Synthesis Of Manganese Oxide Research Articles

Optimizing Energy Storage Performance: In situ Synthesized Manganese Oxide (Mn3O4) Nanoparticle‐Based Symmetric Supercapacitor on a Paper Substrate

AbstractIn this study, a redox reaction is employed to synthesize manganese oxide (Mn3O4) nanoparticles using potassium permanganate as a precursor in the presence of diethyl amine. The structural characterization reveals the formation of the tetragonal phase of Mn3O4 nanoparticles with a space group of I41/amd. A free‐standing Mn3O4‐based paper electrode is fabricated and its electrochemical performances are investigated. The electrode exhibits a maximum specific capacitance value of ~353 F g−1 and an areal capacitance of ~530 mF cm−2 at a current density of 0.2 A g−1. A symmetric supercapacitor‐based device is also designed using Mn3O4 nanoparticles as an active material in a gel electrolyte configuration. The Mn3O4 device achieves specific and areal capacity values of ~208 mAh g−1 and 260 mA cm−2, respectively, at a current density of 0.3 A g−1. The device delivers maximum energy and power density values of ~104 Wh kg−1 and ~220 W kg−1, respectively, with ~92 % specific capacity retention at 0.3 A g−1 after 5000 cycles. The above results suggest that the Mn3O4‐based device has the potential for energy storage applications.

Tagetes erecta-Mediated Biosynthesis of Mn3O4 Nanoparticles: Structural, Electrochemical, and Biological Investigations.

Mn3O4 nanoparticles (NPs) find diverse applications in the fields of medicine, biomedicine, biosensors, water treatment and purification, electronics, electrochemistry, and photoelectronics. The production of Mn3O4 NPs was reported earlier through various physical, chemical, and green routes, but no studies have still been performed on their biosynthesis from Tagetes erecta. We synthesized manganese oxide NPs, i.e., (Mn3O4)L and (Mn3O4)P NPs, by utilizing leaves and petals, respectively, of T. erecta as reducing and stabilizing agents. The investigated green path is eco-friendly and does not involve any hazardous raw materials. The structural properties of NPs were determined by X-ray diffraction (XRD) analysis, spectroscopies (Fourier transform infrared (FTIR), Raman, and UV-visible), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The NPs were also evaluated for their electrochemical properties by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD). XRD analysis was performed to verify their tetragonal geometry, and the crystallite size (19.24 nm) of (Mn3O4)P was smaller than that (20.84 nm) of (Mn3O4)L NPs. SEM images displayed a porous and spherical morphology with a diameter of 14-35 nm. FTIR spectra of (Mn3O4)L and (Mn3O4)P displayed Mn-O vibrations at 605.69 and 616.87 cm-1, respectively, and the hydrous nature of the material. Raman spectroscopy revealed the existence of tetrahedral and octahedral units along with A1g, T2g, and Eg active modes of Mn3O4 and 2TO mode. UV-visible analyses of (Mn3O4)L and (Mn3O4)P NPs showed absorption peaks at 272.3 and 268.8 nm, along with band gaps of 4.83 and 5.49 eV, respectively. TGA curves displayed good thermal stabilities up to 600 °C and a loss of moisture content. DSC curves exhibited exothermic/endothermic peaks with glass transition temperatures of 258.9 and 308.7 °C for (Mn3O4)P and (Mn3O4)L, respectively. The CV curves showed redox peaks and confirmed that the electrochemical reaction takes place in the Mn3O4 material. GCD scans revealed the capacitive behavior of NPs and their suitability as electrodes in energy storage devices. However, (Mn3O4)L will act as a good material for energy storage applications as compared to (Mn3O4)P NPs. The synthesized NPs were also tested for their antibacterial efficacy by biofilm inhibition and agar well diffusion methods. The NPs showed higher activities against Staphylococcus aureus (Gram-positive) than against Escherichia coli (Gram-negative), and (Mn3O4)P was more bioactive than (Mn3O4)L.

Tetragonal crystalline MnO nanoparticles alleviate Pb stress in wheat by modulating antioxidant enzymes in leaves.

Agriculture ecosystems are seriously threatened by lead (Pb) contamination, which impacts plant growth and productivity. In this study, green synthesized manganese oxide nanoparticles (MnO NPs) using citrus peel were used for priming of wheat seeds. For the synthesis of MnO nanoparticles, peel extract of Citrus paradisi and 1mM solution of manganese acetate were stirred and calcinated at 500°C. Successful synthesis of MnO NPs was determined using advanced techniques. In Fourier-transform infrared spectroscopy (FTIR), the presence of amines, alkanes, aldehydes, and alcohol molecules, on the surface of MnO NPs, confirmed their stability. X-ray diffraction analysis described their average size (22nm), while scanning electron microscopy showed tetragonal crystalline shape and nano-flowers structure of MnO NPs. Sharp peaks of energy dispersive x-ray analysis described the presence of oxygen (28.81%) and manganese (71.19%) on MnO NPs. Priming of wheat seeds with synthesized MnO NPs significantly improved the growth attributes of wheat seedlings including the size of leaf, root length, size of shoots, chlorophyll and carotenoid contents, relative water content, decreased relative electrolyte leakage, high proline accumulation and decreased concentration of malondialdehyde. Application of MnO NPs also helped plants to accumulate antioxidant enzymes in their leaves. These results proved that the priming of MnO NPs can greatly reduce lead-induced stress in wheat seedlings and these NPs can alsobe used for the priming of other crops.

Green, environmentally friendly synthesis of MnO Nanoparticles for corrosion inhibition in mild steel

<p>This study uses green, environmentally friendly methods to synthesize manganese oxide nanoparticles (MnO-NPs) that can be applied on mild steel as a safe and eco-friendly material with corrosion inhibition attributes. Mukia madaraspatana leaf extract is effective in the green synthesis of Mno-NPs. Several critical parameters can influence the corrosion rate and inhibition efficiency of the MnO-NPs, including the dose of nanoparticles in parts per million (PPM), acid concentration, temperature, and exposure time. Response Surface Methodology-Box Behnken Design (RSM-BBD) was employed to optimize these parameters. An optimal dosage of 550 parts per million (ppm) of nanoparticles, an acid concentration of 0.9 M, a temperature of 37°C, and an exposure time of 3.2 hours resulted in an inhibition efficiency of 92.5%. It reduced the corrosion rate to 0.652 (mm/Y) in an independent validation run. These findings demonstrate that the environmentally friendly synthesized MnO-NPs have great potential as an anti-corrosive agent for mild steel.</p>

A facile green synthesis of manganese oxide nanoparticles using gum karaya polymer as a bioreductant for efficient photocatalytic degradation of organic dyes and antibacterial activity

The release of organic dyes into water systems, mainly textile industries, poses a significant threat to human and animal health. This approach shows great potential for effectively removing harmful dyes and microorganisms from wastewater treatment for environmental remediation. This study utilized gum karaya polymer bio-reductant to synthesize manganese oxide (MnO2) nanoparticles through a green approach. The synthesized MnO2 nanoparticles were characterized and confirmed by various analytical techniques. These results revealed their nanoscale dimensions, morphology, chemical purity, crystal nature, decolorized intermediate, and band gap. The photocatalytic degradation of hazardous Congo red and methyl orange dyes using KRG-MnO2 nanoparticles under visible light irradiation. Furthermore, the results demonstrated that Congo red dye degradation efficiency of 93.34 % was achieved. The dye concentration (8 to 16 mg/L), pH concentration, and radical trapping were studied. This suggests that holes and hydroxyl radicals play a crucial role in degrading the Congo red dye and demonstrate superior recyclability after three successive cycles and good stability. The possible intermediates from the Congo red dye degradation were identified through LC-MS analysis. The polymer composite MnO2 NPs have displayed notable antibacterial activity against pathogenic bacteria such as Staphylococcus aureus and Escherichia coli. The research indicates that MnO2 nanoparticles functionalized with polymers can efficiently remove pathogens and organic dyes from diverse industrial water treatment processes.

Efficient degradation of acetaminophen by activated peroxymonosulfate using Mn/C composites: Performance and mechanism

The synthesis of manganese oxide (MnOx) composites often leads to particle aggregation and the formation of larger metal nanoparticles, which greatly reduces the efficient use of manganese (Mn) as catalyst. Additionally, the structurally unstable Mn matrix composites increase the risk of metal precipitation during the reaction process. To address these issues, a series of Mn-carbon (Mn/C) co-doped composites (Mn@CA400, Mn@CA500, and Mn@CA600) were synthesized using potassium permanganate (KMnO4) and citric acid (CA) as precursors. The Mn@CA400 exhibited exceptional catalytic activity towards peroxymonosulfate (PMS) resulting in complete removal of 10 mg/L acetaminophen (ACT) within 10 min. Furthermore, Mn@CA400 demonstrated significant selectivity and resistance in complex matrices to interference for pollutant degradation. The results showed that Mn@CA400 exhibited higher catalytic activity and better stability compared with the reported Mn-based composites. Quenching experiments, electron paramagnetic resonance (EPR), solvent exchange experiments, and electrochemical analysis confirmed that singlet oxygen (1O2) and electron transfer pathways were responsible for ACT degradation. The mechanism analysis revealed that ACT could be degraded under three pathways. The current study not only presents an effective method to solve the problem of metal agglomeration and precipitation in the synthesis of MnOx composites but also establishes an efficient and selective oxidation system. In addition, it greatly improves the understanding of PMS activation and ACT degradation mechanisms.

Impacts of Biosynthesized Manganese Dioxide Nanoparticles on Antioxidant Capacity, Hematological Parameters, and Antioxidant Protein Docking in Broilers.

Using green tomato extract, a green approach was used to synthesize manganese oxide nanoparticles (MnO2NPs). The synthesis of MnO2NPs was (20.93-36.85 nm) confirmed by energy-dispersive X-ray (EDX), scanning and transmission electron microscopy (SEM and TEM), Fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy (UV-vis) analyses. One hundred fifty-day-old Arbor Acres broiler chicks were randomly divided into five groups. The control group received a diet containing 60 mg Mn/kg (100% NRC broiler recommendation). The other four groups received different levels of Mn from both bulk MnO2 and green synthesized MnO2NPs, ranging from 66 to 72 mg/kg (110% and 120% of the standard level). Each group comprised 30 birds, in three replicates of 10 birds each. Generally, the study's results indicate that incorporating MnO2NPs as a feed additive had no negative effects on broiler chick growth, antioxidant status, and overall physiological responses. The addition of MnO2NPs, whether at 66 or 72 mg/kg, led to enhanced superoxide dismutase (SOD) activity in both serum and liver tissues of the broiler chicks. Notably, the 72 mg MnO2NPs group displayed significantly higher SOD activity compared to the other groups. The study was further justified through docking. High throughput targeted docking was performed for proteins GHS, GST, and SOD with MnO2. SOD showed an effective binding affinity of -2.3 kcal/mol. This research sheds light on the potential of MnO2NPs as a safe and effective feed additive for broiler chicks. Further studies are required to explore the underlying mechanisms and long-term effects of incorporating MnO2NPs into broiler feed, to optimize broiler production and promote its welfare.

The Effect of Hydrothermal Reaction Time on the Antibacterial Activity of Synthesized Manganese Oxide Nanoparticles

In the context of growing antibiotic resistance and the associated side effects of traditional antibiotics, this research explores the use of nanosized manganese oxide (Mn3O4) as a novel antibacterial agent. This study pioneers the synthesis of Mn3O4 through an eco-friendly hydrothermal method, varying reaction times (2, 4 and 6 hours) at a consistent temperature of 180 °C. Characterization techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy and Scanning electron microscopy, provide insights into their crystallinity, functional groups and morphology. The synthesized Mn3O4 demonstrates remarkable antibacterial efficacy, with larger inhibition zones against both Gram-positive and Gram-negative strains compared to standard antibiotics. This research presents the synthesizing of an eco-friendly, cost-effective antibacterial agent through a straightforward hydrothermal method. Varying reaction times unveil distinctive antibacterial capabilities, making Mn3O4 a promising candidate for future antimicrobial systems and medical applications.

Synthesis of manganese oxide from manganese ore of bajaur agency khyber Pakhtunkhwa (KPK), Pakistan

In the present work manganese sulphate developed from the Bajaur (KPK, Pakistan) manganese ore was utilized successfully for the synthesized Manganese Oxide chemically by an alkali-oxidation of manganese sulphate using the co-precipitation method. The advantages of this eco-friendly co-precipitation method include quick and easy preparation, simple control of particle size, and cost-effective composition using local ore. Because of the readily available raw materials and the controlled reaction conditions, this method is widely used in industry. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the synthetic manganese oxide. Fourier transforms infrared spectroscopy (FTIR) Infrared reveals that the O-Mn-O vibrational mode occurs in pure manganese oxide at wavelengths between 600 and 500 cm-1. The chemical composition was obtained by EDX analysis and confirmed the presence of Mn and O in the sample. Experimental optimization was done for the manganese oxide precipitation conditions. The findings show that a variety of parameters have an impact on the product yield; the precursor ratio and reaction temperature are the most important variables, and the reaction time and pH value have the greatest impact on the quality of crystallization. Bangladesh J. Sci. Ind. Res. 58(4), 221-230, 2023

Different quantities of manganese oxide nanoparticles incorporated feed on the growth and haematological traits of common carp Cyprinus carpio var. communis

In recent times, nanoparticles have been used as raw ingredients for biofertilizers, mineral supplements in animal feed, and pharmaceuticals. Manganese plays a vital role in enhancing fish's growth and biological function. The present research work aimed to analyze the various quantities of manganese oxide nanoparticles on common carp growth and its haematological traits. Synthesized manganese oxide (Mn3O4) nanoparticles were illustrated using UV-visible Spectroscopy (UV-Vis), Scanning Electron Microscope (SEM), Energy Dispersive X–Ray Spectroscopy (EDAX), X–Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Six different feeds were prepared by incorporating different quantities of manganese oxide nanoparticles (Feed I (control-0mg), Feed II(3mg/100g), Feed III(6mg/100g), Feed IV(9mg/100g), Feed V(12mg/100g), and Feed VI(15mg/100g)) with common ingredients such as groundnut oil cake, fish meal, tapioca flour, and wheat flour. On the completion of 21 days, feed utilization and haematological characteristics of Common carp were assessed. The UV-Vis showed that manganese oxide nanoparticles exhibit strong adsorption peaks at 220nm. SEM image observed at the wavelength range from 9.22 nm to 9.35 nm. The size of the particles was in the 45-55 nm range. The EDAX spectrum recorded two peaks between 0.40 and 6 kev. The XRD graph shows that the diffraction peaks are indexed as 103, 004, 213, 204, 303, and 215. FT-IR spectrum measured at the wavelength range from 500-4000cm-1. Most of the growth parameters and haematological parameters were higher in feed III, containing 6mg of Manganese oxide nanoparticles. Therefore, results show that manganese oxide incorporated feed enhances the growth and haematological traits in common carp compared to control feed.

Phase variation of manganese oxide in the MnO@ZnO nanocomposite with calcination temperature and its effect on structural and biological activities

Having powerful antibacterial and antioxidant effects, zinc oxide and manganese oxide nanomaterials are of great interest. Here we have synthesized manganese oxide decorated zinc oxide (MZO) nanocomposites by co-precipitation method, calcined at different temperatures (300–750 °C) and studied various properties. Here the crystalline structure of the nanocomposite and phase change of the manganese oxide are observed with calcination temperature. The average crystalline size increases and the dislocation density and microstrain decrease with the increase in calcined temperature for the same structural features. The formation of composites was confirmed by XRD pattern and SEM images. EDAX spectra proved the high purity of the composites. Here, different biological properties change with the calcination temperature for different shapes, sizes and structures of the nanocomposite. Nanomaterial calcined at 750 °C provides the best anti-microbial activity against Escherichia coli, Salmonella typhimurium, Shigella flexneri (gram-negative), Bacillus subtilis and Bacillus megaterium (gram-positive) bacterial strain at 300 µg/mL concentration. The nanomaterial with calcination temperatures of 300 °C and 450 °C provided better antioxidant properties.

Efficient scalable co-precipitated carbon dots and silver bromide doped manganese dioxide for catalytic and antimicrobial activity with evidential in-silico analysis

In this research, a co-precipitation approach was used to synthesize manganese oxide (MnO2) nanorods (NRs) doped with varying concentrations (2, 4 wt.%) of silver bromide (AgBr) and fixed amounts of carbon dots (CDs). CDs exhibit high photostability and a high electron transfer rate. AgBr can improve the activity of metal oxide owing to its electron-trapping effect. The new characteristics of as-prepared AgBr/CDs doped MnO2 NRs have a larger surface area, charge transport capabilities, and lower recombination chances, associating the synthesized material as a suitable choice for environmental cleanup. The removal of organic dye pollutants from wastewater and the elimination of harmful bacteria by the use of antibacterial activity were the goals of this research. The NRs demonstrated outstanding catalytic activity (CA) against rhodamine B (RhB) dye degradation. AgBr/CDs-doped MnO2 nanocatalyst indicates efficient dye degradation (96.39 %) in an acidic medium relative to other basic and neutral media. The fundamental components for generating reactive oxygen species (ROS) are electrons and hole pairs responsible for killing pathogenic bacteria. Compared to ciprofloxacin the substantial inhibition zones against Escherichia coli (E. coli) bacteria were measured at 2.95 mm. In silico molecular docking study of AgBr/CDs-doped MnO2 NRs proposed as promising DNA gyrase E. coli inhibitors.

Synthesis and characterization of highly efficient Te-doped Mn3O4 and s-g-C3N4 /Te- Mn3O4 nanocomposites as an excellent antimicrobial and photocatalytic agent

This work aims to synthesize manganese oxide nanoparticles (Mn3O4NPs) using a co-precipitation method and analyzed them through XRD, SEM and FT-IR. The XRD analysis confirmed the tetragonal hausmanite structure of the Mn3O4 NPs, while SEM revealed an average particle size of 9–20 nm. Kinetic studies demonstrated the efficient photooxidation of methylene blue with first-order kinetics under UV or visible light. Degradation efficiencies varied between 82% and 93% depending on the light source. Furthermore, we used the zone inhibition approach to assess the antibacterial potency of various Mn3O4 NP contents alongside human pathogenic bacteria, namely Escherichia coli and Staphylococcus aureus. The results of the qualitative antibacterial tests revealed that E. coli, a Gram-negative bacterium, is more sensitive to Mn3O4 NPs than are Gram-positive bacteria, with a maximum zone diameter of 28 mm (S. aureus). Alternatively, it was determined that S-g-C3N4/Te-Mn2O3 had the maximum antifungal activity against Alternaria solani at 28.9 mm and against. Colletotrichum gloeosporioides at 47.3 mm.

Biosynthesis and characterization of MnO2 and Zn/Mn2O4 NPs using Ziziphus spina-Christi aqueous leaves extract: Effect of decoration on photodegradation activity against various organic dyes

An aqueous leaf extract of Ziziphus spina-Christi is used to synthesize manganese oxide nanoparticles (MnO2 NPs) and zinc-coated manganese oxide nanoparticles (Zn/Mn2O4 NC). The study aims to investigate the photocatalytic degradation efficiency of MnO2 NPs and Zn/Mn2O4 NC in relation to the azo dyes methylene blue (MB), m-Toluidine (mT), and P-Toluidine (pT). X-ray diffraction analysis (XRD) confirmed the crystalline nature of the biosynthesized MnO2 NPs and Zn/Mn2O4, revealing their respective crystallite sizes to be approximately 14.65 nm and 22.97 nm. The scanning electron microscope (SEM) images demonstrated that the MnO2 NPs exhibit a tetragonal and spherical shape, while the Zn/Mn2O4 particles possess a spherical shape. UV–vis spectroscopy measurements indicated that the MnO2 NPs and Zn/Mn2O4 exhibit indirect bandgaps with energy values of 1.46 eV and 1.14 eV, respectively. Fourier transform infrared (FTIR) analysis revealed the presence of organic compounds containing CO and OH groups, such as carbohydrates, phenolic acids, tannins, and flavonoids derived from Ziziphus spina-Christi, suggesting a high likelihood of stability for the biosynthetic MnO2 and Zn/Mn2O4 materials. Interestingly, the photocatalytic degradation of the biosynthetic MnO2 and Zn/Mn2O4 provided good efficacy against the Methylene Blue (MB), m-Toluidine (mT), and P-Toluidine (pT) where the Zn/Mn2O4 exhibit an excellent degradation were 99.2, 99.8 and 98.4 % after 75 min. The biosynthetic MnO2 NPs and Zn/Mn2O4 NCs resulting from using aqueous ZSCLE were cost-effective and eco-friendly, and the decoration of MnO2 NPs by Zn improved their effectiveness.

Sonochemical Synthesized Manganese Oxide Nanoparticles as Fluorescent Sensor for Selenium (IV) Quantification. Application to Food and Drink Samples.

Manganese oxide nanoparticles (MnO Nps), sonochemical synthesized and characterized in our laboratory, are proposed as fluorescent sensor for selenium (Se) determination. The new methodology has been developed based on the enhancing effect of the Se(IV) on fluorescent emission of MnO Nps. Experimental variables that influence on fluorimetric sensitivity were optimized. The calibration graph using zeroth order regression was linear from 0.189ng L-1 to 8.00 × 103µg L-1, with correlation coefficient better than 0.99. Under the optimal conditions, the limits of detection and quantification were of 0.062ng L-1 and 0.189ng L-1, respectively. The trueness of the methodology was assessed through standard addition method obtaining recovery near to 100%. This method showed good tolerance to foreign ions, particularly to Se(VI), and was applied to determination of Se(IV) trace in food and drink samples with satisfactory results. With the intention of preserving the environment from harmful effects, a degradation study of the used nanomaterials has been included for their subsequent disposal.

Light-Mediated Electrochemical Synthesis of Manganese Oxide Enhances Its Stability for Water Oxidation.

New methods are needed to increase the activity and stability of earth-abundant catalysts for electrochemical water splitting to produce hydrogen fuel. Electrodeposition has been previously used to synthesize manganese oxide films with a high degree of disorder and a mixture of oxidation states for Mn, which has led to electrocatalysts with high activity but low stability for the oxygen evolution reaction (OER) at high current densities. In this study, we show that multipotential electrodeposition of manganese oxide under illumination produces nanostructured films with significantly higher stability for the OER compared to films grown under otherwise identical conditions in the dark. Manganese oxide films grown by multipotential deposition under illumination sustain a current density of 10 mA/cm2 at 2.2 V versus reversible hydrogen electrode for 18 h (pH 13). Illumination does not enhance the activity or stability of manganese oxide films grown using a constant potential, and films grown by multipotential deposition in the dark undergo a complete loss of activity within 1 h of electrolysis. Electrochemical and structural characterization indicate that photoexcitation of the films during growth reduces Mn ions and changes the content and structure of intercalated potassium ions and water molecules in between the disordered layers of birnessite-like sheets of MnOx, which stabilizes the nanostructured film during electrocatalysis. These results demonstrate that combining multiple external stimuli (i.e., light and an external potential) can induce structural changes not attainable by either stimulus alone to make earth-abundant catalysts more active and stable for important chemical transformations such as water oxidation.

A halophilic Chromohalobacter species from estuarine coastal waters as a detoxifier of manganese, as well as a novel bio-catalyst for synthesis of n-butyl acetate.

Anthropogenic pollution due to ferro-manganese ore transport by barges through the Mandovi estuary in Goa, India is a major environmental concern. In this study a manganese (Mn) tolerant, moderately halophilic Chromohalobacter sp. belonging to the family Halomonadaceae was isolated from the sediments of a solar saltern adjacent to this Mandovi estuary. Using techniques of Atomic absorption spectroscopy, Scanning electron microscopy-Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy and Atomic Force Microscopy, the Chromohalobacter sp. was explored for its ability to tolerate and immobilize Mn in amended and unamended media with 20% natural salt concentration (w/v). In aqueous media supplemented with 0.1 mM Mn, the Chromohalobacter sp. was capable of sequestering up to 76% Mn with an average immobilization rate of 8 mg Mn /g /day. Growth rate kinetic analysis using Gompertz mathematical functions was found to model the experimental data well. The model inferred that the maximum growth rate of Chromohalobacter sp. was at 10% natural salt concentration (w/v). The Chromohalobacter sp. was further found to be multimetal tolerant showing high tolerance to Iron (Fe), Nickel (Ni) and Cobalt (Co), (each at 4 mM), and tolerated Manganese (Mn) up to 6 mM. Morphologically, the Chromohalobacter sp. was a non-spore forming, Gram negative motile rod (0.726 μ× 1.33 μ). The adaptative mechanism of Chromohalobacter sp. to elevated Mn concentrations (1 mM) resulted in the reduction of its cell size to 0.339 μ× 0.997 μ and the synthesis of an extracellular slime, immobilizing Mn from the liquid phase forming Manganese oxide, as confirmed by Scanning Electron Microscopy. The expression of Mnx genes for manganese oxidation further substantiated the finding. This bacterial synthesized manganese oxide also displayed catalytic activity (∼50% conversion) for the esterification of butan-1-ol with CH3COOH to yield n-butyl acetate. This Chromohalobacter sp. being indigenous to marine salterns, has adapted to high concentrations of heavy metals and high salinities and can withstand this extremely stressed environment, and thus holds a tremendous potential as an environmentally friendly "green bioremediator" of Mn from euryhaline environments. The study also adds to the limited knowledge about metal-microbe interactions in extreme environments. Further, since Chromohalobacter sp. exhibits commendable catalytic activity for the synthesis of n-butyl acetate, it would have several potential industrial applications.

Chemically synthesized manganese oxide nanorods for effectual organic dye removal and energy storage application

Manganese oxide nanoparticles (MnO2) are successfully synthesized by using a facile chemical co-precipitation and reflux-assisted co-precipitation method with varying annealing temperatures and reflux time respectively. The synthesized samples' structural, optical and thermal properties are investigated by XRD, FTIR spectra, Ultraviolet–Visible spectroscopy, Thermogravimetric Analysis and BET surface area analyzer. The average crystallite sizes assessed by Scherrer's equation (Williamson- Hall plot) of prepared samples are in the range of 6–8 nm (6–7 nm) for the reflux-assisted method and 15–30 nm (20–46 nm) for the co-precipitation method respectively. The presence of peaks associated with Mn-O bonds in FTIR spectra confirmed the formation of MnO2 nanoparticles. FESEM studies revealed the nanorod-type morphologies of samples. The prepared samples showed pseudocapacitive behaviour and significant photocatalytic degradation of brilliant green dye.

Nanoscale chemical and structural investigation of solid solution polyelemental transition metal oxide nanoparticles

Although it has been shown that configurational entropy can improve the structural stability in transition metal oxides (TMOs), little is known about the oxidation state of transition metals under random mixing of alloys. Such information is essential in understanding the chemical reactivity and properties of TMOs stabilized by configurational entropy. Herein, utilizing electron energy loss spectroscopy (EELS) technique in an aberration-corrected scanning transmission electron microscope (STEM), we systematically studied the oxidation state of binary (Mn,Fe)3O4, ternary (Mn, Fe, Ni)3O4, and quinary (Mn, Fe, Ni, Cu, Zn)3O4 solid solution polyelemental transition metal oxides (SSP-TMOs) nanoparticles. Our findings show that the random mixing of multiple elements in the form of solid solution phase not only promotes the entropy stabilization but also results in stable oxidation state in transition metals spanning from binary to quinary transition metal oxide nanoparticles.

Hydrothermal synthesis of manganese oxide (Mn3O4) with granule-like morphology for supercapacitor application

In the present work, we have synthesized manganese oxide (Mn3O4) nanoparticles (NPs) using the facile hydrothermal route at different pH (9, 10. 11). The effect of the pH variation on the structural and electrochemical properties of the synthesized Mn3O4 NPs have studied. Synthesized NPs are characterized using XRD, SEM, EDS, TEM, BET, cyclic voltammetry, galvanic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) for various properties. The preferred orientation of Mn3O4 growth is along the (211) plane with granule-like morphology. The Mn3O4 electrodes were fabricated and investigated for electrochemical characterizations. The capacitance of the Mn3O4 electrode was calculated from cyclic voltammetry (CV) and galvanometric charge-discharge curves at different scan rates and current densities, respectively. The specific capacitance values of the Mn3O4 electrode (pH 11) were estimated from CV and GCD viz 277 F/g and 262 F/g, respectively, with the higher capacitance retention. Charge transfer resistance was calculated from electrochemical impedance spectroscopy (EIS) measurements. The equivalent series resistance for Mn3O4 at pH 11 is around 0.015 Ω. Nanostructured MnO2 electrodes can be the potential materials for supercapacitor application.