MnO2 Nanomaterials Research Articles

Irregularly Shaped Mn2O3 Nanostructures with High Surface Area for Water Oxidation

Water oxidation is an energy-consuming, four-electron-transfer reaction and is essential for solar fuel production from water. Catalysts based on precious metals such as RuO2 and IrO2 show high efficiency for oxygen evolution reaction. However, these catalysts are less abundant and expensive. To date, earth-abundant water oxidation catalysts still exhibit less activity for water oxidation. Herein, we report the synthesis of high surface area Mn2O3 nanomaterials for an efficient photocatalytic water oxidation catalyst. The synthesis process involves three simple steps. In the first step, CaMnO3 is synthesized by the citrate-gel method. In the second step, CaMnO3 is transformed into freestanding layers of ε-MnO2 by selective removal of Ca2+. In the third step, these layers are converted into irregularly shaped two-dimensional Mn2O3 flakes (AD-Mn2O3) by calcination at 550 °C. These AD-Mn2O3 nanostructures show 4 times higher surface area (127 m2 g–1) when compared to the irregularly shaped Mn2O3 nanoparticles (CG-Mn2O3) synthesized by the citrate-gel method at the same temperature. The AD-Mn2O3 nanostructures show super hydrophilicity with a contact angle of zero degree. This material exhibits excellent photocatalytic water oxidation activity with a turnover frequency of 1.53 × 10–3 s–1, which is twice the activity shown by CG-Mn2O3. This study can help in developing an earth-abundant, cost-effective, efficient catalyst for overall water splitting.

Biodegradable flower-like manganese for synergistic photothermal and photodynamic therapy applications.

A flower-like nanostructured MnO2 with near-infrared (NIR) light-triggered high photothermal conversion capability of 30% and reactive oxygen species (ROS) generation ability was successfully developed. Different from the reported MnO2 nanomaterials those were used in the nanomedicine field for only relieving tumor hypoxia and/or imaging, the flower-like MnO2 inherently acts as a competent agent for simultaneously enhanced photothermal and photodynamic therapy. A flower-like nanostructured MnO2 with near-infrared (NIR) light triggered high photothermal conversion capability of 30% and reactive oxygen species (ROS) generation ability was successfully developed.

Exploring Aluminum‐Ion Insertion into Magnesium‐Doped Manjiroite (MnO2) Nanorods in Aqueous Solution

AbstractAqueous aluminum‐ion batteries are promising for sustainable energy storage given the abundance of aluminum and the ease of recycling. However, finding suitable electrode materials that can intercalate Al ions remains challenging. Here, we investigate Mg‐ion‐doped MnO2 nanorods in the manjiroite structure that allow Al‐ion insertion into the open tunnels of this material. The electrode material is characterized before and after Al‐ion insertion with X‐ray diffraction and X‐ray photoelectron spectroscopy, and the insertion process is studied via in situ transmission electron microscopy, which highlights a change in the length of the MnO2 nanorod. The results indicate that Al ions can be successfully inserted into the MnO2 nanorods, which has also been determined by density functional theory calculations to be an energetically favorable process. The electrochemical data indicate that diffusion‐controlled Al insertion as well as a surface pseudocapacitive effect occur. This indicates that MnO2 nanomaterials synthesized in the presence of metal cations is potentially a viable route for facilitating their use as electrode materials in aqueous Al‐ion batteries or supercapatteries.

Review on Current Progress of MnO2‐Based Ternary Nanocomposites for Supercapacitor Applications

AbstractManganese dioxide (MnO2) has proved itself as a popular pseudocapacitive material with low fabrication cost, high availability, low toxicity, and improved handling safety compared to many other inorganics or carbon‐based systems existing in the market. However, the specific capacitance reported to date has been far inferior to that of the theoretically predicted value (ca. 1370 Fg−1), which is mainly attributed to the issues associated with poor conductivity, nanostructure agglomeration, low porosity, rapid electrolyte‐mediated dissolution, and so forth, which have considerably limited its commercial effectiveness. Thus, to bring about improvement in the electrochemical performance of MnO2‐based supercapacitors, novel designs of MnO2 nanomaterials through composite formations with other substances, such as nanocarbons, conducting polymers or inorganic materials, namely metal oxides and sulfides, have been comprehensively explored. Extensive studies on these MnO2 binary nanocomposites revealed significant improvement in the electrochemical features compared to pristine phases; nevertheless, the achieved state is still far below practicability. Hence, scientists have opted for MnO2‐based ternary nanocomposites achieved by blending appropriate proportions the three components (MnO2 nanostructures being one of the constant components) that would promote synergism to attain suitable dimensions, crystallinity, crystal structure, conductivity, mass loading, and electrolyte selectivity so as to confer superior capacitance, charge transfer kinetics, better utilization of electroactive materials, energy and power densities, as well as improved mechanical stability and environmental adaptability. Herein, recent developments and advancements in the research of various MnO2‐based ternary nanocomposites employed for supercapacitor applications have been discussed and are compared with binary analogs with special emphasis on correlating their composition, morphology, and the electrochemical properties that are noticeably modified upon introduction of the third component. The associated challenges encountered in their progress toward commercialization and the probable ideas of persuading better strategic designs of these ternary systems for high‐performance supercapacitor applications have also been delineated.

Enhanced visible light driven Photocatalytic activity of MnO2 nanomaterials and their hybrid structure with carbon nanotubes

MnO2 nanomaterials were synthesized using a simple wet redox method. Crystal structure of as prepared pure and Al doped MnO2 nanomaterials was investigated using X-ray diffraction (XRD) technique. Crystal structure was further confirmed by FTIR analysis. Morphology of pure MnO2, Al doped MnO2, MnO2/CNT hybrid structure and Al doped MnO2/CNT hybrid structure was studied using scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy confirmed the presence of all the constituent atoms in the crystal structure of all the samples. Bandgap value was found to decrease with the modification (doping and hybrid structure). Photocatalytic efficiency of all the MnO2 samples was studied using the photodegradation of methylene blue (MB) under the visible light (solar radiation). Effect of different intermediates on the photodegradation efficiency was studied using different scavengers.

MnO2 nanomaterials functionalized with Ag and SnO2: An XPS study

The present study is devoted to the characterization of MnO2-Ag and MnO2-SnO2 nanocomposites of technological interest as gas sensors for food quality control and security applications. In particular, MnO2 nanomaterials were deposited on polycrystalline alumina substrates by plasma enhanced-chemical vapor deposition and functionalized with either Ag or SnO2 nanoparticles by means of radio frequency-sputtering. The target materials were investigated by a multitechnique approach, evidencing the successful formation of nanocomposites with tailored morphology, featuring an intimate contact of their components. Herein, the attention is dedicated to the characterization of system surface composition by x-ray photoelectron spectroscopy. Besides wide scan spectra, data obtained by the analysis of the C 1s, O 1s, Mn 2p, Mn 3s, Ag 3d, Sn 3d, and silver Auger signal spectral features are presented and critically discussed. The results highlight the occurrence of phase-pure MnO2 and SnO2 free from other Mn and Sn oxidation states and of appreciable silver surface oxidation in the target nanomaterials.

Preparation of Anisotropic MnO2 Nanocatalysts for Selective Oxidation of Benzyl Alcohol and 5-Hydroxymethylfurfural

Anisotropic MnO2 nanostructures, including α-phase nanowire, α-phase nanorod, δ-phase nanosheet, α + δ-phase nanowire, and amorphous floccule, were synthesized by a simple hydrothermal method through adjusting the pH of the precursor solution and using different counterions. The catalytic properties of the as-synthesized MnO2 nanomaterials in the selective oxidation of benzyl alcohol (BA) and 5-hydroxymethylfurfural (HMF) were evaluated. The effects of micromorphology, phase structure, and redox state on the catalytic activity of MnO2 nanomaterials were investigated. The results showed that the intrinsic catalytic oxidation activity was mainly influenced by the unique anisotropic structure and surface chemical property of MnO2. With one-dimensional and 2D structures exposing highly active surfaces, unique crystal forms, and high oxidation state of Mn, the intrinsic activities for MnO2 catalysts synthesized in pH 1, 5, and 10 solutions (denoted as MnO2-pH1, MnO2-pH5, and MnO2-pH10, respectively) were twice higher than those of other MnO2 catalysts in oxidation of BA and HMF. With a moderate aspect ratio, the α + δ nanowire of MnO2-pH10 exhibited the highest average oxidation state, most abundant active sites, and the best catalytic oxidation activity.

Effect of soft template variation on the synthesis, physical, and electrochemical properties of Mn3O4 nanomaterial

In this study, the effect of surfactant variation has been investigated on the synthesis, the physical, and electrochemical performance of Mn3O4 (M1–M4) nanomaterials. The synthesized nanomaterials were successfully characterized by powder X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-ray analysis. Synthesized nanomaterials exhibited a tetragonal hausmannite phase (Mn3O4) with an average size of 22 nm. The electrochemical performance of these nanomaterials was investigated through cyclic voltammetry. The maximum specific capacitance for M1 was found to be 3.578028 F/g at 5 mV/s scan rate. The relation between power and energy density determined through the Ragone plot was found maximum for synthesized nanomaterials. M1 was found to be an efficient electrode material as compared to others.

Noble Metal/Mn3O4 Nanocomposite Systems:from Design to Applications As Ultra-Sensitive Gas Sensors for Nitrogen Mustard Simulant

The efficient detection of chemical warfare agents (CWAs) is of paramount importance in the development of reliable sensing devices for safety applications. In particular, the increased threats of chemical attacks by terrorist organizations have stimulated a significant interest in the early detection of CWAs. Due to the high toxicity and necessity of special infrastructures for storage/manipulation of CWAs, the activities aimed at their detection are carried out on mimicking compounds compatible with lab test security level. In this context, the recognition of di(propylene glycol) monomethyl ether (DPGME), a simulant of the vesicant nitrogen mustard, is of key importance. Among the various devices adopted for CWA sensing, chemoresistive gas sensors based on nanostructured metal oxides offer various advantages, encompassing low cost, limited power consumption, and good stability/sensitivity. To date, DPGME detection has been performed only in a few cases by the use of SnO2-based systems, and the development of highly efficient sensors for its selective monitoring is of primary importance for next-generation devices.Among metal oxides, p-type Mn3O4, a mixed-valence and environmentally friendly multifunctional system, is an attractive candidate for CWAs detection thanks to the tunable Mn redox chemistry and the inherent catalytic properties. On the other hand, gas sensors based on pure p-type materials like Mn3O4 typically feature responses lower than n-type ones, as well as modest sensitivity/selectivity. To circumvent these drawbacks, a viable alternative is the functionalization with noble metals particles, like Ag and Au, that can act as catalytic promoters of the involved chemical reactions at the nanoscale and/or favor the formation of metal/oxide Schottky junctions, improving charge carrier separation.Based on preliminary results on the development of pure Mn3O4 nanomaterials as gas sensors [1,2], we have reported for the first time on the gas-sensing performances of nanocomposite systems based on Mn3O4-M (M = Ag, Au) in DPGME detection [3]. The target materials were obtained by the initial chemical vapor deposition (CVD) of Mn3O4 on polycrystalline Al2O3 substrates, followed by silver or gold radio frequency (RF) sputtering, with the aim of obtaining a high dispersion of metal nanoparticles.The results yielded by a multi-technique characterization highlighted the formation of phase-pure Mn3O4 nanostructures eventually functionalized with Ag or Au and an intimate contact between metal oxide matrix and nanoparticles. These features enabled us to enhance the system sensitivity in the detection not only of standard volatile organic compounds (acetone and ethanol), but also of DPGME, down to the ppb scale. Moreover, the possibility of discriminating between DPGME, on one side, and acetonitrile (CH3CN) or dimethyl methyl phosphonate (DMMP), simulants of HCN (blood agent gas) and Sarin nerve gas, respectively, demonstrates the system selectivity toward the target warfare gas simulant. To shed light on the origin of enhanced selectivity due to functionalization, density functional theory (DFT) based calculations were performed. The results, providing a molecular insight into the interactions between the target systems and DPGME, enabled us to elucidate a dual-site activation mechanism based on the binding of DPGME to both manganese oxide and gold nanoparticles, accounting for the higher functional performances registered for Au-Mn3O4 sensors.As a whole, this study represents an important step forward in the fabrication of highly efficient sensors based on dual metal oxide-metal NP composites. The obtained results pave the way to mastering next-generation sensing devices for real world applications, which will be pursued by additional investigation of the system long-term stability and humidity influence on the resulting functional performances.

Effect of cobalt doping on the electrochemical performance of trimanganese tetraoxide

Nanostructured transition metal oxides (TMO) are potential materials widely explored by researchers for energy storage applications. In this study, spinel trimanganese tetraoxide (Mn3O4) and cobalt doped trimanganese tetraoxide (Co-Mn3O4) was synthesized by using a simple solvent assisted hydrothermal route. Pure Mn3O4 and Co-Mn3O4 nanomaterials were characterized by an x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), UV-diffuse reflectance spectroscopy (UV-DRS), field emission scanning electron microscope (FESEM), and high resolution transmission electron microscope (HRTEM). XRD analysis revealed the body centered tetragonal spinel structure of Mn3O4 and Co-Mn3O4 with a space group as l41/amd (141) and an approximate crystallite size of 45–33 nm. The presence of an Mn–O bond vibration was confirmed using FTIR and the band gap properties were analyzed through UV-DRS. Surface morphology and average grain size were examined using FESEM and HRTEM micrographs as nanosquares and nanospheres with diameter 126 nm and 118 nm, respectively. Electrochemical properties of Mn3O4 and Co-Mn3O4 were evaluated using cyclic voltammograms, charge–discharge curves, and electrochemical impedance spectra (EIS). Pure Mn3O4 showed a specific capacitance of 971 F g−1 at 0.1 A g−1 current density while Co-Mn3O4 achieved relatively higher specific capacitance of 1852 F g−1 at the same current density. It is observed that the increased specific capacitance of Co-Mn3O4 mainly arises from the doping effect. Electrochemical analysis shows that the Co doped Mn3O4 nanomaterials can be a promising electrode material for supercapacitor.

Effectiveness of surfactants for unique hierarchical Mn2O3 nanomaterials as enhanced oxidative catalysts, antibacterial agents, and photocatalysts

We present the chemical-surfactant-mediated and green-surfactant-mediated synthesis of manganese (III) oxide nanoparticles prepared by the precipitation method using cetyltrimethylammonium bromide and tea extract, respectively, and their structural and optical properties. The nanoparticles were characterized by X-ray diffraction, scanning electron microscopy–energy-dispersive X-ray analysis, UV–Vis spectroscopy, and Fourier transform IR spectroscopy with regard to the diffraction pattern, phase, size, shape, composition of material, etc. The Mn2O3 nanoparticles had an orthorhombic structure with crystallite sizes of 25.96 and 13.17 nm for chemical synthesis and green synthesis, respectively. The chemically synthesized Mn2O3 nanoparticles were cubic and the green-synthesized Mn2O3 nanoparticles were spherical, with average particle sizes of 30–50 nm and 20–40 nm, respectively, and band gaps of 2.2 and 2.1 eV, respectively. The photodegradation of methylene blue was analyzed with Mn2O3 nanoparticles under solar irradiation. The present study also revealed the catalytic ability for oxidation reaction and the antimicrobial activities of the chemically synthesized and green-synthesized Mn2O3 nanoparticles, and their effectiveness was compared.

Hydrogen Gas Sensing Performances of p-Type Mn3O4 Nanosystems: The Role of Built-in Mn3O4/Ag and Mn3O4/SnO2 Junctions.

Among oxide semiconductors, p-type Mn3O4 systems have been exploited in chemo-resistive sensors for various analytes, but their use in the detection of H2, an important, though flammable, energy vector, has been scarcely investigated. Herein, we report for the first time on the plasma assisted-chemical vapor deposition (PA-CVD) of Mn3O4 nanomaterials, and on their on-top functionalization with Ag and SnO2 by radio frequency (RF)-sputtering, followed by air annealing. The obtained Mn3O4-Ag and Mn3O4-SnO2 nanocomposites were characterized by the occurrence of phase-pure tetragonal α-Mn3O4 (hausmannite) and a controlled Ag and SnO2 dispersion. The system functional properties were tested towards H2 sensing, yielding detection limits of 18 and 11 ppm for Mn3O4-Ag and Mn3O4-SnO2 specimens, three orders of magnitude lower than the H2 explosion threshold. These performances were accompanied by responses up to 25% to 500 ppm H2 at 200 °C, superior to bare Mn3O4, and good selectivity against CH4 and CO2 as potential interferents. A rationale for the observed behavior, based upon the concurrence of built-in Schottky (Mn3O4/Ag) and p-n junctions (Mn3O4/SnO2), and of a direct chemical interplay between the system components, is proposed to discuss the observed activity enhancement, which paves the way to the development of gas monitoring equipments for safety end-uses.

Facile Preparation of MnO2 Quantum Dots with Enhanced Fluorescence via Microenvironment Engineering with the Assistance of Some Reductive Biomolecules.

MnO2 nanomaterials have aroused widespread attention because of their nanozyme activity, redox properties, good biocompatibility, and therapy-related activities. However, not many reports on self-luminescent MnO2 materials have been concerned to date, which greatly hampered their further development in various fields. In this paper, luminescent MnO2 quantum dots (MnO2 QDs) have been first prepared via a facile one-step ultrasonic method. With the assistance of bovine serum albumin (BSA) or cysteine (Cys), the synthesized MnO2 QDs (BSA-MnO2 QDs or Cys-MnO2 QDs) display strongly enhanced fluorescence (FL). The prepared BSA-MnO2 QDs with a particle size of about 1 to 2 nm show the maximum excitation and emission peaks at 320 and 410 nm with excellent salt stability, anti-photobleaching ability, and time stability. It is confirmed that BSA plays a dual function as the exfoliating agent to promote the exfoliation of bulk MnO2 nanosheets and as the capping agent to provide a friendly microenvironment for MnO2 QDs. Ag ions can destroy the microenvironment of BSA-MnO2 QDs owing to the in situ formation of Ag nanoparticles (Ag NPs) mediated by BSA on the surface of the QDs. Then, these Ag NPs can quench the FL intensity of the QDs by fluorescence resonance energy transfer. However, the FL strength of the BSA-MnO2 QDs is recovered after adding H2O2 and NaHS since they may react with Ag NPs to produce Ag+ and Ag2S, which further confirmed the role of BSA. This work not only opens up a facile and universal avenue to synthesize luminescent MnO2 QDs with enhanced FL but also provides a possible sensing platform through tuning the microenvironment of the MnO2 QDs. The MnO2 QDs with outstanding performance may show great potential as fluorescent probes in the fields of biological imaging, optical sensing, drug delivery, and therapy.

Quasi-1D MnO2 nanocomposites as gas sensors for hazardous chemicals

Quasi-1D MnO2 nanocomposite materials (A/MnO2 with A = CuO, SnO2) were developed by a two-step plasma-assisted process, involving the plasma enhanced-chemical vapor deposition (PE-CVD) of MnO2 nanomaterials and their functionalization with copper or tin oxides by radio frequency (RF)-sputtering. A thorough characterization by means of specific surface analytical techniques highlighted the formation of high purity nanocomposites, endowed with a controlled morphology and a tailored spatial dispersion of the functionalizing agents. The target materials were tested as gas sensors for the recognition of hazardous gases [H2 and di(propyleneglycol) monomethyl ether (DPGME) / dimethyl methyl phosphonate (DMMP), the latter used as simulants for chemical warfare agents]. Functional data evidenced the obtainment of low detection limits and promising gas responses, whose improvement with respect to the pristine MnO2 was traced back to the formation of built-in p-n and n-n junctions for CuO/MnO2 and SnO2/MnO2 systems, respectively. The possibility of discriminating between the target analytes depending on the functionalizing species already at moderate working temperatures demonstrates the potential of the developed materials for eventual gas sensing applications under real-world conditions.

One-pot enzyme- and indicator-free colorimetric sensing of glucose based on MnO2 nano-oxidizer

To establish more stable and lower cost colorimetric methods for the sensing of glucose, the artificial nanozymes were developed as the substitutes of natural enzymes (glucose oxidase, GOx; peroxidase). However, the common utilized nanozymes cannot show both the tandem enzymatic activities and the color indicating performance at the same time, which lead to the further addition of natural enzyme or color indicator. To overcome these problems, we fabricate a novel one-pot enzyme- and indicator-free method for the colorimetric sensing of blood glucose levels based on the direct redox reaction of MnO2/glucose. The MnO2 nanomaterial is acted as an active nano-oxidizer, and a color nano-indicator for the sensing of blood glucose levels. In the presence of target glucose, the MnO2 nano-oxidizers is reduced to Mn2+, leading to the dramatic decreasing absorbance and fading color of yellow MnO2 solution. This nanosystem demonstrates wide liner range from 10 μM to 5 mM with low detectable limit of 10 μM. In addition, it shows favorable applicability for the glucose monitoring in human blood sample. Our proposed strategy takes advantage of the direct redox reaction of glucose and MnO2, which eliminates the use of natural enzymes (GOx, peroxidase) and the color indicator, and realized a sensitive, low-cost and convenient method for the colorimetric sensing of glucose.

Shape-Dependent Interactions of Manganese Oxide Nanomaterials with Lipid Bilayer Vesicles.

Interactions of transition-metal-oxide nanomaterials with biological membranes have important environmental implications and applications in ecotoxicity and life-cycle assessment analysis. In this study, we quantitatively assess the impact of MnO2 nanomaterial morphology-one-dimensional (1D) nanowires, 2D nanosheets, and 3D nanoflowers-on their interaction with phospholipid vesicles as a model for biological membranes. Confocal microscopy suggests visual evidence for the interaction of undisrupted vesicles with dispersed MnO2 nanomaterials of different morphologies, and it further supports the observation that minimal dye leakage of the vesicle inner solution was detected during the interaction with MnO2 nanomaterials during the dye leakage assay. Upon titration of vesicles to dispersions of MnO2 nanowires, nanosheets, and nanoflowers, each roughly 10 times larger than the vesicles, dynamic light scattering reveals two diffusive time scales associated with aggregates in the mixture. While the longer time scale corresponds to the dispersed MnO2 control population, the appearance of a shorter timescale with vesicle addition indicates interaction between the dispersed metal oxide nanomaterials and the vesicles. The interaction is shape-dependent, being more pronounced for MnO2 nanowires than for nanosheets and nanoflowers. Furthermore, the shorter diffusive time scale is intermediate between the vesicle and nanomaterial controls, which may suggest a degree of metal oxide aggregate breakup. Vesicle adsorption isotherms and zeta potential measurements during titration corroborate vesicle attachment on the nanomaterials. Our results suggest that the dispersed nanomaterial shape plays an important role in mediating nondestructive vesicle-nanomaterial interactions and that lipid vesicles act as efficient surfactants for MnO2 nanomaterials.

A Rapid Synthesis of Mesoporous Mn2O3 Nanoparticles for Supercapacitor Applications

Mn2O3 nanomaterials have been recently composing a variety of electrochemical systems like fuel cells, supercapacitors, etc., due to their high specific capacitance, low cost, abundance and environmentally benign nature. In this work, mesoporous Mn2O3 nanoparticles (NPs) were synthesized by manganese acetate, citric acid and sodium hydroxide through a hydrothermal process at 150 °C for 3 h. The synthesized mesoporous Mn2O3 NPs were thoroughly characterized in terms of their morphology, surfaces, as well as their crystalline, electrochemical and electrochemical properties. For supercapacitor applications, the synthesized mesoporous Mn2O3 NP-based electrode accomplished an excellent specific capacitance (Csp) of 460 F·g−1 at 10 mV·s−1 with a good electrocatalytic activity by observing good electrochemical properties in a 6 M KOH electrolyte. The excellent Csp might be explained by the improvement of the surface area, porous surface and uniformity, which might favor the generation of large active sites and a fast ionic transport over the good electrocatalytic surface of the Mn2O3 electrode. The fabricated supercapacitors exhibited a good cycling stability after 5000 cycles by maintaining ~83% of Csp.

Facile synthesis of three-dimensional Mn3O4 hierarchical microstructures for efficient catalytic phenol oxidation with peroxymonosulfate

Hierarchical porous materials have a wide application prospect in heterogeneous catalysis because they can provide plentiful surface active sites and well-developed mass transfer channels while being easily separable, as compared with their nanosized counterparts. In this study, three-dimensional hausmannite (Mn3O4) hierarchical micron-sized materials (Mn3O4-H) were synthesized by a simple room-temperature aqueous solution route. The catalytic performance was evaluated by activation of peroxymonosulfate (PMS) to oxidize phenol, a model organic pollutant, in aqueous solution. The Mn3O4-H showed a higher efficiency in activating PMS for phenol oxidation than two Mn3O4 nanomaterials, i.e., nanoparticles and nanorods, attributed to the higher specific surface area and more surface reactive sites arising from the hierarchical structure. The Mn3O4-H also showed high catalytic stability, with low Mn leaching during phenol degradation tests. Phenol degradation reaction kinetics followed the pseudo-first-order rate laws, and the reaction was accelerated at higher temperature. In addition, the effects of important operation parameters such as catalyst loading and PMS concentration on catalytic performance of Mn3O4-H were evaluated. The present research provides a facile approach for synthesis of green and effective catalytic materials to be used in PMS-based advanced oxidation processes for environmental remediation.

Versatile High-Performance Electrochemiluminescence ELISA Platform Based on a Gold Nanocluster Probe.

This report outlines a versatile high-performance electrochemiluminescence (ECL) enzyme-linked immunosorbent assay (ELISA) platform, which combines the merits of high-quantum-yield Au nanocluster (AuNC) probe-based ECL technology, the efficient ECL-resonance energy-transfer (ECL-RET) strategy, and highly sensitive and specific ELISA technology. The ECL detection procedure was performed on a recyclable MnO2/AuNC-modified glassy carbon electrode interface by taking advantage of the ECL-RET between the AuNC probe and MnO2 nanomaterials (NMs) to quench the ECL intensity. The etching of MnO2 NMs by the product of ALP-based ELISA recovers the ECL signal. Notably, the ELISA process and the ECL detection procedure in this system are independent. Thus, the ECL-ELISA system can effectively avoid the influence of complex biological samples, and the ECL efficiency of the AuNC probe can be used readily. As demonstrated on TNF-α, because of the abovementioned characteristics, the ECL-ELISA platform presented an extremely wide dynamic range, with a detection limit of 2 orders lower than ELISA. Moreover, the system was also applicable for ultrahigh sensitive detection of various disease-related proteins and able to detect trace biomarkers in real serum samples. Therefore, this multifunctional ECL assay platform is versatile, facile, ultrasensitive, recyclable, and sufficiently straightforward for trace biomarker detection in complex biological samples. This approach not only enriches the foundational study of ECL devices but also greatly expands the potential application of ECL sensors in biological testing and clinical high-throughput diagnosis.

Sonochemical-Assisted Coprecipitation Synthesis of Body-Centered Tetragonal Mn3O4 Spinel Nanostructures Using Polyethylene Glycol Template Agent

The excellent characteristics of Mn3O4 nanomaterials have driven many experts to carry on exploring improved approaches for Mn3O4 fabrication. Herein, Mn3O4 nanostructures have been synthesized via sonochemical-assisted coprecipitation method. Polyethylene glycol (PEG-6000) with various concentrations was employed as a surface coating. The combination of coprecipitation and ultrasonication has led to the formation of Mn3O4 nanoparticles which were well-confirmed by three different characterization instruments, i.e., X-ray diffraction (XRD), scanning electron microscopy (SEM) along with energy dispersive X-ray (SEM-EDX), and Fourier transform infrared (FTIR). The XRD data collection and analysis reveal the presence of single-phase of Mn3O4 spinels. The Rietveld refinement dictates the establishment of tetragonal distortion along the c-axis creating a body-centered tetragonal spinel structure with a space group of I41/AMDS. In addition, the SEM-EDX and FTIR data support the experimental results obtained by XRD.