Increase In Mn2 Research Articles

Ratiometric fluorescence probe based on carbon dots and p-phenylenediamine-derived nanoparticles for the sensitive detection of manganese ions.

A ratiometric fluorescence probe based on carbon quantum dots with 420nm emission (bCQDs) and a p-phenylenediamine-derived fluorescence probe with 550nm emission (yprobe) is constructed for the detection of Mn2+. The presence of Mn2+ results in the enhanced absorption band at 400nm of yprobe, and the fluorescence of yprobe is significantly enhanced based on the chelation-enhanced fluorescence mechanism. The fluorescence of bCQDs is then quenched based on the inner filtration effect. The ratio (I550/I420) linearly increases with the increase of Mn2+ concentration within 2.00 × 10-7-1.50 × 10-6M, and the limit of detection is 1.76 × 10-9M. Given the fluorescence color changing from blue to yellow, the visual sensing of Mn2+ is feasible based on bCQDs/yprobe coupled with RGB value analysis. The practicability of the proposed method has been verified in tap water, lake water, and sparkling water beverage, indicating that bCQDs/yprobe has promising application in Mn2+ monitoring.

Dissolved Mn2+ promotes microbially-catalyzed protodolomite precipitation in brackish oxidized water

Manganese (Mn) is a common trace element in dolomite, yet its precise role in dolomite precipitation, if any, has not been explored. This study aims to investigate carbonate mineral formation in the presence of extracellular polymeric substances produced by Bacillus licheniformis Y1 in 14 cross-over experiments within the MgCl2-CaCl2-MnCl2 system. The study involved the analysis and comparison of water chemistry, mineralogy and bacterial metabolites. The findings indicate that B. licheniformis Y1 induces the formation of Mg-free calcite and low-Mg calcite in Mn-free solutions (Mg/Ca < 2). The addition of 0.001 mol/L Mn2+ results in the precipitation of Mg-rich calcite. In the presence of a relatively high Mg2+ content in the solution (Mg/Ca > 6), B. licheniformis Y1 in a Mn-free solution induces the formation of aragonite and dypingite, whereas the addition of 0.001 mol/L Mn2+ leads to the formation of Mn-bearing dolomite in the precipitate. Notably, at Mg/Ca = 6, an increase in Mn2+ content of the fluid to 0.002 and 0.003 mol/L yields Mn-rich dolomite. The Mn-bearing dolomite exhibits a regular spherical aggregate morphology with diameters ranging from 15 to 60 μm. The 2θ position of the (104) crystal face is close to that of dolomite, and the thermal decomposition temperature is lower than that of calcite. XPS results show that MnO bonds exist on the mineral surface. Acidic amino acids such as glutamic acid as well as humic acid in EPS, especially fulvic acid analogues, actually rise with increasing Mn2+ concentration and contain a large number of functional groups including carboxyl groups. Molecular dynamics simulations show that fulvic acid can effectively promote the dehydration of Mg-water complexes, thus promoting the formation of dolomite. These experiments indicate that the presence of Mn ions in the solution, along with bacteria and EPS, promote the precipitation of protodolomite.

Mn-Doped M2CdCl4 (M = CH3NH3+, C2H8N+, and C3H10N+) Layered Hybrid Perovskite and Its Flexible Film Based on Simple Mechanochemical Synthesis.

Layered hybrid perovskites show significant advantages in the field of optoelectronics. However, the low quantum efficiency and complex preparation methods limit their applications. In this work, we developed a series of perovskite powders with a two-dimensional (2D) layered structure of organic-inorganic hybrid metal halides M2CdCl4:x%Mn (M = CH3NH3+, C2H8N+, C3H10N+) via facile mechanochemical methods. The prepared manganese Mn-doped MA2CdCl4 produces orange emission at 605 nm under both 254 and 420 nm excitation, which originates from a dual excitation channel competition mechanism, and its excitation channel could be changed with the increase of Mn2+ ion concentration. Typically, MA2CdCl4:20%Mn powder exhibits high photoluminescence quantum yield (PLQY) close to 90% at 605 nm due to the organic amine ions enlarging the Mn-Mn interlayer distances. In addition, we prepared MA2CdCl4:x%Mn@PVA flexible films, which also exhibit good luminescence at 254 nm excitation and were unexpectedly found to have a better response to Cs+, which could be a candidate for anticounterfeiting applications.

Divalent manganese stimulates the removal of nitrate by anaerobic sludge.

This study investigated the effect of different concentrations of Mn2+ on the removal of nitrate by anaerobic sludge and changes in the microbial communities through batch experiments. The results showed that the addition of Mn2+ promoted nitrate removal by anaerobic sludge; the nitrate was completely removed within 6 d in the treatment group with >5 mM Mn2+. With the increase in Mn2+, the concentration of nitrite and nitrous oxide increased in the first 4 d and then decreased to 0 μM after 8 d of incubation. The increasing tendency of ammonium increased firstly and then decreased with the addition of Mn2+ compared to A. Moreover, the Mn2+ removal efficiency gradually decreased with the increase of Mn2+ concentration. The changes of microflora structure in sludge before and after adding Mn2+ were analyzed, and the results revealed that the microbial communities in the sludge may have evolved towards an energy-efficient association of short-cut nitrification, denitrification, and anaerobic ammonia oxidation after adding Mn2+. Mn2+ stimulated the removal of nitrate by anaerobic sludge mainly by promoting the growth of PHOS-HE36.

Soft X-ray induced color-tunable long afterglow phosphors Ca9-xTb(PO4)7:xMn2+ based on Mn2+ modulation and energy transfer

In this paper, X-ray induced color-tunable long afterglow luminescent material Ca9-xTb(PO4)7:xMn2+ was synthesized by high-temperature solid state reaction. The effects of Mn2+ doping concentration on the properties of the samples were studied by XRD, SEM, fluorescence and afterglow spectra. The results showed that there was a very efficient energy transfer between Tb3+and Mn2+under X-ray excitation, with a transfer efficiency of up to 94.6%, which also contributed to the tunable green-red emission. With the increase of Mn2+ concentration, the green afterglow emissions of Tb3+ mainly at 546.9 nm gradually decreased and even disappeared, while the red afterglow emissions of Mn2+ at 647.3 nm gradually increases due to excellent energy transfer. When the doping concentration of Mn2+ was 0.07, the red afterglow emissions were the strongest. Furthermore, even at low-dose radiation (3 mGy), the sample still possessed excellent afterglow performance, which can persist for more than 5 h. In addition, the samples also showed excellent photostimulated luminescence properties, which can be persist for many cycles by the irradiation of 980 nm laser. The thermoluminescence results revealed that the doping Mn2+ ions can not only enhance the trap concentrations obviously but also created new deep traps with trap depth of 0.864 eV, which thus resulted in better long afterglow luminescence and photostimulated luminescence properties of Ca9Tb(PO4)7:Mn2+.

White‐light emission and red scintillation from Mn2+ ions single‐doped aluminum‐silicate glasses

AbstractA series of Mn2+ single‐doped 0.2Gd2O3‐0.2Al2O3‐0.6SiO2 (GAS: xMn2+) glasses with Si3N4 as reducing agent were prepared. The presence of [SiO4‐x] defects and Mn2+ ions was determined from the absorption and excitation spectra of the glasses. With the increase of Mn2+ concentration, the intensity of blue emission decreases, while the intensity of red emission increases. The color coordinate of GAS: 6Mn2+ glass is (0.264, 0.226). The lifetime of the glasses was tested. Under the monitoring of 440 nm, the fast components (τf) are between 17 and 85 μs, and the slow components (τs) are between 200–650 μs. The former belongs to [SiO4‐x] defects, and the latter is [4E(G), 4A1(G)]→6A1(S) transition of Mn2+ ions. Under the monitoring at 630 nm, the τf are between 110 and 300 μs, and the τs are between 680 and 1220 μs, which are due to 4T1(G)→6A1(S) transition of Mn2+ ions and Mn2+ pairs, respectively. The energy transfer mechanism of [SiO4‐x] defect→Mn2+ ions are explained. The efficient [SiO4‐x] defect →Mn2+ ions energy transfer process was demonstrated by time‐resolved photoluminescence, and the energy transfer efficiency is over 85%. The maximum photoluminescence quantum yield (PL QY) of the glasses can reach 15.87%. The thermal activation energy of the glasses was calculated. In addition, X‐ray excited red luminescence spectra and the mechanism of the glasses were investigated.

Color-adjustable fluorescence and red persistent luminescence of rare earth-free CaAlSiN3:Mn2+ phosphors prepared by combustion synthesis

Increasing interests have been focused on non-rare earth ion of Mn2+-activated nitride phosphors due to their unique luminescent properties. Although rare earth ions (e.g. Eu2+, Ce3+) doped CaAlSiN3 have been extensively studied in phosphor-converted white light emitting diodes (w-LEDs), there have been very few literatures on the fluorescence and persistent luminescence of rare earth-free CaAlSiN3 phosphors. In this work, a series of rare earth-free CaAlSiN3:x Mn2+ (x = 0.05–5%) phosphors have been successfully prepared through the efficient combustion synthesis. With the increase of Mn2+ ions in CaAlSiN3, the adjustment of emission color from yellow to red can be achieved with its transition to be attributed to 4T1 → 6A1 of Mn2+ at the Al/Si sites (yellow) and Ca sites (red) with diverse occupancy ratios in the CaAlSiN3 host. Moreover, a striking red-color persistent phenomenon originated from the emission of Mn2+ at the Ca sites was observed in these phosphors, among which CaAlSiN3:0.2% Mn2+ showed the best afterglow performance due to its appropriate trap depth of ∼0.7 eV. We believe that this work is supposed to be an inspiration for exploring novel luminescent materials in rare earth-free nitride material systems.

A single‐phase, thermally stable and color-tunable white light emitting Na2Ca1-x-yCexMnyP2O7 phosphors for white light emitting diodes via energy transfer

The solid-state reaction method was used to develop a series of Na2Ca1-x-yCexMnyP2O7 phosphors in an H2–N2 environment. The crystal structure of the pyrophosphate host, valence state of dopants (Ce, Mn), emission behavior of dopants, energy transfer mechanism, and thermal quenching behavior were thoroughly examined. Doping with Ce3+ and Mn2+ ions enhanced the photoluminescence characteristics of Na2Ca1-x-yCexMnyP2O7 while having negligible effect on the host's phase purity. Under 365 nm UV light irradiation, the addition of Ce3+ ion in the Na2CaP2O7 host revealed an asymmetric band with the typical blue emission around 415 nm and a shoulder around 455 nm. To obtain white light, Mn2+ ion was supplementarily substituted to the present system. When the Mn2+ ions concentration was elevated in the Na2CaP2O7 host, the emission intensity of 560 nm peak corresponding to Mn2+ transition enhanced significantly at the cost of Ce3+ emission of 415 nm. The systematic decrease of Ce3+ emission intensity and corresponding increase in the Mn2+ intensity with the increase in Mn2+ concentration indicated the possibility of effective energy transfer from Ce3+ to Mn2+ ions. The obtained results indicated that energy transfer from the Ce3+ to Mn2+ ions governed by dipole-quadrupole interaction. Because of the efficient energy transfer, the blue emission from Ce3+ and the orange red emission of Mn2+ provide white light from a single host along with high value of activation energy and low thermal quenching behaviour make the present phosphors to be suitable for high-power LEDs.

A feasibility study on production, characterisation and application of empty fruit bunch oil palm biochar for Mn2+ removal from aqueous solution

Empty fruit bunch oil palm (EFBOP) is one of the byproducts after oil palm fruitlet is removed in oil palm processing and is considered as waste. In this study, EFBOP was converted to biochar (BC-EFBOP) at 350–700 °C, with an overarching aim of determining the feasibility of adsorptive removal of manganese (a second dominant element in acid mine drainage) from water. Results showed that with increasing temperature, the BC-EFBOP yield decreased from 44.34% to 26.74%, along with the H/C (0.89%–0.29%) and O/C ratios (0.38%–0.23%), and the carbon content increased (62.7%–73.93%). As evidenced by Fourier Transform InfraRed spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS), abundant oxygen-containing surface functional groups such as hydroxyl (-OH), carboxyl (-COOH), and ether (C–O–C) were retained, and aromatic CC groups were largely generated in the biochar. Pyrolysed biochar at 350 °C (BC350), with the least surface area (0.5 m2 g−1), exhibited the highest Mn2+ adsorption capacity (8.2 mg g−1), whereas for BC700, with the largest surface area (2.19 m2 g−1), had the lowest capacity for Mn2+ (1.2 mg g−1). Regardless of the temperature, solution pH of 5 was found to be optimal for Mn2+ removal from water. The Langmuir isotherm model best described the equilibrium adsorption data with a maximum adsorption capacity of 1.2–8.2 mg g−1 for initial concentrations of 5–250 mg L−1, whereas the adsorption kinetics followed the pseudo-second-order model. There was nearly four-fold increase in Mn2+ ions removal with increased biochar dosage (0.05–0.5 g), at initial Mn2+ concentration of 100 mg L−1. The study showed that a low-cost, environmentally friendly BC-EFBOP with optimal surface chemistry could potentially remediate Mn2+ ions from aqueous media. However, a proper cost-benefit and techno-economic analysis is needed prior to potential pilot scale studies.

Application of Mn x Fe1-x Fe2O4 (x = 0-1) Nanoparticles in Magnetic Fluid Hyperthermia: Correlation with Cation Distribution and Magnetostructural Properties.

Optimization of manganese-substituted iron oxide nanoferrites having the composition Mn x Fe1-x Fe2O4 (x = 0-1) has been achieved by the chemical co-precipitation method. The crystallite size and phase purity were analyzed from X-ray diffraction. With increases in Mn2+ concentration, the crystallite size varies from 5.78 to 9.94 nm. Transmission electron microscopy (TEM) analysis depicted particle sizes ranging from 10 ± 0.2 to 13 ± 0.2 nm with increasing Mn2+ substitution. The magnetization (M s) value varies significantly with increasing Mn2+ substitution. The variation in the magnetic properties may be attributed to the substitution of Fe2+ ions by Mn2+ ions inducing a change in the superexchange interaction between the A and B sublattices. The self-heating characteristics of Mn x Fe1-x Fe2O4 (x = 0-1) nanoparticles (NPs) in an AC magnetic field are evaluated by specific absorption rate (SAR) and intrinsic loss power, both of which are presented with varying NP composition, NP concentration, and field amplitudes. Mn0.75Fe0.25Fe2O4 exhibited superior induction heating properties in terms of a SAR of 153.76 W/g. This superior value of SAR with an optimized Mn2+ content is presented in correlation with the cation distribution of Mn2+ in the A or B position in the Fe3O4 structure and enhancement in magnetic saturation. These optimized Mn0.75Fe0.25Fe2O4 NPs can be used as a promising candidate for hyperthermia applications.

Effects of Mn2+ on Cd accumulation and ionome in rice and spinach.

Health risks caused by food containing Cd is a concern worldwide. Interaction between Mn and Cd has been widely studied in normal hydroponic solution with high ion activities (e.g., the study on sharing of transporter Natural Resistance-Associated Macrophage Protein 5 between Mn and Cd in rice [Oryza sativa L.]). However, interaction of Mn and Cd in crops like rice and spinach (Spinacia oleracea L.) at field ion activity level is still unknown. Thus, an ethyleneglycoltetraacetate-buffered solution experiment was conducted to explore the effect of Mn on the uptake and accumulation of Cd and other mineral elements in rice and spinach. In rice, antagonism of Mn and Cd was only observed in roots at deficient and toxic levels of external Mn2+ . Compared with those at Mn2+ sufficiency (pMn2+ 6.7-5.3), average root Cd levels were elevated significantly by 1.85-3.05 times at Mn2+ deficiency (pMn2+ 8.2) but decreased by 1.57-2.59 times at Mn2+ toxicity (pMn2+ 4.8). The antagonism between Mn and K/Mg in rice shoots might be caused by their common role in physiological processes in plants. Antagonism of Mn/Ni in spinach in this work was consistent with their shared transporters in dicots. Results about the antagonism of root Cd/Mn at Mn2+ deficiency suggest that sufficiently available Mn2+ is significant to reduce Cd uptake in rice under field levels of ion activity, but it was not for spinach because the change of tissue Cd was insignificant with the increase of Mn2+ activity from deficiency to toxicity.

What levels of soil Mn2+ can pulse and legume crops tolerate when grown in rotation with paddy rice?

Elevated concentrations of manganese (Mn2+) can persist after drainage in soil following wetland rice production, leading to toxicity in subsequent legume crops. To evaluate Mn2+ concentration causing adverse impacts on crop establishment and growth, a controlled environment experiment using hydroponics was designed. Germination and growth of field pea, faba bean and mung bean were evaluated over 21 d with an increase in Mn2+ (0 − 50 mg Mn2+L−1). Germination of all crops was impacted significantly with an increase in concentration of Mn2+. Leaf chlorophyll content as well as all plant growth parameters assessed (dry weight, height) were negatively impacted (p < 0.05) by increasing concentrations of Mn2+. Field peas and faba beans proved more sensitive to Mn2+ than did mung beans at concentrations of 5 − 10 mg L−1. Field pea and faba bean specifically exhibited reduced height (30 − 60% and 4 − 41%, respectively), root length (12 − 30% and 20 − 25%, respectively), and shoot weight (41 − 69% and 47 − 81%, respectively). Mung bean was less impacted in terms of plant height with 23% reduction at 25 mg Mn2+ L−1 and shoot dry weight reduced by 48% at 50 mg Mn2+ L−1. Total chlorophyll content of mung bean was severely affected (86% reduction at 50 mg Mn2+ L−1), with field pea least impacted. Our findings suggest that significant Mn2+ toxicity could potentially occur in terms of legume germination and overall growth if legume crops are sown into post-rice soils with ≥5 mg Mn2+L−1. Soil Mn2+ level must be considered when developing cropping strategies following flooded rice.

Theoretical and Experimental Investigate for the Magnetic and Optical Properties of Mn-ZnO Nanowire Microspheres

A Mn-ZnO nanowire microsphere was prepared by using the hydrothermal method. The effects of Mn doping concentration and hydrothermal growth conditions on the crystal structures, morphologies, magnetic and optical properties of ZnO nanowire microsphere were studied. The characterization results showed Mn-ZnO nanowire microsphere with uniform and dense distributions along the [0001] direction with a hexagonal wurtzite structure. No impurity phases were detected in microsphere specimens. The room-temperature ferromagnetism of the Mn-ZnO nanowire microsphere was detected, with the saturation magnetization of 2.4 × 10−1 emu/g and a coercive field of 369 Oe. Furthermore, with the increase of Mn2+ ions doping concentration, the luminescence intensity of the sample decreases in both UV and visible regions, and slight blueshift in the visible light regions was observed. The theoretical results presented obvious spin polarization near the Fermi level, with strong Mn 3d and O 2p hybridization effects. The magnetic moments were mainly generated by Mn 3d and partial contribution of O 2p orbital electrons. Therefore, the Mn-ZnO nanowire microsphere can be used as a potential magneto-optical material.

Study on the Mechanical and Leaching Characteristics of Permeable Reactive Barrier Waste Solidified by Cement-Based Materials.

The durability against wet-dry (w-d) cycles is an important parameter for the service life design of solidified permeable reactive barrier (PRB) waste. This study introduces the potential use of cement, fly ash, and carbide slag (CFC) for the stabilization/solidification (S/S) of PRB waste. In this study, solidified PRB waste was subjected to different w-d cycles ranging in times from 0 to 10. By analyzing the mass loss, the unconfined compressive strength (UCS), initial resistivity (IR), and the leaching concentration under different durability conditions, the results demonstrate that these variables increased and then tended to decrease with the number of w-d cycles. The UCS of contaminated soil is significantly correlated with IR. Moreover, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses indicate that the hydration products calcium silicate hydrate (C-S-H) and ettringite (AFt) are the main reasons for the enhancement of the UCS. However, the increase in concentration leads to a decrease in hydration products and the compactness of solidified soil, which has negative effects for the UCS and the leaching ion concentration. In general, the durability exhibited by the PRB waste treated with S/S in this paper was satisfactory. This study can provide theoretical guidance for practical engineering applications.

Preparation of nano manganese oxides by H2O2 in-situ oxidation: effect of regulation mechanism on physical and chemical properties

Manganese oxides showed many special physicochemical properties in many fields such as electrochemistry, adsorption and catalysis. They were widely used in cathode materials for lithium batteries, molecular sieves, catalytic materials and adsorbents. In this paper, in situ oxidation of manganese sulfate solution was conducted with H2O2 as oxidant, and the characterization means of XRD, SEM and BET were used. The purpose was to study the effects of different regulation mechanisms on the physical and chemical properties of manganese oxides such as morphology, phase composition, surface properties and specific surface area. The adsorption properties of γ-MnO2 for Co and Ni in manganese ore leaching solution were tested. The results showed as follows. Under alkaline conditions, the main product of manganese sulfate solution oxidized by H2O2 was Mn3O4 spherical particles with a radius of about 50 nm, these particles had micropores or mesopores, the oxidation reaction rate was rapid, and the specific surface area and N2 adsorption capacity changed with the change of reaction conditions.The temperature had a great influence on the micro morphology of the product.The micro morphology was slender nanorod when the temperature was 20 °C. With the increase of temperature, the length of nanorod became shorter. When the temperature rises to 50 °C, the rod became spherical. When the pH value decreased from 9 to 7, the diffraction peak of each crystal plane in the product Mn3O4 decreased gradually. The diffraction peak of γ-MnO2 appeared when the pH value decreased to 5. All the products were γ-MnO2 when the pH value decreased to 3. With the increase of Mn2+ concentration, the grain size decreased and agglomeration was easy to occur. The optimum conditions were obtained as follows: the temperature was 30 °C, pH was 3, reaction time was 90 min, the mole ration of H2O2 to Mn2+ was 1:1, and Mn2+ concentration was 10 g l−1. Under the optimum conditions, γ-MnO2 with high specific surface area (172.41 m2 g−1) was prepared. This γ-MnO2 has a good adsorption effect on Co and Ni in manganese ore leaching solution, and the adsorption efficiency could be reached 94.75% and 95.67%. This study would provide a reference for the preparation of manganese oxides with different physical and chemical properties.

Thermal Properties of Red Zero-Phonon Luminescence Line from Mn2+ Ions in Oxide Crystals

Temperature dependence of emission properties of sharp, zero-phonon line (ZPL) associated with 4T1g →6A1g transition of Mn2+ ions doped in LiMgPO4 is studied, together with the Mn2+-concentration dependence. The ZPL is observed at 611.8 nm at temperatures below 120 K. The intensity relative to the intensity of superimposed phonon sidebands is increased in proportion to T2 with increasing temperature from 18 K. The peak energy and full width at half maximum (FWHM) are increased in proportion to coth 1/2 (hν/2kBT). Unlike the phonon sideband emission which shows single exponential decay and decrease of decay time with increase of temperature, the ZPL emission has the fast and slow decay components and shows temperature-independent decay times. A blue shift of the ZPL peak energy is observed with increase of Mn2+ concentration x doped in LiMg1−x Mn x PO4 from 0.0015 to 0.0050 at 18 K, while a broadening of line width is observed with increase of the concentration. Each of the peak energy and FWHM is approximated by a quadratic equation in the form a+bx+cx 2. It is suggested that these results are understood by the interaction of the excited 4T1g state with phonons and crystal field, from comparison with the theoretically expected formulae.

Effect of Pr, Mn doping on the structure and properties of BiFeO3

The powders of Bi1-xPrxFeO3 (x = 0, 0.05, 0.1) and Bi0.95Pr0.05Fe1-yMnyO3 (y = 0.05, 0.1) were prepared by hydrothermal method. The effects of Pr and Mn doping content on the structure, morphology, magnetic, and photocatalytic properties of BiFeO3 (BFO) have been studied. X-ray diffraction (XRD) demonstrated that the compounds are distorted rhombohedral perovskite structure without any other heterogeneity and structural transition. Field emission scanning electron microscope (FESEM) reflected that the surface of compounds is a dense, agglomerated sphere, and the morphology changes with the addition of Pr, Mn. Energy spectrum analysis (EDS) shows that the Bi0.95Pr0.05Fe0.95Mn0.05O3 sample is mainly composed of 5 elements (Bi, Fe, O, Pr, Mn), and the atomic ratio matches the formula well. Integrating the vibrating sample magnetometer (VSM) into the physical property measurement system (PPMS-9) shows that the introduction of Pr3+and Mn2+ ions can enhance the magnetic properties of BFO at room temperature. In addition, doping with Pr3+ and Mn2+ ions can improve the photocatalytic performance of BFO, and with the increase of Mn2+ concentration, the photocatalytic performance of BFO first rises and then decreases, and its catalytic performance is getting better and better.

Photoluminescence properties of Tb3Al5O12:Ce3+, Mn2+ phosphor ceramics for high color rendering index warm white LEDs

Abstract Tb3Al5O12:Ce3+, Mn2+ (TAG:Ce3+, Mn2+) phosphor ceramics with different doping of Mn2+-Si4+ ions pair were fabricated by the high temperature solid state reaction in a flowing oxygen atmosphere. The emission colors could be changed from yellow-green to orange-red through controlling the doping concentration of Mn2+-Si4+ ions in the TAG:Ce3+, Mn2+ phosphor ceramics. The red emission from the phosphor ceramics mainly came from the 4T1→6A1 transition of Mn2+ ions via the Ce3+→Mn2+ energy transfer under the 460 nm excitation. With the increase of Mn2+ doping concentration, the emission peak of the emission spectrum could reach 605 nm. By combining the optimized phosphor ceramic with the 460 nm commercial blue light emitting diode (LED) chip, the white light with low correlated color temperature (CCT) of 3426 K and high color rendering index (CRI) of 84.4 was obtained, indicating the good potential of TAG:Ce3+, Mn2+ phosphor ceramics for warm white LED applications.

Synthesis, luminescent properties and crystal stabilization of GdAG:Mn2+/Ce3+ via Y3+ doping for warm w-LED application

Abstract In this paper, the (Gd,Y)AG:Mn2+,Ce3+ phosphors were synthesized by high temperature solid-state reaction method. The lattice stabilization, microstructure and fluorescence properties were systematically investigated via XRD, FE-SEM, PLE/PL spectra and fluorescence decay analysis, respectively. Under the excitation of 461 nm, two emission peaks appear at 585 nm and 740 nm, which can be assigned to the transition 5d→4f of Ce3+ and 4T1→6A1 of Mn2+. The color of (Gd,Y)AG:Mn2+,Ce3+ phosphor can be adjusted from yellow to orange-red by changing the doping concentration of Mn2+, and the quenching mechanism of Mn2+ in (Gd,Y)AG: Mn2+,Ce3+ system is attributed to the electric multipole interactions. With the increase of Mn2+ concentrations, the fluorescence lifetime reduced from 152 ns to 9 ns, and the energy transfer efficiency of Ce3+→Mn2+ can be calculated to increase from 35.32% to 95.89%. The underlying mechanisms were thoroughly investigated and elucidated. Furthermore, the thermal stability of (Gd,Y)AG:Mn2+,Ce3+ phosphor systematically studied. The excellent fluorescence properties and high stability of (Gd,Y)AG:Mn2+,Ce3+ phosphor is expected to be widely used in lighting and display areas.

Optical and EPR studies of zinc phosphate glasses containing Mn2+ ions

A set of glass samples with composition based on ternary 50P2O5–30Na2O–20ZnO (PNZ) matrix doped with different MnO contents was prepared via melt-quenching technique. Thermal, structural and spectroscopic properties were investigated by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Raman spectroscopy, UV–visible absorption, photoluminescence (PL) and by electron paramagnetic resonance (EPR) using Mn2+ as probe. Glass compositions (100-x)PNZ:xMn (0.01 ≤ x ≤ 1.0 in mol% of MnO) were characterized as glasses after careful analysis of the thermal and structural data. While DSC curves show the presence of the glass transition phenomenon (Tg), XRD analysis identified the non-crystalline arrangement, compatible with glass structure. Raman spectra of PNZ:xMn samples showed that the successive increase in Mn2+ content leads to rise of vibrational modes assigned to phosphate Q1 units, suggesting the breakdown of phosphate glass network chains. UV–Vis absorption spectra of glasses presented absorption bands centered at 250, 318, 341, 358 and 408 nm attributed to the Mn2+ electronic transitions. Glass samples containing above 0.06 mol% of MnO presented a broadband absorption centered at 511 nm assigned to the presence of traces of Mn3+. Additionally, UV–Vis, PL and EPR data showed that Mn2+ ions are occupying octahedral arrangements. Besides, EPR results suggest that the increase in MnO concentration influences on the EPR signal and hyperfine splitting constant suggests the presence of a moderately ionic bond between Mn2+ and PNZ glass network.