Hollow Manganese Oxide Research Articles

Investigation and risk assessment of dibutyl phthalate in a typical region by a high-throughput dual-signal immunoassay

The systematic investigation and risk assessment of dibutyl phthalate (DBP) were performed using an ultrasensitive dual-signal immunoassay in Zhenjiang, Jiangsu Province. In this study, C-dots@H-MnO2 nanohybrid were synthesized and labelled on the secondary antibody to generate fluorometric and colorimetric signals. Attributed to the efficient catalysis of carbon dots (C-dots) and the high C-dots loading of hollow manganese (IV) oxide (H-MnO2), the excellent sensitivity and low detection limits (0.243 and 0.692 μg/L respectively) were produced. Based on the proposed method, 25 water and 119 beverage samples were investigated. DBP was found in all water samples and 65.5% of beverage samples, with the concentrations varying in 16.5–32.1 μg/L and 0–553 μg/L, respectively. In addition, the mean concentration (22.9 μg/L) in waters was decreased significantly compared with that detected in 2016 (43.5 μg/L) by our Lab. For beverages, a similar phenomenon was observed by the measured concentrations from coffee. Furthermore, the potential ecological risks of DBP were evaluated, the results indicated that human activities had caused serious pollution and high risks to the local aquatic ecosystem. On the other hand, the results of health risk assessment suggested that DBP in beverages might not cause obvious side effects to local residents.

Inner structure- and surface-controlled hollow MnO nanocubes for high sensitive MR imaging contrast effect

Manganese oxide (MnO) nanocubes were fabricated and their surface were modified by ligand encapsulation or ligand exchange, to render them water-soluble. And then, MnO formed the hollow structure by etching using acidic solution (phthalate buffer, pH 4.0). Depending on the ligand of the MnO surface, it increases the interaction between MnO and water molecules. Also, the hollow structure of MnO, as well as the ligand, can greatly enhance the accessibility of water molecules to metal ions by surface area-to-volume ratio. These factors provide high R1 relaxation, leading to strong T1 MRI signal. We have confirmed T1-weighted MR contrast effect using 4-kinds of MnO nanocubes (MnOEn, MnOEnHo, MnOEx and MnOExHo). They showed enough a MR contrast effect and biocompatibility. Especially, among them, MnOExHo exhibited high T1 relaxivity (r1) (6.02 mM−1 s−1), even about 1.5 times higher sensitivity than commercial T1 MR contrast agents. In vitro/in vivo studies have shown that MnOExHo provides highly sensitive T1-weighted MR imaging, thereby improving diagnostic visibility at the disease site.

Supercritical Fluid-Assisted Fabrication of Manganese (III) Oxide Hollow Nanozymes Mediated by Polymer Nanoreactors for Efficient Glucose Sensing Characteristics.

Despite their inherent efficacy in significantly accelerating the rate of chemical reactions in biological processes, the applicability of natural enzymes is often hindered because of their intrinsic limitations such as high sensitivity, poor operational stability, and relatively high cost for purification as well as preparation. Thus, the fabrication of catalytically active nanomaterials as artificial enzymes (nanozymes) has become a newly burgeoning area of research in bionic chemistry, aiming in designing functional nanomaterials that mimic various inherent properties of natural enzymes. To address these issues, we present the supercritical fluid (SCF)-assisted fabrication of discrete, monodisperse, and uniform-sized manganese (III) oxide (Mn2O3)-based hollow containers as high-efficiency nanozymes for glucose sensing characteristics. Initially, the core-shell nanoreactors based on polyvinylpyrrolidone (PVP)-encapsulated manganese (III) acetylacetonate (Mn(acac)3) as precursors are fabricated using the SCF technology and subsequent calcination resulted in the Mn2O3 hollow nanoparticles (MHNs). This eco-friendly approach has resulted in the PVP-coated Mn(acac)3 nanoreactors with an average diameter of 220 nm and subsequent calcined hollow products are about one-fifth to that of the precursor. Such MHNs conveniently catalyzed 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) as a prominent peroxidase mimic, resulting in the oxidation products (TMB*+) at a specific absorption (UV-vis) maxima of 652 nm. Following typical Michaelis-Menten theory, this approach is further utilized to develop visual nonenzymatic sensing of glucose in a linear range of 0.1-1 mM at a detection limit of 2.31 μM. Collectively, this reliable as well as a cost-effective system with high precision potentially allows rapid detection of analytes, providing a convenient way for its utilization in diverse fields.

Enhanced Electro-Oxidation of Urea Using Hollow Structured Nickel Manganese Oxide Catalysts

The utilization of urea has attracted more attention due to its various applications such as fuel cell, hydrogen production, wastewater remediation, and electrochemical sensors. [1] Especially, urea is a crucial biomarker to detect various human metabolic disorders such as renal function and liver disease. Therefore, the measurement of the urea level plays an important role in monitoring metabolic activity of human. Electrochemical sensing method is considered one of the most promising technique for urea detection due to its simplicity and reliable sensing. [2] The enzyme-based catalyst is widely used for urea oxidation. However, the enzyme has the stability issue due to the denaturing of the enzyme. Hence, non-enzymatic biosensors by metal-based catalysts have been studied. Compared with noble metal catalysts, nickel-based catalysts are inexpensive and abundant. Furthermore, bimetallic nickel-based oxides (nickel cobalt oxide [3], nickel molybdenum oxide [4], and nickel manganese oxide [5]) have been developed for efficient urea oxidation reaction in alkaline medium. Despite many efforts to achieve higher catalytic effect with bimetallic oxides, the improvement of catalytic property of urea oxidation is still challenging due to the low exposure of active sites and low electrical conductivity The hollow structured catalyst can improve the performance of urea detection by providing structural stability of catalyst and facile transport channels for electrolyte with exploiting its inner and outer surface as active sites. With introducing the template-free hydrothermal method with SDBS, Ni-Mn-based oxide is synthesized. Due to the synergetic catalytic effect between NiO and MnO and morphological effect of hollow structure, higher oxidation current and lower onset potential could be achieved. In this study, nickel manganese oxide catalyst with the variation of Ni:Mn atomic ratios were synthesized by one-pot template-free hydrothermal method. Structure and morphologies of synthesized nickel and manganese oxide hollow structure were characterized by XRD and SEM. And the atomic ratio of nickel manganese oxide was confirmed by EDS. CV measurement was conducted in a three-compartment cell with a potentiostat 1M KOH with 0.33M urea. CA measurement was also performed to measure the selectivity and limit of detection. Detailed mechanism and discussion of the formation of structure and sensing properties of nickel manganese oxide catalyst will be presented.

Promoting polythionate intermediates formation by oxygen-deficient manganese oxide hollow nanospheres for high performance lithium-sulfur batteries

Mediating polysulfides redox by forming surface-bound insoluble intermediates on metal oxides is an efficient strategy to curtail polysulfides shuttling. Herein, the formation of surface-bound insoluble intermediates is further promoted by surface engineering of manganese oxide host via introducing oxygen vacancies. Hollow MnO2 nanospheres are first synthesized via a facial hard-template method, which provide a huge void for sulfur immobilization and volumetric expansion. Surface oxygen vacancies are then introduced by heating the products in a reduction atmosphere. These oxygen vacancies are proposed to accelerate the formation of polythionate intermediates, and which can adsorb polysulfides species more strongly than normal oxide sites and assist in their dissociation to lithium sulfide. The cathode based on oxygen-deficient manganese oxide hollow nanospheres achieves high initial discharge capacity of 1053 mAh g−1 at 0.5 C and high reversible capacity of 551 mAh g−1 at 2 C over 400 cycles, while only initial discharge capacity of 918 mAh g−1 and reversible capacity of 410 mAh g−1 are obtained for pristine MnO2. This work provides a novel strategy to establish cathode with engineered surface chemistry of metal oxides for high performance Li-S batteries.

Anchoring Ligand-Effect on Bright Contrast-Enhancing Property of Hollow Mn3O4 Nanoparticle in T1-Weighted Magnetic Resonance Imaging

Here, we describe and conceptualize the influence of surface engineering for hollow manganese oxide nanoparticles (HMONs)-based contrast agents for magnetic resonance imaging (MRI). A systematic study has been conducted for enhancing the relaxivities of HMONs by functionalizing their surface with various capping ligands having different anchoring groups (carboxylate, alcohol, thiol, and amine). Among all studied ligands, carboxylate-anchored ligands exhibit significant increase in magnetization value upon surface capping of HMON. Contrary to the previous hypotheses based on the surface-Mn2+ ions accessibility to water molecules, we proposed surface capping induced magnetization in HMON is responsible for the enhanced relaxivity (r1) value. Further, in vivo imaging efficacy of oleate-capped HMON (OA-HMON) has been demonstrated in mouse brain. This study provides an insightful understanding of contrast enhancement and modulation by surface ligands on manganese oxide-based T1-contrast agents.

Alkaline electrochemical water oxidation with multi-shelled cobalt manganese oxide hollow spheres.

Multi-shelled hollow spheres of cobalt manganese oxides (CMOs) deposited on Ni foam exhibited superior alkaline electrochemical water oxidation activity and surpassed those of bulk CMO and commercial noble metal-based catalysts. A higher amount of cobalt in the spinel structure resulted in the transformation of the tetragonal to the cubic phase with a decrease in the overpotential of oxygen evolution.

Hollow manganese oxide nanoparticle-enhanced MRI of hypoxic-ischaemic brain injury in the neonatal rat.

To determine the utility of hollow manganese oxide nanoparticle (HMON)-enhanced MRI in depicting and monitoring apoptotic area following hypoxic-ischaemic injury in a neonatal rat brain and to evaluate the longitudinal evolution of hypoxic-ischaemic brain injury (HII) up to 21 days. The institutional animal care and use committee approval was obtained. The Rice-Vannucci model of HII was used in 7-day-old rat pups (n = 17). MRI was performed 1, 3, 7, 14 and 21 days after HII with intraperitoneal injection of HMON. Relative contrast values in the injured hemisphere and mean apparent diffusion coefficient values were calculated at each time point. Apoptosis and reactive astrogliosis were detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling (TUNEL) and glial fibrillary acidic protein staining, and the distribution and intensity of immunohistochemical staining were directly compared with those of HMON enhancement on MRI. The dorsolateral thalamus, hippocampus and remaining cortex of the injured hemisphere showed HMON enhancement from 3 to 21 days after HII. The mean relative contrast values in the dorsolateral thalamus showed an increase from a negative value at 1 day to 16.5 ± 4.8% at 21 days. The apoptotic cells and reactive astrocytes were observed on immunohistochemical staining from 1 to 21 days after HII. The accumulation of apoptotic cells regionally matched with the areas of HMON enhancement, while that of reactive astrocytes did not. The areas of HMON enhancement showed best spatial agreement with those of apoptosis on TUNEL staining. Both HMON enhancement and TUNEL-positive cells were observed up to 21 days after HII. Advances in knowledge: The strength of our study is the visualization of apoptotic area in vivo using HMON-enhanced MRI, and we also showed that HII has a prolonged evolution lasting for several weeks.

Controlled Synthesis of Hollow Manganese Oxide Nanocrystals.

Carbon spheres have been prepared from glucose under hydrothermal conditions to facilitate the synthesis of hollow manganese oxides. The phases of manganese oxide are controlled by changing annealing temperature of the manganese monoxide on a carbon sphere template. The particles on the carbon surface get an agglomeration and make dense oxide shell during the calcination step, which result in typical hollow structures. The electrochemical properties of hollow manganese oxides have been investigated to elucidate their relative catalytic activities.

Hierarchical architecture of hybrid carbon-encapsulated hollow manganese oxide nanotubes with a porous-wall structure for high-performance electrochemical energy storage

Uniquely designed hierarchical architecture of hybrid carbon-encapsulated porous hollow nanotubes with favorable routes and sites for Li ion insertion/extraction, resulting in improved high-rate performance and cycling stability.

Synthesis of multi-shelled MnO2 hollow microspheres via an anion-adsorption process of hydrothermal intensification

Multi-shelled manganese oxide hollow microspheres can be synthesized via an anion-adsorption process of hydrothermal intensification with controlled valence and shell number.

Influence of Fe, Cu, V, and Ce doping on morphology and catalytic activity of amorphous manganese oxide hollow spheres

Manganese oxide hollow spheres have been prepared by a facile, self-assembly synthesis and doped with Fe, Cu, V, and Ce. The materials have high surface areas and shells consisting of nanoplatelets. Two different sets of reactions were carried out: (1) with constant butyric acid concentration using 10:1 BA:Mn and (2) with adjusted butyric acid concentration using 10:1 BA:total metal (Mn+dopant). Dopants promote the formation of yolk structures within the hollow spheres, and at higher dopant:Mn ratios cause the spheres to fill. Increasing the butyric acid concentration likewise promotes yolk formation and sphere filing, as well as larger sphere size and loss of monodispersity. Manganese oxide hollow spheres are active catalysts in converting isopropanol to acetone, although doping does not improve catalyst performance except in the case of Cu.

Hollow Inorganic Nanoparticles as Efficient Carriers for siRNA Delivery: A Comprehensive Review.

Small interfering RNAs (siRNA) are emerging as a new opportunity for treatment of various diseases, including viral and cancer diseases via knocking down a specific gene that involves in disease development. But their clinical application is hampered because of susceptibility to degradation and difficult delivery of siRNA into cells. So it is needed to develop an efficient carrier that stabilizes and delivers siRNA efficiently and specifically into cells. Hollow inorganic nanoparticles have gained considerable attention as an efficient drug and gene delivery system. This is due to their biocompatibility, simple preparative processes, easy functionalization and high capacity for drug loading. Several nanoparticle platforms for siRNA delivery have been developed to overcome the major limitations facing the therapeutic uses of siRNA. Recently, researchers have developed a wide range of inorganic nanocarriers to increase efficacy of si-RNA-based drugs and gained efficient siRNA delivery both in vitro and in vivo. This review covers a broad spectrum of hollow inorganic nanoparticles as non-viral siRNA delivery systems. These nanoparticles are developed for enhanced cellular uptake and targeted gene silencing in vitro and in vivo and their characteristics and opportunities for clinical applications of therapeutic siRNA are discussed in this article. Various types of inorganic hollow nanovectors including: mesoporous silica nanoparticles, carbon nanotubes, graphene oxide, fullerenes, calcium phosphate nanoparticles, hollow manganese oxide, gold nanoshells, and layered double hydroxide nanoparticles used to deliver siRNA are introduced and the development of theranostics and combinational treatment is also discussed.

A Hybrid Silica Nanoreactor Framework for Encapsulation of Hollow Manganese Oxide Nanoparticles of Superior T1 Magnetic Resonance Relaxivity

A new hybrid nanoreactor framework with poly(ethylene oxide)‐perforated silica walls is designed to encapsulate hollow manganese oxide nanoparticles (MONs) of high distinctness and homogeneity. Achieved by an interfacial templating scheme, the nanoreactor ensures that acidic etching of MONs by an acetate buffer solution is highly controlled for precise control of the hollow interior. As such, hollow MONs with different nanostructures are developed successfully through a facile acetate buffer solution etching. The resultant hollow MONs are integrated within the hybrid nanoreactor and demonstrate superior r1 relativity of up to 2.58 mm−1 s−1 for T1 magnetic resonance imaging (MRI). By modifying the nanoreactor architecture, it is also demonstrated that the efficacy of MONs as T1 MRI contrast agents can be significantly improved if an optimal cluster of hollow MONs is encapsulated into the hybrid silica framework. The evolution of core morphology with time is studied to elucidate the etching mechanism. It is revealed that the hollow formation arises due to the surface stabilization of MONs by acetate ions and the subsequent acidic etching of the interior core in a sporadic manner. This is different from the commonly reported nanoscale Kirkendall effect or the selective etching of the core–shell MnO/Mn3O4 structure.

Nano-Hierarchical Hollow Manganese Oxide Anode Material with High Performance for Lithium-Ion Battery

Lithium-ion batteries (LIBs) are expected to continue playing important roles in energy storage for mobile communication and electric vehicle (EV) and renewable energy applications in the foreseeable future. Graphite as a commercial anode material for LIB possesses the advantages of high coulombic efficiency and good cycle stability. However, its theoretical capacity is only 372mAh/g, and this limits the total capacity of the full battery. The demand for higher energy capacity of the energy storage cell has been driving the development of alternative anode materials with higher capacities. Certain nanocrystalline metal oxides have been shown to be able to work as a reversible anode through heterogeneous conversion reaction.The high theoretical capacity and density give metal oxides the edge over graphite as high energy density anodes for LIB. Nevertheless, due to the high kinetic barrier of the conversion reaction at room temperature, metal oxide anodes typically exhibits large potential hysteresis between lithiation and de-lithiation cycles. The hysteresis reduces the operating voltage window as well as the energy efficiency of the LIB cell. Furthermore, the poor conductivity and large volume expansion arising from lithiation of the metal oxide particles are major shortcomings that may cause poor cycling stability. Compared with other conversion–type metal oxide anodes, manganese oxide (MnOx) shows smaller potential hysteresis and lower operation potential. In addition, MnOxhave the advantages of being environment friendly and abundant.In this work, we have prepared hierarchical hollow MnO2 by utilizing a SiO2-templating hydrothermal process. The results revealed that the novel hollow nanostructure MnO2 electrode had a specific charge capacity as large as 1364 mAh/g at 0.1 C-rate, and it unprecedentedly demonstrates high rate performance, retaining 878 mAh/g at 2 C-rate and good cycle stability.

Synthesize and Application of Novel Nano-Hierarchical Hollow Manganese Oxide Anode Material with Outstanding Performance for Sodium Ion Battery

Based on the wide availability and low cost of sodium, ambient temperature sodium–ion batteries (SIBs) have the potential for meeting large scale grid energy storage needs. In addition, since sodium is so abundant, SIBs could provide an alternative chemistry to lithium batteries. However, many anode materials for lithium–ion batteries (LIBs) have not yet been explored for SIBs. Among several kinds of metal oxide anode materials, manganese (Mn) salts are naturally abundant, inexpensive, and environmentally friendly. The utilization of MnOx or their composites as anode material for SIBs is a prospect that should not be neglected. However, most of transition metal oxide anodes suffer from low rate performance and fast capacity fade due to their poor electronic conductivity and large volume changes during the conversion reaction. Nanostructured materials have the potential for achieving high capacity and rate capability resulting from the large specific surface area and the short electronic and ionic transport length in nanoscale.For the first time, we have prepared hierarchical hollow MnO2 by utilizing a SiO2-templating hydrothermal process. Different from the conventional methods, the SiO2 was only partially dissolved so that the residue serves as a framework to support MnO2. The results revealed that the novel hollow nanostructure MnO2 electrode had a specific charge capacity as large as 499 mAh/g at 0.1 C-rate, and it unprecedentedly demonstrates good cycling stability, retaining 89.4% capacitance after 500 cycles at 1 C-rate at 50 oC.

Synthesis of Amourphous and Crystalline Hollow Manganese Oxide Nanotubes with Highly Porous Walls Using Carbon Nanotube Templates and Enhanced Catalytic Activity

A novel rapid fabrication method was developed for the first time to prepare hollow manganese oxide nanotubes with porous walls, using sacrificial carbon nanotube templates. Multiwalled carbon nanotubes (CNTs) are coated with amorphous manganese oxide layers by acidic reduction of potassium permanganate solution. The rapid synthesis process with the evolution of gaseous byproduct yields very high porosity in the coated manganese oxide layers. Subsequent heat treatment leads to the removal of CNT templates, resulting in the formation of amorphous and crystalline hollow manganese oxide nanotubes with highly porous walls. The porous hollow nanotubes were found to provide excellent catalytic performances in the degradation of organic dye at ambient conditions by virtue of the very high surface reaction sites within the porous hollow tubular structures. These novel nanostructures of hollow nanotubes with porous walls are promising for a series of applications such as hydrogen storage, sensing, supercapacitance, and catalysis, among others.

Copper Doped Hollow Structured Manganese Oxide Mesocrystals with Controlled Phase Structure and Morphology as Anode Materials for Lithium Ion Battery with Improved Electrochemical Performance

We develop a facile synthesis route to prepare Cu doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology using manganese carbonate as the reactant template. It is shown that Cu dopant is homogeneously distributed among the hollow manganese oxide microspherical samples, and it is embedded in the lattice of manganese oxide by substituting Mn(3+) in the presence of Cu(2+). The crystal structure of manganese oxide products can be modulated to bixbyite Mn2O3 and tetragonal Mn3O4 in the presence of annealing gas of air and nitrogen, respectively. The incorporation of Cu into Mn2O3 and Mn3O4 induces a great microstructure evolution from core-shell structure for pure Mn2O3 and Mn3O4 samples to hollow porous spherical Cu-doped Mn2O3 and Mn3O4 samples with a larger surface area, respectively. The Cu-doped hollow spherical Mn2O3 sample displays a higher specific capacity of 642 mAhg(-1) at a current density of 100 mA g(-1) after 100 cycles, which is about 1.78 times improvement compared to that of 361 mA h g(-1) for the pure Mn2O3 sample, displaying a Coulombic efficiency of up to 99.5%. The great enhancement of the electrochemical lithium storage performance can be attributed to the improvement of the electronic conductivity and lithium diffusivity of electrodes. The present results have verified the ability of Cu doping to improve electrochemical lithium storage performances of manganese oxides.

Preparation and capacitance behavior of manganese oxide hollow structures with different morphologies via template-engaged redox etching

A variety of amorphous manganese oxide electrode materials with uniform nonspherical hollow interiors are prepared via sacrificial template-engaged redox etching of the corresponding shape-controlled Cu2O nanocrystals in KMnO4 aqueous solution at room temperature. The obtained materials are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption. The amorphous manganese oxide hollow materials not only well inherit the size and shape of Cu2O nonspherical precursor, but also show a manganese average oxidation state of 3.7 and large specific surface area (about 198 m2 g−1). The electrochemical measurements show that the capacitance of the as-prepared amorphous manganese oxide electrode materials with uniform nonspherical hollow interiors is connects with their specific surface area. The amorphous manganese oxide star hollow architecture exhibits not only high specific capacitance of 366 F g−1 at a scan rate of 5 mV s−1, but also relatively good cycle stability (93.1% capacitance retention after 1000 cycles at a scan rate of 20 mV s−1), which make it have a potential application as a supercapacitor electrode material.

Magnetic resonance imaging of amyloid plaques using hollow manganese oxide nanoparticles conjugated with antibody aβ1–40 in a transgenic mouse model

In this study, we have shown the feasibility of hollow manganese oxide nanoparticles (HMON) conjugated with an antibody of Aβ1-40 peptide (abAβ40) (HMON-abAβ40) for MRI of amyloid plaques in APP/PS1 transgenic mice. MR brain images in APP/PS1 transgenic mice and their nontransgenic littermates were acquired using a 7.0 T MRI system before, and 24 and 72 h after an injection of HMON-abAβ40. After the injection of HMON-abAβ40, we found hyperenhanced spots in the frontal cortex area on T1-weighted MR images for transgenic mice, which corresponded qualitatively to amyloid plaques detected by thioflavin-S staining. For quantitative analysis, percent MR signal changes in six brain regions (olfactory cortex, frontal cortex, cerebral cortex, thalamus, hippocampus, and cerebellar cortex) were compared between transgenic and wild-type mice. We found significant increases in the percent MR signal changes in the olfactory cortex, frontal cortex, cerebral cortex, and hippocampus, but there were no significant differences in the thalamus and cerebellar cortex for transgenic mice compared with wild-type mice. This unique strategy allowed us to detect brain regions subjected to amyloid plaque deposition in Alzheimer's disease transgenic mouse models and has a potential to be developed for human applications, which has a current utility in preclinical research, particularly in monitoring therapeutic response for drug development in Alzheimer's disease.