.

Because of their innate chemical stability, the ubiquitous perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been dubbed "forever chemicals" and have attracted considerable attention. However, their stability under environmental conditions has not been widely verified. Herein, perfluorooctanoic acid (PFOA), a widely used and detected PFAS, was found to be spontaneously degraded in aqueous microdroplets under room temperature and atmospheric pressure conditions. This unexpected fast degradation occurred via a unique multicycle redox reaction of PFOA with interfacial reactive species on the droplet surface. Similar degradation was observed for other PFASs. This study extends the current understanding of the environmental fate and chemistry of PFASs and provides insight into aid in the development of effective methods for removing PFASs.

Deciphering the Role of Nickel in Electrochemical Organic Oxidation Reactions

AbstractOrganic oxidation reactions (OORs) powered by renewable energy sources are gaining importance as a favorable alternative to oxygen evolution reaction, with the promise of reducing the cell potential and enhancing the overall viability of the water electrolysis. This comprehensive review delves into the electrochemical oxidation of diverse organic compounds, including alcohols, aldehydes, amines, and urea, as well as biomass‐derived renewable feedstocks such as hydroxymethylfurfural and glycerol. The key focus centers on the role of nickel (Ni)‐based catalysts for these OORs. The unique redox activity and chemical nature of Ni have been proven instrumental for the sustainable and cost‐effective oxidation of various organic molecules more efficiently and selectively. This review article discusses how strategic choices, such as the selection of foreign metals, intercalating species, vacancies, defects, and a secondary element (e.g. chalcogens and non‐metals), contribute to tuning the electrochemical performances of a Ni‐based (pre)catalyst for OORs. Moreover, this review provides insights into the active species in various reaction environments and further explores reaction mechanisms, to apparent phase changes of the catalyst with the most relevant examples. Finally, the review not only elucidates the limitations of the current approaches but also outlines potential avenues for future advancements in OOR.

Unveiling Phenoxazine's Unique Reversible Two-Electron Transfer Process and Stable Redox Intermediates for High-Performance Aqueous Zinc-ion Batteries.

The low specific capacity determined by the limited electron transfer of p-type cathode materials is the main obstruction to their application towards high-performance aqueous zinc-ion batteries (ZIBs). To overcome this challenge, boosting multi-electron transfer is essential for improving the charge storage capacity. Here, as a typical heteroaromatic p-type material, we unveil the unique reversible two-electron redox properties of phenoxazine in the aqueous electrolytes for the first time. The second oxidation process is stabilized in the aqueous electrolytes, a notable contrast to its less reversibility in the non-aqueous electrolytes. A comprehensive investigation of the redox chemistry mechanism demonstrates remarkably stable redox intermediates, including a stable cation radical PNO⋅+ characterized by effective electron delocalization and a closed-shell state dication PNO2+. Meanwhile, the heightened aromaticity contributes to superior structural stability during the redox process, distinguishing it from phenazine, which features a non-equivalent hybridized sp2-N motif. Leveraging these synergistic advantages, the PNO electrodes deliver a high capacity of 215 mAh g-1 compared to other p-type materials, and impressive long cycling stability with 100 % capacity retention over 3500 cycles. This work marks a crucial step forward in advanced organic electrodes based on multi-electron transfer phenoxazine moieties for high-performance aqueous ZIBs.

A Cu2+ fluorescent chemosensor suitable for quantitative detection of tyrosinase in potatoes over a wide pH range.

Cu2+ as an important trace element plays an essential role in various biologic processes due to the unique redox active nature. For this reason, much effort has been made to develop effective methods for Cu2+ detection. In this study, a novel structure fluorescent chemosensor, 1-(6-(((5-(5, 5-difluoro-1, 3, 7, 9-tetramethyl-5H-4λ4, 5λ4-dipyrrolo[1, 2-c:2', 1'-f][1, 3, 2] diazaborinin-10-yl)quinolin-8-yl)oxy)methyl)pyridin-2-yl)-N, N-bis(pyridin-2-ylmethyl)methanamine (1), was synthesized and characterized by 1H and 13C nuclear magnetic resonance spectroscopy, and electrospray ionization mass spectrometry. Sensor 1 showed an obviously "on-off" fluorescence response to Cu2+ with a 1:1 binding stoichiometry by UV-vis and fluorescence spectrophotometry. The detection limit of sensor 1 to Cu2+ was determined to be 1.9µM, and the stable pH range for Cu2+ detection was from 3 to 13. Sensor 1 can be used for recognition and detection of tyrosinase in potatoes.

New type of tri‐pyridyl inhibitor‐loaded polyaniline nanospheres for durable protection anticorrosion coatings

AbstractPolyaniline (PANI) is considered as one of the most promising corrosion inhibitors because of its unique redox and environmental stability. Pyridine and its derivatives can chelate metal ions during corrosion, forming an inert protective layer on the metal surface to achieve the anticorrosion effect. Therefore, polyaniline is combined with pyridine together to achieve deep anticorrosion in this work. 4‐((2,2′:6′,2″‐terpyridin)‐4′‐yl)aniline (TPY) and 1,3,5‐benzenetricarbonyl chloride (TMC) were applied to synthesize a novel corrosion inhibitor N1, N3, N5‐tri (4‐((2,2′: 6′, 2′‐tri‐pyridine)‐4′‐yl) phenyl) benzene‐1,3,5‐tri‐formamide (TBT). Then, TBT was in situ loaded onto the PANI surface to obtain the composite TPANI. The TPANI was successfully dispersed in epoxy resin (EP) at various dosages to prepare composite coatings. Electrochemical impedance spectroscopy and salt fog tests were employed to evaluate the performance of the coatings. After experimentation, we discovered that when the TPANI content was 0.25 wt%, the impedance value remained stable at 5.83 × 109 Ω cm2 after immersing the coatings in a 3.5 wt% NaCl solution for 28 days. In contrast, the EP coating exhibited a resistance decrease ranging from 9.56 × 109 to 7.8 × 108 Ω cm2 within the same soaking time, decreasing by an order of magnitude, while the TPANI‐0.25% coating still maintaining a high order of magnitude. These results indicated that the TPANI filler effectively preserved long‐term stability and provided persistent protection against corrosion. The protective mechanism of TPANI composite coatings was further elucidated through detailed analysis. Overall, the incorporation of TPANI into the epoxy resin yielded promising results, demonstrating its potential as an effective corrosion inhibitor for protective coatings.

Bioinspired polyoxometalates as light-driven water oxidation catalysts

The design of molecular systems with capabilities to carry out the water oxidation reaction and thereby overcome the bottleneck of artificial photosynthesis is one of the scientific fields of most significant interest and urgency due to its potential to address energy demand and climate change. Nevertheless, the search for efficient and robust catalysts has been limited by the degradation of carbon-based ligands under oxidative conditions, leading to the search for fully inorganic catalysts. Polyoxometalates (POMs), an emerging class of carbon-free ligands with oxygen-enriched surfaces, offer a unique alternative as inorganic scaffolds to self-assemble and stabilize transition-metal clusters with unique redox properties. Under catalytic working conditions, POMs can undergo electron transfer reactions coupled to O2 formation without modifying their parental structure. As a result, these materials have recently entered the scene as catalytic players in designing new artificial photosynthetic platforms for water oxidation. We focus on the methods used to create these compounds, their unique structural characteristics, and how effectively they function as catalysts. We also explore the proposed mechanisms behind their ability to produce O2 and their potential use in designing photosynthetic devices.

Exploring the potency of EDTA-based Ni-Co-MOF nanospheres for highly durable battery-supercapacitor hybrids

Metal Organic Frameworks (MOFs) have emerged as a captivating avenue and advancement in electrode materials, revealing remarkable progress in diverse electrochemical applications. However, despite their apparent potential the persistent hurdles related to specific capacity, degradation in specific energy and power, and reproducibility of results emphasized the demand for focused investigation. This study is objectized to improve the storage capability, stability, and replicability of electrochemical outcomes in a MOF-based battery-supercapacitor hybrid system. To achieve the quest Ethylenediaminetetraacetic acid (EDTA) based Ni-Co-MOF nanospheres were synthesized via hydrothermal route. The bimetallic MOF demonstrates unique redox behavior with a specific capacity of 474.56 C/g at a current density of 1 A/g. Simulating the experimental analysis, it was confirmed that the MOF material exhibits a dominant battery-like nature, with 94.68 % diffusion attributes at a scan rate of 3 mV/s. Integrating nanospheres MOF into an asymmetric hybrid architecture, serving as the positive electrode material, exceptional specific energy and power characteristics reaching 72.58 Wh/kg and 8500 W/kg respectively. Moreover, the MOF-based hybrid configuration demonstrated remarkable cycle stability, retaining 93.2 % of its capacity after undergoing 10,000 charge discharge cycles. Notably, the hybrid device exhibited excellent reproducibility, with a specific energy output of 71.43 Wh/kg after 40 days and 70.33 Wh/kg after 80 days under standard environmental conditions. Additionally, the simulation approach results indicated that the battery-supercapacitor hybrid device exhibited a diffusion dominance of 76.42 % at a scan rate of 30 mV/s and a capacitive contribution of 61.66 % at 100 mV/s. These promising findings underscore the potential of Ni-Co-MOF-based hybrid configuration as a strong entrant for practical applications in efficient energy storage systems.

Transition‐metal Substituted Polyoxometalates as Soluble RedOx Mediators in Electrocatalytic Biomass Conversion

AbstractPolyoxometalates (POMs) are known for their unique redox properties, making them interesting candidates as redox mediators in electro‐organic transformations. We investigated derivatives of H3[PMo12O40], a classical Keggin‐type POM, as a potential redox mediator in the indirect electrolysis of biobased glyceraldehyde (GLAD), focusing on the effects of double substitution of the Mo framework metal by redox active transition metals (Mo replaced by V, Ni, Co, Mn). By combining electrochemical techniques with HPLC, UV‐Vis spectroscopy, and 31P‐NMR spectroscopy, a comprehensive overview of the reaction pathways, as well as the electronic and structural changes of the POM during the reaction were revealed. This work not only contributes to the fundamental understanding of POMs as redox mediators, but also paves the way for innovative development of sustainable and environmentally friendly electro‐organic transformations.

Observations regarding the synthesis and redox chemistry of heterobimetallic uranyl complexes containing Group 10 metals

Abstract Literature reports have demonstrated that Schiff-base-type ligands can serve as robust platforms for the synthesis of heterobimetallic complexes containing transition metals and the uranyl dication (UO2 2+). However, efforts have not advanced to include either synthesis of complexes containing second- or third-row transition metals or measurement of the redox properties of the corresponding heterobimetallic complexes, despite the significance of actinide redox in studies of nuclear fuel reprocessing and separations. Here, metalloligands denoted [Ni], [Pd], and [Pt] that contain the corresponding Group 10 metals have been prepared and a synthetic strategy to access species incorporating the uranyl ion (UO2 2+) has been explored, toward the goal of understanding how the secondary metals could tune uranium-centered redox chemistry. The synthesis and redox characterization of the bimetallic complex [Ni,UO2] was achieved, and factors that appear to govern extension of the chosen synthetic strategy to complexes with Pd and Pt are reported here. Infrared and solid-state structural data from X-ray diffraction analysis of the metalloligands [Pd] and [Pt] show that the metal centers in these complexes adopt the expected square planar geometries, while the structure of the bimetallic [Ni,UO2] reveals that the uranyl moiety influences the coordination environment of Ni(II), including inducement of a puckering of the ligand backbone of the complex in which the phenyl rings fold around the nickel-containing core in an umbrella-shaped fashion. Cyclic voltammetric data collected on the heterobimetallic complexes of both Ni(II) and Pd(II) provide evidence for uranium-centered redox cycling, as well as for the accessibility of other reductions that could be associated with Ni(II) or the organic ligand backbone. Taken together, these results highlight the unique redox behaviors that can be observed in multimetallic systems and design concepts that could be useful for accessing tunable multimetallic complexes containing the uranyl dication.

Single-Site Nanozymes with a Highly Conjugated Coordination Structure for Antitumor Immunotherapy via Cuproptosis and Cascade-Enhanced T Lymphocyte Activity.

The extracellular matrix (ECM) in the tumor microenvironment (TME) and upregulated immune checkpoints (ICs) on antitumor immune cells impede the infiltration and killing effect of T cells, creating an immunosuppressive TME. Herein, a cholesterol oxidase (CHO) and lysyl oxidase inhibitor (LOX-IN-3) co-delivery copper-dibenzo-[g,p]chrysene-2,3,6,7,10,11,14,15-octaol single-site nanozyme (Cu-DBCO/CL) was developed. The conjugated organic ligand and well-distributed Cu-O4 sites endow Cu-DBCO with unique redox capabilities, enabling it to catalyze O2 and H2O2 to ·O2- and ·OH. This surge of reactive oxygen species (ROS) leads to impaired mitochondrial function and insufficient ATP supply, impacting the function of copper-transporting ATPase-1 and causing dihydrolipoamide S-acetyltransferase oligomerization-mediated cuproptosis. Moreover, multiple ROS storms and glutathione peroxidase 4 depletion also induce lipid peroxidation and trigger ferroptosis. Simultaneously, the ROS-triggered release of LOX-IN-3 reshapes the ECM by inhibiting lysyl oxidase activity and further enhances the infiltration of cytotoxic T lymphocytes (CD8+ T cells). CHO-triggered cholesterol depletion not only increases ·OH generation but also downregulates the expression of ICs such as PD-1 and TIM-3, restoring the antitumor activity of tumor-infiltrating CD8+ T cells. Therefore, Cu-DBCO/CL exhibits efficient properties in activating a potent antitumor immune response by cascade-enhanced CD8+ T cell viability. More importantly, ECM remodeling and cholesterol depletion could suppress the metastasis and proliferation of the tumor cells. In short, this immune nanoremodeler can greatly enhance the infiltration and antitumor activity of T cells by enhancing tumor immunogenicity, remodeling ECM, and downregulating ICs, thus achieving effective inhibition of tumor growth and metastasis.

Se-Glargine: Chemical Synthesis of a Basal Insulin Analogue Stabilized by an Internal Diselenide Bridge.

Insulin has long provided a model for studies of protein folding and stability, enabling enhanced treatment of diabetes mellitus via analogue design. We describe the chemical synthesis of a basal insulin analogue stabilized by substitution of an internal cystine (A6-A11) by a diselenide bridge. The studies focused on insulin glargine (formulated as Lantus® and Toujeo®; Sanofi). Prepared at pH 4 in the presence of zinc ions, glargine exhibits a shifted isoelectric point due to a basic B chain extension (ArgB31 -ArgB32 ). Subcutaneous injection leads to pH-dependent precipitation of a long-lived depot. Pairwise substitution of CysA6 and CysA11 by selenocysteine was effected by solid-phase peptide synthesis; the modified A chain also contained substitution of AsnA21 by Gly, circumventing acid-catalyzed deamidation. Although chain combination of native glargine yielded negligible product, in accordance with previous synthetic studies, the pairwise selenocysteine substitution partially rescued this reaction: substantial product was obtained through repeated combination, yielding a stabilized insulin analogue. This strategy thus exploited both (a) the unique redox properties of selenocysteine in protein folding and (b) favorable packing of an internal diselenide bridge in the native state, once achieved. Such rational optimization of protein folding and stability may be generalizable to diverse disulfide-stabilized proteins of therapeutic interest.

Phenyl Tellurosulfides as Cathode Materials for Rechargeable Lithium Batteries.

Phenyl ditelluride (PDTe) as a cathode material for rechargeable batteries has a low specific capacity (130.9 mAh g-1) due to limited active sites (two). To increase its capacity, additional active species need to be added to the structure of PDTe, like sulfur. Here, phenyl tellurosulfide (PDTeS) and phenyl tellurodisulfide (PDTeS2) can be formed via addition reactions and have specific capacities of 242.8 and 339.6 mAh g-1, respectively. The products are characterized by mass spectrometry and Raman spectroscopy. The Li/PDTeSn (n = 1-2) cells exhibit high material utilization (>85%) and unique redox mechanism. They can be cycled stably for more than 1000 cycles at an areal mass loading of 1.1 mg cm-2 and maintain capacity retentions of >72% after 100 cycles with PDTeSn loading of ∼6 mg cm-2. Moreover, the Li/PDTeS2 cell achieves a specific energy of up to 695 Wh kg-1 even when the electrolyte/PDTeS2 ratio is as low as 2.5 μL mg-1. The successful synthesis and application of PDTeSn prove that they are promising cathode materials for rechargeable lithium batteries.

Controllable Synthesis of Flower-like Hierarchical CuCo2S4 Nanostructure Arrays for High-Performance Hybrid Supercapacitors

Transition metal sulfides (TMSs) are considered as attractive materials in the areas of energy storage because of their unique redox properties, excellent electronic conductivity, as well as environmental friendliness. However, poor cyclic stability and limited electrochemical active sites hinder their further application. To address this issue, a flower-like hierarchical CuCo2S4 structure is constructed by a two-step hydrothermal method. In this nanostructure, CuCo2S4 grows outward to form a tightly bound hierarchical structure on the nickel foams (NFs). This oriented structure can provide more laminar gaps for electrolyte ion diffusion, exposing more reaction sites to increase the ion transport efficiency between the layers, reducing the ion transport resistance and improving the reaction kinetics. Thus, the CuCo2S4 electrode exhibits excellent energy storage performance, exhibiting a high specific capacity of 1415.6 F g−1 at 1 A g−1. After 10,000 cycles of 10 A g−1, it still has 91.9% of the initial performance. In addition, an asymmetrical supercapacitor (ASC) was constructed by choosing CuCo2S4 as the anode and RGO as the cathode, which has the maximum energy density (61.8 Wh Kg−1) at 812.1 W Kg−1 and significant cycling endurance (92.05% retention) at 10,000 turns. Briefly, the researchers successfully constructed an array of CuCo2S4 flower-like hierarchical nanostructures and confirmed their potential application in supercapacitors.

Functional Composite Dual-Phase In Situ Self-Reconstruction Design for High-Energy-Density Li-Rich Cathodes.

The unique anionic redox mechanism provides, high-capacity, irreversible oxygen release and voltage/capacity degradation to Li-rich cathode materials (LRO, Li1.2Mn0.54Co0.13Ni0.13O2). In this study, an integrated stabilized carbon-rock salt/spinel composite heterostructured layers (C@spinel/MO) is constructed by in situ self-reconstruction, and the generation mechanism of the in situ reconstructed surface is elucidated. The formation of atomic-level connections between the surface-protected phase and bulk-layered phase contributes to electrochemical performance. The best-performing sample shows a high increase (63%) of capacity retention compared to that of the pristine sample after 100 cycles at 1C, with an 86.7% reduction in surface oxygen release shown by differential electrochemical mass spectrometry. Soft X-ray results show that Co3+ and Mn4+ are mainly reduce in the carbothermal reduction reaction and participate in the formation of the spinel/MO rock-salt phase. The results of oxygen release characterized by Differential electrochemical mass spectrometry (DEMS) strongly prove the effectiveness of surface reconstruction.

What are the effects of environmental factors on Co speciation at the magnetite surface?

Magnetite nanoparticles are abundant in the environment and are notably used for environmental applications due to their unique magnetic, adsorption and redox properties.