γ-MnOOH Nanowires Research Articles

Efficient degradation of bentazone via peroxymonosulfate activation by 1D/2D γ-MnOOH-rGO under simulated sunlight: Performance and mechanism insight

An innovative 1D/2D γ-MnOOH-rGO catalyst was successfully synthesized by anchoring γ-MnOOH nanowires on rGO nanosheets. Its catalytic activity was comprehensively evaluated by bentazone degradation in PMS/simulated sunlight system. Results showed that the γ-MnOOH-rGO catalyst achieved 96.1% decomposition of bentazone within 90 min in the coupled system, improving by 26.7% compared to that obtained in the γ-MnOOH mediated system. Moreover, the newly-designed γ-MnOOH-rGO exhibited stability, recyclability and practicability for bentazone elimination. Mechanism insight highlighted that more active sites exposed on γ-MnOOH-rGO surface, providing more opportunities for PMS activation and bentazone degradation. Besides, the rGO could transfer photo-induced electrons, accelerating radical-based reactions. More importantly, ∙OH and 1O2 appeared in γ-MnOOH-rGO/PMS/simulated sunlight system, which played an overwhelming role in bentazone removal. In prospect, the γ-MnOOH-rGO showed promising potential for refractory contaminants remediation from aquatic environment in PMS/photocatalytic system.

Correction: Hydrothermal synthesis of γ-MnOOH nanowires using sapless leaves as the reductant: an effective catalyst for the regio-specific epoxidation of β-ionone

Correction for ‘Hydrothermal synthesis of γ-MnOOH nanowires using sapless leaves as the reductant: an effective catalyst for the regio-specific epoxidation of β-ionone’ by Yuqing Luo et al., Sustainable Energy Fuels, 2019, 3, 2572–2576, DOI: 10.1039/C9SE00536F.

A green and facile hydrothermal synthesis of γ-MnOOH nanowires as a prospective anode material for high power Li-ion batteries

In the present work, an oxidation-crystallization-reduction route in the hydrothermal systems has been demonstrated to be facile and feasible in the large-scale production of γ-MnOOH nanowires. The whole is green and cheap only using Mn2+ and polyvinylpyrrolidone without adding any oxide agent or template. The structure and morphology of the as-synthesized samples are characterized by X-ray diffraction, scanning electron microscopy, Transmission electron microscopy, Infrared active spectrum, Raman spectrum, thermogravimetry, cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. As anode of lithium-half cells, γ-MnOOH nanowires exhibit enhanced cycling performance and rate capacity in comparison with the previous reports. A high capacity of up to 393.9 mAh g−1 with a Coulombic efficiency of nearly 100% is obtained at 0.1C after 100 cycles, which presents a promising application as anode materials for lithium power batteries.

γ-MnOOH Nanowires Hydrothermally Reduced by Leaves for High-Efficiency Electrocatalysis of the Glucose Oxidation Reaction

Among various manganese-based oxides or hydroxides, manganite (γ-MnOOH) has been regarded as an important participant for high-performance electrochemical energy storage and electrocatalysis. Effor...

A colorimetric paper sensor based on the domino reaction of acetylcholinesterase and degradable γ-MnOOH nanozyme for sensitive detection of organophosphorus pesticides

Despite the tremendous achievements of existing sensing techniques, sensitive and portable sensing of organophosphorus pesticides (OPs) in a non-polluting manner remains a challenging issue. This work proposed a facile colorimetric paper sensor using γ-MnOOH nanowires (NWs) as a degradable nanozyme and 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic indicator for rapid and sensitive screening of OPs and acetylcholinesterase (AChE) activity. The sensing mechanism was based on the easy disintegration of the oxidase-like γ-MnOOH NWs into invalid Mn2+ ions by the selective reaction with thiocholine (TCh) produced by AChE and acetylthiocholine iodide (ATCh), triggering a remarkable activity loss of MnOOH nanozymes towards TMB oxidation. The concentration of OPs, as an AChE inhibitor, was measured by the changes in absorbance at 652 nm or blue color of oxTMB products. Such detection platform in solution state achieved relatively low limits of detection (LODs) for AChE activity (0.007 mU mL−1), and for two typical OPs, i.e., omethoate (0.35 ng mL−1) and dichlorvos (0.14 ng mL−1), respectively. Further, the portable assembly of such AChE-nanozyme tandem reaction on test paper performed well, reaching LODs of 0.1 mU mL−1 for AChE, 10 ng mL−1 for omethoate, and 3 ng mL−1 for dichlorvos, respectively. Meanwhile, this sensing system showed great selectivity and anti-interfering capacity in both solution and solid states, and worked well in real serum and vegetable samples. The abovementioned results, along with evidence of its good ecological sustainability, demonstrated the superiority of this well-performing platform for application in the food, environmental, and medical fields.

Hydrothermal synthesis of γ-MnOOH nanowires using sapless leaves as the reductant: an effective catalyst for the regio-specific epoxidation of β-ionone

γ-MnOOH nanowires were hydrothermally synthesized using sapless leaves and then used as a catalyst for the regio-specific epoxidation of β-ionone.

Magnetic coupling in Mn3O4-coated γ-MnOOH nanowires

Mn3O4-coated γ-MnOOH nanowires were synthesized by using the hydrothermal method. X-ray diffraction and transmission electron microscopy studies reveal that the nanowires have a core (γ-MnOOH)–shell (Mn3O4) structure. The magnetic transition temperature of Mn3O4 is slightly lower than the previously reported value because of the increased thermal disturbance for nanomaterials and the influence of the helical magnetism of γ-MnOOH. The hysteresis loop at 50 K keeps the same shape as was measured below the Néel temperature of Mn3O4 because of the short-range order of γ-MnOOH above the transition temperature. The short-range ordering is responsible for the deviation of the hysteresis loop at 300 K from the linear behavior of a normal paramagnetic phase. The magnetic coupling behavior between Mn3O4 and γ-MnOOH also induces an exchange bias effect in the system. The hysteresis loop shifts to the positive direction with increasing measurement temperature. A lower barrier energy is requested for the reversal of magnetic moments on the interface to generate the exchange bias behavior because of the asymmetric magnetic natures of Mn3O4 and γ-MnOOH, which should possess shorter responsive time compared with the traditional antiferromagnetic-ferromagnetic coupling induced exchange bias systems.

Structural and morphological evolution of mesoporous α-MnO2 and β-MnO2 materials synthesized via different routes through KMnO4/H2C2O4 reaction

Mesoporous α-MnO2 and β-MnO2 were prepared using KMnO4 and H2C2O4 (Oxalate) as precursors via aqueous and hydrothermal routes respectively. The morphological and structural evolution of the MnO2 materials were tracked by Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The preparation of MnO2 materials was found to proceed through four steps: well-crystallized α-MnO2 was formed first in aqueous solution, and then translated into microcrystalline α-MnO2 microspheres consisting of nanoparticles and nanowires via a dissolution-recrystallization process. Subsequently, the microcrystalline α-MnO2 microspheres collapsed, and γ-MnOOH nanowires were formed. Finally, β-MnO2 nanowires were obtained after calcining the γ-MnOOH nanowires in air at 400°C for 6h. During the process, oxalate acted as an important reagent and played an important role for the structural and morphological evolution of MnO2. Nitrogen sorption analysis showed that the as-prepared α-MnO2 and β-MnO2 materials all exhibited type IV isotherms, indicating mesoporous characters. In addition, the performance of the MnO2 materials as a catalyst was evaluated in the complete catalytic oxidation of a typical volatile organic compound (VOCs), o-xylene.

High aspect ratio β-MnO2 nanowires and sensor performance for explosive gases

High aspect ratio β-MnO2 nanowires have been synthesized based on a facile and green technique without any chemical additive. The precursor solution of Mn3O4 nanocrystals was first synthesized by laser ablation of a manganese target in deionized water. Due to the high reactive and fresh surface of Mn3O4 nanocrystals produced by laser ablation in liquid, these nanocrystals were spontaneously assembled into the γ-MnOOH nanowires in the precursor solution after aging at room temperature. The high aspect ratio β-MnO2 nanowires were finally produced by the γ-MnOOH nanowires annealing at 300 °C for 3 h. For the high aspect ratio β-MnO2 nanowires, the high specific surface area is advantaged for gas absorption and the unique tunnel structure is good for gas molecule trapping. A gas sensor was made from the β-MnO2 nanowires for explosive gases. The investigations were carried out for the detection of various concentration of H2 at different temperatures, and the results demonstrated that the fabricated gas sensor can detect H2 down to 20 ppm with the sensitivity of 0.5 at 300 °C and short response time of 10s. For sensing CO and ethanol, the detecting concentration reached to 20 ppm at an operation temperature of 150 and 250 °C, respectively. These results can be comparable to that of the current advanced gas sensors made from metal oxide such as ZnO and SnO2, which showing that high aspect ratio β-MnO2 nanowires can be regarded as desirable candidate materials for fabricating gas sensors.

A Study about the Synthesis Characterization and Electrochemical Properties of γ-MnOOH Nanowires

In this paper, manganite (γ-MnOOH) nanowires have been synthesized, using KMnO4 and CTAB as raw materials, by a hydrothermal method at 180°C for 12h. The samples were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscope (SEM),and thermogravimetric analysis (TG) for the information of crystal form, size, d-spacings, morphology and the weight-loss course. The results showed the manganite nanowires diameter range from 15 nm to 150 nm,length range from 5μm to 20 μm. Moreover, the properties of manganite (γ-MnOOH) nanowires as anode materials for Li-ion batteries had been studied. The first-discharge capacity is 1660 mAh g-1 and corresponds to a consumption of about 5.5 moles of Li per mole of MnOOH, which made this material maybe one of the candidates for the negative materials.

Supercapacitive Properties of Hydrothermally Synthesized γ-MnOOH Nanowires

γ-MnOOH nanowires have been synthesized via a simple hydrothermal process without any template at relatively low temperature. The as-obtained sample was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the γ-MnOOH nanowires were investigated by cyclic voltammetry and galvanostatic charge-discharge methods. And a high specific capacitance calculated from the galvanostatic discharge curve was 191 F•g-1at the current density of 0.1 A•g-1, which remain a good specific capacitance of 143 F•g-1at the current density of 1.0 A•g-1. The electrochemical analysis results demonstrate that γ-MnOOH nanowires should be a good candidate as electrode material for supercapacitor.

A study about γ-MnOOH nanowires as anode materials for rechargeable Li-ion batteries

Manganite (γ-MnOOH) nanowires have been synthesized using a hydrothermal method and their electrochemical properties as the anode materials for rechargeable Li-ion batteries have been measured. The results show that the hydroxide ions present in γ-MnOOH do not interfere with the lithium uptake and extraction, making the manganite nanowires able to reversibly react with large amount of Li. The working mechanism of γ-MnOOH as the anode active material for rechargeable Li-ion batteries is examined by TEM and the corresponding SAEDs, and is confirmed to be conversion reactions: during the first discharge, the γ-MnOOH nanowires are reduced into clusters of metallic Mn embedded in an amorphous matrix of Li2O and LiOH; the subsequent cycles are reversible redox reactions between metallic Mn and Mn3O4 nanoparticles. The discharge capacity is 1660mAhg−1 for the first cycle and can stabilize at about 400mAhg−1 after 20 cycles, which implies that this material can also be a candidate for the anode electrodes for Li-ion batteries.

Phase transition of manganese (oxyhydr)oxides nanofibers and their applications to lithium ion batteries and separation membranes

Mn5O8, MnO2, Mn2O3 nanofibers were obtained by annealing β-MnOOH nanofibers. Through β-MnOOH treated under hydrothermal conditions γ-MnOOH nanowires that were 40–100 nm in diameter and a few micrometres in length were derived. High resolution transmission electron microscopy (HRTEM) revealed that synchronous “oriented attachment” and dissolution–recrystallization mechanisms were both involved in the transition between these two manganese oxyhydroxides. Lithium ion battery performance of Mn5O8 nanofibers is presented for the first time in this work. Manganese oxides showed a great improvement in lithium storage (almost four times) compared to their corresponding bulk counterparts. The differences in lithium ion battery performance of these oxides are discussed based on their crystal structures. We propose that the interplanar trigonal prisms in Mn5O8 might hinder the movement of lithium ions, while they could diffuse freely in the tunnels formed by MnO6 octahedra in MnO2. Fibrous membranes were prepared from γ-MnOOH nanowires. By a deep filter mechanism, the membrane had a 93% rejection for 100 nm particles and 70% for 30 nm particles at a flux of 11000 L m−2 h−1 bar−1.

High aspect ratio γ-MnOOH nanowires for high performance rechargeable nonaqueous lithium–oxygen batteries

High aspect ratio γ-MnOOH nanowires (MNWs) are synthesized by a simple one-step hydrothermal method and used as catalysts in rechargeable nonaqueous lithium-oxygen batteries. When the nanowires are employed, great improvements in discharge capacity, cycle stability, and rate retention are obtained, which are attributed to the high catalyst efficiency and the cathode porosity.

Organization of Mn3O4nanoparticles into γ-MnOOHnanowiresvia hydrothermal treatment of the colloids induced by laser ablation in water

We report a simple and green strategy to organize Mn3O4 nanoparticles into single-crystalline γ-MnOOH nanowires on the basis of hydrothermal treatment of the colloids induced by laser ablation in water. Evidence obtained from a transmission electron microscopy investigation revealed that the organization mainly involved the following steps: nanoparticles → polycrystalline nanochains → single crystalline nanowires.

Preparation of α-MnO 2 nanowires through a γ-MnOOH precursor route

In the absence of extra surfactant or template, single crystalline γ-MnOOH nanowires were prepared directly via a hydrothermal method using KMnO 4 and CO(NH 2) 2 as starting materials at 120 °C for 12 h; and single crystalline α-MnO 2 nanowires could be obtained after calcining the γ-MnOOH nanowire precursor in air at 320 °C for 5 h. Various measurements were used to characterize the structure, morphology and electrochemical behavior of the resultant products. The urea acted as an important reagent and its participation was believed to contribute to the formation and growth of γ-MnOOH nanowires and even benefit the improvement of the electrochemical properties of the prepared α-MnO 2 nanowires.

Simple hydrothermal preparation of [formula omitted]-MnOOH nanowires and their low-temperature thermal conversion to β-MnO 2 nanowires

Without the use of any extra surfactant or template, γ-MnOOH single crystalline nanowires were synthesized directly through the hydrothermal reaction between KMnO 4 and toluene in distilled water at 180 °C for 24 h; and β-MnO 2 single crystalline nanowires could be obtained just by calcination of the γ-MnOOH nanowires in air at 280 °C for 5 h. The as-prepared γ-MnOOH and β-MnO 2 nanowires were characterized by X-ray powder diffraction, atomic absorption spectroscopy, Fourier transformed infrared spectroscopy, scanning electron microscope, transmission electron microscope, high-resolution transmission electron microscope and selected area electron diffraction.

Facile preparation of single-crystalline nanowires of γMnOOH and βMnO2

A facile method has been developed to synthesize single-crystalline manganese (oxyhydr)oxide nanowires. A pure phase of single-crystalline γMnOOH nanowires with the lengths of several hundred nanometres to several micrometers and the diameters of 5–40 nm was synthesized by hydrothermal transformation of commercial granular γ- or βMnO2 in water, and single-crystalline βMnO2 and polycrystalline αMn2O3 nanowires formed after subsequent calcination at 300 and 600 °C of the as-prepared γMnOOH nanostructures, respectively. These low-dimensional nanostructured materials may find novel properties and provide more possible applications in lithium batteries and catalysis.

Preparation of Mn 3O 4 nanocrystallites by low-temperature solvothermal treatment of γ-MnOOH nanowires

The preparation of trimanganese tetroxide (Mn 3O 4) nanocrystallites from γ-MnOOH nanowires under mild conditions has been achieved by two steps: first, γ-MnOOH nanowires with a mean diameter of about 12 nm and lengths of up to several micrometers were directly prepared via hydrothermal reaction between KMnO 4 and toluene in water at 180°C for 24 h; then, pure Mn 3O 4 nanocrystallites could be obtained by solvothermal treatment of the γ-MnOOH nanowires in ethylenediamine (EDA) and ethylene glycol (EG) at 150°C for 24 h. It was found that the Mn 3O 4 product obtained in EDA comprised well-defined nanocrystallites with the size in the range of 15–35 nm, while the one obtained in EG consisted of aggregated nanoparticles with the size of less than 18 nm.The possible formation mechanism of nanocrystalline Mn 3O 4 in EDA and EG and reasons for the different effects of various solvents on the products were also proposed.