Mn Doping Research Articles

Accelerating Ce3+/Ce4+ Conversion in CeO2 via Mn doping to Endow Scaffolds with Chemodynamic Therapy Properties

CeO2 nanozymes have garnered significant attention in chemodynamic therapy due to their peroxidase-like activity and ability to deplete glutathione. However, their catalytic efficiency is constrained by the low conversion rate of Ce3+/Ce4+. To overcome this limitation, the electron transfer was accelerated by introducing the transition metal Mn atom as a valence electron donor through lattice charge transfer. In detail, we introduced Ce1-xMnxO2 into the poly-L-lactic acid (PLLA) scaffold fabricated by selective laser sintering. The conversion from Ce3+ to Ce4+ promoted the decomposition of H2O2 within the tumor microenvironment to generate hydroxyl radicals with high oxidative activity, consequently inducing oxidative stress. The conversion from Ce4+ to Ce3+ depleted intracellular antioxidant glutathione, disrupting redox balance in tumor cells. This continuous redox cycle ultimately triggered apoptosis in tumor cells. Using a first-principles Hubbard-corrected approximate density-functional method, the analysis of the electron band structure revealed the presence of donor energy levels within the bandgap of Ce1-xMnxO2, enabling electron transfer channels around 0.645 eV. Electrochemical experiments confirmed that Ce0.8Mn0.2O2 significantly reduced the activation overpotential from 0.907 V to 0.646 V, enhancing its redox capacity. As a result, the scaffold exhibited a threefold increase in tumor-killing rate. These findings highlight the immense potential of CeO2 nanozymes in enhancing chemodynamic therapy for effective tumor treatment.

Evolution of Mn-Bi2O3 from the Mn-doped Bi3O4Br electro(pre)catalyst during the oxygen evolution reaction.

Mn-doped Bi3O4Br has been synthesized using a solvothermal route. The undoped Bi3O4Br and Mn-Bi3O4Br materials possess orthorhombic unit cells with two distinct Bi sites forming a layered atomic arrangement. The shift in the (020) plane in the powder X-ray diffraction (PXRD) pattern confirms Mn-doping in the Bi3O4Br lattice. Elemental mapping indicated 7% Mn doping in the Bi3O4Br lattice structure. A core-level X-ray photoelectron study (XPS) indicates the presence of BiIII and MnII valence-states in Mn-Bi3O4Br. Doping with a cation (MnII) containing a different charge and ionic radius resulted in vacancy/defects in Mn-Bi3O4Br which further altered its electronic structure by reducing the indirect band gap, beneficial for electron conduction and electrocatalysis. The irreversible MnII to MnIII transformation at a potential of 1.48 V (vs. RHE) precedes the electrochemical oxygen evolution reaction (OER). The Mn-doped electrocatalyst achieved 10 mA cm-2 current density at 337 mV overpotential, while the pristine Bi3O4Br required 385 mV overpotential to reach the same activity. The pronounced OER activity of the Mn-Bi3O4Br sample over the pristine Bi3O4Br highlights the necessity of MnII doping. The superior activity of the Mn-Bi3O4Br catalyst over that of Bi3O4Br is due to a low Tafel slope, better double-layer capacitance (Cdl), and small charge-transfer resistance (Rct). The chronoamperometry (CA) study depicts long-term stability for 12 h at 20 mA cm-2. An electrolyzer fabricated as Pt(-)/(+)Mn-Bi3O4Br can deliver 10 mA cm-2 at a cell potential of 2.05 V. The post-CA-OER analyses of the anode confirmed the leaching of [Br-] followed by in situ formation of Mn-doped Bi2O3 as the electrocatalytically active species. Herein, an ultra-low Mn-doping into Bi3O4Br leads to an improvement in the electrocatalytic performance of the inactive Bi3O4Br material.

Effects of Mn doping on electronic and quantum transport in PbPdO2 thin films.

PbPdO2, a gapless semiconductor, can be transformed into a spin gapless semiconductor structure by magnetic ion doping. This unique band-gap structure serves as the foundation for its distinctive physical properties. In this study, PbPd1-xMnxO2 (x = 0.05, 0.1, 0.15) thin films with (002) preferred orientation were prepared by laser pulse deposition (PLD). The structural, electroresistive and magnetoresistive properties were systematically characterized, and the results suggest that films with different Mn doping ratios exhibit a current-induced positive colossal electroresistance (CER), and the CER values of PbPd1-xMnxO2 thin films increase with the increase of Mn doping concentration. The CER values are several fold magnitudes higher compared to those of the previously reported PbPdO2 films possessing identical (002) orientation. Combined with first-principles calculation, the underlying influence mechanism of Mn doping on CER is elucidated. In situ X-ray photoelectron spectroscopy (XPS) demonstrates a close correlation between the positive CER and the band gap change induced by oxygen vacancies in PbPd1-xMnxO2. Additionally, it is observed that Mn-doped films exhibit weak localization (WL) and weak anti-localization (WAL) quantum transport. Moreover, it is found that Mn doping can lead to a transition from WAL to WL; a small amount of Mn doping significantly enhances the weak anti-localization effect. However, with increasing Mn concentration, the WAL effect is conversely weakened. The results of studies suggest strongly that PbPdO2, one of the few oxide topological insulators, can display novel quantum transport behavior by ion doping.

Improving the magnetic moment of Ca2Ge and promoting the conversion of semiconductors to diluted magnetic semiconductors using Mn-doping.

The dilute magnetic properties of materials have important potential applications in the field of electronic science and technology. Intrinsic Ca2Ge is a new environmentally friendly semiconductor material, and exhibits cubic and orthorhombic phases. The crystal structure characteristics of Ca2Ge indicate that the modulation of its dilute magnetic properties can theoretically be achieved by doping with magnetic elements. The study of band structures shows that Ca2Ge is a semiconductor, while Mn doped Ca2Ge is a semi-metal. The results of density of states and atomic population analysis show that Mn doped Ca2Ge exhibits ferrimagnetism with a magnetic moment of 5 μB, and the orbital splitting energy of the Mn atom is 1.0 eV. Mn-doping changes the cubic crystal field of Ca2Ge, and the charge transfer and electron polarization of Ca d and Ge p orbitals are affected by Mn atoms. The Ca d orbital is split into dzz, dzy, dzx, dxx-yy and dxy orbitals, and the contribution of spin of each d split orbital to the magnetic moment of the Ca d orbital is in the order dxy > dyz > dxz > dxx-yy > dzz. The Ge p orbital is split into px, py and pz orbitals, and the spin contribution of each p orbital to the magnetic moment of the Ge p orbital is in the order py > pz > px. The analysis of atom populations shows that the charge transfer and spin of Ca and Ge change with Mn doping, and the difference between spin up and spin down increases, improving the magnetism of Ca2Ge and forming a dilute magnetic semiconductor.

On the origin of the improved hydrogen evolution reaction in Mn- and Co-doped MoS2.

In the field of hydrogen production, MoS2 demonstrates good catalytic properties for the hydrogen evolution reaction (HER) which improve when doped with metal cations. However, while the role of sulfur atoms as active sites in the HER is largely reported, the role of metal atoms (i.e. molybdenum or the dopant cations) has yet to be studied in depth. To understand the role of the metal dopant, we study MoS2 thin films doped with Co and Mn ions. We identify the contribution of the electronic bands of the Mn and Co dopants to the integral valence band of the material using in situ resonant photoemission measurements. We demonstrate that Mn and Co dopants act differently: Mn doping favors the shift of the S-Mo hybridized band towards the Fermi level, while in the case of Co doping it is the less hybridized Co band that shifts closer to the Fermi level. Doping with Mn increases the effectiveness of S as the active site, thus improving the HER, while doping with Co introduces the metallic site of Co as the active site, which is less effective in improving HER properties. We therefore clarify the role of the dopant cation in the electronic structure determining the active site for hydrogen adsorption/desorption. Our results pave the way for the design of efficient materials for hydrogen production via the doping route, which can be extended to different catalytic reactions in the field of energy applications.

The prospect of spray pyrolyzed pure, Mn-doped, and Zn-doped nickel oxide thin films as TCO material

Nickel Oxide films with Manganese (Mn) and Zinc (Zn) doping (NiO, Ni1-xMnxO, and Ni1-xZnxO; where x = 0, 0.02, 0.04, and 0.06) were fabricated using the spray pyrolysis technique on the glass substrates at 400 °C (673K) temperature. The XRD spectra revealed a polycrystalline nature of the films with cubic crystal structure and a favored growth orientation towards the (111) plane. The SEM micrographs revealed a smooth, homogeneous, and uniform surface, while the EDS spectra confirmed the presence of Ni, O, Zn, and Mn elements in the films. Optical analysis using UV–visible absorption spectroscopy demonstrated high transparency of the films in the visible region (400 nm–900 nm), and the transparency increased with higher Zn doping, reaching ∼85 % in Ni0.94Zn0.06O films. Conversely, Ni1-xMnxO films show a slight transmission decline with increasing Mn doping concentrations. The sheet resistance of the films was found to be decreased for low-concentration doping and again began to increase for highly doped Ni0.94Zn0.06O and Ni0.94Mn0.06O films. Among all the films, Ni0.98Zn0.02O exhibited the maximum figure of merit, showing the prospect for optoelectronic applications.

Chemodynamic PtMn Nanocubes for Effective Photothermal ROS Storm a Key Anti-Tumor Therapy in-vivo.

Chemodynamic therapy (CDT) is a new treatment approach that is triggered by endogenous stimuli in specific intracellular conditions for generating hydroxyl radicals. However, the efficiency of CDT is severely limited by Fenton reaction agents and harsh reaction conditions. Bimetallic PtMn nanocubes were rationally designed and simply synthesized through a one-step high-temperature pyrolysis process by controlling both the nucleation process and the subsequent crystal growth stage. The polyethylene glycol was modified to enhance biocompatibility. Benefiting from the alloying of Pt nanocubes with Mn doping, the structure of the electron cloud has changed, resulting in different degrees of the shift in electron binding energy, resulting in the increasing of Fenton reaction activity. The PtMn nanocubes could catalyze endogenous hydrogen peroxide to toxic hydroxyl radicals in mild acid. Meanwhile, the intrinsic glutathione (GSH) depletion activity of PtMn nanocubes consumed GSH with the assistance of Mn3+/Mn2+. Upon 808 nm laser irradiation, mild temperature due to the surface plasmon resonance effect of Pt metal can also enhance the Fenton reaction. PtMn nanocubes can not only destroy the antioxidant system via efficient reactive oxygen species generation and continuous GSH consumption but also propose the photothermal effect of noble metal for enhanced Fenton reaction activity.

Ultrasmall catechol-PEG-anchored ferrite nanoparticles for highly sensitive magnetic resonance angiography.

Highly sensitive iron oxide nanoparticles with stable, safe and efficient surface functionalization, as potential substitutes for gadolinium-based contrast agents (GBCAs) with increasing biosafety concerns, exhibit great potential for high-performance magnetic resonance angiography (MRA). Herein, we developed ultrasmall catechol-PEG-anchored ferrite nanoparticles (PEG-UMFNPs) for highly sensitive MRA. The obtained nanoprobe has a high T1 relaxivity value (7.2 mM-1 s-1) due to its ultrasmall size and Mn doping. It has a suitable hydrodynamic size of 20 nm, which prevents rapid vascular extravasation and renal clearance and prolongs its blood circulation time. In vivo MRA at 3.0 T using the nanoprobe shows that the arteries and veins of rats, even blood vessels as small as 0.32 mm, are distinctly visible, and the contrast enhancement can last for at least 1 h. In addition, due to the outstanding contrast enhancement and long circulation time, the stenosis and recanalization process of the rat's carotid artery can be continuously monitored with a single injection of the nanoprobe. Our study indicates that PEG-UMFNPs are outstanding MR imaging nanoprobes that can be used to diagnose vascular diseases without the biosafety issues of GBCAs.

Enhanced photocatalytic activity in Mn-doped multiferroic BiFeO3

Mn doping in ferroelectric BiFeO3 enhanced photocatalytic activity through the synergistic effect of the enhanced band bending on the surface as a result of internal screening of polarization bound charges and formation of inter-band energy levels while shifting the energy bands closer together.

Exploring phase formation and magnetic transitions in Sm(Fe1−xMnx)14B by Mössbauer spectroscopy

The Sm2(Fe1−xMnx)14B (0 ≤ x ≤ 0.3) rare earth alloy was prepared by a reduction-diffusion method, and a corresponding reduction-diffusion model was established. The crystal structure, microscopic morphology, and magnetic properties were systematically characterized to investigate the effect of Mn doping. The results show that the diffusion of Sm into FeB proceeded with the formation of the Sm2Fe14B phase from the very beginning of the reaction. Sm2(Fe1−xMnx)14B alloy undergoes a transition from the ferromagnetic phase (x = 0) to the paramagnetic phase (x = 0.2), and the average magnetic moment of Fe decreases from 2.066 to 0.719 µB as observed by 57Fe Mössbauer spectroscopy. In addition, the Curie temperature decreases rapidly from 620 to 230 K. In other words, a wide temperature-regulation of TC can be achieved by adjusting the Mn content, which is attributed to the fact that Mn doping greatly weakens the atomic exchange interactions. These results provide value for potential applications of Re–Fe-based alloys in room temperature magnetic refrigeration.

First principles and molecular dynamics simulations of effect of dopants on properties of high strength steel for hydrogen storage vessels

High-pressure gaseous hydrogen storage is an important way of hydrogen energy storage and transport at present, while high-strength steel material is one of the main materials used for hydrogen storage vessels. However, their internal doping elements and inherent defects often lead their mechanical properties to decrease, thus reducing the pressure-bearing capability and storage life of the vessel. At present, the mechanism of doping elements influencing the mechanical properties of high-strength steels is still unclear. In this work, a first-principles approach is used to study the influence of elemental doping (Cr, Mn, Mo, As, Sb, Bi, Sn, Pb) on the mechanical properties of Fe single crystals and Fe-C systems. The results show that among the above elements, Mn doping can increase the elastic modulus, bulk modulus, and shear modulus compared with those of pure Fe, while the doping by remaining elements will reduce the three moduli above, with the non-transition metal elements having a greater effect on the three moduli than the transition metal elements. Electronic structure analysis shows that the transition metal elements have better compatibility with the Fe lattice. Molecular dynamics results further show that the injection of H atoms significantly disrupts the lattice ordering of the Fe polycrystalline doped by C, Cr, and Mn elements, while the doping of Cr elements can significantly enhance the dislocation density of the system. The effects of doping elements on the mechanical properties of single-crystal and polycrystalline Fe, which are studied in this work, are of great significance in guiding the mechanistic study of the effects of doping and defects on the strength of Fe-based materials.

Simultaneous Mn and Cl doping on Na3V2(PO4)3 with high performance for full sodium-ion batteries.

Nowadays, the poor conductivity and unstable structure have become obstacles for the popularization of Na3V2(PO4)3 (NVP). In the current work, a dual-modified Mn0.1Cl0.3-NVP composite doped with Mn and Cl is prepared by a facile sol-gel method. When Mn2+ with a large ionic radius replaces small V3+, it can improve the stability of the NVP crystal structure. In addition, the replacement of V3+ by Mn2+ in a low valence state can generate redundant hole carriers, which is conducive to the rapid transport of electrons. The substitution of PO43- by Cl-, which is more electronegative, can reduce the impedance and facilitate the movement of Na+. Owing to the synergistic effect of Mn and Cl co-substitution, the structural stability of NVP was systematically enhanced, and the electron transfer and ion diffusion were effectively improved. Consequently, the optimized Mn0.1Cl0.3-NVP sample demonstrated superior electrochemical performance and kinetic properties. It exhibited a high reversible capacity of 109.2 mA h g-1 at 0.1C. Even at 15 and 30C, high discharge capacities of 70.3 mA h g-1 and 68.2 mA h g-1 were observed after 2000 cycles with capacity retention above 80%. Moreover, it delivered remarkable capacities of 77.1 and 73.4 mA h g-1 at 100 and 200C with retained capacity values of 50.3 and 47 mA h g-1, respectively, after 2000 cycles. Furthermore, the assembled Mn0.1Cl0.3-NVP//HC full cell delivered a high value of 94.7 mA h g-1 and lit LED bulbs, indicating its excellent application potential.

Probing compositional engineering effects on lead-free perovskite-inspired nanocrystal thin films using correlative nonlinear optical microscopy.

We introduce the use of correlative third-harmonic generation and multiphoton-induced luminescence microscopy to investigate the impact of manganese (Mn) doping on bismuth (Bi)-based perovskite-inspired nanocrystal thin films. The technique was found to be extremely sensitive to the microscopic features of the perovskite film and its structural compositions, allowing the unambiguous detection of compositionally different emitters in the perovskite film and manipulation of their nonlinear optical responses. Our work unveils a new way to investigate, manipulate, and exploit perovskite-inspired functional materials for nonlinear optical conversion at the nanoscale.

A NiCo2S4 octahedral configuration doped by Mn, Zn and Cu for the oxygen evolution reaction.

Transition metals with similar atomic radius were used for doping spinel NiCo2S4 to adjust the octahedral configuration. Mn dopants adjusted the morphology and surface charge distribution, and optimized the electron transport and catalytic activity of the surface site. Mn-NiCo2S4 showed an OER overpotential of 269 mV and water splitting voltage of 1.59 V.

Stable Pt catalysts anchored by Mn-SBA-15 support for propane dehydrogenation

The development of stable Pt-based catalysts is important for propane dehydrogenation process. In this work, Mn-SBA-15 supports with different Mn doping amounts were prepared by in situ hydrothermal method using citric acid and urea. Compared with Pt/SBA-15 catalyst, the significantly improved dispersion and stability of Pt on Pt/Mn-SBA-15 catalysts were demonstrated by X-ray diffraction and transmission electron microscopy results. CO DRIFT spectra analysis showed the electron transfer from Mn to Pt occurred, which led to an increase in the electron density of Pt. And the propane dehydrogenation performances over Pt/Mn-SBA-15 were enhanced significantly. Among them, the Pt/10Mn-SBA-15 shows the highest initial propane conversion of 51.2% and lowest deactivation rate constant of 0.013 h−1. The reason may be that appropriate amount of Mn can modify Pt by both electronic effect and geometric effect. And the strong metal-support interaction formed by highly dispersed MnOx anchor sites in Mn-SBA-15 support maintains the stability of Pt during the propane dehydrogenation reaction.

Influence of dimensionality on optical properties of doped assembly of gold nanoclusters

Doping-induced size variation and optical property shift in gold nanocluster assemblies are reported.

Mn Doped ZnO Film for Ethanol Vapor Detection

It has become a major challenge to develop highly sensitive and selective ZnO gas sensors to detect the leakage of toxic and explosive gases due to their high operating temperature. This article reports the design, characterization, and application of a Mn-doped ZnO thin film for ethanol gas vapor detection at a relatively lower temperature. To achieve this, undoped (0%) and Mn doped ZnO thin films were prepared using a spin coating technique and their structural, morphological and optical characterizations were carried out using XRD, SEM, EDX and UV-vis spectrophotometer. The XRD analysis showed a polycrystalline ZnO structure with the preferred orientations along (100), (002), (101), (102), (110), (103), and (200) planes. Upon Mn doping, the average crystallite size and band gap of ZnO were found to be decreased, which indicated that Mn ions substitute into the lattice of ZnO. Interestingly, SEM images revealed the grainy like porous ZnO surfaces. The EDX results confirmed the presence of Mn dopant in the ZnO lattice. In the doped films, the changes in particle size and grain boundaries of nanocrystalline ZnO resulted changes in sensitivity and operating temperature of ZnO gas sensor. The sensitivity measurements towards ethanol vapor showed significant decrease of the operating temperature from 220°C to 160°C as Mn concentration was increased from 0 to 5%. As-prepared Mn-doped ZnO sensors will be useful for sensing ethanol vapor at relatively low temperature.

Synthesis and investigation; influence of Mn doping on biological, optical, dielectric and electrochemical characteristics of Bi2O4 nanostructures

In this research, bismuth oxide thin films were synthesized with the variation of Mn dopant (1-5 wt %) on a glass slide by sol-gel dip coating method. XRD corroborated the creation of a monoclinic phase for all the samples after annealing at 450 °C for 4 h. The non-uniform cuboid-like granular structures were observed by SEM with a significant number of grain boundaries. Different functional groups were examined by using FTIR spectroscopy. The optical band gap was reduced from 2.01 to 1.81eV by increasing the concentration of Mn dopant. The contribution of grain and grain boundaries to the material electrical response in various frequency ranges was distinguished by impedance analysis. The polaron mechanism was used to investigate conductivity with time variation. The efficiency of supercapacitors was significantly enhanced by using the monoclinic Bi2O4 phase of bismuth oxides, promoting the specific capacitance in the range of 2518.2–6890.2 Fg-1 with high energy and power density. That leads them to the fabrication of supercapacitors in advanced electronic devices. Magnetic analysis showed that saturation magnetization and remanent frequency decreased while coercivity of thin films increased with increasing Mn concentration which was successfully explained by the critical size effect and Néel's collinear two sub-lattice models, making them plausible candidates in spintronics. As from photocatalyst analysis, the number of reactive oxygen species ROS was increased by increasing Mn doping in the Bi2O4 crystal lattice. These species degraded the water pollutants under simple exposure to sunlight (i-e visible range). The production of ROS in the photocatalytic process was also correlated with antibacterial activity. Mn-doped Bi2O4 was found to be more effective towards K. pneumonia than other bacteria. The prepared Mn:Bi2O4 nanostructures with a higher percentage of manganese were effectively used for the treatment of bloodstream infections, meningitis, pneumonia, and urinary tract infections and stopped further bacterial growth.

Elucidating the Mn-Doping Induced Phase Transition from Orthorhombic Pnma to Rhombohedral R3c in LaFeO3: Insights from Mössbauer Spectroscopy

LaFe1-xMnxO3 (0≤x≤0.9) samples were synthesized through the sol-gel method. According to X-ray diffraction (XRD) results, with the increase of Mn doping, the crystal structure of the sample changes from orthogonal Pnma structure to rhombohedral R3c structure, and a two-phase coexistence phenomenon exists within the range of 0.4≤x≤0.7. Using Mössbauer spectroscopy, the coexistence range of the two phases and the iron content in each phase were identified. At x=0.4, the Pnma phase contribution (91.1%) dominates, with only a slight R3c phase contribution (8.9%). As the amount of Mn doping gradually increases, the R3c phase becomes dominant at x=0.6 (74.6%), and the Pnma phase completely disappears at x=0.8. This work will provide an important perspective for future researchers studying similar phase coexistence systems.

Bonding State and Thermal Expansion Coefficient of Mn-Doped Ba0.5Sr0.5FeO3-δ Perovskite Oxides for IT-SOFCs.

The oxygen vacancy formation behavior and electrochemical and thermal properties of Ba0.5Sr0.5Fe1-xMnxO3-δ (BSFMnx, x = 0-0.15) cathode materials were investigated. For thermogravimetric analysis, the weight decreased from 1.98% (x = 0) to 1.81% (x = 0.15) in the 400-950 °C range, which was due to oxygen loss from the lattice. The average oxidation state of the B-site increased, the Oads/Olat ratio decreased, and the binding energy of the Olat peak increased with Mn doping. These results indicate that Mn doping increases the strength of the metal-oxygen bond and decreases the amount of oxygen vacancies in the lattice. The electrical conductivity of BSFMnx increased with the temperature due to the thermally activated small-polaron hopping mechanism showing a maximum value of 10.4 S cm-1 (x = 0.15) at 450 °C. The area-specific resistance of BSFMn0.15 was 0.14 Ω cm2 at 700 °C and the thermal expansion coefficient (TEC) gradually decreased to 12.7 × 10-6 K-1, which is similar to that of Ce0.8Sm0.2O2 (SDC) (12.2 × 10-6 K-1). Mn doping increased the metal-oxygen bonding energy, which reduced the oxygen reduction reaction activity but improved the electrical conductivity and thermal stability with SDC.