Manganese Doping Research Articles

Relaxivity Enhancement of Hybrid Micelles via Modulation of Water Coordination Numbers for Magnetic Resonance Lymphography.

Considerable efforts have been made to develop nanoparticle-based magnetic resonance contrast agents (CAs) with high relaxivity. The prolonged rotational correlation time (τR) induced relaxivity enhancement is commonly recognized, while the effect of the water coordination numbers (q) on the relaxivity of nanoparticle-based CAs gets less attention. Herein, we first investigated the relationship between T1 relaxivity (r1) and q in manganese-based hybrid micellar CAs and proposed a strategy to enhance the relaxivity by increasing q. Hybrid micelles with different ratios of amphiphilic manganese complex (MnL) and DSPE-PEG2000 were prepared, whose q values were evaluated by Oxygen-17-NMR spectroscopy. Micelles with lower manganese doping density exhibit increased q and enhanced relaxivity, corroborating the conception. In vivo sentinel lymph node (SLN) imaging demonstrates that DSPE-PEG/MnL micelles could differentiate metastatic SLN from inflammatory LN. Our strategy makes it feasible for relaxivity enhancement by modulating q, providing new approaches for the structural design of high-performance hybrid micellar CAs.

Preparation of manganese-doped cubic carbon electrode based on ZIF-8 and its capacitive deionization performance for fluoride removal

Fluoride pollution will cause serious harm to the human ecological environment. The capacitive deionization method for fluoride removal has the advantages of low cost, low energy consumption, and convenient operation. Electrode material is crucial for desalination performance. In this study, a novel manganese doped hollow cubic carbon material (MHCC) was prepared by constructing ZIF-8 with hollow cubic morphology as a precursor and carbonizing it with manganese acetate as a manganese source. Then, the derived MHCC material was characterized and tested for capacitive fluoride removal. The adsorption capacity of MHCC10 (the mass ratio of carbon material to manganese acetate tetrahydrate was 10:1) reached 6.2 mg/g and 25.5 mg/g at the initial NaF concentration of 30 mg/L and 150 mg/L respectively. It could maintain 85.5% of the initial capacity after 10 adsorption–desorption cycles. The CDI defluoridation mechanism of MHCC was analyzed. The hollow porous structure inherited from etched ZIF-8 can promote the formation of electric double layers. An appropriate amount of manganese doping has a pseudocapacitive effect, which helps to increase adsorption capacity and improve cycling performance. This work provides a new approach for the design and preparation of novel capacitive fluoride removal electrode materials.

Enhanced photo-Fenton-like performance of biotemplated manganese-doped cobalt silicate catalysts

Cobalt-based catalysts are one of the preferred materials for effective activation of hydrogen peroxide, and metal element doping and active site dispersion are effective methods to enhance their catalytic activity. In this work, manganese-doped cobalt silicate@diatomite composites with enhanced photo-Fenton-like oxidation performance were prepared and used for degradation of methyl orange (MO) dyes. Experiments showed that manganese doping increased the specific surface area of the samples and decreased the band gap energy of the materials. Moreover, the samples doped with manganese elements had better photo-Fenton-like properties. The degradation of methyl orange by Co0.25MnSi@DE/H2O2-UV reached more than 95%. In addition, density-functional theory (DFT) calculations showed that the Mn-doped samples were more prone to activate H2O2 than non-manganese-doped samples, and the synergistic effect from using a bimetallic catalyst increased the photo-Fenton oxidation activity in the system. ESR spectroscopy and bursting tests indicated that the possible degradation mechanism consisted of hydroxyl radicals and superoxide radicals generated by the synergistic effect of cobalt ions and manganese under UV radiation. This study thus presents a feasible idea for the preparation of cobalt-based photo-Fenton catalysts that also provides a basis for understanding the catalytic mechanism analysis of other types of bimetallic catalysts.

Novel microporous manganese phosphonate-derived metal oxides as prospective cathode materials for superior flexible asymmetric micro-supercapacitor device

Developing high-power supercapacitors is tremendously relevant to the current energy demand and implementation of renewable energy storage. The template-free microporous organic-inorganic hybrid material manganese phosphonate (MnPIm) and their derivatives heteroatom doped manganese oxides (NP/MnO2500, NP/MnO2700, NP/MnO2900) are synthesized under hydrothermal condition and following the pyrolysis at different temperatures. Due to heteroatoms doped on material, a significant synergistic effect enhances the electrochemical performance in supercapacitor applications. The unique globular morphology with a hollow structure of materials possesses a high surface area, leading to extraordinary specific capacitance. Among these, NP/MnO2700 electrode material displays the superior specific capacitance value of 1362 F g−1 at 1 mV s−1 in three-electrode assembly with 99.6 % retention of its initial capacitance up to the 2000th cycle. It demonstrates the exceptional specific capacitance of 263 F g−1 in two electrode asymmetric device with an energy density of 72.6 Wh kg−1 at the power density of 1306 W kg−1. The NP/MnO2700 material is used to fabricate a flexible asymmetric micro-supercapacitor device (MSC) with an areal capacitance of 32.8 mF cm−2. The energy density of MSC is estimated to be 18.2 μWh cm−2 at the power density value of 65.6 μW cm−2 with 84.2 % retention up to the 5000th cycle.

Growth Process, Structure and Electronic Properties of Cr2GeC and Cr2-xMnxGeC Thin Films Prepared by Magnetron Sputtering

The growth and phase formation features, along with the influence of structure and morphology on the electronic, optical, and transport properties of Cr2GeC and Cr2-xMnxGeC MAX phase thin films synthesized by magnetron sputtering technique, were studied. It was found that the Cr:Ge:C atomic ratios most likely play the main role in the formation of a thin film of the MAX phase. A slight excess of carbon and manganese doping significantly improved the phase composition of the films. Cr2GeC films with a thicknesses exceeding 40 nm consisted of crystallites with well-developed facets, exhibiting metallic optical and transport properties. The hopping conduction observed in the Cr2-xMnxGeC film could be attributed to the columnar form of crystallites. Calculations based on a two-band model indicated high carrier concentrations N, P and mobility μ in the best-synthesized Cr2GeC film, suggesting transport properties close to single crystal material. The findings of this study can be utilized to enhance the growth technology of MAX phase thin films.

Manganese doping of hematite enhancing oxidation and bidentate-binuclear complexation during As(III) remediation: Experiments and DFT calculation

Iron and manganese oxides are commonly found in nature, such as hematite and pyrolusite, which strongly affect the migration and transformation of As(III). In this study, a series of hematite materials modified by MnO2 (Hm-Mn) were synthesized to achieve the adsorption-oxidation bifunctionality of hematite toward As(III). The maximal As(III) adsorption capacity of Hm-Mn (80.0 mg g−1) was nearly 3 times higher than that of pure hematite (28.5 mg g−1). The ratio of As(V) immobilized on Hm-Mn reached 71.5%, which was significantly higher than that of Hm (17.9%). The kinetic results indicated that chemisorption is the dominant adsorption behavior. Density functional theory (DFT) calculations revealed that manganese modification reduced the adsorption and oxidation energy of Hm-Mn, confirming that manganese modification was beneficial to both of the adsorption and oxidation of As(III). Bidentate-binuclear complex was the primary coordination type of arsenic binding on the Hm-Mn facets. Crystal orbital Hamilton population (COHP) analysis implied that the bonding of Hm-Mn with arsenic was stable. Specially, the bonding of Fe-O-As was stronger than that of Mn-O-As. Altogether, Hm-Mn provides a feasible solution for arsenic-contaminated water, and the fundamental theoretical data offer new perspective for understanding the remediation mechanisms of variable valence metal pollutants.

Electron density mapping and bonding in Mn doped CoFe2O4 using XRD, and its correlation with room temperature optical and magnetic properties

Single-phase Mn-doped Cobalt spinel ferrite prepared via the self-combustion method shows mixed spinel structure. Cation occupancy in tetrahedral A and octahedral B sites was observed through XPS, XRD, and VSM analysis. Crystallite size, porosity, surface area, and energy band gap results pave a path to optical absorption related applications. The energy band gap of MnxCo1-xFe2O4 nanoparticles were estimated using the Tauc plot and the values ranging from 1.123 eV to 1.247 eV. XPS-based energy level splitting of Mn 2p3/2 and Mn 2p1/2 confirms the occupation of Mn2+ and Mn3+ in octahedral and tetrahedral sites, respectively. The magnetic hysteresis from VSM depicts the formation of semi-hard ferrite with a maximum saturation magnetization of 79.612 emu/g and a coercivity of 1056 Oe, and the magnetic parameters decrease with the increase in manganese doping concentration. The Maximum Entropy Method (MEM)-based electron density mapping shows the electronic structure and bonding nature. Using MEM, a novel and favourable maximal coercivity condition is correlated with the high and moderate numerical bond critical density of 1.123 e/Å3 for A-O and 0.413 e/Å3 for B-O interactions, respectively. Strong A-O covalent bonds and feeble B-O covalent bonds are characteristics of spinel ferrites with high magnetization. The oxygen positional parameter values for all the samples not exceed 0.377 which is very close to the ideal value of 0.375.

Effect of manganese doping on structural, optical, morphological, and dielectric properties of Ba(Ti1-xMnx)O3 lead-free ceramics for energy storage in supercapacitors.

A supercapacitor (SC) is considered to be one of the best energy storage devices due to its high-power density, long lifespan, fast charge storage capability, and eco-friendliness. Ceramics with low-cost, nontoxic, high efficiency, and stability are the suitable and promising materials for performed supercapacitors at room temperature. As proposal, we synthesized by sol-gel method the ceramics Ba(Ti1-xMnx)O3 (where x = 0, 1, 2, or 3%) to study the effect a low rate of manganese doping on their morphological, structural, dielectric, and optical properties. The microstructure of the sintered ceramics was examined using scanning electron microscope (SEM), and the results reveal that the average grain size (AGS) of the ceramics (0.663-1.018μm) increases with increasing Mn doping content. The optical behavior was studied by UV-visible spectroscopy, and the results indicate that Mn doping reduces the band gap (Eg) from 3.27 to 2.79eV thus, the possibility of using these materials in photocatalyze applications. The dielectric properties of all studied samples were investigated at the temperature range 30-400°C and frequency range 103-106Hz. Significant modification in dielectric permittivity and an appreciable decrease in dielectric losses were observed when adding Mn2+ ions to BaTiO3 ceramics. Variations in dielectric properties and AC conductivity, as a function of frequency, reveal a relaxation mechanism related to the Maxwell-Wagner interfacial polarization. The obtained results suggest the use of prepared ceramics in capacitor and actuator applications at room temperature (RT).

Synthesis and Characterization of a Tertiary Composite of Cu, Mn, and g-C3N4: An Efficient Visible Light-Active Catalyst for Wastewater Treatment.

In this study, a tertiary composite of graphitic carbon nitride (GCN) with copper and manganese is utilized for photocatalytic degradation to add to efforts for tackling environmental pollution problems. The photocatalytic efficiency of GCN is enhanced with the doping of copper and manganese. This composite is prepared using melamine thermal self-condensation. The formation and characteristics of the composite Cu-Mn-doped GCN are affirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet (UV), and Fourier transform infrared spectroscopy (FTIR). This composite has been used for the degradation of an organic dye (methylene blue (MB)) from water at neutral conditions (pH = 7) of the solution. The percentage photocatalytic degradation of MB by Cu-Mn-doped GCN is higher than that of Cu-GCN and GCN. The prepared composite enhances the degradation of methylene blue (MB) from 5 to 98% under sunlight. The photocatalytic degradation is enhanced owing to the reduction of hole-electron recombination in GCN, enhanced surface area, and extended sunlight utilization by the doped Cu and Mn.

Optical and temperature-dependent magnetic properties of Mn-doped CoFe2O4 nanostructures

Understanding and untangling magnetic materials are essential to implanting these materials for practical industrial applications. This work demonstrates how manganese (Mn) doping can significantly advance cobalt ferrite's magnetic and optical characteristics. We applied the hydrothermal approach to synthesize cobalt ferrite nanostructures, followed by Mn doping, to acquire CoMnxFe2−xO4 (0 ≤ x ≤ 0.1) nanostructures. The crystal structure of all the specimens confirms the formation of Fd-3 m space growth with a typical cubic structure. The estimated crystallite size values vary between 19.8 and 25.8 nm, and the lattice parameter significantly enhances from 8.31 Å to 8.38 Å as a result of Mn substitution. The fast Fourier transform infrared spectroscopy (FTIR) was performed between 400 and 4000 cm-1. The lattice vibrations ranging υ1 = 614–607 cm-1 and υ2 = 428–426 cm-1 were assigned to tetrahedral and octahedral sites, respectively. The high-resolution transmission electron microscopy (HRTEM) analysis further confirms the crystalline structure of CoMnxFe2−xO4. The room temperature magnetic measurements investigate that the magnetic coercivity of CoMn0.2Fe1.8O4 nanostructures is maximum (∼ 800 Oe) which was opted for temperature-dependent measurements. The low-temperature magnetic characteristics agree with Bloch's and Kneller's laws for saturation magnetization and coercivity of CoMn0.2Fe1.8O4 nanostructures. The optical properties confirm a blueshift and slight increment in bandgap energy of CoMnxFe2−xO4 nanostructures.

Stabilizing sulfur doped manganese oxide active sites with phosphorus doped hierarchical nested square carbon for efficient asymmetric supercapacitor

The introduction of heteroatom species into hollow carbon lattice networks (HCLN) and metallic oxides have been exploited as an effective approach to enhance the performance of the electrochemical electrodes. Herein, square hierarchical P-doped porous carbon/S-doped manganese oxide (S-Mn5O8@PPC) is designed via a solvothermal, chemical vapor deposition and wet chemical growth method from the solid-state gas-steaming operation of zinc of square acids, offering a unique nested hierarchical and stable integrated structure. As a result, the as-fabricated S-Mn5O8@PPC and PPC demonstrated impressive electrochemical capacitance of 1819.8F g−1 and 325.1F g−1 at 1 A g−1, respectively, which both superior than the Mn5O8@PPC and porous carbon (PC, 1604.0F g−1 and 193.2F g−1). Especially, the specific capacitance of the PPC is preferred to that of most non-metallic heteroatom-doped MOFs-derived carbons. More importantly, two supercapacitor (SC) electrodes - square hierarchical P-doped porous carbon (PPC) and S-doped manganese oxide coated PPC - are further self-assembled a hybrid SC device, which possesses a wide voltage of 0–1.6 V, outstanding electrochemical capacitance of 154.8F g−1, impressive energy storage performance and a reliable capacitive stability (87.24% after 5000 cycles), apart from the ideal energy density and power density (55.1 W h kg−1 at 800.0 W kg−1). Such excellent features originate from the large specific surface area of the porous hierarchical hollow structure, the doping of heterogeneous P and S, the dispersive loading of manganese oxide, and harmonious matching of positive and negative electrodes.

Flexible metal/semiconductor/metal type photodetectors based on manganese doped ZnO nanorods

High-performance flexible photodetectors are one of the most interesting research areas due to their great possibilities for a variety of applications such as portable and wearable optoelectronics. This study verifies the performance of flexible metal/semiconductor/metal-type photodetector based on pristine and manganese doped ZnO nanorods (ZnO-NRs) prepared in two different concentrations of zinc precursors and manganese dopant at low temperatures. The photodetectors having ZnO-NRs with high aspect ratios were investigated by various material characterization techniques such as electron paramagnetic resonance and photoluminescence spectroscopy to confirm the relationship between defect concentrations and photodetector performance parameters. It has been calculated that the detectivity (D*) and responsivity (R) of the ZnO nanorod-based photodetectors increased 20 and 18 folds, respectively by increasing the concentration of zinc precursor. Besides the D* and R values of the photodetectors, prepared by the 16.5 mM zinc precursor, increased 18 and 4.5-fold, respectively, after manganese doping. We confirmed that even a very low concentration of zinc precursor could produce a photodetector with high performance in photo-response characteristics, flexibility, and stability against 10,000 cycles of convex/concave bending.

Unveiling the Localized Exciton-Based Photoluminescence of Manganese Doped Cesium Zinc Halide Nanocrystals

Lead-free metal halide nanocrystals (NCs) have aroused increasing attention due to their unique optoelectronic properties based on localized excitons (LEs). However, the vital influencing factors for the LEs based photoluminescence (PL) are still not well-understood due to the coupling of various intrinsic and extrinsic factors of the NCs. Herein, by engineering the phase, size, morphology, and chemical composition, we are able to decouple the intrinsic and extrinsic factors of manganese doped cesium zinc-halide NCs. We found both the intrinsic metal-halide coordination field and the extrinsic crystal defects have significant influences on the LEs' recombination and energy transfer processes, and hence determine the PL efficiency. Unlike for the free excitons (FEs) based PL, the phase as well as the crystal morphology do not play major roles for the LEs based PL. This work provides a new insight for the study of LE dynamics of metal halide NCs.

Hypoxia mitigation by manganese-doped carbon dots for synergistic photodynamic therapy of oral squamous cell carcinoma.

Photodynamic therapy (PDT) is widely used for cancer treatment due to its non-invasive and precise effectiveness, however, hypoxia in the tumor microenvironment greatly limits the efficacy of photodynamic therapy. Compared with conventional photosensitizers, carbon dots (CDs) have great potential. Therefore, developing a water-soluble, low-toxicity photosensitizer based on CDs is particularly important, especially one that can enhance the photodynamic efficacy using the tumor microenvironment to produce oxygen. Herein, manganese-doped carbon dot (Mn-CDs, ∼2.7nm) nanoenzymes with excellent biocompatibility were prepared by a solvothermal method using ethylenediaminetetraacetic acid manganese disodium salt hydrate and o-phenylenediamine as precursors. TEM, AFM, HR-TEM, XRD, XPS, FT-IR, ζ potential, DLS, UV-Vis, and PL spectra were used to characterize the Mn-CDs. Cancer resistance was assessed using the CCK-8 kit, calcein AM versus propidium iodide (PI) kit, and the Annexin V-FITC/PI cell apoptosis assay kit. The obtained Mn-CDs have excellent near-infrared emission properties, stability, and efficient 1O2 generation. Notably, the manganese doping renders CDs with catalase (CAT)-like activity, which leads to the decomposition of acidic H2O2 in situ to generate O2, enhancing the PDT efficacy against OSCC-9 cells under 635nm (300mW·cm-2) irradiation. Thus, this work provides a simple and feasible method for the development of water-soluble photosensitizers with oxygen production, presenting good biosafety for PDT in hypoxic tumors.

Photoluminescence and Fourier Transform Infrared Spectral Studies of Varying Levels of Manganese Doping in Zinc Phosphate Oxide Glasses

Photoluminescence and Fourier Transform Infrared Spectral Studies of Varying Levels of Manganese Doping in Zinc Phosphate Oxide Glasses

Effect on ethanol sensing ability of zinc oxide thin films with manganese doping

Effect on ethanol sensing ability of zinc oxide thin films with manganese doping

Mesoporous Hollow Manganese Doped Ceria Nanoparticle for Effectively Prevention of Hepatic Ischemia Reperfusion Injury.

Hepatic ischemia-reperfusion injury (HIRI) is the main reason for liver dysfunction or failure after liver resection and liver transplantation. As excess accumulation of reactive oxygen species (ROS) is the leading factor, ceria nanoparticle, a cyclic reversible antioxidant, is an excellent candidate for HIRI. Manganese doped mesoporous hollow ceria nanoparticles (MnOx-CeO2 NPs) were prepared, and the physicochemical characteristics, such as particle size, morphology, microstructure, etc. were elucidated. The in vivo safety and liver targeting effect were examined after i.v. injection. The anti-HIRI was determined by a mouse HIRI model. MnOx-CeO2 NPs with 0.40% Mn doped exhibited the strongest ROS-scavenging capability, which may due to the increased specific surface area and surface oxygen concentration. The nanoparticles accumulated in the liver after i.v. injection and exhibited good biocompatibility. In the HIRI mice model, MnOx-CeO2 NPs significantly reduced the serum ALT and AST level, decreased the MDA level and increased the SOD level in the liver, prevent pathological damages in the liver. MnOx-CeO2 NPs were successfully prepared and it could significantly inhibit the HIRI after i.v. injection.

Influence of doping and thickness on domain avalanches in lead zirconate titanate thin films

In undoped lead zirconate titanate films of 1–2 μm thick, domain walls move in clusters with a correlation length of approximately 0.5–2 μm. Band excitation piezoresponse force microscopy mapping of the piezoelectric nonlinearity revealed that niobium (Nb) doping increases the average concentration or mobility of domain walls without changing the cluster area of correlated domain wall motion. In contrast, manganese (Mn) doping reduces the contribution of mobile domain walls to the dielectric and piezoelectric responses without changing the cluster area for correlated motion. In both Nb and Mn doped films, the cluster area increases and the cluster density drops as the film thickness increases from 250 to 1250 nm. This is evident in spatial maps generated from the analysis of irreversible to reversible ratios of the Rayleigh coefficients.

UiO66-Derived Catalyst for Low Temperature Catalytic Reduction of NO with NH3.

Diesel exhaust emissions are major outdoor air pollutants. Reducing the emission of NOx by diesel commercial vehicles and related machineries is at present a great challenge. In this study, we synthesize a catalyst for low-temperature catalytic reduction of NO using calcinated UiO-66(Zr) as a host for the doping of cerium, manganese, and titanium by the incipient wetness impregnation, followed by the dispersion of 1.0 wt % platinum. A solid solution of Ce0.15Zr0.54Mn0.11Ti0.20O2/1.0Pt (CZMTO/Pt) is synthesized as evident by the structural characterizations. The catalyst demonstrates significant NO reduction in the laboratory due to the synergistic effect of various elements, with NO conversion above 80% at 160 °C.

Effect of manganese doping on the PbO2 electrode for the enhanced electrochemical oxidation of anthracene: Optimization and mechanism

Effect of manganese doping on the PbO2 electrode for the enhanced electrochemical oxidation of anthracene: Optimization and mechanism