Valence State Of Mn Research Articles

The Stability of Manganese Oxides Under Laser Irradiation During Raman Analyses: I. Compact Versus Channel Structures

ABSTRACTManganese oxides/oxyhydroxides (MnOx) are based on Mnn+O6 and Mnn+O4 polyhedra arranged such as to form compact, channel or layered structures. In geology, they are precious archives of past redox conditions for palaeoclimatic reconstructions; in material sciences, they are used for a variety of applications, from pigments to environmental remediation and energy storage. Thus, the fast, remote and non‐destructive identification of MnOx is critical in several disciplines. Micro‐Raman spectroscopy is often used for this purpose, although a systematic characterization of their stability under the laser beam is still lacking. In this work, we present our results on the behaviour of the most common MnOx having compact and channel structures when a 532‐nm laser with intensity between ~23 μW/μm2 and ~36.8 mW/μm2 is used. The compact structures of manganosite (NaCl‐like) and hausmannite (spinel‐like) are stable up to ~36.8 mW/μm2. The stability of oxides with channel structures depends on channel size, charge of channel cations and valence state of Mn. Hausmannite is the final degradation product of all MnOx with channel structures, irrespective of the starting phase. Pyrolusite, manganite, hollandite and romanéchite are relatively stable under the laser beam, and the transition to the spinel structure occurs above 2.5 mW/μm2 while the degradation of cryptomelane and todorokite starts ~226 μW/μm2. The analysis of MnOx thus needs very accurate experimental conditions to avoid misleading and incorrect phase identifications. Based on our data, we propose an analytical protocol for a proper characterization of these minerals via Raman spectroscopy.

High-Entropy Layered Oxide Cathode Materials with Moderated Interlayer Spacing and Enhanced Kinetics for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) with low cost and environmentally friendly features have recently attracted significant attention for renewable energy storage. Sodium layer oxides stand out as a type of promising cathode material for SIBs owing to their high capacity, good rate performance, and high compatibility for manufacturing. However, the poor cycling stability of layer oxide cathodes due to structure distortion greatly impacts their practical applications. Herein, a high entropy doped Cu, Fe, and Mn-based layered oxide (HE-CFMO), Na0.95Li0.05Mg0.05Cu0.20Fe0.22Mn0.35Ti0.13O2 for high-performance SIBs, is designed. The HE-CFMO cathode possesses high-entropy transition metal (TM) layers with a homogeneous stress distribution, providing a moderated interlayer spacing to maintain the structure stability and enhance Na+ ion diffusion. In addition, Li doping in TM layers increases the Mn valence state, which effectively suppresses John-Teller effect, thus stabilizing the layered structure during cycling. Furthermore, the use of nontoxic and low-cost raw materials benefits future commercialization and reduces the risk of environmental pollution. As a result, the HE-CFMO cathode exhibits a super cycling performance with a 95% capacity retention after 300 cycles. This work provides a promising strategy to improve the structure stability and reaction kinetics of cathode materials for SIBs.

Self-protected Chlorella@Mn catalyst with excellent resistance to alkali/alkaline earth metal for NOx reduction by NH3

In the selective catalytic reduction of NOx by NH3 (NH3-SCR), conventional Mn-based denitration catalysts often suffered from susceptibility to poisoning by alkali and alkaline earth metals, this paper presented an innovative self-protected Chlorella@Mn denitration catalyst. Remarkably, in the presence of high concentrations (2 wt%) of alkali and alkaline earth metal oxides, the Chlorella@Mn catalyst sustained a NOx conversion exceeding 96 % at 175 °C. At an even higher concentration (4 wt%), NOx conversion above 90 % at 175 °C, surface analysis revealed that POMn sites acted as sacrificial sites, binding to the alkali and alkaline earth metals, the Chlorella@Mn catalyst surface naturally carried a spectrum of acidic species (such as SO42−, PO3−, SiO32−), proficient in capturing alkali/alkaline earth metal effectively, elements such as S, P, and Si formed bonds with K, Na, Ca, and Mg. The synergistic protection of the active sites and the surface elements avoided the deactivation of the catalyst. The detrimental effects of high concentrations of alkali and alkaline earth metals were primarily due to promoting an excessively high valence state of Mn on the catalyst surface and the reduction or loss of NH3 adsorption and activation at Brønsted acid sites. This research provided valuable insights for advancing the development of low-temperature denitration catalysts with improved resistance to alkali and alkaline earth metal poisoning.

Insight into formaldehyde decomposition over MOFs-derived CeO2-MnOx bimetallic oxides

The ubiquitous presence of formaldehyde as a pollutant has aroused significant environmental and health concerns. The design and performance of (OR: transition metal oxide) catalysts in the catalytic oxidation method continue to face a myriad of challenges. Herein, a series of CeO2-x-MnOx catalysts are synthesized using manganous nitrate impregnated Ce-metal–organic-frameworks as the precursor, followed by a traditional calcination step. Interestingly, we found that the gases released during the pyrolysis of metal–organic-frameworks significantly affect the valence states of Ce and Mn, which are key factors responsible for catalytic activity. Characterizations results show that the CeO2-x-MnOx-2.5 sample contains a large amount of Ce3+, a high Mn3+/Mn4+ ratio, and an abundance of reactive oxygen species on its surface. Density functional theory results demonstrate that oxygen vacancies not only effectively suppress charge loss of Mn and Ce atoms but also significantly enhance the adsorption strength of CeO2-x-MnOx-2.5 for both formaldehyde and O2. These structural features jointly influence the adsorption as well as the rapid oxidation of formaldehyde molecules, leading to the excellent catalytic performance towards formaldehyde oxidation. This study provides a promising platform for designing straightforward, cost-effective, and highly efficient bimetallic catalysts suitable for low-temperature formaldehyde oxidation.

A stable ZnMn2O4 cathode for aqueous Zn-ion batteries via Ni doping to suppress Mn dissolution

ZnMn2O4 (ZMO) emerges as a promising cathode for aqueous Zn-ion batteries due to its high theoretical capacity of 224 mAh g−1 and operating voltage of ∼1.9 V (vs. Zn2+/Zn). However, it suffers from capacity degradation over cycling, attributed to the dissolution of redox-active Mn through Mn3+ disproportionation. In this study, we propose a strategy to stabilize ZMO cathodes by transforming Mn3+ into Mn4+ via Ni doping, aiming for charge balance. The ZnMn2−xNixO4 (x = 0, 0.5, 1.0, and 1.5) with different Ni amounts was prepared by straightforward precipitation and calcination. The mitigation of redox-active Mn dissolution enhanced the specific capacity of all Ni-doped ZMO compared to 201 mAh g−1 of ZMO. ZnMn1.5Ni0.5O4 and ZnMnNiO4 exhibit 277 and 278 mAh g−1, respectively, surpassing ZMO’s theoretical capacity (224 mAh g−1) of ZMO. This additional capacity was attributed to MnOx deposition on the cathode and the charge storage reaction with Zn-ion within the MnOx deposit. Furthermore, Ni doping induces a structural transition of the tetragonal into a cubic spinel, expanding the unit cell volume. This structural modification combined with suppressed Mn dissolution contributes to improved cycling stability. ZnMnNiO4 exhibits 80 % retention of initial capacity after 1000 cycles, outperforming ZMO (57 % retention). The expanded unit cell reduces repulsion between inserted Zn ions, enabling a higher rate performance than pure ZMO. The change in Mn valence states induced by Ni doping enhanced the lifespan and rate capability of ZMO cathodes, underscoring their potential as cathodes for Zn-ion batteries.

Regulating the Manganese Valence State Improves the Kinetic Properties of Manganese‐Based Cathodes

AbstractManganese (Mn)‐based lithium (Li)‐ion batteries with high energy density and low cost have recently attracted considerable attention. One drawback of Mn‐based batteries is the severe capacity attenuation caused by the Jahn‐Teller effect, which distorts the crystal structure and reduces the kinetics of Li‐ion insertion/extraction in the cathodes. In this study, the Mn valence state is regulated on the surface of Mn‐based oxide particles and oxygen vacancies are introduced to facilitate rapid Li‐ion transport and charge storage by adding succinonitrile (SN) to Mn‐based cathodes. Because of the reaction between SN and Mn‐based cathode particles, the contents of Mn3+ ions and oxygen vacancies increase, leading to an improvement in the Li‐ion kinetic properties of the cathodes as well as a reduction in the dissolution of Mn from the cathodes. By regulating the Mn valence state, Li‐ion and Li metal batteries with LiMn2O4 or Li‐rich Mn‐based layered oxide cathodes show significantly enhanced discharge capacity and improved cyclic performance. This study demonstrates that regulating the valence state of Mn ions is an effective strategy for enhancing the electrochemical performance of Mn‐based Li batteries and that adding SN to the cathodes is a cost‐effective method for mass production.

Exploring the dynamic evolution of lattice oxygen on exsolved-Mn2O3@SmMn2O5 interfaces for NO Oxidation

Lattice oxygen in metal oxides plays an important role in the reaction of diesel oxidation catalysts, but the atomic-level understanding of structural evolution during the catalytic process remains elusive. Here, we develop a Mn2O3/SmMn2O5 catalyst using a non-stoichiometric exsolution method to explore the roles of lattice oxygen in NO oxidation. The enhanced covalency of Mn–O bond and increased electron density at Mn3+ sites, induced by the interface between exsolved Mn2O3 and mullite, lead to the formation of highly active lattice oxygen adjacent to Mn3+ sites. Near-ambient pressure X-ray photoelectron and absorption spectroscopies show that the activated lattice oxygen enables reversible changes in Mn valence states and Mn-O bond covalency during redox cycles, reducing energy barriers for NO oxidation and promoting NO2 desorption via the cooperative Mars-van Krevelen mechanism. Therefore, the Mn2O3/SmMn2O5 exhibits higher NO oxidation activity and better resistance to hydrothermal aging compared to a commercial Pt/Al2O3 catalyst.

Oxygen vacancy–rich K-Mn3O4@CeO2 catalyst for efficient oxidation degradation of formaldehyde at near room temperature

Synthesis of catalysts with high catalytic degradation activity for formaldehyde (HCHO) at room temperature is highly desirable for indoor air quality control. Herein, a novel K-Mn3O4@CeO2 catalyst with excellent catalytic oxidation activity toward HCHO at near room temperature was reported. In particular, the K addition in K-Mn3O4@CeO2 considerably enhanced the oxidation activity, and importantly, 99.3 % conversion of 10 mL of a 40 mg/L HCHO solution at 30 °C for 14 h was achieved, with simultaneous strong cycling stability. Moreover, the addition of K species considerably influenced the chemical valence state of Mn from +4 (ε-MnO2) to +8/3 (Mn3O4) on the surface of CeO2, which obviously changed the tunnel structure and the number of oxygen vacancies. One part of K species is uniformly dispersed on K-Mn3O4@CeO2, and the other part exists in the tunnel structure of Mn3O4@CeO2, which is mainly used to balance the negative charge of the tunnel and prevent collapse of the structure, providing enough active sites for the catalytic oxidation of HCHO. We observed a phase transition from tunneled KMnO2 to Mn3O4 to tunneled MnO2 with the decreasing K+ content, in which K-Mn3O4@CeO2 exhibited higher HCHO oxidation activity. In addition, K-Mn3O4@CeO2 exhibited lower oxygen vacancy formation and HCHO adsorption energies in aqueous solution based on density functional theory calculations. This is because the K species provide more active oxygen species and richer oxygen vacancies on the surface of K-Mn3O4@CeO2, promote the mobility of lattice oxygen and the room-temperature reduction properties of oxygen species, and enhance the ability of the catalyst to replenish the consumed oxygen species. Finally, a possible HCHO catalytic oxidation pathway on the surface of K-Mn3O4@CeO2 catalyst is proposed.

The enhancement and impact of Se doping on the electrochemical properties of LiMn2O4 cathode material for aqueous Li-ion batteries

Spinel LiMn2O4 is a promising cathode material for lithium-ion batteries. However, due to the Jahn-Teller effect and Mn dissolution, its capacity decreases seriously in the cycle process, which hinders its wider application. In the course of our research, we discovered that a modest infusion of Se-doping is capable of significantly augmenting the oxygen vacancy within the material, improve the conductivity of the LiMn2O4 material and promotes superior battery performance. Moreover, due to Se-doped the average valence state of Mn is raised, which effectively mitigates the Jahn-Teller effect. The optimized sample exhibits high capacity, long cycle life, and superior rate capability, with an initial discharge specific capacity of 101.0 mAh·g−1 at 7 C and capacity retention of 87.3 % after 200 cycles. The maximum specific discharge capacity of the full battery during the cycle was 97.9 mAh·g−1, the capacity retention rate after 200 cycles was 78.2 %, and the maximum energy density during the cycle is 145.1 Wh·Kg−1, which was nearly twice that of the single lithium-ion battery in this paper. The effect of Se-doped on the properties of LiMn2O4 cathode materials provides a new idea for the development of high-performance spinel lithium manganese oxide cathode materials.

Synergistic effect to unlock the activity and stability for oxygen evolution reaction in spinel LiMn2O4 via d-block metal substitution

An effective strategy using d-block metal hybridization was proposed to induce electronic interaction and promote the synergistic effect, aiming to enhance the OER performance of cost-effective spinel LiMn2O4. Indeed, we deployed a series of LiNixMn2-xO4 catalysts substituted with Ni, yielding the increase of Mn valence states from Mn3.5+ to Mn4+. The LiNi0.5Mn1.5O4 catalyst achieved an excellent OER performance in alkaline media, with an overpotential reduction more than 320 mV at 10 mA cm−2 compared to the unsubstituted LiMn2O4, as well as the electrochemical stability. It was shown to be superior to the most reported Mn-based oxides OER electrocatalysts. Theoretical calculations demonstrated that Ni doped holes in the Mn site, leading to an increase in Mn4+, and that the shared covalent network of Ni 3d-O 2p-Mn 3d optimized an easier desorption of intermediates. These results pave a new example for modulating the chemisorption strength, thus enabling activating the activity and stability of OER process for cost-effective electrocatalysts based on spinel Mn oxides.

MnO@Mn2O3 nanocrystals embedded in biochar networks for sustainable anode of lithium-ion batteries

MnO is an alternative for commercial graphite as anode material for lithium-ion batteries (LIBs), if the issue of unstable performance caused by volume changes, poor conductivity, and changes in valence state of Mn is addressed. In this study, a series of nano MnO/biochar-containing composite materials were prepared with Mn(NO3)2, urea and pomelo peel as raw materials, via simple hydrothermal treatment and calcination, as anode materials for LIBs, where the biochar was used as inexpensive conductive medium and volume buffer. The electrochemical performance of the composite materials shows complicated correlation with the biochar contents, which associate with different carbonization temperatures. Elaborate characterizations with XRD, SEM, TEM, and Mn 2p, Mn 3s XPS spectra were conducted and jointly analyzed, which revealed that the surface of MnO nanocrystals undergoes different degrees of oxidation. The thickness of the surface amorphous Mn2O3 layer on the MnO nanocrystals influences the long-term electrochemical stability more significantly than the circumstances of biochar encapsulation, which was proved through cyclic voltammetry (CV) measurements. A composite material with moderate biochar content and thin layer of Mn2O3 coating on MnO nanocrystals will show more stable electrochemical performance. Based on this principle, one regulated composite material (MnOx/BC-650) gives an ultra-stable capacity of 446.9 mAh∙g−1 at 500 mA∙g−1 after 200 cycles. This study provides new insight for both revealing the true structure of manganese oxides and developing long-term stable MnO-containing anode materials for LIBs.

Regulation of Fe2+ contents in yttrium iron garnet by doping with different valence states of Mn and its dielectric and magnetic properties

Regulation of Fe2+ contents in yttrium iron garnet by doping with different valence states of Mn and its dielectric and magnetic properties

Superoxide radical-induced rapid valence cycling of Mn(II/III/IV) for efficient degradation of organic pollutants

Transition metal oxides are one of the commonly used catalysts for ozone oxidation, and the slow redox cycling of different valence metal components inside the catalysts currently becomes a key bottleneck limiting their catalytic activity. In this work, the superoxide radicals generated at the N/C sites were used to reduce the neighboring high-valence metal components to low-valence states to construct a new mechanism for the rapid cyclic transition of Mn (II/III/IV) valence states. What's more, N/C sites enhanced the ozone adsorption and conversion ability, synergized with the adjacent MnO2 sites to generate interfacial hydroxyl radicals and superoxide radicals, and effectively inhibited the quenching effect of inorganic salt ions (e.g., Cl-, SO42-) on the free radicals. For the actual printing and dyeing wastewater, the COD (chemical oxygen demand) removal rate was as high as 70 % in 60 min and remained stable in 10 cycles with almost no manganese ions leaching. In addition, characterization such as EPR combined with DFT calculations showed that the dual-site structure significantly increased the oxygen vacancy content and Lewis acidity, and the synergistic interaction between graphite N and MnO2 was the most favorable for ozone conversion with the lowest reaction energy barriers.

Improved catalytic activity in peroxymonosulfate activation over manganese-based perovskite oxides with acid treatment

Increasing attention has been paid to the perovskite oxides activating peroxymonosulfate (PMS) for wastewater treatment. In this article, the La0.65Sr0.35MnO3 (LSMO) treated with dilute HNO3 was explored for PMS activation. The La0.65Sr0.35MnO3/Mn3O4 composite is obtained after acid etching. The valence state of B-site Mn and surface oxygen vacancies are populated by etching different time. The LSMO-3 h (etching for 3 h) exhibits the best catalytic performance due to the activation of lattice oxygen, which induces improved redox ability. Minimal reactive oxygen species (ROS) such as OH, SO4−, 1O2, and O2− are generated, contributing little to bisphenol A (BPA) degradation. The Mn(III)-PMS complex and highly oxidative Mn(IV) under the acidic environment are responsible for the excellent degradation. The findings demonstrate an effective strategy of surface etching in enhancing the catalytic performance of perovskite oxides for advanced oxidation.

Spontaneous Multi-scale Supramolecular Assembly Driven by Noncovalent Interactions Coupled with the Continuous Marangoni Effect.

Reported herein is the multi-scale supramolecular assembly (MSSA) process along with redox reactions driven by supramolecular interactions coupled with the spontaneous Marangoni effect in ionic liquid (IL)-based extraction systems. The black powder, the single sphere with a black exterior, and the single colorless sphere were formed step by step at the interface when an aqueous solution of KMnO4 was mixed with the IL phase 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (C2OHmimNTf2) bearing octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO). The mechanism of the whole process was studied systematically. The phenomena were related closely to the change in the valence state of Mn. The MnO4- ion could be reduced quickly to δ-MnO2 and further to Mn2+ slowly by the hydroxyl-functionalized IL C2OHmimNTf2. Based on Mn2+, Mn(CMPO)32+, elementary building blocks (EBBs), and [EBB]n clusters were generated step by step. The [EBB]n clusters with the large enough size that were transferred to the interface, together with the remaining δ-MnO2, assembled into the single sphere with a black exterior, driven by supramolecular interactions coupled with the spontaneous Marangoni effect. When the remaining δ-MnO2 was used up, the mixed single sphere turned completely colorless. It was found that the reaction site of C2OHmim+ with Mn(VII) and Mn(IV) was distributed mainly at the side chain with a hydroxyl group. The MSSA process presents unique spontaneous phase changes. This work paves the way for the practical application of the MSSA-based separation method developed recently. The process also provides a convenient way to observe in situ and characterize directly the continuous Marangoni effect.

Site-substitution in GdCrO3: Effects of Mn valence states on structural, magnetic and electric properties

GdCr1-xMnxO3 (0 ≤ x ≤ 0.3) was prepared by sol-gel method, the effect of Mn doping on the microstructure, magnetic and electric properties of GdCrO3 were studied. The results indicate that all samples have a good orthogonal perovskite structure. The main diffraction peak and lattice parameter varied non-monotonically with the increase of Mn ions in XRD. This is related to the change in valence state of Mn ions, which has been confirmed by X-ray photoelectron spectroscopy (XPS). The positron annihilation lifetime spectrum indicates that vacancy defects and local electron density are related to the valence states of Mn ions. It can be noted from UV-Vis spectroscopic measurements that the doping of Mn ions leads to a decrease in the optical band gap (Eg) from 3.11 eV to 2.13 eV for GdCrO3. The temperature dependence curve of the magnetization intensity curves show that TN(Cr) decreases with Mn ions. The nonmonotonic variations of magnetic moment and remanent magnetization strength are associated with the valence state of Mn ions and the magnetic interactions after doping, respectively. In addition, the samples have low dielectric constants at low doping and the reverse at high doping, which is also related to the valence state variation of Mn ions.

Effects of manganese doping on the lattice structure and iron ion states in La2/3Ca1/3Fe1-xMnxO3-δ

In this paper, La2/3Ca1/3Fe1-xMnxO3-δ(x = 0–0.6) nano particles have been prepared by the sol-gel method. X-ray diffraction (XRD) analysis revealed that with the increase of Mn doping content, the main diffraction peak shifted to the right, the lattice parameters decreased overall, and the degree of lattice distortion gradually reduced. X-ray photoelectron spectroscopy (XPS) analysis indicates that the valence states of Fe and Mn in the system coexist as trivalent and tetravalent, and with the increase in Mn doping, the ratio of Fe3+/Fe4+ decreases, while the ratio of Mn3+/Mn4+ slightly increases. The results of Mössbauer spectrum analysis revealed that as the Mn doping content increased, some Fe ion valence states in the system gradually changed from Fe3+ to Fe4+, and the presence of the paramagnetic phase became increasingly prominent. Furthermore, with the increase of Mn doping content, the degree of lattice distortion in the system decreased, which is consistent with the results obtained from the XRD analysis. This work will provide a reference for future research on the effects of manganese doping in similar systems.

A novel sugarcane residue-derived bimetallic Fe/Mn-biochar composite for activation of peroxymonosulfate in advanced oxidation process removal of azo dye: Degradation behavior and mechanism

Metal-biochar composites with varying Fe/Mn ratios were synthesized for activating peroxymonosulfate (PMS) oxidative degradation of azo dye Orange G (OG) were investigated. The 1Fe2Mn-BC composite based on 1:2 molar ratio impregnation of Fe/Mn salt concentrations of efficient sugarcane harvest residue showed the best catalytic performance under aqueous pH 3–10 and had the least impacts from coexistence of inorganic anions and humic acids. The OG degradation by 1Fe2Mn-BC/PMS system optimized at catalyst:oxidant:pollutant ratio of 1:1.25:0.5 on g/L basis was found to follow pseudo-first-order kinetic and achieved 100 % degradation efficiency within 30 min. Apparent activation energy for OG degradation by 1Fe2Mn-BC/PMS was 16.91 kJ mol−1, and increasing reaction temperature from 293 to 313 K enhanced degradation rate constant by 49 %. Electron paramagnetic resonance (EPR) and radical quenching experiments revealed dominant non-radical 1O2 and radical O2− pathways in the OG oxidation removal by the 1Fe2Mn-BC/PMS system, although SO4− and OH radicals also participated. XPS spectra of 1Fe2Mn-BC before and after OG degradation indicated dominant surface composition of Fe(III) and Mn(II) valence states over other FeMn-biochar composites. The novel optimized one-step pyrolysis Fe/Mn bimetal biochar composite provides an efficient PMS activation for advanced oxidation process (AOP) treating of azo dyes in wastewater decontamination.

Ca & Mn dual-ion hybrid nanostimulator boosting anti-tumor immunity via ferroptosis and innate immunity awakening

Limited by low tumor immunogenicity and the immunosuppressive tumor microenvironment (TME), triple-negative breast cancer (TNBC) has been poorly responsive to immunotherapy so far. Herein, a Ca & Mn dual-ion hybrid nanostimulator (CMS) is constructed to enhance anti-tumor immunity through ferroptosis inducing and innate immunity awakening, which can serve as a ferroptosis inducer and immunoadjuvant for TNBC concurrently. On one hand, glutathione (GSH) depletion and reactive oxygen species (ROS) generation can be achieved due to the mixed valence state of Mn in CMS. On the other hand, as an exotic Ca2+ supplier, CMS causes mitochondrial Ca2+ overload, which further amplifies the oxidative stress. Significantly, tumor cells undergo ferroptosis because of the inactivation of glutathione peroxidase 4 (GPX4) and accumulation of lipid peroxidation (LPO). More impressively, CMS can act as an immunoadjuvant to awaken innate immunity by alleviating intra-tumor hypoxia and Mn2+-induced activation of the STING signaling pathway, which promotes polarization of tumor-associated macrophages (TAMs) and activation of dendritic cells (DCs) for antigen presentation and subsequent infiltration of tumor-specific cytotoxic T lymphocytes (CTLs) into tumor tissues. Taken together, this work demonstrates a novel strategy of simultaneously inducing ferroptosis and awakening innate immunity, offering a new perspective for effective tumor immunotherapy of TNBC.

Giant enhancement of photoluminescence in Mn4+-activated Ba2CaWO6 phosphors via heterovalent doping with rare-earth ions

Currently, Mn4+-activated phosphors have attracted extensive attention for their versatile applications in general lighting, display and plant cultivation. Owing to 3d3 electronic configuration of Mn4+ ion, modifying its local coordination environment emerges as a potent method to tailor its luminescence behavior. Herein, a heterovalent substitution strategy is reported to greatly enhance the photoluminescence (PL) of Ba2CaWO6:Mn4+. The effects of the substitution of rare-earth ions (Ln3+ = Lu3+, Y3+, Gd3+, La3+) for Ca2+ ions on the PL properties of the phosphor are studied in detail. The PL spectral change of Mn4+ induced by Ln3+ substitution is clarified in terms of the local structure of [WO6] octahedron and the valence state of Mn. By selection of Ln3+ ions and optimization of Ln3+ doping concentration, the emission intensity of Ba2Ca0.85Gd0.15WO6:0.25Mn4+ phosphor reaches up to 46.3 times as that of Ba2CaWO6:0.25Mn4+. Besides, the Ba2Ca0.85Gd0.15WO6:0.25Mn4+ phosphor exhibits an internal quantum yield of 56.9 % and a thermal stability of 72.6 %@423 K. Finally, Ba2Ca0.85Ln0.15WO6:Mn4+ based phosphor conversion LED devices are demonstrated, which can be potentially employed for indoor plant lighting.