Concentration Of Mn2 Research Articles

Determination of the detectable concentration of manganese used in neuronal MEMRI and its effect on cortical neurons in vitro

Objective: Manganese (Mn2+)-enhanced magnetic resonance imaging (MEMRI) has received increasing attention because of its functional and anatomic value in brain studies. However, the contrast agent, Mn2+, will lead to neurotoxicity at high concentrations, which limits its use in biomedical research. This study was designed to determine whether Mn2+ can significantly enhance the signal intensity (SI) of primary cultured cortical neurons at non-toxic levels.Method: Neurons were incubated with different concentrations of Mn2+ (control and 0·01, 0·05, 0·10, and 0·20 mM), then a cellular MRI was performed in vitro and the intracellular Mn2+ concentrations were analyzed by ICP-MS. At the same time, the cell viability, LDH release assay, intracellular ROS level, and apoptosis were measured 24 h after treatment.Results: (1) After the neurons were treated with Mn2+ at a low concentration (0·01 mM), there was no impact on cell viability and cytotoxicity, and no significant signal was enhanced on MEMRI. (2) When the neurons were exposed to higher concentrations of Mn2+ (0·05, 0·1, and 0·2 mM), a significant increase in signal quality was achieved, but cell viability was significantly reduced and the intracellular ROS formation and percentage of TUNEL-positive cells were increased significantly.Conclusion: At Mn2+ concentrations > 0·05 mM, significant enhancement of MEMRI SI occurred, but with overt cytotoxicity.

Removal of Water-Soluble Manganese Ions from Electrolytic Manganese Residues by Hydrometallurgical Process

Electrolytic manganese residues containing a substantial amount of manganese are a potential pollution. Removing water-soluble manganese ions from electrolytic manganese residues by hydrometallurgical process was discussed. In the work, the basic property of the electrolytic manganese residues was analyzed. Based on it, we proposed the suitable method to remove Mn2+ from the slag by pollution-free oxidation in alkaline solution. The results shown that the best conditions to remove Mn2+ were pH 10.5, temperature 55 °C, the flow rate of hydrogen peroxide 0.50 mL·L-1·min-1 and agitation speed 250 r/min. At the optimum condition, the removal ratio of water-soluble Mn2+ exceeded 99.9% and the concentration of Mn2+ in the final solutions was about 3 mg/L.

Formation of Bundle-Shaped β-NaYF4 Upconversion Microtubes via Ostwald Ripening

In this work, the uniform bundle-shaped microtubes composed of six half-pipes are synthesized for the first time in hydrothermal solutions via an intentional delayed phase transition pathway induced by Mn(2+) doping. The structural and kinetic factors that govern the phase and shape evolution of NaYF4 microcrystals have been carefully studied, and the influences of Mn(2+) to RE(3+) ratio, the amount of trisodium citrate, and the pH value in conjunction with the intrinsic character of RE(3+) ions on the phase and shape evolution are systematically discussed. It is found that the proper Mn(2+) to RE(3+) ratio is mainly responsible for delayed phase transition process and induces interior density gradient of solid aggregate for creating hollow bundle-shaped microtubes. While the amount of trisodium citrate and the pH value are the keys for the shape control of the NaYF4 microcrystals such as prismatic microtubes, prismatic short rods, thin plates, and particles. The up and downconversion emissions were obtained independent of whether α- or β-NaYF4:Er(3+)/Yb(3+) samples doped with Mn(2+), but the significant tuning of output color was only obtained in cube NaYF4 nanoparticles rather than in hexagonal microtubes via adjusting the amount of Mn(2+) ions. These spectral measurements and EDX analyses indicate that the distribution or concentration of Mn(2+) in hexagonal phase solid solution has changed, which supports Ostwald ripening growth mechanism and rules out agglomeration or oriented attachment growth mechanism. We designed crystal growth mode by simply addition of dopant may provide a versatile approach for fabricating a wide range of hollow nano/microcrystals and thus bring us a clearer understanding on the interaction between the dopant reagents and the nano/microcrystals.

Study on Treatment of Polyvinyl Alcohol in Water by Ozone Catalytic Ozonation

The paper has studied the degradation effect of the polyvinyl alcohol in the Ozone catalytic oxidation oxygenated water, include three kind of catalyst of Fe2+, Mn2+, Cu2+. The results as below, the degradation effect of the polyvinyl alcohol by Ozone catalytic oxidation is higher than ozone alone obviously, and it is related with the concentration of catalyst, the degradation effect will increase with the increase of concentration of Fe2+, and to the maximum value, the degradation is 85%; it will decrease with the increase of concentration of Mn2+, the optimum content is about 5mg/L, the degradation rate is 85%; when Cu2+ is added, the degradation rate is 53% in 35mg/L, and the degradation of other contents is not obvious. When the content of three kinds of catalyst are all 35mg/L and the reaction time is 3h, the sort of degradation effect is Fe2+>Cu2+>Mn2+.

An improved Hummers method for eco-friendly synthesis of graphene oxide

An improved Hummers method without using NaNO3 can produce graphene oxide nearly the same to that prepared by conventional Hummers method. This modification does not decrease the yield of product, eliminating the evolution of NO2/N2O4 toxic gasses and simplifying the disposal of waste water because of the inexistence of Na+ and NO3− ions. For the first time, we also developed a prototype method of post-treating the waste water collected from the systems of synthesizing and purifying graphene oxide. The content of Mn2+ ions in the purified waste water was measured to be lower than the guideline value for drinking water.

The Alleviative Effects of Salicylic Acid on the Activities of Catalase and Superoxide Dismutase in Malting Barley (Hordeum uhulgare L.) Seedling Leaves Stressed by Heavy Metals

AbstractAs toxic divalent heavy metal ions, Zn2+, Cu2+, Mn2+, Cd2+, Hg2+, and Pb2+ exert certain negative effects on plant growth and development, which has been paid huge amount of attention to in the management of heavy metal pollution. As a novel kind of endogenous plant hormone, salicylic acid (SA) is considered to exert beneficial physiological effects on plants. In this paper, the activities of catalase (CAT) and superoxide dismutase (SOD) in seedling leaves of a malting barley variety (called Ganpi No.4) cultured under hydroponic cultivation was measured under different treatments of Zn2+, Cu2+, Mn2+, Cd2+, Hg2+, and Pb2+ and under different treatments of SA alleviation, respectively, and such values were then compared and analyzed. The results showed that all treatments of different ions and the activities of CAT and SOD and all SA‐alleviated treatments and the activities of CAT and SOD exhibited nonlinear relationships. Zn2+, Cu2+, Mn2+ exerted less severe stresses on the activities of CAT and SOD at lower concentrations, and led to significantly inhibitive effects on the activities of CAT and SOD at higher concentrations. And Cd2+, Hg2+, and Pb2+ exerted significantly repressing effects on the activities of CAT and SOD. As for SA's alleviative effects, such effects were salient for most concentrations of Mn2+, Zn2+, and Cu2+ treatments and lower concentrations of Cd2+, Hg2+, and Pb2+ treatments, while were not significant for higher concentrations of Cd2+, Hg2+, and Pb2+ treatments. These data provided theoretical references for studies on physiological mechanism of cereal crops' resistance or tolerance to heavy metal stress as biomarkers.

Upconversion luminescence properties of Mn2+-doped NaYF4:Yb/Er nanoparticles

NaYF4:Yb/Er upconversion nanoparticles doped with Mn2+ were synthesized by hydrothermal method. The upconversion photoluminescence measured by 975 nm continuous wave laser indicates that the as-synthesized samples generated green and red color emission with various intensity ratio ranging from 3.25 to 548.35, which is highly correlative to the dopant concentration of Mn2+. However, there is no red emission enhancement observed in Cu2+-doped NaYF4:Yb/Er nanoparticles.

Impact of Nitrogen Pressure on the Structural, Morphologic and Magnetic Properties of the GaMnN Thin Films

GaMnN thin films were fabricated by using pulsed laser deposition followed by annealing. In our experiments, the impact of the background nitrogen pressure on the crystal quality, morphology and the ferromagnetism of the GaMnN thin films were studied systematically. It is found that the samples deposited at 0.75 Pa have the best crystal quality. All the annealed samples showed ferromagnetic behavior, and the Curie temperature was estimated up to 340 K. We found the magnetization of our samples changes depending on the concentration of Mn3+ ions, and the origin of the room temperature ferromagnetism of our samples can be explained by bound magnetic polaron theory. The nitrogen vacancies may cause the ferromagnetism to be weakened.

Application of microwave-irradiated manganese dioxide in the removal of polychlorinated biphenyls from soil contaminated by capacitor oil

The removal of polychlorinated biphenyls (PCBs) from soil contaminated with capacitor oil, using microwave (MW)-irradiated manganese dioxide (MnO2), was examined under different conditions. The effects of different types of MnO2 added as oxidant, as well as the initial amount of water, MnO2, and sulphuric acid solution, were also investigated. The removal efficiencies for dichlorobiphenyls, trichlorobiphenyls, tetrachlorobiphenyls, pentachlorobiphenyls, hexachlorobiphenyls, heptachlorobiphenyls, and octachlorobiphenyls were approximately 95.9%, 82.5%, 52.0%, 71.6%, 62.5%, 28.6%, and 16.1%, respectively, by 800 W MW irradiation for 45 min with the assistance of 0.1 g δ-MnO2 and 0.2 mL water in 1.0 g severely PCB-contaminated soil (∑PCB=1560.82 mg/kg); meanwhile, the concentrations of Mn2+ ions detected were from 10.6±1.9 mg/kg at 0 min to 108.2±7.8 mg/kg after 45 min MW irradiation, indicating that MnO2 acted as not only a MW absorber but also an oxidizer. Removal efficiencies of PCBs from contaminated soil increased with increasing the amounts of water and MnO2 added. The type of MnO2 also affected the removal of PCBs, following an order of . The addition of low concentration of sulphuric acid (such as 1.0 mol/L) solution was favourable for the removal of low chloro-substituted PCBs, but the addition of more than 1.0 mol/L sulphuric acid reduced the removal of all PCBs. The pronounced removal of PCBs from contaminated soil in a short treatment time indicates that MW irradiation with the assistance of MnO2 is an efficient and promising technology for the remediation of PCB-contaminated soil.

Electrodeposition of Zn–Mn alloys at high current densities from chloride electrolyte

The Zn–Mn alloy electrodeposition on a steel electrode in chloride electrolyte was investigated with the aim of obtaining deposits with as high as possible Mn percent. It was found that the deposition current density and concentration of Mn2+ ion in the chloride electrolyte significantly affect the Mn content in the alloy coating as well as the coating surface morphology. There was a transition from dendritic and spongy to smooth, bright, and amorphous structure of Zn–Mn deposits, when some critical deposition current density was reached, probably due to the metal oxyhydroxide inclusion in the coatings. Several plating additives were tested in order to decrease the hydroxide content and to improve surface appearance of the deposits. The 4-hydroxy-benzaldehyde was found to decrease oxygen and increase Mn percent in the coatings, and to significantly improve their surface morphology.

Distributions and Species of MnO<sub>x</sub> Included in MnO<sub>x</sub>/TiO<sub>2</sub> Catalysts for Denitration at Low Temperature

MnOx/TiO2 catalysts are active and stable at low temperature, and it is appropriate for cement production to enforce NOx emissions. In this study, the denitration process was promoted by the transformation of a variety of MnOx forms in the SCR reaction. The efficiency and selectivity of catalysts depended on the form and dispersion degree of MnOx. By changing the precursors, calcination temperatures, synthesis methods and calcination atmospheres, a series of MnOx/TiO2 catalysts were prepared. The contents and distributions of Mn2+, Mn3+ and Mn4+ in catalysts were tested through the titration method. The titration results showed that the content of Mn4+ was the highest during the precursor was Mn (NO3)2, while the content of Mn2+ in the catalysts calcinated in nitrogen atmosphere was the highest. The mechanisms of different MnOx states in the catalytic process were discussed. It was found that a mixture of more MnOx with low valence state and less MnOx with high valence state were beneficial to the catalytic process.

Effect of Air Annealing on the Structural and Magnetic Properties of LaMnO3 Perovskite Produced by Reactive Spark Plasma Sintering Route

Perovskite-type lanthanum manganite (LaMnO3) was synthesized from Mn2O3 and La2O3 precursor powders using the Spark Plasma Sintering technique (SPS). The in situ reaction proceeds in a few minutes at 1000 °C under 50 MPa with a very high heating rate of 100 °C/min. The Rietveld refinement of the X-ray powder diffraction shows that LaMnO3 sample crystallizes in a perovskite structure of O′-type orthorhombic symmetry with Pbnm space group. After annealing at 1000 °C in air for 10 hrs, the symmetry changes to rhombohedral with R-3c space group. For the as prepared sample, two critical temperature points in the temperature dependence of the ZFC and FC magnetization occurring at 125 K and 145 K are observed. They are suggested to be related to A-type antiferromagnetic Neel temperature and ferromagnetic short range order, respectively. The ferromagnetic component in the annealed sample increases indicating the expected variation in the concentration of Mn3+ and Mn4+ ions, which was attributed to the oxygen stoichiometry effects.

Coexistence of antiferromagnetism and ferromagnetism in Mn2+/CdS nanocrystals and their photophysical properties

Manganous ion doped CdS nanocrystals with different concentrations of Mn2+ have been synthesized by a chemical synthesis route. The as-synthesized Mn2+/CdS nanocrystals evince interesting optical emission properties; the intensity of cadmium vacancy emissions VCd decreases on the addition of the dopant ion, proving the displacement of cadmium by manganese which is accompanied by the appearance and enhancement of the Mn2+ d–d emission, 4T1 → 6A1. However, the intensity of the latter emission decreases on further increase in [Mn2+] due to strong cluster formation, such as Mn2+–Mn2+. The low temperature electron paramagnetic resonance measurements suggest strong antiferromagnetism due to strong exchange coupling between the spins of nearby Mn2+ centres both in pre- and post-annealed 5% Mn2+/CdS samples. These magnetic properties for pre- and post-annealed 5% Mn2+/CdS samples are explained by a core/shell (antiferromagnetism/ferromagnetism) model. The pre-annealed sample, on one hand, shows antiferromagnetic behavior with weak ferromagnetism below the Neel temperature, the latter due to uncompensated surface spins. On the other hand, annealing leads to the formation of more Mn2+–Mn2+ dimers or clusters due to ionic migration. This will result in increased antiferromagnetic character as compared to the pre-annealed sample. Both are confirmed by magnetization hysteresis curves at various temperatures. The electron microscopy images confirm the morphology prediction by XRD.

Kinetics of Manganese Oxides Dissolution in Sulphuric Acid Solutions Containing Oxalic Acid

The kinetics of the interaction of MnO2, Mn2O3, and Mn3O4, with sulphuric acid solutions and the effect of oxalic acid on this process are studied. As the sulphuric acid concentration is increased from 0.1 to 5 N, the dissolution rate of Mn2O3, Mn3O4 to MnO2 and Mn2+ ions decreases, whereas it increases with the concentration of Mn2+ ions. Upon the addition of H2Ox, the complete dissolution of Mn3O4 occurs more quickly. The reaction order with respect to the H+ and O x2- ions is +0.5 ± 0.1. A mechanism of MnO2 dissolution promotion by O x2- is proposed. The dissolution rate was found to depend on the concentrations of MnHOx - ions and was highest at pH 1.6 ± 0.2. A rate law and mechanism are suggested for manganese oxides dissolution.

Mn2+ induced luminescence regulation and enhancement of Lu-based nanocrystals

Transformation from Lu-based nanocrystals in hexagonal and cubic mixed phases to pure cubic phase was observed through adjusting the doping concentration of Mn2+. The mechanism for the phase transformation was discussed in detail. Studies on the time and frequency domain spectra indicated that the semi-pure red emissions in cubic Na5Lu9F32: 40% Mn2+, 20% Yb3+, 2% Ln3+ (Ln=Er3+, Ho3+) nanocrystals were caused by a two-step energy transfer between Mn2+ and Ln3+ ions. After incorporating of Mn2+ ions into the host lattices, the local symmetry around the luminescent ion was reduced, which induced the increase of radiative rates for transitions that were mainly contributed by electric dipole radiations. Considerable enhancements in upconversion and downconversion luminescence were accompanied. The result of the current study has great application potential in bioimaging and solar cells.

Selectivity in changes of fluorescence emission of 1,4-naphthoquinone derivatives by manganese and cadmium ions

Interactions of various metal ions with pyridine tethered 1,4-naphthoquinone derivatives (1–4) are studied by fluorescence spectroscopy. The fluorescence emission of 2-(pyridine-2-yl-methylamino) naphthalene-1,4-dione (1) is influenced by various metal ions and show highly selective fluorescence emission with Mn2+ ions and fluorescence ON and OFF states can be generated at different concentrations of Mn2+ ions. Sequential addition of Ni2+ and Mn2+ ions to a solution of 1 also generates ON and OFF emission states. The fluorescence responses towards the metal ions by two isomers 2-(pyridine-n-yl-methylamino)naphthalene-1,4-dione (n=3,4) are non-specific. The 2-(pyridine-2-yl-ethylamino)naphthalene-1,4-dione (4) shows fluorescence response to various metal ions; but its fluorescence response upon interaction with cadmium ions is very unique. Three stages in emission upon increase in concentration of Cd2+ ions, namely OFF–ON–ON are observed.

Combined effects of hypoxia and excess Mn2+ on oxidative stress and antioxidant enzymes in tomato seedlings

Effects of high level of Mn2+ on the changes in ROS generation, root cell viability, antioxidant enzyme activities, and related gene expression in tomato (Solanum lycopersicum L., cv. Zhongza 9) seedlings were studied under normoxic and hypoxia conditions. Mn2+ concentrations, ranged between 10 and 200 μM, led to significantly higher activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APOD), glutathione reductase (GR), and also ascorbic acid (AsA) content in leaves and roots, improved root cell viability, and decreased O2·− accumulation compared with the higher Mn2+ level under hypoxia stress, which indicated that low Mn2+ could eliminate the active oxygen and protect the membrane lipid from the hypoxia hurt. When the concentration of Mn2+ reached 400–600 μM under hypoxia stress, the activities of SOD, POD, APOD, and GR and AsA content were decreased remarkably. In contrast, the MDA content was increased at the higher Mn2+ concentration. A number of antioxidant-related genes showed high expression at the lower level of Mn2+. The expression levels of SOD, POD, CAT, APOD, and GR genes were 7.95, 5.27, 3.18, 5.54, and 8.81 times compared to control, respectively. These results illustrated that the appropriate amount of Mn2+ could alleviate the detrimental effects of hypoxia stress, but reversely, the high level of Mn2+ just aggravated the existing damage to the tomato seedlings.

Polyol-synthesized Zn0.9Mn0.1S nanoparticles as potential luminescent and magnetic bimodal imaging probes: synthesis, characterization, and toxicity study

We report here the synthesis, by the polyol method, of Mn-doped ZnS nanocrystals with the zinc blende structure. Phase transfer of the as-produced quantum dots from organic solvent into water was achieved by surface complexation with mercaptoacetate ligands. The magnetic and optical properties of the powders and aqueous colloids obtained were evaluated by SQUID magnetometry as well as electronic absorption and emission spectroscopies, to test their potential as magnetic and luminescent bimodal probes for medical imaging. With a 10 % concentration of Mn2+, the nanoparticles are paramagnetic at body temperature, and the aqueous colloids they form have high relaxivity with a r 1 value of 20 mM−1 s−1 at 3 T. They are highly luminescent with a blue–green emission on 405-nm excitation. Viability assays and genotoxicity tests on Chinese hamster ovarian cells revealed neither acute cellular death, nor cell toxicity, nor damage to the nucleus after exposure for 24 h to particle doses of up to 100 μg mL−1.

Electron Spin Resonance Spectroscopy for the Identification of Irradiated Foods with Complex ESR Signals

Electron spin resonance (ESR) spectroscopy for the detection of irradiated food could provide complex spectra due to the presence of different nonirradiation-specific paramagnetic species in the sample. Particularly, ESR signals from naturally present Mn2+ could limit the ESR-based detection of irradiated foods of plant origin. In this study, the effects of different concentrations of Mn2+ on the radiation-specific ESR spectral features of radiation-induced crystalline sugar or cellulose radicals were examined. Soy sauce powder with Mn2+ was irradiated at 10 kGy and its effect on the identification of radiation-induced sugar (pak choi, 10 kGy) and cellulose (red pepper powder, 10 kGy) radicals was evaluated. In the blends of red pepper and soy sauce, the left (g 1 = 2.025) and central (g 2 = 2.005) peaks of the cellulose signal significantly decreased with the decline of red pepper content (R 2 = 0.9384, g 1; 0.8819, g 2). However, the right peak (g 3 = 1.988) significantly increased (R 2 = 0.9353, g 3) with an escalation in the soy sauce content. The cellulose radical signals were identifiable from the blends containing more than 50 % red pepper powder. In the blends of soy sauce and pak choi, the ESR intensity of crystalline sugar radicals significantly decreased with the decline in pak choi content (R 2 = 0.9887). However, Mn2+ signal didn’t overlap with the sugar radical signals. The ESR signals from radiation-induced crystalline sugar remained unaffected; however, the signals from cellulose radicals provided a reduced detectionability depending upon the concentration of Mn2+ in the sample.

Colorimetric detection of Mn2+ using silver nanoparticles cofunctionalized with 4-mercaptobenzoic acid and melamine as a probe

A facile, selective and highly sensitive method is proposed for colorimetric detection of manganese ions using 4-mercaptobenzoic acid (4-MBA) and melamine (MA) modified silver nanoparticles (AgNPs). The presence of Mn2+ induces the aggregation of AgNPs through cooperative metal–ligand interaction, resulting in a color change from bright yellow to purple. The cofunctionalized AgNPs showed obvious advantages over the ones functionalized only by 4-MBA or MA in terms of selectivity. Mn2+ could be monitored by colorimetric response of AgNPs by a UV–vis spectrophotometer or even naked eyes. The absorbance ratio (A550nm/A408nm) is linear with the concentration of Mn2+ ranging from 5×10−7mol/L to 1×10−5mol/L with a correlation coefficient of 0.993, and the detection limit is as low as 5×10−8mol/L. Particularly, this cost-effective process also allowed rapid and simple determination of the Mn2+ in drinking water.