Mn Doping Research Articles

Microstructure and mechanical properties of extruded Mg–Zn–Mn–Ca alloys

In this work, the influence of Mn and Ca doping on the microstructure and mechanical properties of Mg–3Zn, Mg–3Zn-0.5Mn, and Mg–3Zn-0.5Mn-1.2Ca alloys is systematically investigated. The addition of Mn elements is shown to exert no obvious effect on the microstructure of as-cast, as-homogenized, and extruded Mg–3Zn alloys. In contrast, the introduction of Ca into the extruded Mg–3Zn-0.5Mn alloy promotes the formation of nano-sized compounds and enhances grain refinement compared to the other two alloys. The extruded Mg–3Zn-0.5Mn alloy exhibits the higher yield strength (YS, 155 MPa) and ultimate tensile strength (UTS, 183 MPa) but the lower elongation (13%) than the extruded Mg–3Zn alloy (YS of 130 MPa, UTS of 175 MPa, and elongation of 25%). The improved strength of the extruded Mg–3Zn-0.5Mn alloy is mainly attributed to the refined grains, while both the lack of twinning deformation and strong texture result in ductility loss. The most optimal combination of strength and ductility is achieved in an extruded Mg–3Zn-0.5Mn-1.2Ca alloy (YS of 180 MPa, UTS of 250 MPa, and elongation of 26%). This suggests that fine grains and high volume fraction of nano-sized MgZn2 compounds contribute mainly to the strength of Mg–3Zn-0.5Mn-1.2Ca alloy. Although the grain refinement also facilitates the suppression of twinning in the extruded Mg–3Zn-0.5Mn-1.2Ca alloy, the weak texture and fine homogeneous grains are conducive to the high ductility.

Enhanced polarization fatigue behavior in lead-free ferroelectric (K, Na)NbO3 thin films by Mn doping

Enhanced polarization fatigue behavior in lead-free ferroelectric (K, Na)NbO3 thin films by Mn doping

Size Uniformity of CsPbBr3 Perovskite Quantum Dots via Manganese-Doping.

The achievement of size uniformity and monodispersity in perovskite quantum dots (QDs) requires the implementation of precise temperature control and the establishment of optimal reaction conditions. Nevertheless, the accurate control of a range of reaction variables represents a considerable challenge. This study addresses the aforementioned challenge by employing manganese (Mn) doping to achieve size uniformity in CsPbBr3 perovskite QDs without the necessity for the precise control of the reaction conditions. By optimizing the Mn:Pb ratio, it is possible to successfully dope CsPbBr3 QDs with the appropriate concentrations of Mn²⁺ and achieve a uniform size distribution. The spectroscopic measurements on single QDs indicate that the appropriate Mn²⁺ concentrations can result in a narrower spectral linewidth, a longer photoluminescence (PL) lifetime, and a reduced biexciton Auger recombination rate, thus positively affecting the PL properties. This study not only simplifies the size control of perovskite QDs but also demonstrates the potential of Mn-doped CsPbBr3 QDs for narrow-linewidth light-emitting diode applications.

To study structural morphological and ferromagnetic behaviour of Sn1−xMnxO2 thin films

SnO2 is diamagnetic in nature and represent paramagnetic, ferromagnetic and anti-ferromagnetic behaviours after inducing Mn in the host matrix. Mn doped SnO2 thin films prepared by PLD technique. XRD and AFM measurements confirm the reducing crystallite and grain size of the samples with increasing doping of Mn. In this research authors focused on magnetization effect of SMO thin films with the help of SQUID-VSM magnetometer. Magnetic analysis reflects strong ferromagnetic behaviour for (10 % Mn) doping and further increase upto (15 %) shift to ferromagnetic to anti-ferromagnetic behaviour. The above observation will be useful for the core elements for the spintronic devices.

Manipulating Dual-Metal Catalytic Activities toward Organic Upgrading in Upcycling Plastic Wastes with Inhibited Oxygen Evolution.

Electrorefinery of polybutylene terephthalate (PBT) waste plastic, specifically conversion of a PBT-derived 1,4-butanediol (BDO) monomer into value-added succinate coupled with H2 production, emerges as an auspicious strategy to mitigate severe plastic pollution. Herein, we report the synthesis of Mn-doped NiNDA nanosheets (NDA: 2,6-naphthalenedicarboxylic acid), a metal-organic framework (MOF) through a ligand exchange method, and its utilization for electrocatalytic BDO oxidation to succinate. Interestingly, the transformation of doped layered-hydroxide (d-LH) precursors to MOF promotes BDO oxidation while hindering the competitive oxygen evolution reaction. Experimental and theoretical results indicate that the MOF has a higher affinity (i.e., alcoholophilic) for BDO than the d-LH, while Mn doping into NiNDA results in electron accumulation at Ni sites with an upward shift in the d-band center and convenient spin-dependent charge transfer, which are all beneficial for BDO oxidation. The as-constructed two-electrode membrane-electrode assembly (MEA) flow cell, by coupling BDO oxidation and hydrogen evolution reaction, attains an industrial current density of 1.5 A cm-2@1.82 V at 50 °C, corresponding to a specific energy consumption of 3.68 kWh/Nm3 H2. This represents an energy saving of >25% for hydrogen production on an industrial scale compared to conventional water electrolysis (∼5 kWh/Nm3 H2) in addition to the production of valuable chemicals.

Study on the electromagnetic properties and microwave absorption properties of Co2Si by non-magnetic metal Cu and Mn single doping

In this study, Co2Si and Co2Si-doped powder materials with different Cu,Mn proportions were prepared by mechanical alloying and thermal sintering. The effects of Cu,Mn doping on the crystal structure, magnetic properties, and microwave absorption properties of Co2Si were investigated. The results showed that all the sample peaks obtained by XRD measurement were consistent with the standard card (ICDD: 98–005–2281) of Co2Si.The Ms values corresponding to 2 at%, 4 at%, and 8 at% Cu doping were 25.79 emu/g, 23.79 emu/g, and 21.75 emu/g, respectively. The saturation magnetization of Co2Si samples doped with 2 at%, 4 at% and 8 at% Mn was 8.26 emu/g, 20.33 emu/g and 14.65 emu/g, respectively.The doping of Cu significantly improved the comprehensive absorption performance of Co2Si alloy, and the lowest reflection loss was obtained when Cu was doped with Co2Si alloy, with an RLmin value of -67.61 dB and an EAB of 2.40 GHz. The comprehensive absorption performance of Mn doped Co2Si was also improved, and the RLmin value of Mn doped with 4 at% was -67.04 dB, and the EAB was 2.39 GHz.This is because that the small Co2-xMxSi (M=Cu,Mn) alloy can produce multiple reflection and scattering effects, which increase the propagation path of the electromagnetic wave and optimize the impedance matching characteristics of the material.

Cu/Mn-mediated electron shuttle and high-valent metals enhance hydroxyl radicals production during the electrochemical oxidation on the CuMn-Sb-SnO2 electrode

In this work, a novel CuMn-Sb-SnO2 anode is developed by a simple, low-cost preparation process. The doping of Cu and Mn causes surface reconstruction, which optimizes its electronic structure, compared to the Sb-SnO2 anode. Experimental results demonstrate that the levofloxacin degradation kinetics constant in the CuMn-Sb-SnO2 system (0.188 min−1) was 8.5 times higher than that in the Sb-SnO2 system, which is surpassing most reported anodes. Moreover, electrochemical characterization also revealed that the CuMn-Sb-SnO2 anode possessed more active sites, higher OEP potential, and lower charge transfer resistance. Notably, electrochemical characterization and EPR experiments confirmed the formation of Cu (III), highlighting their crucial role in promoting the generation of •OH during the catalytic process. Additionally, theoretical calculations and XPS analysis revealed that Cu and Mn rely on self-mediated redox shuttles to act as “electron porters”, significantly accelerating internal electron transfer between Sn and Sb to enhance the production of •OH. Furthermore, the CuMn-Sb-SnO2 anode exhibits great practicability due to its efficient degradation of various antibiotics. This study offers valuable new insights into developing novel electrodes for the efficient degradation of antibiotic wastewater.

Interfacial interaction mechanism between Mn doped highly conjugated biochar and berberine hydrochloride

MnSO4-modified biochar (Mn-BC) was synthesized to remove berberine hydrochloride (BH) from wastewater by utilizing tea waste as raw material and MnSO4 as modifier. Brunel Emmett Taylor (BET) analysis reveals that the specific surface area (SSA) and average pore size (Dave) of Mn-BC are 1.4 and 7 times higher than those of pristine biochar apart, attributing to the dissociation effect can promote the dispersion of MnSO4 in the pores of the biochar. Meanwhile, the doping of Mn not only introduces additional oxygen-containing functional groups (OCFGs), but also modulates the π electron density. Furthermore, Response surface method (RSM) analysis reveals that Mn-BC dosage has the most significant effect on BH removal, followed by BH concentration and pH value. Kinetic and isothermal studies reveal that the BH adsorption process of Mn-BC was mainly dominated by chemical and monolayer adsorption. Meanwhile, density functional theory (DFT) calculations confirm the contribution of Mn doping to the conjugation effect in the adsorption system. Originally proposed Mn-BC is one potentially propitious material to eliminate BH from wastewater, meanwhile this also provides a newfangled conception over the sustainable utilization of tea waste resources.

Cr and Mn doping AgNbO3 for high Curie temperature ferromagnetic half-metals

The alterations in the electronic and magnetic properties of AgNbO3 induced by Cr and Mn doping at two concentrations (6% and 14%) are investigated within the framework of density functional theory (DFT), both with and without the Hubbard correction (U) as well as HSE method. Half-metallic ferromagnetic behavior with 100% polarization is observed for all dopants. Double exchange coupling is the mechanism responsible for the ferromagnetic interaction in these materials. Our results also indicates that the correction with U-term and HSE method provide consistent values that closely align with experimental measurements, and significantly improve the standard DFT description. Finally, the value of the Curie temperature, which reaches 425.49 (K), exceeds the ambient temperature, revealing the potential use of this doped material for new spintronic devices.

Mn-doped CeO2 derived from Ce-MOF porous nanoribbons as highly active catalysts for the synthesis of dimethyl carbonate from CO2 and methanol.

It is desirable but challenging to develop highly-efficient catalysts for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. The vacancy-mediated incorporation of heteroatom into surface reconstruction is an efficient method of defect engineering for enhancing the catalytic properties. In this work, manganese-doped cerium oxide porous nanoribbons (Mn/CeO2-BTC) were prepared derived from a Ce-BTC by a sacrificial template approach. It is found that the catalytic activity of Mn/CeO2-BTC catalysts can be readily controlled by varying the amount of Mn dopants and the as-synthesized 0.1-Mn/CeO2-BTC exhibited an outstanding activity for the synthesis of DMC from CO2 and methanol, which reached a high DMC yield (6.53 mmolDMC/gcat.) without any dehydrating agents. Based on characterization results, the enhanced performance may be attributed to the defective structures caused by Mn doping and the porous nanoribbons of the CeO2 crystals, which provide more surface oxygen vacancies and acidic-basic sites, favoring adsorption and activation of CO2 and methanol.

Low-coordinated Mn–N2 sites in graphene oxide induce peroxydisulfate activation for tetracycline degradation: Process optimization and theoretical calculation

Atom-dispersed low-coordinated transition metal-Nx catalysts exhibit excellent efficiency in activating peroxydisulfate (PDS) for environmental remediation. However, their catalytic performance is limited due to metal-N coordination number and single-atom loading amount. In this study, low-coordinated nitrogen-doped graphene oxide (GO) confined single-atom Mn catalyst (Mn-SA/NGO) was synthesized by molten salt-assisted pyrolysis and coupled to PDS for degradation of tetracycline (TC) in water. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) analysis showed the successful doping of single-atom Mn (weight percentage 1.6%) onto GO and the formation of low-coordinated Mn–N2 sites. The optimized parameters obtained by Box-Behnken Design achieved 100% TC removal in both prediction and experimental results. The Mn-SA/NGO + PDS system had strong anti-interference ability for TC removal in the presence of anions. Besides, Mn-SA/NGO possessed good reusability and stability. O2•−, •OH, and 1O2 were the main active species for TC degradation, and the TC mineralization reached 85.1%. Density functional theory (DFT) calculations confirmed that the introduction of single atoms Mn could effectively enhance adsorption and activation of PDS. The findings provide a reference for the synthesis of high-performance single-atom catalysts for effective removal of antibiotics.

One single-atom Mn doping strategy enabling two functions of oxygen reduction reaction and pseudocapacitive performance

Single-atom metal species as highly effective active sites are crucial for enhancing energy storage and conversion properties. However, achieving the simultaneous construction of single-atom sites and the regulation of matrix structures to enable their application in both energy storage and conversion remains a challenge. Here, we have successfully developed unique MnN2C2 active sites, atomically dispersed on N-doped mesoporous graphitic carbon sheets (MnSAs/NMC). This is accomplished through the strategic utilization of MnCl2 salt, which serves dual roles of a pore-forming agent and a template. The MnSAs/NMC catalyst demonstrates compelling electrocatalytic activity for the oxygen reduction reaction (ORR), with an impressive half-wave potential (E1/2 = 0.90 V), alongside superior capacitance reaching 444 F g-1 at 0.5 A g-1 for supercapacitors. Crucially, both experimental and theoretical simulations validate that the single-atom dispersed MnN2C2 optimizes the adsorption energy of reactants and intermediates in the ORR process and pseudocapacitive behavior, leading to excellent ORR activity and capacitive performance. Interestingly, MnSAs/NMC-based Zn-air batteries exhibit concurrently high-power density derived from capacitive property and high energy density enhanced by ORR process. This study presents a novel preparation method for single-atom catalysts, which paves the way for the commercial application of super energy storage and conversion devices.

Ultra‐Stable and Bright Pure‐Red Perovskite Nanocrystals for Backlit Displays

AbstractMetal halide perovskite nanocrystals (NCs) have emerged as an alternative to conventional phosphors for wide color gamut displays. However, the issues of poor stability and low emission efficiency of pure‐red CsPbBrxI3‐x NCs set an obstacle to their practical application. Herein, the synergistic effect of Mn doping and mesoporous SiO2 sealing is reported through in situ formation of Mn‐doped NCs into mesoporous SiO2 nanospheres (MnNCs@SiO2) to structurally and spatially stabilize the perovskite NCs for bright and stable pure‐red emitter. The large bonding energy of Mn‐halogen effectively suppresses the halide vacancy defects, prompting the highest photoluminescence quantum yield (PLQY) up to 84% (634 nm) among the pure‐red composite analogs. More importantly, the nanocrystal structure stability is fundamentally improved by the enhanced formation energy with Mn doping, together with the spatial isolation by SiO2 nanospheres. The MnNCs@SiO2 films exhibit impressive stabilities against high‐temperature heating, thermal cycle test, UV irradiation, water, and acid/alkali erosion, representing one of the most stable pure‐red perovskite emitters. By integrating fabricated all‐perovskite CsPbX3 single color conversion film into the liquid crystal display (LCD) modules, a wide color gamut of 128% of NTSC is achieved, enabling an excellent color rendition for high‐saturation object colors toward practical applications.

Achieving High Substitutional Incorporation in Mn-Doped Graphene.

Despite its broad potential applications, substitution of carbon by transition metal atoms in graphene has so far been explored only to a limited extent. We report the realization of substitutional Mn doping of graphene to a record high atomic concentration of 0.5%, which was achieved using ultralow-energy ion implantation. By correlating the experimental data with the results of ab initio Born-Oppenheimer molecular dynamics calculations, we infer that direct substitution is the dominant mechanism of impurity incorporation. Thermal annealing in ultrahigh vacuum provides efficient removal of surface contaminants and additional implantation-induced disorder, resulting in Mn-doped graphene that, aside from the substitutional Mn impurities, is essentially as clean and defect-free as the as-grown layer. We further show that the Dirac character of graphene is preserved upon substitutional Mn doping, even in this high concentration regime, making this system ideal for studying the interaction between Dirac conduction electrons and localized magnetic moments. More generally, these results show that ultralow energy ion implantation can be used for controlled functionalization of graphene with substitutional transition-metal atoms, of relevance for a wide range of applications, from magnetism and spintronics to single-atom catalysis.

Mn doping as a simple strategy for improving energy storage in BaBi4Ti4O15 thin films

To obtain high energy storage density in ferroelectric films, polarization and breakdown field Eb are two crucial factors. The inversely coupled relationship between polarization and Eb is commonly observed and it remains a challenge to realize high Eb without deteriorating polarization. Selecting a suitable element doping should largely enhance the Eb since of the optimization of microstructures as well as the decrease in defects, meanwhile the doping should induce extra polarization contribution from lattice distortion. In this work, we reported that Eb can be largely enhanced via Mn doping in BaBi4Ti4O15 thin films due to grain refining, densification, and oxygen vacancy reduction. Interestingly, the polarization is not deteriorated since of the Mn doping effect induced extra polarization from the lattice distortion. Consequently, an ultrahigh energy storage density of 96 J/cm3 with a high efficiency of 76.6% was achieved in BaBi4Ti3.95Mn0.05O15 thin films with excellent stability and reliability. This work will provide a simple and effective route to improve the energy storage in dielectric capacitors.

Investigations on the photoelectric properties of the Mn doped inorganic CsSnCl3 perovskite

Mn dopant significantly improves the photoluminescent performance of CsSnCl3. To find the exact interactions induced by Mn dopant into the CsSnCl3 crystal, we studied the geometric, electronic and excitonic properties for these systems. We found an increased formation energy of the VSn defect, which promoting the stability and the luminescence properties of CsSnCl3 accordingly. Via analyses from the crystal field theory and the COHP calculations, we revealed that the transition of the 3d orbital of Mn2+ ion from 4T1→6A1 plays a crucial role in enhancing the luminescence of CsSnCl3. Also, we show that with the introduction of Mn dopant, the exciton binding energy increases, generating the more tight bounding interactions between the electron and hole pairs which results in the higher luminescence efficiency. Therefore, our results show that Mn doping indeed enhances the photoluminescence properties of CsSnCl3 and facilitates its application in the field of light-emitting devices.

Exploring the structural, magnetic and shielding performance of Mn doped Yb2O3 and Eu2O3 nanostructures

Re2-xMnxO3 (ReYb or Eu, x = 0.0, 0.05, 0.1, 0.15) nanostructures were produced utilizing the sol-gel procedure. The crystal structure and microstructure of all samples were analyzed based on XRD measurements using the Rietveld profile approach. The lattice parameter, cation distribution of different cations between different crystallographic sites, bond lengths of different polyhedrons, crystallite size, micro-strain and distortion index of the different polyhedrons of the formed sample were determined. Mn cations were found to prefer the 8b sites of the cubic bixbyite structure. The average crystallite size decreased following doping, while the microstrain experienced a significant increase. The low temperature dependent magnetizations for Yb1.85Mn0.15O3 and Eu1.85M0.15O3 nanostructures under a magnetic field of 200 Oe were investigated. Curie–Weiss law was employed to determine the magnetic configuration of the samples. The values of the effective magnetic moments μeff are 4.89 μB and 3.77 μB for Yb1.85Mn0.15O3 and Eu1.85M0.15O3, whereas the calculated values are 4.531 μB and 3.535 μB, respectively. The shielding properties of Re2-xMnxO3 (ReYb or Eu) nanostructures were studied using the Phy-X/PSD simulation program. The linear attenuation coefficients (LAC) and mass attenuation coefficients (MAC) values of the Yb2-xMnxO3 samples are greater than those of the Eu2-xMnxO3 samples. The half value length (HVL) and tenth value length (TVL) values increased as Mn was added to Re1.85Mn0.15O3 nanostructures. Yb1.85Mn0.05O3 and Eu1.85Mn0.05O3 nanostructures have the highest mean free path (MFP) values of 3 cm and 4 cm, respectively, at an energy of 5 MeV. The exposure build-up factor (EBF), and energy absorption build-up factor (EABF) values affected by the host rare earth oxide and the amount of Mn doping. The Re1.85Mn0.15O3 nanostructures exhibit a greater capacity to absorb photons with lower energy rather than higher energy. Yb1.85Mn0.15O3 nanostructure demonstrates exceptional neutron shielding capacities.

Lattice Oxygen Activation through Deep Oxidation of Co4N by Jahn–Teller–Active Dopants for Improved Electrocatalytic Oxygen Evolution

AbstractTriggering the lattice oxygen oxidation mechanism is crucial for improving oxygen evolution reaction (OER) performance, because it could bypass the scaling relation limitation associated with the conventional adsorbate evolution mechanism through the direct formation of oxygen–oxygen bond. High‐valence transition metal sites are favorable for activating the lattice oxygen, but the deep oxidation of pre‐catalysts suffers from a high thermodynamic barrier. Here, taking advantage of the Jahn–Teller (J–T) distortion induced structural instability, we incorporate high‐spin Mn3+ ( ) dopant into Co4N. Mn dopants enable a surface structural transformation from Co4N to CoOOH, and finally to CoO2, as observed by various in situ spectroscopic investigations. Furthermore, the reconstructed surface on Mn‐doped Co4N triggers the lattice oxygen activation, as evidenced experimentally by pH‐dependent OER, tetramethylammonium cation adsorption and online electrochemical mass spectrometry measurements of 18O‐labelled catalysts. In general, this work not only offers the introducing J–T effect approach to regulate the structural transition, but also provides an understanding about the influence of the catalyst's electronic configuration on determining the reaction route, which may inspire the design of more efficient catalysts with activated lattice oxygen.

Lattice Oxygen Activation through Deep Oxidation of Co4N by Jahn-Teller-Active Dopants for Improved Electrocatalytic Oxygen Evolution.

Triggering the lattice oxygen oxidation mechanism is crucial for improving oxygen evolution reaction (OER) performance, because it could bypass the scaling relation limitation associated with the conventional adsorbate evolution mechanism through the direct formation of oxygen-oxygen bond. High-valence transition metal sites are favorable for activating the lattice oxygen, but the deep oxidation of pre-catalysts suffers from a high thermodynamic barrier. Here, taking advantage of the Jahn-Teller (J-T) distortion induced structural instability, we incorporate high-spin Mn3+ ( ) dopant into Co4N. Mn dopants enable a surface structural transformation from Co4N to CoOOH, and finally to CoO2, as observed by various in situ spectroscopic investigations. Furthermore, the reconstructed surface on Mn-doped Co4N triggers the lattice oxygen activation, as evidenced experimentally by pH-dependent OER, tetramethylammonium cation adsorption and online electrochemical mass spectrometry measurements of 18O-labelled catalysts. In general, this work not only offers the introducing J-T effect approach to regulate the structural transition, but also provides an understanding about the influence of the catalyst's electronic configuration on determining the reaction route, which may inspire the design of more efficient catalysts with activated lattice oxygen.

High-temperature hydrogen sensor based on MOFs-derived Mn-doped In2O3 hollow nanotubes

Developing high-temperature hydrogen (H2) sensors with fast response speed is urgently demanded in harsh application environments, especially for chemical industries and the aerospace field. Herein, we have reported a facile strategy to synthesize Mn-doped In2O3 hollow nanotubes (Mn-In2O3) by solvothermal and annealing route using In-MOFs as precursors. The experimental results indicate that the obtained products possess hollow nanotube structures with plenty of holes and Mn doping greatly boosts the gas-sensing performance of In2O3-based sensors towards H2. In particular, the responses of 3 mol% Mn-In2O3 are 2.57 and 2.3 towards 50 ppm H2 at 360 °C and 400 °C, respectively, which are much higher than those of bare In2O3 hollow nanotubes. Besides, the sensor based on 3 mol% Mn-In2O3 exhibits a low limit of detection (25 ppb), excellent selectivity, rapid response/recovery speed (∼4 and ∼15 s@20 ppm), and excellent stability at high temperature (360 °C). Such enhancement of H2-sensing properties can be put down to the hollow structure derived from In-MOFs and abundant oxygen vacancy defects produced by Mn doping. The Mn-In2O3 hollow nanotubes could be regarded as promising materials for selectively detecting H2 in a wide range of concentrations.