Manganese Atoms Research Articles

(Invited) Atomic-Scale Functionalization and Characterization of 2D Materials

As 2D materials set their path into our next generation nanoelectronics, enriching their functionalities and complementing their limitations become more important. In particular, novel strategies for controllable incorporation of substitutional and intercalated atoms need to be developed. Here, we report on modifying 2D materials at the atomic-scale by ultra-low energy ion implantation to functionalize their properties and explore their limits. I will present our recent work on graphene on two topics: substitutional manganese (Mn) atoms for magnetic doping [1] and intercalation of noble gases to produce nanobubbles with small radii and high aspect ratios. On the one hand, we have characterized in detail the atomic structure of substitutional Mn and graphene’s Dirac-like band structure doped with up to 1% substitutional Mn. On the other hand, the structural inspection of our graphene nanobubbles has revealed a so far unexplored small-radius limit, associated with high aspect ratios as well as extreme pressure and strain. Our approach is based on a wide range of characterization techniques (structural and electronic), including scanning tunneling microscopy and spectroscopy (STM/STS), Raman spectroscopy, synchrotron-based X-ray photoelectron spectroscopy (XPS), angle-resolved photoemission spectroscopy (ARPES), X-ray magnetic circular dichroism (XMCD), among others. These experimental studies are complemented by density functional theory (DFT) and molecular dynamics (MD) simulations.[1] P. C. Lin et al., ACS nano 15(3), 5449-5458 (2021). Figure 1

Magnetic properties and electronic structure of Mn-Al alloys in the β-Mn structure

In this work, the electronic structure and magnetic properties of the Mn-Al alloys with different Mn and Al concentrations in the β-Mn-type structure have been theoretically investigated. The structural stability of different types of aluminum and manganese atoms occupations of the 12d and 8c site positions are compared. For the Mn3Al with 5Al in the 12d positions we obtained the most energetically preferable arrangement of Mn and Al ions in this alloy. Further occupation of this type of position by the Al atoms might be responsible for the lower effective magnetic moment estimated from the experimental data. Our theoretical calculations demonstrate the complex character of the magnetic properties and electronic structure of the Mn-Al alloys.

Boosting the activity of non-platinum group metal electrocatalyst for the reduction of oxygen via dual-ligated atomically dispersed precursors immobilized on carbon supports

This paper describes the use of both atomically dispersed precursors (ADPs) and conductive carbon dispersion towards the synthesis of iron-based single atom electrocatalysts for the oxygen reduction reaction (ORR). For non-platinum group metal (non-PGM) catalysts, single iron, cobalt or manganese atoms coordinated with nitrogen are the most active structures towards the ORR. Achieving a high density of active sites made of single atoms is still challenging, requiring careful controls of pyrolysis to reduce the sintering of metal active sites. Herewith, we present a new strategy to synthesize iron-based single atom ORR electrocatalysts using a two-pronged approach. We first designed a dual-ligated metal organic framework (MOF) precursor. This MOF was then immobilized onto Ketjen black carbon that serves as a conductive dispersion medium for creating the highly dispersed single atom sites. We demonstrate a near complete dispersion of the iron sites without obvious formation of nanoparticles. The activity of the resulting electrocatalyst exhibited an onset potential of 0.96 V and a half-wave potential of 0.84 V vs. reversible hydrogen electrode (RHE).

An Infrared Radiation Photoresistor Based on Silicon with Nanoclusters of Manganese Atoms

An Infrared Radiation Photoresistor Based on Silicon with Nanoclusters of Manganese Atoms

Estimation of radiative parameters for atomic manganese from the point of view of possible clock transitions and laser cooling schemes

In this article the values of the radiative parameters for atomic manganese were determined by means of a semi-empirical method. The eigenvector amplitudes determined in our previously published research were adopted. The calculated values of oscillator strengths and lifetimes are, in the majority of cases, in good agreement with experimental data. The results were also compared with available theoretical calculations. On the basis of the calculations performed, as well as related available literature data on transition probabilities and excited levels’ lifetimes, possible clock transitions in neutral 55Mn were proposed; three candidate transitions were considered in this context. Possibilities of laser cooling of manganese atoms were also discussed.

Correlation of manganese in hairs with some biochemical parameters in blood serum of pigs

Currently, along with an in-depth study of the gene pool and the phenotype pool of farm animals of different breeds and species in the zones of their breeding, special attention is paid to the production of environmentally friendly and safe products of the agro-industrial complex for the end consumer. Therefore, water, feed, soil, animal organs and tissues are carefully monitored for the content of chemical elements. Manganese, like magnesium and other divalent ions, is a non-specific activator of enzymes: hydrolases, kinases, decarboxylases, etc. The absolute need for Mn is confirmed by the metalloenzymes pyruvate carboxylase of the liver mitochondria and muscle oxaloacetate carboxylase. The first contains four manganese atoms and four biotin molecules and catalyzes the carboxylation of pyruvic acid to oxaloacetic acid. The removal of Mn leads to the irreversible loss of enzyme activity, which is not restored with the subsequent introduction of the endogenous metal. The purpose of the research was to establish the correlations of the accumulation of manganese in the hairs with some biochemical parameters in the blood of pigs of Kemerovskaya breed. During the work the correlations of manganese in the hairs with some biochemical parameters of blood serum of pigs have been studied. When comparing the obtained data with the studies of other scientists, all the correlations were described except for the content of manganese in the hairs with serum chlorides (r=–0,43), since this correlation was not confirmed by the data of the scientific literature. A positive correlation has been established between the level of Mn with cholesterol and Mg at the level of 0,542 and 0,417, respectively. The change in the magnitude and direction of the correlation between the concentration of Mn in the hairs and the biochemical composition of the blood can be caused by some animal diseases.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Study on the relationship between vacuum denitrification and manganese evaporation behaviours of manganese steel melts

Herein, the manganese evaporation and denitrification behaviours of manganese steel melts with various initial manganese and nitrogen contents, refining times, and vacuum conditions were experimentally investigated. Thermodynamic and kinetic analyses were performed to evaluate the interaction mechanism between manganese evaporation and denitrification. The results indicated that the denitrification process was in good agreement with 1.5th-order reaction kinetics, while the denitrification process followed 1st-order and 2nd-order reaction kinetics under high final pressure and high initial nitrogen content, respectively. The denitrification rate constant significantly increased with increasing initial nitrogen content. Furthermore, it was found that a high initial nitrogen content can promote manganese evaporation, which is attributed to the partial demanganisation reaction proceeding at the nitrogen bubble–metal interface. Moreover, denitrification is blocked by an increase in the manganese content in the steel melt, which is related to the strong affinity between nitrogen and manganese atoms, consistent with thermodynamic calculations. Ultimately, it was found that moderately increasing the pressure and reducing the refining time can both rapidly remove nitrogen and slow down manganese evaporation. This work provides a theoretical basis for the vacuum melting of manganese steel with high cleanliness.

Hardness, magnetic, elastic, and electronic properties of manganese semi-boride synthesized by high pressure and high temperature

Transition metal (TM) interaction induces many fantastic properties in transition metal light element compounds (TMLEs). Here, we report the synthesis of polycrystalline Mn2B specimen with strong Mn–Mn interaction by high pressure and high temperature (HPHT) method. Magnetic characterization gives anti-ferromagnetic and spin-glass behavior with Néel temperature of 43 ​K. Micro-hardness measurement yields an asymptotic Vickers hardness of 14.1 ​GPa which is far higher than manganese metal. To interpret the mechanical and magnetic properties, the chemical bond and electronic structure were investigated by first principle calculation. Although the distance between manganese atoms has been enlarged by inserting boron atoms, anti-ferromagnetic behavior is attributed to the insufficient Mn–Mn distance enlargement. Based on the bonds character, these manganese atoms layers are pinned together by quasi-boron-chains which is contradictory with fully isolated boron atoms configuration. Quasi-covalent boron chains and partial covalent Mn–B bonds attribute to its high hardness. Tuning Mn–Mn interaction is demonstrated as a promising method to modulate d-electron related magnetic and hardness property.

Aerogel Constructed by Ultrasmall Mn-Doped Silica Nanoparticles for Superior Lithium-Ion Storage.

The high internal stress during (de)lithiation, poor ionic/electronic conductivity, and relatively low specific capacity are the three critical issues for the applications of silica (SiO2) anodes. Herein, a high-performance SiO2 anode is designed from the microscale to the atomic scale, and for the first time, an aerogel constructed by the graphene and manganese atom (Mn)-doped ultrasmall SiO2 nanoparticles (around 50 nm) is proposed to overcome the three issues. From the aspect of microscale, the ultrasmall SiO2 nanoparticles and the porous feature of aerogel improve the structural stability during (de)lithiation and the lithium-ion diffusion kinetics. From the aspect of atomic scale, the doping of Mn introduces the impurity level, expands the coordination environment, and enhances the adsorption for Li+, boosting the ionic/electronic conductivity and the amount of the Li+ intercalation. Therefore, the anode ranks among the best SiOx (0 < x ≤ 2) anodes. For example, the capacity is almost constant after 2000 cycles, and the specific capacities are around 1800, 1600, and 1300 mAh/g at 0.5, 1, and 3 A/g, respectively. Moreover, the reinforced reasons are revealed based on the density functional theory simulations and experiments.

Anomalous Photoelectric Phenomena in Silicon with Nanoclusters of Manganese Atoms

Anomalous Photoelectric Phenomena in Silicon with Nanoclusters of Manganese Atoms

Synthesis, structural and physicochemical properties of a series of manganese(II) complexes with a novel N5 tripodal-amidate ligand and their potential use as water oxidation catalysts

Water oxidation plays a crucial role in both natural and artificial photosynthesis, which is an attractive solution to the depletion of fossil fuels as energy sources due to the increasing consumption. Thus, the search for oxygen evolution reaction catalysts is a hot topic of research. Reaction of the N5-tripodal amidate ligand, N-{2-[(bis(pyridine-2-ylmethyl)amino)methyl]phenyl}picolinamide (Htrip) with MIIX2 (X = Cl-, Br-, I-), in anhydrous ethyl alcohol, and C2H5ONa yields the complexes [MnII(trip)Cl] (1), [MnII(trip)Br] (2), and [MnII(trip)I] (3). Single crystal X-ray structure analysis of 1–3 revealed that the manganese(II) atom in the three manganese compounds occupies the center of a distorted octahedral coordination sphere consisting of two pyridine, one picoline and one amino nitrogen atoms on the equatorial plane, while the axial positions are occupied by one amido nitrogen atom and the halogen anion. The three manganese(II) complexes 1–3 constitute the first examples of mononuclear {MnII(N5trip)X} species to be reported. Magnetic susceptibility measurements showed that these complexes are high-spin d5 systems. Cyclic voltametric study of 1–3 revealed an unexpected two electron, electrochemically reversible redox process, assigned to the oxidation of MnII to MnIV. The electrochemical properties for oxygen evolution reaction of complexes 1–3 showed that the oxidized trip- ligand is responsible for the electrocatalytic oxidation of water to dioxygen.

Dynamic strain aging mechanisms in a metastable austenitic stainless steel

Discontinuous plastic flow due to dynamic strain aging (DSA) in a Fe–13Cr–3.4Mn–0.47C metastable stainless steel was studied by uniaxial tensile tests in the temperature range from 20 °C to 500 °C. A complex picture of the discontinuous flow and its disappearance in an intermediate temperature interval was interpreted in terms of an existing model, which had to be modified. Different mechanisms of DSA were proposed for different temperature intervals. DSA at temperatures up to 200 °C was attributed to deformation-induced martensitic transformation within glide bands. Immobilization of dislocations at martensite/austenite boundaries and emission of fresh dislocations into the adjacent austenite was considered as a major process in this temperature regime. Rapid diffusion of carbon from martensite to the martensite/austenite boundaries was considered as an additional pinning mechanism contributing to discontinuous plastic flow. Serrations on the deformation curves at temperatures between 200 °C and 300 °C were associated with dislocation pinning due to carbon diffusion in austenite. This regime of DSA did not involve high diffusivity martensite. In spite of an increase in the diffusivity of carbon in the temperature range of 350-450 °C, a serration-free regime was observed there. The absence of intermittent dislocation pinning/unpinning events responsible for serrations implied continuous solute drag by carbon atoms according to the Cottrell mechanism. Serrations reappeared at 500 °C and were attributed to dislocation pinning by substitutional chromium and manganese atoms.

Effect of the diffusion temperature on interaction of clusters with impurity atoms in silicon

In this paper, the results of studies of the effect of the diffusion temperature on interaction of clusters of manganese atoms with the sulfur ones have been presented. It has been shown that the electrical parameters of the samples simultaneously doped with sulfur and manganese completely coincide with the parameters of the initial material, i.e. as if they do not contain not only sulfur and manganese, but also thermodonors are not formed. The obtained results make it possible to exclude the possibility of gettering of impurity atoms or formation of some kind of solid solutions, if taking into account the impurity atoms of manganese and sulfur, which complicates their diffusion in the crystal bulk. It has been established that for the initial p-type silicon with the resistivity close to p ~ 10 Ω·cm, the diffusion temperature of 1100 °C is the most optimal one to form clusters with the maximum participation of the introduced sulfur and manganese atoms.

Manganese(III) porphyrin oligomers as high-relaxivity MRI contrast agents

Manganese(III) porphyrins (MnIIIPs) as MRI contrast agents (CAs) have drawn particular attention due to their high longitudinal relaxivity (r1) and unique biodistribution. In this work, two MnIIIP-based oligomers, MnPD and MnPT, were designed to further improve the relaxivity with ease of synthesis. The two compounds were fully characterized and their nuclear magnetic relaxation dispersion (NMRD) profiles were acquired with a fast field cycling NMR relaxometer. Both of the compounds exhibited extended high molar r1 at high fields, higher than that of Gd-DTPA, the first clinical gadolinium(III)-based MRI CA. The r1 value of per manganese atom increased with the increasing number of MnIIIP building blocks, suggesting rotational correlation time (τR) played dominant role in the r1 dispersion. The toxicity of the two MnIIIPs and the imaging effectiveness were estimated in vitro and in vivo. With good biocompatibility, significant contrast enhancement, and complete excretion in 24 h, MnPD and MnPT are both promising for high field clinical applications. The applied strategy also potentially provided a facile approach for creation of more MnIIIP oligomer as efficient T1 MRI CAs.

Synthesis, Structural and Physicochemical Properties of a Series of Manganese(II) Complexes with a Novel N5 Tripodal-Amidate Ligand and Their Potential Use as Water Oxidation Catalysts

Water oxidation plays a crucial role in both natural and artificial photosynthesis, which is an attractive solution to the depletion of fossil fuels as energy sources due to the increasing consumption. Thus, the search for oxygen evolution reaction catalysts is a hot topic of research. Reaction of the N5-tripodal amidate ligand, N-{2-[(bis(pyridine-2-ylmethyl)amino)methyl]phenyl}picolinamide (Htrip) with MIIX2(X=Cl-, Br-, I-), in anhydrous ethyl alcohol, and C2H5ONa yields the complexes [MnII(trip)Cl] (1), [MnII(trip)Br] (2), and [MnII(trip)I] (3). Single crystal X-ray structure analysis of 1-3 revealed that the manganese(II) atom in the three manganese compounds occupies the center of a distorted octahedral coordination sphere consisting of two pyridine, one picoline and one amino nitrogen atoms on the equatorial plane, while the axial positions are occupied by one amido nitrogen atom and the halogen anion. The three manganese(II) complexes 1-3 constitute the first examples of mononuclear {MnII(N5trip)X} species to be reported. Magnetic susceptibility measurements showed that these complexes are high-spin d5 systems. Cyclic voltametric study of 1-3 revealed an unexpected two electron, electrochemically reversible redox process, assigned to the oxidation of MnII to MnIV. The electrochemical properties for oxygen evolution reaction of complexes 1-3 showed that the oxidized trip- ligand is responsible for the electrocatalytic oxidation of water to dioxygen.

Influence of γ – radiation on the properties of silicon with clusters impurity atoms of manganese and nickel

In works [1-4], it was shown that a number of new physical phenomena are observed in silicon with nanoclusters, such as high-temperature negative magnetoresistance (NMR), anomalously high impurity photoconductivity, giant residual photoconductivity, etc. All these phenomena are directly related to the presence of multiply charged, magnetic clusters of manganese atoms in the silicon lattice. It is shown that, on the basis of such materials, it is possible to create fundamentally new, highly sensitive magnetosensors, photodetectors of infrared radiation operating in the μm region and photomagnetic devices.

Studies on redox and axial ligand properties of Meso-Mn(III) porphyrin by cyclic voltammetry and UV–Visible spectrophotometry

Manganese (III) complex with meso-5,10,15,20-Tetrakis(2,5-dimethoxy-phenyl) porphyrin, Mn[T(2,5-(OCH3)2)PP], has been prepared utilizing meso-5,10,15,20-Tetrakis(2,5-dimethoxyphenyl)porphyrin, [T(2,5-(OCH3)2)PP], and Manganese (II) acetate by complexation method. The prepared complex is characterized by UV–Vis spectrophotometric and cyclic voltammetric (CV) studies. The formation of Mn(III) porphyrin complex may be due to a significant metal-porphyrin π interaction. In Mn(III) porphyrin, Mn is in high spin d4 configuration. The strongest σ bonding amongst the Mn and the porphyrin with four pyrrole nitrogen donors is responsible for the octahedral geometry. The change in geometry of the complex from octahedral to tetragonal is due to the presence of two axial amines supplied by the addition of secondary amine. Addition of primary amine leads to the formation of square pyramidal Mn(II) porphyrin, wherein the central metal atom is in high-spin d5 configuration with the occupied d(x2-y2) orbital whose orbital energy is low. This indicates that Mn(III) will be out of the plane of porphyrin. The change in the oxidation state of the central manganese atom and shape of the complex were supported by UV–Vis spectrophotometric studies. Cyclic voltammogram confirmed the oxidation and reduction behaviors of Mn porphyrin complex and the oxidation of Mn(III) into Mn(IV) at 0.3209 V.

Long-range magnetic ordering in Li2MnGeO4 and precursor short-range spin correlations

Long-range magnetic ordering and short-range spin correlations in layered noncentrosymmetric orthogermanate ${\mathrm{Li}}_{2}\mathrm{MnGe}{\mathrm{O}}_{4}$ were studied by means of polarized and unpolarized neutron scattering. The combined Rietveld refinement of synchrotron and neutron powder diffraction data at room temperature within the $Pmn{2}_{1}$ space group allowed us to specify the details of the crystal structure. According to the additional Bragg peaks in low-temperature neutron diffraction patterns a long-range antiferromagnetic ordering with the propagation vector $k=\phantom{\rule{0.16em}{0ex}}(1/2\phantom{\rule{0.16em}{0ex}}1/2\phantom{\rule{0.16em}{0ex}}1/2)$ has been found below ${T}_{N}\ensuremath{\approx}8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Symmetry analysis revealed the model of the ground state spin structure within the ${C}_{a}c$ (no. 9.41) magnetic space group. It is represented by the noncollinear ordering of manganese atoms with a refined magnetic moment of $4.9\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/{\mathrm{Mn}}^{2+}$ at 1.7 K, which corresponds to the saturated value for the high-spin configuration $S=5/2$. Diffuse magnetic scattering was detected on the neutron diffraction patterns at temperatures just above ${T}_{N}$. Its temperature evolution was investigated in detail by polarized neutron scattering with the following XYZ-polarization analysis. Reverse Monte Carlo simulation of diffuse scattering data showed the development of short-range ordering in ${\mathrm{Li}}_{2}\mathrm{MnGe}{\mathrm{O}}_{4}$, which is symmetry consistent on a small scale with the long-range magnetic state below ${T}_{N}$. The reconstructed radial spin-pair correlation function $S(0)\phantom{\rule{0.16em}{0ex}}S(r)$ displayed the predominant role of antiferromagnetic correlations. It was found that spin correlations are significant only for the nearest magnetic neighbors and almost disappear at $r\ensuremath{\approx}12\phantom{\rule{0.16em}{0ex}}\AA{}$ at 10 K. Temperature dependence of the diffuse scattering implies short-range ordering long before the magnetic phase transition. Besides, the spin arrangement was found to be similar in both cases above and below ${T}_{N}$. As a result, an exhaustive picture of the gradual formation of magnetic ordering in ${\mathrm{Li}}_{2}\mathrm{MnGe}{\mathrm{O}}_{4}$ is presented.

Effects of Chemically-Modified Polypyridyl Ligands on the Structural and Redox Properties of Tricarbonylmanganese(I) Complexes.

Carbonyl complexes with manganese(I) as the central metal are very attractive catalysts. The introduction of redox-active ligands, such as quinones and methyl viologen analogs into these catalysts, would be expected to lead to superior catalyst performances, since they can function as excellent electron carriers. In this study, we synthesized four tricarbonylmanganese(I) complexes containing typical bidentate polypyridyl ligands, including 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) frameworks bound to redox-active ortho-quinone/catechol or methyl viologen-like units. The molecular structures of the resulting complexes were determined by X-ray crystallography to clarify their steric features. As expected from the infrared (IR) data, three CO ligands for each complex were coordinated in the facial configuration around the central manganese(I) atom. Additionally, the structural parameters were found to differ significantly between the quinone/catechol units. Electrochemical analysis revealed some differences between them and their reference complexes, namely [MnBr(CO)3(phen)] and [MnBr(CO)3(bpy)]. Notably, interconversions induced by two-electron/two-proton transfers between the quinone and catechol units were observed in the phenanthroline-based complexes. This work indicated that the structural and redox properties in tricarbonylmanganese(I) complexes were significantly affected by chemically modified polypyridyl ligands. A better understanding of structures and redox behaviors of the present compounds would facilitate the design of new manganese complexes with enhanced properties.