Interaction Of Mn Research Articles

Catalytic oxidation of CO on mesoporous codoped ceria catalysts: Insights into correlation of physicochemical property and catalytic activity

Codoping approach is an appealing strategy to further improve the catalytic activity of Ce-based catalysts. In the present study, Mn and/or Cu doped ceria solid solutions MnxCuyCe1–x–yO2, CuxCe1–xO2, MnxCe1–xO2 and pure CeO2 were prepared by CTAB-assisted hydrothermal method for CO oxidation. XRD, SEM, EDS, BET, Raman, H2-TPR, XPS and in situ DRIFTS techniques were carried out to study the physicochemical properties and to correlate them to the activity. The doped samples maintain the cubic fluorite structure of CeO2 with high crystallinity and small crystallite size, forming Ce-based solid solutions. The obtained catalysts have large mesoporous structure with average pore size of 10–14 nm. The doped transition metal enhances the oxygen vacancies and improves reducibility of the solids. The synergistic interaction of Mn and Cu codoping induces more oxygen vacancies, promoting the increase of surface adsorbed oxygen and the transfer of bulk oxygen of catalyst, thereby enhancing the catalytic activity for CO oxidation. Besides, the decomposition rate of the carbonate species which is derived from in situ DRIFTS for each catalyst can provide a measure to evaluate its catalytic activity of CO oxidation.

Updating physiologically based pharmacokinetic models for manganese by incorporating rapid association/dissociation processes in tissues

Previously, we developed a series of physiologically based pharmacokinetic (PBPK) models for manganese (Mn) in which saturable tissue binding and dose-dependent increases in biliary excretion captured key aspects of Mn homeostasis biology. These models reproduced the non-linear behavior of Mn kinetics in different tissues, accounting for dose-dependent changes in Mn kinetics. The original model construct had relatively slow association and dissociation rate constants for Mn binding in tissues. In this updated model, both rates of entry into tissue and the interaction of Mn with binding sites are rapid, and the step limiting Mn accumulation is the saturation of tissue binding sites. This binding reflects general cellular requirements for Mn with high affinity but rapid exchange between bound and free forms, which we captured using a dissociation constant (KD) of ~ 0.5 μM across tissues while maintaining different maximum binding capacities in each tissue. Variability in the binding capacities accounted for different background levels of Mn in particular tissues. This alternative structure successfully described Mn kinetics in tissues in adult rats exposed to Mn either in their diet or by inhalation, indicating that both the original and the present models capture the dose-dependent and tissue-specific kinetic behavior of Mn in adult rats. Although the published models that emphasize the role of smaller tissue binding rate constants in non-linear behaviors capture all relevant dose-dependent kinetic behaviors of this metal, increasing biological relevance of the model structure and parameters should provide greater confidence in applying the Mn PBPK models to risk assessment.

Interaction of Mn+1AXn phases with oxygen-poor, static and fast-flowing liquid lead-bismuth eutectic

Select MAX phase-based ceramics were screened with respect to their potential susceptibility to environmentally-assisted degradation in an oxygen-poor liquid lead-bismuth eutectic (LBE) environment, both under static and fast-flowing exposure conditions. The majority of the MAX phases exposed to oxygen-poor (CO ≤ 2.2 × 10−10 mass%) static liquid LBE for at least 1000 h at 500 °C showed exceptional chemical compatibility with the heavy liquid metal, i.e., no evidence of LBE dissolution attack was observed, despite the absence of a continuous oxide scale on the surface of the exposed MAX phase ceramics. The local LBE interaction observed only with the Zr-rich MAX phases consisted in the partial substitution of Al by Pb/Bi in the MAX phase crystal structure and the in-situ formation of Pb/Bi-containing solid solutions. Moreover, the interaction of Zr-based MAX phases with static liquid LBE was accompanied by the dissolution of parasitic intermetallic phases, which facilitated the further LBE ingress into the ceramic bulk. The erosion resistance of select MAX phase ceramics was also assessed in oxygen-poor (CO ≈ 5 × 10−9 mass%) fast-flowing (v ≈ 8 m/s) liquid LBE for 1000 h at 500 °C. Despite the moderate LBE oxygen concentration, oxidation was the predominant corrosion mechanism, while no erosion damages were observed in the exposed MAX phase ceramics. The resistance of the MAX phase ceramics to both dissolution corrosion and erosion in contact with oxygen-poor static and fast-flowing liquid LBE, respectively, was compared to that of the 316L reference structural stainless steel.

Tuning magnetic and magnetocaloric properties around room temperature via chromium substitution in La0.65Nd0.05Ba0.3MnO3 system

Abstract In this paper, we report the structural, magnetic and magnetocaloric properties of La0.65Nd0.05Ba0.3Mn1−xCrxO3 (0 ≤ x ≤ 0.15) system synthesized by conventional solid-state reaction method. Phase identification is performed by X-ray diffraction analysis, which shows the rhombohedra crystal structure with R -3 c as a space group. Magnetic measurements show that all our samples undergo a second order paramagnetic (PM) – ferromagnetic (FM) transition when the temperature decreases. However, The M(T) shows a decrease in a Curie temperature (TC) from 330 K for x = 0 to 275 K for x = 0.15 as a Cr ion increases. This decrease can be explained by the decreasing number of hopping electrons, which reduces the double exchange (DE) interaction of Mn3+-O-Mn4+. The role of the trivalent ions Cr3+ is merely to dilute the DE interactions between Mn sites. Moreover, the maximum magnetic entropy change −ΔSM calculated from the M(μ0H) measurements are found to be 4.26, 4.03, 3.97 and 3.55 Jkg−1K−1 under an external field change of 5 T for x = 0, 0.05, 0.1 and 0.15, respectively. However, the temperature-averaged entropy change (TEC) over 10 K temperature span under same field, TEC (10 K, 5 T), are 4.19, 3.91, 3.86 and 3.47 Jkg−1K−1. This finding suggests that our samples can be used as a magnetic refrigeration material around room temperature. Furthermore, the ΔSM –T curves collapse onto a single master curve confirming the second order phase transition. Additionally, a phenomenological universal model is used to predict the magnetocaloric properties for Cr substituted samples.

Investigation of interaction of Co, Mn and Fe atoms with the calcite by X-ray photoelectron spectroscopy

Adsorption of atoms of Co, Mn, Fe on the calcite surface in ultra-high vacuum and the interaction of the formed adsorption systems with the water have been studied by means of X-ray photoelectron spectroscopy. It is shown that Mn and Fe form solid solutions CaCO3/Mn(Fe)CO3 on the calcite surface, whereas Co preferentially forms CoO and Co3O4. Upon interaction with water the surface compounds formed by Mn and Fe do not undergo notable changes, unlike the Co oxides which partially transform into soluble hydroxylated complexes.

XANES, EXAFS, EPR, and First-Principles Modeling on Electronic Structure and Ferromagnetism in Mn Doped SnO2 Quantum Dots

The effect of Mn dopant on the electronic structure and magnetic properties of SnO2 quantum dots was investigated using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), electron paramagnetic resonance, and first-principles modeling. The results demonstrated that dilute Mn atoms substituted for Sn generates numerous oxygen vacancies. Interestingly, lower Mn doping concentration (2%) favored the formation of Mn3+ structures and increase of Mn doping to higher concentration (10% Mn) led to predominance of Mn3+ with a small fraction of Mn2+ configuration. The slight increase in bond length observed for 10% Mn doped SnO2 QDs in EXAFS also corroborates with the XANES results where the absorption edge was shifted to lower energy, giving an indication of a very small presence of Mn in the +2 oxidation state. Electron paramagnetic resonance studies revealed the exchange coupled Mn interactions and also changes in distribution of local magnetic configurations with the ...

Supramolecular association involving nitrile–nitrile interactions in polymeric Mn(II) coordination complexes: A combined experimental and theoretical study

Two new Mn(II) coordination polymers viz. [Mn(p-NBz)2(4-CNpy)2]n (1) and [Mn(4-CNpy)2(H2BTC)2]n (2) [p-NBz = p-nitrobenzoate, H3BTC = 1,3,5-benzenetricarboxylic acid and 4-CNpy = 4-cyanopyridine] have been synthesized at room temperature and characterized by single crystal X-ray diffraction, FT-IR spectroscopy, electronic spectroscopy, elemental analyses and thermogravimetric analysis (TGA). The complexes are stabilized by several non-covalent interactions along with a rather uncommon nitrile(π)–nitrile(π) interactions resulting in layered structures. The supramolecular association in both the polymers results in 3D network structures involving CH⋯O interactions in the direction perpendicular to the existing layers. The anti-parallel CN⋯CN interaction observed in the polymeric chains of the complexes are studied using DFT calculations and characterized using the Bader’s theory of “atoms-in-molecules”. The interaction energy of the anti-parallel nitrile–nitrile interactions is similar to hydrogen bonds which are enhanced by the coordination of 4-CNpy to the Mn(II) metal centre.

The effect of the orientation of the Jahn-Teller distortion on the magnetic interactions of trinuclear mixed-valence Mn(ii)/Mn(iii) complexes.

Two new trinuclear manganese complexes, [Mn3(L1)(μ-OCH3)2(N3)2]·CH3OH (1) and [Mn3(L2)(μ-OCH3)2(N3)2]·CH3OH (2), have been obtained from the reaction of Mn(OAc)2 4H2O, NaN3 and the preformed N6O4-donor H4L1 or H4L2 compartmental ligands, which are synthesized via Schiff base condensation of pentaethylenehexamine with 2-hydroxybenzaldehyde or 2-hydroxy-3-methoxybenzaldehye, respectively. Complexes 1 and 2 have been characterized by spectroscopic methods and single-crystal X-ray analysis. The structural studies indicate that both 1 and 2 are mixed-valence complexes containing angular Mn(iii)-Mn(ii)-Mn(iii) cores in which the metal centers are connected to each other by phenoxido and methoxido bridging groups. The coordination environment around the manganese ions is analogous in both complexes, but for a change in the direction of the Jahn-Teller distortion around the external Mn(iii) ions when going from 1 to 2, which is mainly attributed to the steric effect of different substituents on the phenyl rings of the ligands. The analysis of the magnetic susceptibility data indicates the presence of antiferromagnetic intramolecular coupling in both complexes, but the interaction in 1 was found to be nearly one order of magnitude weaker than that in 2. This fact is rationalized on the basis of the different orientation of the Jahn-Teller distortion, which modifies the magnetic exchange pathway through the phenoxido bridges from the equatorial-axial connection type observed in 1 to the axial-axial linkages displayed by 2.

UNO DMRG CAS CI calculations of binuclear manganese complex Mn(IV)2 O2 (NHCHCO2 )4 : Scope and applicability of Heisenberg model.

Both direct exchange and super-exchange interactions cooperate to realize inter-spin magnetic interaction in binuclear manganese complex Mn(IV)2 O2 (NHCHCO2 )4 with a di-μ-oxo path. We revisited this spin system using DMRG CAS methods and CAS selection procedures. Our results indicate that our previous "dynamically extended spin polarization" (DE-SP) procedure for organic polyradicals and so forth does not work well. Thus, we have examined another selection procedure, the "dynamically extended super-exchange" (DE-SE) procedure. DMRG CASCI [18,18] by UB3LYP(HS)-UNO(DE-SE) can realize antiferromagnetic J values similar to experimental ones (-87 cm-1 ). In addition, all J values between all spin states (HS[septet],IS[quintet],IS[triplet],LS[singlet])were also shown to be correct under sufficiently large M values. © 2018 Wiley Periodicals, Inc.

Enhanced Removal of Chlorophene and 17β-estradiol by Mn(III) in a Mixture Solution with Humic Acid: Investigation of Reaction Kinetics and Formation of Co-oligomerization Products.

Reaction with soluble Mn(II) has been considered as a main decay pathway for superoxide in natural waters, accompanied by an important Mn redox cycling. In this study, the interaction of Mn(II) and humic acid (HA) was investigated in visible light irradiated water. Our results indicate that HA may play a dual role to act as a photosensitizer to produce superoxide anions (O2-) and as a strong ligand to stabilize the Mn(III), forming soluble Mn(III)L species for substrate transformation. Furthermore, the reaction kinetics, products, and mechanisms of chlorophene (CP) and estradiol (E2) mixture in the Mn(II)/HA/visible light reaction systems were assessed. The removal of CP and E2 was enhanced by 24.3% and 13.2%, respectively, in mixture solution at initial concentration of 1.0 μM for each target contaminant, as compared to the case of single-compound degradation. Product identification and density functional theory calculations indicated that cross-coupling reaction of CP and E2 radicals was more likely to occur than the self-coupling reaction in mixture solution. In addition, estrogenic activities of initial reaction solution were also effectively decreased during the transformation process. These findings provide new insights into Mn(III)-mediated reactions to better understand the environmental fate of organic contaminant mixture in waters.

Manganese(II) complexes of tolfenamic acid or naproxen in polymeric structures or encapsulated in [15-MC-5] manganese(III) metallacrowns: Structure and biological activity

The interaction of MnCl2 with the non-steroidal anti-inflammatory drugs tolfenamic acid (Htolf) or naproxen (Hnap) in the presence of salicylhydroxamic acid (H3shi) led- to the formation of the hexanuclear mixed-valence MnIIMnIII5 clusters [Μn6(tolf)2(shi)5(py)6], 1 and [Μn6(nap)(Hsal)(shi)5(py)6], 2 (where H2sal = salicylic acid) which were characterized as 15-metallacrown-5 complexes accommodating the Mn(II) ion and the monoanionic carboxylato ligands tolf−1, nap−1 and Hsal−1. The interaction of Mn(II) with deprotonated naproxen led to the formation of the polymeric Mn(II) complex [Μn(nap)2(CH3OH)]n, 3. All three complexes were characterized by physicochemical and spectroscopic techniques and by single-crystal X-ray crystallography. The in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs irinotecan, cisplatin, paclitaxel and 5-fluorouracil. The interaction of complexes 1–3 with calf-thymus (CT) DNA and bovine serum albumin (BSA) was investigated in vitro by diverse techniques. In addition, the cytotoxic activity of the previously reported polymeric complex [Μn(tolf)2(DMF)2]n, 4 was also investigated and its behavior towards CT DNA and BSA was compared to that of complexes 1–3.

Ba4[Mn3N6], a Quasi-One-Dimensional Mixed-Valent Nitridomanganate (II, IV)

The mixed-valent nitridomanganate Ba4[Mn3N6] was prepared using a gas–solid high temperature route. The crystal structure was determined employing high resolution synchrotron powder diffraction data: space group Pbcn, a = 9.9930(1) Å, b = 6.17126(8) Å, c = 14.4692(2) Å, V = 892.31(2) Å3, Z = 4. The manganese atoms in the structure of Ba4[Mn3N6] are four-fold coordinated by nitrogen forming infinite corrugated chains of edge-sharing [MnN4] tetrahedra. The chains demonstrate a complete charge order of Mn species. Magnetization measurements and first principle calculations indicate quasi-one dimensional magnetic behavior. In addition, chemical bonding analysis revealed pronounced Mn–Mn interactions along the chains.

Styrene-co-divinylbenzene/silica hybrid supports for immobilization transitional metals and their application in catalysis

The functionalization of S–1% DVB copolymer was carried out with aminophosphonate groups, and then the samples were covered with silica to obtain hybrid materials. The obtained hybrid materials were used as supports for impregnation of transition metal ions [Cu(II) and Mn(II)], and they were subsequently used as catalysts in oxidation reactions. The supports and catalysts were characterized by FTIR and UV–Vis spectroscopy, thermal analysis, SEM, and TEM electron microscopy. The results of FTIR spectroscopy indicated the formation of a hybrid of silica and an aminophosphonate polymer by the sol–gel route. The UV–Vis spectra showed a strong interaction of Cu(II) and a weak interaction of Mn(II) with aminophosphonate groups of the supports. The catalytic tests confirm different interactions between the metal cations and obtained supports. The formation of the immobilized Cu(II) complexes shows the possibility of using these materials selectively in oxidation of various organic compounds (anisole, cyclohexene, toluene, styrene, phenol). The purpose of this article is to develop some new poly(aminophosphonates)/silica hybrid materials immobilized with transition metal such as Cu(II) and Mn(II) ions for future use in the oxidation process.

Magnetic and magnetoelectric properties of hybrid-frustrated Bi2Ir2−xMnxO7 pyrochlores

The present paper investigates the magnetic and magnetoelectric properties of Bi2Ir2−xMnxO7 compounds with respect to the degree of Mn doping denoted by x. It is found that the antiferromagnetic (AFM) interactions are initially enhanced with increasing x, but are then weakened with further increases in x. These findings are explained on the basis of the competition among AFM Ir–Ir, AFM Ir–Mn, and ferromagnetic Mn–Mn interactions. In addition, the electric transport properties at the temperature range studied present a metal-insulator transition in the range 0.05 ≤ x ≤ 0.15, while an insulating state occurs for x > 0.15 because of electron localization. At low temperatures, a small positive magnetoresistance (MR) effect is observed for x = 0, whereas a negative MR effect is observed for all Mn-doped samples. The 3d–5d electron interactions play a dominant role in determining the magnetic properties of the doped samples.

Sorption of Pb in chemical and particle-size fractions of soils with different physico-chemical properties

Lead (Pb) sorption capacity (PbSmax) and distribution in chemical and particle-size fractions of six soils with different physico-chemical properties were investigated to explore the principal properties of soils that affect Pb sorption. A series of experiments of Pb sorption and soil chemical and particle-size fractionation of sorbed Pb were conducted with six soils of different texture, mineralogy, organic matter concentration, cation exchange capacity (CEC), and Fe-Mn concentrations. Soils either developed from volcanic ash or containing smectite showed relatively higher PbSmax than the other soils. Across the soils, clay content, organic matter concentration, and total Fe concentrations were significantly (p < 0.05) correlated with PbSmax. Concentrations of Pb bound with Fe-Mn and exchangeable Pb sorbed on to negatively charged sites were greater than the other chemical fractions. In the particle-size fractions, clay-sized particles had the greatest Pb concentration, suggesting that this fraction was most responsible for Pb sorption. The Pb concentration in coarse particle fractions (silt and sand) showed a positive relationship with organic matter concentration, indicating that organic matter in coarse particles was a factor determining Pb sorption. However, such relationship was not found for clay-sized particles, suggesting that complexation with organic matter was not a key mechanism for Pb sorption onto clay-sized particles. Our study which combined sorption and chemical and particle-size fractionation experiments suggests that complexation of Pb with Fe and Mn oxides and interaction with negatively charged sites of clay-sized particles are the key processes of Pb sorption in the studied soils. For coarse particles, it was suggested that association with organic matter is a Pb sorption mechanism.

Post-plasma-catalytic removal of toluene using MnO2–Co3O4 catalysts and their synergistic mechanism

To improve toluene removal efficiency and reduce unnecessary reaction products, a system combining a dielectric barrier discharge reactor with MnO2–Co3O4 catalysts was developed. The addition of a catalyst enhanced the toluene removal efficiency, energy yield (EY), COx yield and CO2 yield, and markedly suppressed O3 and NO2 generation compared with the non-thermal plasma (NTP) alone system. The Mn/Co molar ratio could alter the physicochemical properties of the catalysts and further influence their catalytic activity. The Mn1Co1 catalyst demonstrated the highest catalytic activity, which might be ascribed to the interactions of Mn and Co species (such as crystal structure, oxygen mobility and redox pairs of Mn4+/Mn3+ and Co2+/Co3+). In the post-NTP-catalytic system over Mn1Co1 catalyst, the toluene removal efficiency, EY, COx yield and CO2 yield were increased by 26.77%, 1.76 g kWh−1, 25.65% and 21.07%, respectively, compared with that in the NTP alone system at specific energy densities of 423.58 J L−1, 92.59 J L−1, 456.76 J L−1 and 456.76 J L−1, respectively. The pathway of toluene degradation in the post-NTP-catalytic system over Mn1Co1 catalyst was also investigated to further understand the synergistic effect of the hybrid system.

Interaction diagrams for FRP strengthened RC rectangular columns with large aspect ratio

The load carrying capacity of reinforced concrete columns (RC) shall be enhanced by providing lateral confinement using fiber reinforced polymer (FRP). As per ACI 440.2R-08 [1], external strengthening using FRP composites is more effective for circular columns than rectangular columns having an aspect ratio greater than 2.0. The main objective is to develop column interaction diagrams for RC rectangular columns having an aspect ratio greater than 2.0 externally strengthened using FRP composites without any shape modification and subjected to combined axial load (Pn) and bending moment (Mn) due to lateral loading. Tests are conducted and semi-empirical equations developed for FRP strengthened RC rectangular columns with large aspect ratio. Pn–Mn interactions diagrams are developed using the semi-empirical solutions and validated with 3D finite element analysis. The column interaction diagrams are developed by varying the unconfined compressive strength of concrete, yield strength of steel, percentage of steel reinforcement and thickness of FRP composite. These diagrams shall be used for the design of FRP strengthened RC rectangular columns with large aspect ratio.

Effect of C and N and their absence on the kinetics of austenite-ferrite phase transformations in Fe-0.5Mn alloy

Investigating the partitioning effect of substitutional and interstitial elements on the migration of transformation interfaces during austenite-ferrite phase transformation in steels with the conventional experimental method is extremely challenging due to interaction between the solute atoms and the transformation interfaces. Additionally, the simultaneous nucleation of new phases during phase transformations limits the accuracy of extracted growth rates from experimental kinetics measurements of phase fractions. In a novel experimental approach, the cyclic partial phase transformation concept is used to avoid the effect of nucleation on total kinetics of phase transformations. In this study, a Fe-0.5Mn alloy in the presence and absence of interstitial C and N additions is subjected to different cyclic transformation routes to examine the possible interaction between solute atoms and migrating interfaces. The experimental results are in semi-quantitative agreement with modelling predictions made by the local equilibrium approach and provide indirect evidence of Mn partitioning at austenite/ferrite interface in absence of any interstitial elements. It is also confirmed that the presence of interstitial elements promotes Mn interaction with the interface, whereas N promotes more Mn partitioning at transformation interface compared to C.

FRP Strengthened RC Rectangular Columns Under Combined Axial and Lateral Loading: Analytical Study

Semi-empirical solutions are proposed to predict the axial and lateral capacities of reinforced concrete (RC) rectangular columns having aspect ratio greater than 2.0 strengthened using fiber reinforced polymer (FRP) composites without any shape modification and subjected to axial, lateral and combined axial and lateral loading. 3D finite element models are generated for the analysis of FRP strengthened RC columns. Semi-empirical solutions and finite element models are validated with the test results. Column interaction diagram between axial capacity Pn and bending moment Mn is generated using the proposed semi-empirical solutions and compared with Pn - Mn interaction diagram generated as per ACI 440.2R-08 [1] procedure. From this study, it is concluded that the proposed semi-empirical solutions shall be used for the design of RC rectangular columns having aspect ratio greater than 2.0 strengthened with FRP composites and without any shape modification.

A Model for Manganese interaction with Deinococcus radiodurans proteome network involved in ROS response and defense

A complex network of regulatory proteins takes part in the mechanism underlying the radioresistance of Deinoccocus radiodurans bacterium (DR). The interaction of Mn(II) ions with DR-proteins and peptides seems to be responsible for proteins protection from oxidative damage induced by Reactive Oxygen Species during irradiation.In the present work we describe a combined approach of bioinformatic strategies based on structural data and annotation to predict the Mn(II)-binding proteins encoded by the genome of DR and, in parallel, the same predictions for other bacteria were performed; the comparison revealed that, in most of the cases, the content of Mn(II)-binding proteins is significantly higher in radioresistant than in radiosensitive bacteria. Moreover, we report the in silico protein–protein interaction network of the putative Mn(II)-proteins, remodeled in order to enhance the knowledge about the impact of Mn-binding proteins in DR ability to protect also DNA from various damaging agents such as ionizing radiation, UV radiation and oxidative stress.