Doped Mn Atoms Research Articles

A Single-Atom Mn/MoO3- x Nanoagonist for Cascade cGAS/STING Activation in Tumor-Specific Catalytic Metalloimmunotherapy.

The cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway plays a crucial role in initiating anti-tumor immunity. Despite the development of various STING agonists, their effectiveness is often limited by suboptimal activation efficiency and poor sustainability. To address this, a Mn/MoO3- x nanoagonist featuring Mn single-atom sites is presented, designed for cascade cGAS/STING activation in tumor-specific catalytic metalloimmunotherapy. The single-atom nanoagonist (SANA) is meticulously crafted by doping Mn atoms into defective molybdenum oxide (MoO3- x), enabling robust peroxidase-mimicking catalysis and inducing severe double-stranded DNA (dsDNA) damage in tumors. Of note, Mn2+ and MoO4 2- can be responsively released from Mn/MoO3- x SANA and enhance the sensitivity of cGAS to dsDNA. Importantly, MoO4 2- with a relatively slow-release profile and facile cellular accumulation compensates for Mn2+ that has poor cellular accumulation due to continuous efflux, thus continuatively triggering the secretion of type I interferon for beyond 72 h. Remarkably, Mn/MoO3- x SANA significantly inhibits tumor growth and metastasis without supplementary STING agonists or external stimulation. This study offers a promising cascade cGAS/STING activation approach to enhance the efficacy and sustainability of catalytic metalloimmunotherapy.

Impact of Mn Alloying on Phase Stabilities, Magnetic Properties and Electronic Structures in Fe.

Impacts of Mn alloying on lattice stabilities, magnetic properties, electronic structures of the bcc and fcc phases and the fcc→bcc phase transition in Fe16-xMnx (x = 0, 1 and 2) alloys are studied by first-principles calculations. Results show that the doped Mn atom prefers ferromagnetic and antiferromagnetic interaction with the host Fe atoms in the bcc and fcc phases, respectively. In these two phases, the magnetic moment of Mn is smaller and larger than Fe, respectively. The local moment of Fe is decided by the Fe-Mn distance in the bcc phase, whereas in the fcc phase, it is determined by spatial orientation with Mn. In the different phases, Mn prefers different site occupations, which can be understood from the electronic density of states near Fermi energy, implying a possibility of element redistribution during phase transition. The driving force of phase transition decreases with Mn alloying. Both destabilized bcc phase and stabilized fcc phase contribute to the inhibited phase transition, but the latter plays a dominant role. Antiferromagnetism is recognized as the key reason for the enhanced stability of the fcc phase by Mn alloying.

Near-infrared-IIb fluorescent nanozymes for imaging-guided treatment of traumatic brain injury

Traumatic brain injury (TBI) often results in damage to the blood–brain barrier (BBB), leading to secondary effects such as neuroinflammation mediated by reactive oxygen species (ROS), which can increase the risk of long-term neurological dysfunction. Therefore, it is crucial to remove excessive ROS and monitor the status of BBB for timely clinical intervention. Here, we developed a fluorescent nanozyme by doping Mn atoms into PbS/CdS quantum dots (QDs) that emit in the near-infrared-II (NIR-IIb, 1500–1700 nm) region, enabling imaging-guided treatment of TBI. The QD-based nanozyme exhibited excellent antioxidant activity due to uniformly distributed Mn atoms on the surface, which effectively scavenged ROS and inhibited the release of pro-inflammatory factors, thus providing neuroprotective effects for TBI treatment. Additionally, the nanozyme demonstrated exceptional NIR-IIb fluorescence performance, allowing for dynamic monitoring of BBB status with high spatiotemporal resolution to guide precise TBI treatment.

Optimized Ni, Co, Mn Oxides Anchored on Graphite Plates for Highly Efficient Overall Water Splitting

Nickel, cobalt, and manganese oxides are easily obtainable non-noble metal catalysts for water splitting. However, the relationship between composition and catalysts’ performance still needs systematic studies. Herein, guided by theoretical calculations, a low overpotential, easily prepared Mn-doped Co3O4 was deposited on graphite plates for water splitting. The 30% Mn-doped Co3O4 (Co2.1Mn0.9O4) required the lowest overpotential for oxygen evolution reaction (OER), in which the Co2.1Mn0.9O4 reached 20, 30, and 50 mA cm−2 in the overpotentials of 425, 451, and 487 mV, respectively, with 90% IR compensation. Under overall water-splitting conditions, the current density reached 30 mA cm−2 at an overpotential of 0.78 V without IR compensation. Charge density difference analysis illustrates that doped Mn provides electrons for O atoms, and that Mn doping also promotes the electron fluctuation of Co atoms. XPS analysis reveals that Mn-doping increases the chemical valence of the Co atom, and that the doped Mn atom also exhibits higher chemical valence than the Mn of Mn3O4, which is advantageous to boost the form of based-OOH* radical, then decrease the overpotential. Considering the particular simplicity of growing the Co2.1Mn0.9O4 on graphite plates, this work is expected to provide a feasible way to develop the high-performance Co-Mn bimetallic oxide for water splitting.

Mn-CDs with oxidase activity produces ROS to inhibit cell activity

Carbon dots (CDs) played increasingly important roles in biotechnology due to their potential as alternatives of natural enzymes. However, the fabrication of highly active and durable CDs remains challenging and catalytic reaction mechanisms over CDs needs to be better clarified for future advances. Herein, we synthesized manganese-doped carbon dots (Mn-CDs, ∼5 nm) with excellent oxidase properties which exhibits stable catalytic capacity in various salt solutions at different temperatures. Moreover, by thoroughly investigating catalytic ability of Mn-CDs, we found that doped Mn atoms effectively modulated the spin density and charge distribution of CDs, thus reducing the band gap by forming intermediate energy levels. Besides, it is found that the content of pyrrolic N positively correlated to catalytic capacity of Mn-CDs. As a demonstration, the prepared Mn-CDs could work as pseudo-oxidase in real cell environment. They can easily enter into cells, induce the production of ·O2− under ultraviolet light irradiation, and eventually inhibit the activity of HeLa cells and 4T1 cells. We believe that the as-prepared Mn-CDs would find wide applications as metal-doped artificial nanozymes, and lay a foundation for the application and development of Mn-CDs.

Manganese-doped cobalt spinel oxide as bifunctional oxygen electrocatalyst toward high-stable rechargeable Zn-air battery

High-performance and low-cost bifunctional electrocatalysts for ORR and OER are urgently required for rechargeable Zn-air batteries. Herein, a series of Mn-doped Co3O4 nanoparticles grown on carbon nanotubes (Mn-Co3O4@CNTs) bifunctional electrocatalysts are designed. Owing to the moderate doped Mn atoms, the Mn-Co3O4 heightens ORR activity via the synergistic effect between Co and Mn atoms, and more Co3+ active sites are exposed on the surface of Mn-Co3O4 to enhance the OER rate. As a result, the 40% Mn-doped Mn-Co3O4@CNTs electrocatalyst exhibits higher ORR (E1/2 = 0.84 V) and OER (η10 = 356 mV at 10 mA cm−2) performance. More significantly, the Mn-Co3O4@CNTs equipped with rechargeable ZAB displays a high power density of 116 mW cm−2, a low charge-discharge voltage gap of 0.94 V at 10 mA cm−2, and superior cycling stability of over 425 h and 1200 cycles, being much more outperforming than Pt- and Ru-based ZABs.

Bi-Mn diatomic interaction on SOD zeolite substrate promotes electrochemical methanol oxidation

The strategy of diatomic synergy is applied to the in-situ synthesis of electrode catalyst material for methanol fuel cells. During the one-pot synthesis in hydrothermal conditions, the doped Bi and Mn atoms are highly dispersed on and immobilized into the SOD zeolite cage structure as nanocrystals with trace amounts to form the novel Bi/Mn/SOD composite catalyst. The as-synthesized Bi and Mn NPs were confined in a rigid SOD nano-cage to maintain the stability and catalytic activity of the monodisperse state. Several key problems to be solved in methanol fuel cell applications are its energy density, catalytic efficiency, stability, and cost. Through the combined action of Mn and Bi, the composite electrode performed high activity in the methanol oxidation reaction (MOR) with a high current density of 45.9 mA cm−2 without precious metal and with high stability in 10 M methanol without any catalyst poisoning.

Effect of doping and vacancy defects on the adsorption of CO on graphene

The adsorption behavior of CO molecules on graphene has been computationally studied by using the first principles method. Results show that only weak physical adsorption is formed between CO and intrinsic or vacancy defected graphene. However, doping Mn atoms on graphene significantly increases the adsorption energy and charge density between graphene and CO. After the adsorption of CO molecules, impurity band appears in the band structure near the Fermi level of graphene and the total density of states of the adsorption system shifts, which enhances the electrical conductivity of the system. Therefore, doping Mn atoms can greatly improve the adsorption performance of CO molecules on graphene and result in strong chemisorption. Results also show that the adsorption effect of CO on Mn-doped intrinsic graphene is stronger than on Mn-doped vacancy defected graphene. Mn-doped intrinsic graphene is more suitable for making high-performance CO gas sensors.

A novel diluted magnetic semiconductor (Ca,Na)(Zn,Mn)2Sb2 with decoupled charge and spin dopings**Project supported by the National Key Research & Development Program of China (Grant No. 2016YFA0300402) and the Fundamental Research Funds for the Central Universities, China.

We report the successful synthesis of a new diluted magnetic semiconductor (Ca,Na)(Zn,Mn)2Sb2. Na and Mn are doped into the parent compound CaZn2Sb2, which has the same crystal structure as that of “122” type iron-based superconductor CaFe2As2. Na substitution for Ca and Mn substitution for Zn introduce carriers and spins, respectively. Doping Mn atoms alone up to 5% does not induce any type of magnetic ordering. When both Na and Mn are co-doped, a ferromagnetic ordering with maximum TC ∼ 10 K has been observed. Iso-thermal magnetization shows that the coercive field is up to ∼ 245 Oe at 2 K. Below TC, a negative magneto-resistance with MR ∼ 12% has also been achieved.

Mn-Doped Sr/Si(111)-(3 × 2) HCC Surfaces: Antiferromagnetic Semiconductors for Spintronic Applications.

Manganese and manganese silicide as promising candidates for spintronic applications have attracted great interest in recent years. Here, we adopt Sr-induced Si(111)-(3 × 2) honeycomb-chain channel (HCC) surface as a template and perform a systematical study on the structural stability and magnetic and electronic properties of Mn-doped Sr/Si(111)-(3 × 2) HCC surfaces by ab initio calculations. Our energetic and kinetic results show two robust inserting structures M6 and H4, where Mn atoms are located below the honeycomb Si chain and on the top or hollow site of the Si(111) surface. Their high structural stabilities are attributed to the doped Mn atoms that saturate all the dangling bonds of Si(111) surface. In these two structures, Mn atoms prefer antiferromagnetic coupling with the same local magnetic moment of 3 μB. Electronic band structures and band-decomposed charge density distributions reveal that these two stable surface structures have a semiconducting characteristic with a surface band gap of 0.21-0.28 eV. This work provides an antiferromagnetic system for the possible application in spintronics.

Investigation of ferromagnetism in (Mn, Ga) co-doped LiNbO3 by density functional theory

First-principles calculations are performed to investigate the electronic structures and magnetic properties of (Mn, Ga) co-doped LiNbO3. The results show that it is available to tune the magnetism of Mn mono-doped LiNbO3, and the spin-polarized states and the magnetic moments mainly come from the unpaired 3d orbitals of Mn atoms. Furthermore, corresponding to the two Mn doped LiNbO3 system. Eight kinds of Mn atom positions are reviewed and the most stable configuration is verified. Several doping configurations indicate the presence of anti-ferromagnetic (AFM) coupling between two Mn dopants. And then we calculated (2Mn, Ga) co-doped LiNbO3 system. The exciting results show that the existence of ferromagnetic (FM) coupling between Mn and Ga dopants. The results demonstrate that the doped Mn atom will induce additional electron carrier into the LiNbO3. Ga itself does not contribute to magnetism, while (Mn, Ga) co-doped LiNbO3 can induce spin-polarization, indicating that Ga dopant significantly increases FM stability.

Superior arsenate adsorption and comprehensive investigation of adsorption mechanism on novel Mn-doped La2O2CO3 composites

A major challenge for effective decontamination of arsenate from aqueous solution is the development of adsorbent possessing enormous high-active sites with strong affinity to realize both high adsorption capacity and reduction of arsenate down to permissive levels. Here we demonstrate that this challenge may be overcome by doping Mn atoms into La2O2CO3 materials. The synthesized material (5.26%-MnL) achieved an arsenate capture ability superior to most other currently-reported adsorbents, with the maximum adsorption capacity of 555.6 mg/g. Additionally, this novel adsorbent could dramatically reduce the concentration of arsenate from 3775 μg/L to less than 4 μg/L, well below the acceptable value for drinking water (10 μg/L). The adsorption capacity of 5.26%-MnL was demonstrated to be >300 mg/g over a wide pH range from 4 to 9 and the efficiency was maintained >85% even after three cycles of adsorption/desorption. Through a series of characterizations, both surface complexation and ion exchange were proved to contribute to arsenate removal at low molar ratios of As(V)/5.26%-MnL while forming LaAsO4 precipitation played a greater role at higher As(V)/5.26%-MnL ratios. Density Functional Theory (DFT) calculations suggested that Mn atoms acted as active species by not only increasing lattice defects and adsorption sites, but also by activating La3+ in La2O2CO3, which lowered the adsorption energy and facilitated arsenate removal. Due to the high affinity and superior adsorption capacity towards arsenate, Mn-doped La2O2CO3 has been demonstrated to be a promising prospect for the remediation of arsenate-polluted water.

First-principles investigation of vacancy-defected graphene and Mn-doped graphene towards adsorption of H2S

Abstract The effect of vacancy defects and doping Mn atoms on the performance of adsorption between graphene and H2S molecules has been investigated by using first-principles study. The analysis shows that although vacancy defects slightly enhances the adsorption of H2S on graphene, there is no chemical adsorption formed between them. However, after doping graphene with Mn atoms, the adsorption energy and charge transfer between graphene and H2S increase significantly and the maximum values under various adsorption sites and configurations reach 4.3228 eV and 0.171 e, respectively. In addition, the charge density between Mn-doped graphene and H2S molecules is greater than 3.000 × 10−1 e/A3, and the orbitals of Mn and S atoms are hybridized, indicating a formation of chemical bonds. Therefore, Mn doping can significantly enhance the adsorption of H2S on graphene, improving the sensitivity of graphene to H2S. Mn-doped graphene is expected to be a potential sensing material for making high-performance H2S gas sensors.

Magnetism induced by Mn atom doping in SnO monolayer

The structural, magnetic properties, and mechanism of magnetization of SnO monolayer doped with 3d transition metal Mn atom were studied using first-principles calculations. The calculated results show that the substitution doping is easier to realize under the condition of oxygen enrichment. Numerical results reveal that the spin-splitting defect state of the Mn doped system is produced in the band gap and the magnetic moment of 5.0 μB is formed. The induced magnetic moment by Mnsub is mostly derived from the 3d orbital of the doped Mn atom. The magnetic coupling between magnetic moments caused by two Mn atoms in SnO monolayer is a long-range ferromagnetic, which is due to the hole-mediated p–p and p–d interactions. The calculated results suggest that room-temperature ferromagnetism in a SnO monolayer can be induced after substitutional doping of a Mn atom.

Electronic structure of Ba (Zn0.875Mn0.125)2As2

The electronic structure of single-crystalline Ba(Zn0.875Mn0.125)2As2, the parent compound of the recently found high-temperature ferromagnetic semiconductor–(Ba,K)(Zn,Mn)2As2, was studied by high-resolution angle-resolved photoemission spectroscopy. A flat band related to the 3d states of the doped Mn atoms was observed at the binding energy of ∼ −1.6 eV besides the previously reported feature at about −3.3 eV. The spectral weight of this feature is much stronger than that obtained from density functional theory calculations. We proposed that the large spectral weight could originate from the hybridization between Mn and As orbitals. The overall band dispersions agree well with the first-principles calculations of undoped BaZn2As2 except that the total bandwidth of the valence band is larger than that calculated. The increased bandwidth after Mn doping is compatible with the proposed theoretical model.

On the state of Mn in MnxZn1−xO nanoparticles and their surface modification with isonipecotic acid

Mn-doped ZnO (MnxZn1−xO) nanoparticles were synthesized by the co-precipitation method and coated with isonipecotic acid as capping ligand. The structure, composition and morphology of the resulting nanomaterial were investigated by energy disperse X-ray analysis, X-ray diffraction, and transmission electron microscopy data. Such measurements showed that the solid obtained contains 6at% of Mn and it is formed by a highly crystalline material with 3–5nm range of crystallite size, and only a small elongation of its cell parameter with respect to undoped ZnO wurtzite unit cell. Information on the state of manganese atom in the MnxZn1−xO nanostructures formed was obtained from X-ray photoelectron (XPS) and electron energy loss (EELS) spectroscopies. XPS and EELS spectra are composed of four peaks, corresponding to two species of Mn(II) and signals from Mn(III) and Mn(IV). Such spectral data on the state of Mn in the material studied is consistent with the mapping of Mn distribution observed in recorded transmission electron microscopy images, which reveal presence of clusters of Mn atoms. Only a fraction of doping Mn atoms were found forming a solid solution with the host ZnO structure. The functionalization of the nanoparticles system with Isonipecotic acid shows that this molecule remains anchored to the nanoparticles surface mainly through its N basic site. The availability of free carboxylate groups in the capping molecule was tested by conjugation to type IV horseradish peroxidase.

Atomistic simulation of trivalent ions doped in the hexagonal LuMnO3 ferroelectric phase

The interatomic potentials for multiferroic hexagonal LuMnO3 (h-LMO) in its ferroelectric (FE) phase was obtained for empirical fitting procedure and applied to study the effects of a series of trivalent metal and rare-earth dopants on its structural and ferroelectric distortions. The potential parameters found accurately reproduce lattice parameters (error below 0.3%), interatomic distances, pressure effect on the lattice parameters, and tilting angles of the MnO5 polyhedron. We investigated doping at Mn, Lu1 and Lu2 atom sites. It was found that the doped Mn atom site is the most energetically advantageous site for both the metal (Al, Ga, Fe and Cr) and rare-earth (La, Nb, Sm, Eu, Gd, Ho, Er, Yb, Y and Sc) atoms studied. The M-O3/O4 distances decrease when the Mn3+ ion site is doped by trivalent metal ions. The effects on the FE distortion of the material under doping and changes in the tilting angle of the M/MnO5 polyhedron were analyzed.

Structure study on SrRu(1-x)MnxO4 using the extended X-ray absorption fine structure spectroscopy.

The octahedron (BO6) plays a crucial role in ground state for the layered perovskites oxides. Here, we report a structure study of the octahedra in Sr2Ru(1-x)MnxO4 based on Extended X-ray Absorption Fine Structure (EXAFS) method. EXAFS results reveal a clearly structural distortion around the doped Mn atoms, and Jahn-Teller effect in MnO6 octahedra could be expected in the octahedra. This structural distortion may related to the chemical valance change when doping.

Photoemission and x-ray absorption studies of the isostructural to Fe-based superconductors diluted magnetic semiconductorBa1−xKx(Zn1−yMny)2As2

The electronic and magnetic properties of a new diluted magnetic semiconductor (DMS) Ba$_{1-x}$K$_{x}$(Zn$_{1-y}$Mn$_{y}$)$_{2}$As$_{2}$, which is isostructural to so-called 122-type Fe-based superconductors, are investigated by x-ray absorption spectroscopy (XAS) and resonance photoemission spectroscopy (RPES). Mn $L_{2,3}$-edge XAS indicates that the doped Mn atoms have the valence 2+ and strongly hybridize with the $4p$ orbitals of the tetrahedrally coordinating As ligands. The Mn $3d$ partial density of states (PDOS) obtained by RPES shows a peak around 4 eV and relatively high between 0-2 eV below the Fermi level ($E_{F}$) with little contribution at $E_{F}$, similar to that of the archetypal DMS Ga$_{1-x}$Mn$_{x}$As. This energy level creates $d^{5}$ electron configuration with $S=5/2$ local magnetic moments at the Mn atoms. Hole carriers induced by K substitution for Ba atoms go into the top of the As $4p$ valence band and are weakly bound to the Mn local spins. The ferromagnetic correlation between the local spins mediated by the hole carriers induces ferromagnetism in Ba$_{1-x}$K$_{x}$(Zn$_{1-y}$Mn$_{y}$)$_{2}$As$_{2}$

Fluctuation induced conductivity analysis of Mn doped Cu0.5Tl0.5Ba2Ca2Cu3−xMnxO10−δ (x = 0, 0.1, 0.15) superconductors

A series of superconducting samples of type Cu0.5Tl0.5Ba2Ca2Cu3−xMnxO10−δ (x = 0, 0.1, 0.15) are prepared by using solid state reaction method. The electrical resistivity ρ(T) was measured as a function of temperature. The effect of doped Mn-atoms on the superconducting carriers has been investigated by carrying out fluctuation induced conductivity analyses of conductivity data of Cu0.5Tl0.5Ba2Ca2Cu3−xMnxO10−δ (x = 0, 0.1, 0.15) superconducting samples by Aslamazov-Larkin and Lawrence-Doniach models. The width of both two dimensional and three dimensional conductivity regimes are enhanced with doping of Mn at Cu site. The doping of Mn at the CuO2 planar sites increases the inter-layer coupling and coherence length ξc along the c-axis. A decrease in Bc0(T), Bc1(T), Jc(0) and increase in the values of κ, λp.d is observed. The value of the order-parameter is suppressed from |ψ|2 = 1 in the neighborhood of spin carrying doped Mn atoms, which is compensated by increased penetration of magnetic field lines, consequently resulting into increased penetration depth λp.d with increased Mn-doping.