Mn Pairs Research Articles

Improving the In Vivo Stability of [52Mn]Mn(II) Complexes with 18-Membered Macrocyclic Chelators for PET Imaging.

We report the [natMn/52Mn]Mn(II) complexes of the macrocyclic chelators PYAN [3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane] and CHXPYAN [(41R,42R,101R,102R)-3,5,9,11-tetraaza-1,7(2,6)-dipyridina-4,10(1,2)-dicyclohexanacyclododecaphane]. The X-ray crystal structures of Mn-PYAN and Mn-CHXPYAN evidence distorted octahedral geometries through coordination of the nitrogen atoms of the macrocycles. Cyclic voltammetry studies evidence reversible processes due to the Mn(II)/Mn(III) pair, indicating that the complexes are resistant to oxidation. CHXPYAN forms a more thermodynamically stable and kinetically inert Mn(II) complex than PYAN. Radiochemical studies with the radioactive isotope manganese-52 (52Mn, t1/2 = 5.6 days) evidenced better radiochemical yields for CHXPYAN than for PYAN. Both [52Mn]Mn(II) complexes remained stable in mouse and human serum, so in vivo stability studies were carried out. Positron emission tomography/computed tomography scans and biodistribution assays indicated that [52Mn]Mn-PYAN has a distribution pattern similar to that of [52Mn]MnCl2, showing persistent radioactivity accumulation in the kidneys. Conversely, [52Mn]Mn-CHXPYAN remained stable in vivo, clearing quickly from the liver and kidneys.

Bridged Pt−OH−Mn Mediator in N‐coordinated Mn Single Atoms and Pt Nanoparticles for Electrochemical Biomolecule Oxidation and Discrimination

AbstractThe rational design of efficient catalysts for uric acid (UA) electrooxidation, as well as the establishment of structure‐activity relationships, remains a critical bottleneck in the field of electrochemical sensing. To address these challenges, herein, a hybrid catalyst that integrates carbon‐supported Pt nanoparticles and nitrogen‐coordinated Mn single atoms (PtNPs/MnNC) is developed. The metal‐metal interaction during annealing affords the construction of metallic‐bonded Pt−Mn pairs between PtNPs and Mn single atoms, facilitating the electron transfer from PtNPs to the support and thereby optimizing the electronic structure of catalysts. More importantly, experiments and theoretical calculations provide visual proof for the ‘incipient hydrous oxide adatom mediator’ mechanism for UA oxidation. The Pt−Mn pairs first adsorb OH* to construct the bridged Pt−OH−Mn mediators to serve as a highly active intermediate for N−H bond dissociation and proton transfer. Benefiting from the unique electronic and geometric structure of the catalytic center and reactive intermediates, PtNPs/MnNC exhibits superior electrooxidation performance. The electrochemical sensor based on PtNPs/MnNC enables sensitive detection and discrimination of UA and dopamine in serum samples. This work offers new insights into the construction of novel electrocatalysts for sensitive sensing platforms.

Strain-controlled Néel temperature and exchange bias enhancements in IrMn/CoFeB bilayers

We propose a numerical method, where first-principles calculations are combined with modified Monte Carlo simulations, and study the Néel temperature of antiferromagnetic IrMn and exchange bias effect in antiferromagnet/ferromagnet IrMn/CoFeB bilayers manipulated by the applications of tensile and compressive strains. The results show that both tensile and compressive strains linearly change the magnetic moment of Mn and the magnetocrystalline anisotropy of IrMn, and meanwhile, the uniaxially easy-axis directions under tensile and compressive strains are perpendicular. The strain-triggered increase in antiferromagnetic exchange coupling between Mn–Mn pairs is revealed and induces an up to 1.5 times enhancement of the Néel temperature of IrMn. Furthermore, the spontaneous and conventional exchange bias effects can be both observed under large tensile strains, also sensitive to the cooling field, and strongly enhanced roughly by 800% under 8 T in the application of 1.5% strain, which can be interpreted by the strain-induced high magnetocrystalline anisotropies. Thus, the tensile strains are better for controlling and optimizing the Néel temperature of IrMn and further exchange bias properties in IrMn-based heterostructures. This work establishes the correlations between microscopically and macroscopically magnetic responses to strain, indicating that strain can be an intriguing means of extrinsic manipulation of exchange bias, which is of importance for spintronic device applications.

Effects of dry aging and heating on the structural characteristics and transformation of hexagonal turbostratic birnessite

AbstractNatural birnessite‐like minerals are commonly enriched in various transition metals, such as iron (Fe). Though the fates of metals associated with birnessites during mineral transformation in aqueous conditions are thoroughly studied, we determined the Fe behaviors in Fe‐doped hexagonal turbostratic birnessites during mineral evolution in dry state at room temperature for 8 years and upon thermal treatments at temperatures ranging from 323 to 773 K, covering the temperatures in extreme environments such as wildfires. These Fe‐containing birnessites were very stable upon aging in the dry state. Upon thermal treatment, the birnessite sample with a small amount of Fe (≤2.8 wt.%) was transformed to cryptomelane at 573–673 K, while for the sample with ∼5.6 wt.% Fe, the transformation temperature increased to 673–773 K. This indicated that Fe adsorption enhanced the birnessite's thermal stability. Further, there was a linear relationship between the fraction of edge‐sharing Fe–Fe(Mn) pairs and temperature over 298–473 K. This implied the migration of Fe adsorbed on vacancies into birnessite layers and/or increased edge‐sharing of Fe around vacancies from adjacent layers during heating. The average manganese (Mn) valences in the Mn dioxides were almost constant with the increase in temperature when the layer structure was kept, but greatly increased when the tectomanganate was formed. These results provided deep insights into the mechanisms of Mn dioxide mineral transformation and the fates of associated metals under extreme conditions in terrestrial environments.

Rock drilling performance of rotary ultrasonic tools incorporating PZT piezoceramic and Mn:PIN-PMN-PT piezocrystal

High performance Mn:PIN-PMN-PT piezocrystal material is investigated to understand if its extraordinary properties can replace the traditional hard piezoceramic material for space exploration applications. A bolted Langevin-style ultrasonic drill tool incorporating a pair of Mn:PIN-PMN-PT piezocrystal rings is built to compare with a same configuration ultrasonic drill tool actuated with a pair of hard piezoceramic rings, which are tuned to the first longitudinal mode (L1) at around 20 kHz. From the characterisation results, it is observed that the piezocrystal material presents significantly greater values of relative permittivity, electromechanical coupling coefficient, and piezoelectric charge coefficient than the hard piezoceramic material. Despite these outstanding properties, the piezocrystal driven ultrasonic drill tool shows similar displacement amplitudes to its counterpart. Nonetheless, the impedance magnitude of the piezocrystal driven ultrasonic drill tool at resonance is a magnitude lower than the piezoceramic actuated drill tool, due to the large piezoelectric charge coefficient d33. Ultrasonic rock drilling experiments suggest that the cutting force for sandstone and marble are greatly reduced, but limestone and tuff are less affected.In general, the piezocrystal driven ultrasonic drill tool demonstrates a marginally improved cutting performance than the piezoceramic actuated drill tool, in terms of lower cutting force and motor power consumption, however, the tool wear appears slightly poorer. The research outcome of this paper indicates that the thickness mode of the piezocrystal rings might not be the optimal form of excitation, which could be due to the piezoelectric losses at high excitation levels, so other excitation conditions and vibration modes will need to be explored to fully adopt the extraordinary material properties of the piezocrystal material.

Screening Ba0.9A0.1MnO3 and Ba0.9A0.1Mn0.7Cu0.3O3 (A = Mg, Ca, Sr, Ce, La) Sol-Gel Synthesised Perovskites as GPF Catalysts.

Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) (A = Mg, Ca, Sr, Ce, La) perovskite-type mixed oxides were synthesised, characterised, and used for soot oxidation in simulated Gasoline Direct Injection (GDI) engine exhaust conditions. The samples have been obtained by the sol-gel method in an aqueous medium and deeply characterised. The characterization results indicate that the partial substitution of Ba by A metal in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC) perovskites: (i) favours the hexagonal structure of perovskite; (ii) improves the reducibility and the oxygen desorption during Temperature-Programmed Desorption (O2-TPD) tests and, consequently, the oxygen mobility; (iii) mantains the amount of oxygen vacancies and of Mn(IV) and Mn(III) oxidation states, being Mn(IV) the main one; and (iv) for Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, copper is partially incorporated into the structure. The soot conversion data reveal that Ba0.9La0.1Mn0.7Cu0.3O3 (BMC-La) is the most active catalyst in an inert (100% He) reaction atmosphere, as it presents the highest amount of copper on the surface, and that Ba0.9Ce0.1MnO3 (BM-Ce) is the best one if a low amount of O2 (1% O2 in He) is present, as it combines the highest emission of oxygen with the good redox properties of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) pairs.

Achieving Tunable Cold/Warm White-Light Emission in a Single Perovskite Material with Near-Unity Photoluminescence Quantum Yield

HighlightsHigh-quality Sn2+/Mn2+-co-doped Rb4CdCl6 single crystals and powders were prepared and showed high-performance dual-emission white light with near-unity photoluminescence quantum yield.Short-range and extremely strong interactions between Sn2+ and Mn2+ were observed that lead to an intriguing ultra-high-efficiency Dexter energy transfer process from adjacent Sn2+ ions to Mn2+ ions.The dual-emission intensities were tuned flexibly by varying the fractions of Sn2+ and Sn–Mn pairs to balance their emission proportions for cold/warm white-light generation.

Magnetic coupling for highly efficient and tunable emission in CsCdX3:Mn perovskites

All-inorganic ABX3 (X = Cl,Br,I) can work as an ionic luminescence material in optoelectronic field. Here Mn-doped CsCdCl3 hexagonal perovskite powders were synthesized and found to give bright orange-yellow colored emission at room temperature with an astonishingly quantum yield close to 100% at successful incorporation of 2.1% atomic ratio Mn ions. This enhanced emission comes from the local magnetic polaron—combined STEs with ferromagnetic Mn–Mn pair d-d transition (4T1→6A1) in replacement of Cd dimers in the CsCdCl3 lattice. Compared with CsCdBr3, this local magnetic polaron rely on the magnetic couplings, for example, in the Mn ions in the octahedral point and edge alternately connected 1-d chain and between 1-d chains, upon Mn concentrations. The magnetic coupling can modify the optical absorption edge and photoluminescence quantum yield (PLQY), and tune emission color from yellow to red. The PLQY maximum occurs at 350 K. The more Mn–Mn FM coupling in denser Mn-X octahedra face-shared chains in the bromides lead to a larger emission redshift than in the chloride. The magnetic coupling in the perovskite out of local Mn connection styles (separated, or point, edge and face shared TM ions) can determine its PLQY and emission color, which is useful in the future material design and optoelectronic or spintronic devices.

Exchange Interactions and Magnetic Properties of a Molecular Mn18-Ring Complex.

[Mn3O(OAc)7(HOAc)]6·xAcOH (x = 6-9) represents a rare example of a compound containing molecular Mn18-rings. These are formed by Mn3(µ3-O) subunits in which the high-spin Mn(III) centers are bridged by three pairs of acetate anions (AcO-). An AcOH molecule coordinates to one of the Mn atoms leading to [Mn3(µ3-O)(µ2-OAc)6(AcOH)]-units, designated in short as Mn3-units, that are interconnected by acetate anions via the other two Mn atoms to form Mn18-rings. Magnetic measurements show weak ferromagnetic interactions between them that are suppressed in strong magnetic field. Quantum-chemical calculations on Mn3 model complexes using independently DFT and ab-initio multi reference methods (CASSCF/NEVPT2) show a correlation between the orientation of the pseudo-Jahn-Teller axes of pairs of Mn(III) magnetic centers and corresponding exchange coupling energies. Weak coupling between Mn3-units within the Mn18-ring allowed to simulate the magnetic susceptibility vs temperature dependence in terms of basically uncoupled magnetic moments of each Mn3-unit within the ring.

Luminescence and Mechanism of Mn2+ Substitution in Cs7Cd3Br13 with Two Types of Coordination Number.

Cadmium-based perovskite materials as promising optoelectronic materials have been widely explored, but there are still some special microscopic interaction-dependent properties not fully understood. Here, we successfully synthesized Cs7(Cd1-XMnX)3Br13 crystal by a simple hydrothermal method. In Cs7Cd3Br13 crystals with their intrinsic self-trapped exciton (STE) emission, Cd2+ ions stay in both different coordination sites, and partial replacement of Cd2+ with Mn2+ can modify their luminescence properties significantly. The luminescence peak position of the doped sample was adjusted from 610 nm in the undoped sample to 577 nm in the doped one by the combination of STE and Mn d-d transition, with enhanced photoluminescence quantum yield (PLQY) of ∼50% at a Mn precursor ratio of 40%. Their magnetic responses occur from the coexisting ferromagnetic (FM) and antiferromagnetic (AFM) coupling of Mn pairs in four and six coordination sites, modifying its whole emission profile. This material is valuable for studying the structure-optical properties and finding applications in optoelectronic devices.

Hydroxylation strategy unlocking multi-redox reaction of manganese hexacyanoferrate for aqueous zinc-ion battery

Prussian blue analogues (PBAs), as one of the most promising cathodes due to their open framework and high working voltage (∼1.75 V vs Zn/Zn2+) for rechargeable aqueous zinc ion batteries (RAZIBs), commonly suffer from poor reversible capacity owing to single redox center. Here, a hydroxylation strategy is proposed for activating inactive redox pair of Mn(II)/Mn(III) in manganese hexacyanoferrate (MnHCF) to supply extra capacity. As a result, OH − rich MnHCF cathode renders a high discharge capacity of 136.1 mAh/g (at 100 mA g−1) and a considerable energy density of 228.8 Wh kg−1 benefiting from the unlocked multi-redox reaction, which is much better than the OH − poor MnHCF (58.3 mAh/g and 52.6 Wh kg−1, respectively). Furthermore, the abundant hydroxyl in OH-rich MnHCF can continuously activate the multi-redox centers to provide high capacity in the subsequent cycles. Density functional theory (DFT) calculation reveals that abundant hydroxyl functional group favors to capture Zn2+ on the sites near Mn atoms, thereby facilitating the activation of Mn-redox reaction. This study offers new opportunities for exploiting cathodes with both high working voltage and discharge capacity for RAZIBs.

Transition metals doped (3,3) armchair boron nitride nanosheet as dilute magnetic semiconductors materials for the spintronic application

AbstractMagnetic 2D materials have attracted considerable attention for their significant potential application in spintronic. In this work, the effect of substitutional doping of 3d‐transition metals such as Co, Cr, Mn, and Fe on the magnetic and electronic properties of boron nitride nanosheet (BNNS) was studied based on the spin‐polarized density functional theory. The results revealed that the non‐magnetic and semiconducting behavior of BNNS can be altered by magnetically active dopants. The spin‐polarized density of states suggests that pure BNNS is a nonmagnetic semiconductor with a direct bandgap while transition metals doped BNNS are dilute magnetic semiconductors or half metals (HM). Co doping shows the most stable ferromagnetic phases in the nanosheet. A pair of Mn and Co atoms doped BNNS in edge structure show HM property with 100% spin polarization and seem to be good candidates for spintronic applications and especially as spin filter devices and spin current injectors.

Linear Mn(II)4Ln(III)2 (Ln = Gd, Dy, Tb) heterometallic complexes from a ditopic hydrazone ligand: Slow magnetic relaxation in Mn4Dy2 complex

L4 (C13H12N6O2), a ditopic ligand containing a carbohydrazide with terminal pyridyl moieties, has been successfully used to prepare a new class of heterometallic hexanuclear Mn4Ln2 systems. The reaction of L4 with Ln(NO3)3∙6H2O produced three linear heterometallic compounds with the general formula [Mn4Ln2(L4)4(CH3O)2(H2O)6Cl6][Cl]∙2H2O (Ln = Gd (1), Dy (2), Tb (3)). Monodeprotonated L4 binds lanthanide ions via Ndiazine and Ohydrazone donors in these complexes, while CH3O–, water, and chloride ions occupy the remaining vacant coordination sites. dc magnetic studies have confirmed that ferromagnetic exchange interactions are present in all three complexes with Curie temperatures of 2.32 K, 1.2 K, and 2.21 K, respectively, for 1, 2, and 3. In complex 1, the exchange coupling values between the two Mn(II)-Gd(III) and Mn(II)-Mn(II) pairs were found to be +0.11 and +0.58 cm−1, respectively, with a Lande g-factor of 2.01 for Mn(II) in this complex. ac studies reveal the slow relaxation of magnetization in complex 2 with an energy barrier of 1.5 K, while complexes 1 and 3 have not shown this feature.

Effect and fate of Ni during aging and thermal-induced phyllomanganate-to-tectomanganate transformation

Phyllomanganates are ubiquitous in a variety of environments and commonly enriched in transition metal elements, such as Ni. The effect of such foreign metal cations on phyllomanganate transformation is widely documented under aqueous conditions together with the induced modification of Ni geochemical behavior. A similar knowledge is lacking however on phyllomanganate transformation and on the induced fate of associated metal elements that may occur under dry conditions, that prevail in deserts and arid areas increasingly exposed to severe droughts or wildfires. The present study shows that crystallinity, morphology, Mn oxidation state, and Ni binding mechanisms are essentially unaffected when aging hexagonal birnessite (Mn oxidation state ∼ 3.90 and Ni/Mn molar ratios of 0.00 and 0.13) in the dry state at room temperature for up to 8 years. In contrast, heating aged Ni-doped birnessite to 25–200 °C results in an increased proportion of edge-sharing Ni-Ni(Mn) pairs with increasing temperature induced by the migration of interlayer Ni to birnessite octahedral layers and/or by an increased sharing of coordination oxygens by interlayer Ni/Mn from adjacent layers. Further heating to 400 °C does not change this proportion, with birnessite layer structure being retained. Transformation of Ni-doped birnessite to cryptomelane is complete at 500 °C, while that of Ni-free birnessite is achieved at 400 °C, suggesting that Ni doping increases birnessite thermal stability. Birnessite-to-cryptomelane transformation comes with a strong increase of Mn oxidation state, whereas this parameter remains unchanged in heated birnessite samples. Ni incorporation in the cryptomelane framework, reduces its release during reductive acid dissolution by a factor of 396 ± 15 compared to initial birnessite. These results shed light on mineral transformation affecting layered manganates under dry conditions and on the fate of associated transition metal elements.

Magnetic Properties in Mn-Doped δ-MoN: A Systematic Density Functional Theory Study.

Due to the potential applications of transition metal nitrides in modern electronic and spintronic devices, we have systematically studied the magnetic properties of δ-MoN induced by the Mn dopant, with the goal of identifying the origin of magnetism and figuring out the magnetic coupling mechanism between the Mn dopants. Based on the density functional theory, one Mn atom doped at different Mo sites (2a and 6c in the International Tables) in the unit cell of δ-MoN was firstly studied. It was found that the Mn dopant located at the 2a or 6c site leads to significant spin splitting of the density of states, suggesting that the Mn doping induces magnetism in δ-MoN. The calculations were then extended to a 2 × 1 × 2 supercell, which contains two impurity Mn atoms. Detailed analysis reveals that the different couplings of the Mn–Mn pair cannot be simply attributed to the different Mn–Mn distances but are closely related to the electronic processes that take place in the segment (–N– or –N–Mo–N–) that connects two Mn dopants. The mechanisms responsible for the FM/AFM coupling of the Mn–Mn pairs are the superexchange and the p–d exchange mediated by the N atoms, and the d–d coupling between the host Mo atom and the Mn dopant.

The magnetic polaron modulated luminescence bands of organic-inorganic hybrid ferroelectric anti-perovskite (C3H9N)3Cd2Cl7 doped with Mn2+

Recently, the excellent optical properties of organic-inorganic hybrid metal halides have attracted much attention in the optoelectronic field. However, their complicated preparation processes seriously influence their properties and applications. In this work, we developed a series of organic-inorganic hybrid metal halides (C3H9N)3Cd2Cl7:x%Mn2+ with an antiperovskite structure with ferroelectrics in an early report, giving tunable emissions contemporarily with different manganese (Mn)2+ concentrations via a simple mechanochemical method. Meanwhile, their single crystals were also grown by a slow thermal evaporation method. The as-grown products with Mn dopants exhibited diluted magnetic semiconductor behavior and varied emission profiles by different excitation wavelengths, which could be modified by the heat treatment. All the emission bands come from the different magnetic polarons with enhanced electron-phonon coupling or self-trapped exciton formation. Ferromagnetic coupling Mn–Mn pairs or clusters in the doped lattice favor the magnetic polaron and red emission at room temperature and even give much stronger emission above room temperature. The excitonic magnetic polaron and local excitonic magnetic polaron were detected at about 309 nm and 398 nm, respectively, with Mn doping. Without Mn2+ dopant, the weak emission band at about 398 nm can also be detected from an intrinsically bound exciton or confined exciton from the amine incorporated metal chlorides. This Mn-doped anti-perovskite Cd halides may find applications in the solid display and lighting, as well as the magneto-optical devices.

Dimorphism of MnHAsO4(H2O): natural monoclinic krautite and its synthetic triclinic modification

Abstract The crystal structure of natural krautite, MnHAsO4(H2O), was re-evaluated from a cotype specimen, confirming the previously reported monoclinic symmetry for this mineral (space group P21, Z = 8, a = 8.0093(5), b = 15.9372(10), c = 6.8065(4) Å, β = 96.534(2)° at room temperature, 5662 structure factors, 302 parameters, R1 = 0.0295, wR2 = 0.0770). Although hydrogen atoms could not be located from the single crystal X-ray diffraction study, the higher accuracy and precision of the results allowed to derive the hydrogen-bonding scheme (O⋯O = 2.55–2.90 Å) in the crystal structure of krautite. Crystals of synthetic MnHAsO4(H2O) were grown by mixing aqueous solutions of NH4H2AsO4 and MnSO4 and keeping the formed gel at 105 °C for several days. The obtained triclinic crystals were systematically and polysynthetically twinned by contact on (010). Separation of reflections from two individual domains made it possible to determine and refine the crystal structure (space group P 1 ‾ $P\overline{1}$ , Z = 8, a = 8.0105(16), b = 15.991(4), c = 6.8029(12) Å, α = 92.635(8), β = 96.534(2), γ = 90.151(8)° at room temperature, 7226 structure factors, 255 parameters, R1 = 0.0445, wR2 = 0.1381). The triclinic polymorph of MnHAsO4(H2O) does not show a direct group-subgroup relation with monoclinic krautite. Triclinic MnHAsO4(H2O) is closely related with other triclinic M IIHAsO4(H2O) (M = Co, Cu, Zn, Mg) mineral phases. Quantitative structural comparisons between the five M IIHAsO4(H2O) compounds revealed a high similarity between the Mn and Co members, and between the Zn and Mg members, respectively. Subtle distinctions between the two pairs are ascribed to a different hydrogen-bonding scheme. Although the Cu member has a similar hydrogen-bonding scheme as the Mn and Co pair, its structural similarity with triclinic MnHAsO4(H2O) is low due to the strain of the crystal structure caused by the Jahn-Teller distortions of the [CuO6] octahedra.

Prediction of short-range order in CrMnFeCoNi high-entropy alloy

To theoretically examine the short-range order (SRO) in CrMnFeCoNi high-entropy alloy, we performed first-principles-based Monte Carlo simulations. A significant change in the number of the first and second nearest neighbor (NN) pairs occurred around the Cr atoms: Cr–Cr and Cr–Mn first NN pairs decreased and the other pairs increased. The second NN pair showed the opposite trend. These changes led to the formation of L12-type ordering. This chemical SRO originates from the instability of the parallel-spin first NN pairs around the Cr atoms in the face-centered cubic structure. The Cr and Mn atoms tend to occupy the corner sites of the L12 structure to reduce the number of first NN Cr–Cr and Cr–Mn pairs. The degree of the L12-type ordering is approximately 0.3 in the range of the 2nd NN distance. The elastic modulus is predicted to increase by forming the chemical SRO, whereas the influence of the chemical SRO on the averaged structural properties is small.

Light Emission Enhancement of (C3H10N)4Pb1-xMnxBr6 Metal-Halide Powders by the Dielectric Confinement Effect of a Nanosized Water Layer.

Organic-inorganic hybrid metal halides have been widely studied as a kind of phosphor materials for high-performance white light-emitting diodes. In this paper, a series of organic-inorganic metal-halide (C3H10N)4Pb1-xMnxBr6 powders with different Mn2+ ion doping concentrations were synthesized by mechanochemical methods, giving broadband white light emission with a photoluminescence quantum yield of 36.1% at room temperature, which turn green with a much larger intensity at 80 K. Interestingly, its emission converted from white to red after 100 °C treatments and turned back to white again when exposed to moist air for a while. This emission variation was caused by the adsorbed water layer on the surface of product powders via the dielectric confinement. The red emission from no water powders is identified to occur from the Mn ferromagnetic pair in point-shared octahedral sites, while the broadband white emission originated from the surface water-assisted dielectric confinement and surface polarization which combine the self-trapped excitons and d-d transitions of Mn ions and Mn pairs in the product. Moreover, this white emission can transform into green color at 80 K with a much stronger intensity, caused by the even efficient surface dielectric confinement by the adsorbed frozen water layer. This special compound has the advantages of simple preparation, low cost, and good stability and even contains water molecule in the air, giving a near-perfect white emission, with CIE of (0.33, 0.35) and correlated color temperatures at around 5733 K, which may be used for different applications such as sensing, solid-state lighting, and display.

Catalytic ozonation performance and mechanism of Mn-CeOx@γ-Al2O3/O3 in the treatment of sulfate-containing hypersaline antibiotic wastewater

Herein, we attempted to apply an alumina-based bimetallic (Mn-Ce) catalyst as an O3 activator and explored the feasibility of the treatment of hypersaline organic wastewater. Compared with independent O3 (35.00 ± 4.20%), mineralization of ciprofloxacin (CIP) under the Mn-CeOx@γ-Al2O3/O3 (MCAO) process was elevated to 76.04 ± 2.30%. The synergetic corporation among multivalence redox pairs of Mn (III)/Mn (IV), Ce (III)/Ce (IV) promoted the protonation of the surface hydroxyl group (S-OH2+), and subsequently the dominant reactive oxygen species in the MCAO process, OH and O2−, were generated rapidly. However, the mineralization of CIP decreased in MCAO/SO42− system due to the formation of SO4−, which reacted with CIP more slowly (8.4 × 108 M−1 s−1) than OH (4.1 × 109 M−1 s−1). In MCAO/SO42−/Cl− mixture saline conditions, mineralization of CIP was improved at low Cl− concentration (0.5 wt%) due to the generation of Cl, while inhibited with excessive Cl− (≥1.5 wt%) owing to the formation of residual chlorides (Cl2, Cl2− and ClO−). Meanwhile, the MCAO process possessed promising capability to remediate hypersaline wastewater containing dyes, phenol and pesticides, as well as actual salinity-rich wastewater. Based on the above, the present study would provide new insights into hypersaline organic wastewater treatment by the MCAO process.