scholarly journals Activation of Cadmium Under Simulated Solar Illumination and Its Impact on the Mobility of Cd in Flooded Soils

2021 ◽  
Author(s):  
Bihao Luo ◽  
Chenfeng Xiao ◽  
Yuling Liu ◽  
Li Li ◽  
Liang Peng ◽  
...  
Keyword(s):  
Fold Increase ◽  
Environmental Water ◽  
Solar Irradiation ◽  
Natural Soil ◽  
Release Kinetic ◽  
Flooded Soils ◽  
Paramagnetic Resonance ◽  
Water Ph ◽  
The Stability ◽  
Electron Paramagnetic

Abstract In waterlogged paddy soils, cadmium (Cd) can be precipitated as cadmium sulfide (CdS) under reductive environment, thereby limiting the absorption of Cd by plants. Multiple environmental factors (such as water, pH, Eh, etc.) played a role in the control of Cd mobility and bioavailability. In this study, we investigated the influence of the solar irradiation on the photo-dissolution of synthetic CdS-montmorillonite composites (CdS-M) in solution and the stability of Cdin natural soil. The release kinetic of Cd2+ showed that after the irradiation of simulated sunlight, CdS-M composites became less stable compared to the dark control. The solar irradiation seemed to enhance the release of Cd2+ from CdS significantly and continuously. Electron paramagnetic resonance (EPR) and quenching experiments confirmed that the photogenerated holes, O2·- and •OH were possibly involved in the photo-induced release of Cd2+, while the holes was primarily responsible for the reaction.Irradiation under alkaline solution or the presence of DOM, PO43-, CO32- and urea markedly inhibited the photodissolution process of CdS. The photo-mediated activation of Cd was further confirmed in paddy soil under natural sunlight, with a nearly 3-fold increase in concentration of extractable Cd during the 15 days irradiation. This study highlights the importance of photochemical transformation of Cd in the environmental water and soil.

scholarly journals Novel Nanobiocomposites Based on Natural Polysaccharides as Universal Trophic Low-Dose Micronutrients

2021 ◽  
Vol 22 (21) ◽  
pp. 12006
Author(s):  
Spartak S. Khutsishvili ◽  
Alla I. Perfileva ◽  
Olga A. Nozhkina ◽  
Tatjana V. Ganenko ◽  
Konstantin V. Krutovsky
Keyword(s):  
Low Dose ◽  
Solanum Tuberosum L ◽  
Soil Microflora ◽  
Natural Soil ◽  
Plant Tissues ◽  
Paramagnetic Resonance ◽  
Phytopathogenic Bacterium ◽  
Toxicological Effects ◽  
Potato Plants ◽  
Electron Paramagnetic

New promising manganese-containing nanobiocomposites (NCs) based on natural polysaccharides, arabinogalactan (AG), arabinogalactan sulfate (AGS), and κ-carrageenan (κ-CG) were studied to develop novel multi-purpose trophic low-dose organomineral fertilizers. The general toxicological effects of manganese (Mn) on the vegetation of potatoes (Solanum tuberosum L.) was evaluated in this study. The essential physicochemical properties of this trace element in plant tissues, such as its elemental analysis and its spectroscopic parameters in electron paramagnetic resonance (EPR), were determined. Potato plants grown in an NC-containing medium demonstrated better biometric parameters than in the control medium, and no Mn accumulated in plant tissues. In addition, the synthesized NCs demonstrated a pronounced antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus (Cms) and were proved to be safe for natural soil microflora.

Intrinsic Defects in HPSI 6H-SiC: an EPR Study

2008 ◽  
Vol 600-603 ◽  
pp. 381-384 ◽  
Author(s):  
Patrick Carlsson ◽  
Nguyen Tien Son ◽  
Björn Magnusson ◽  
Anne Henry ◽  
Erik Janzén
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Vapor Deposition ◽  
Thermal Activation ◽  
Chemical Vapor ◽  
Paramagnetic Resonance ◽  
Intrinsic Defects ◽  
Annealing Behavior ◽  
Carbon Vacancy ◽  
The Stability ◽  
Electron Paramagnetic

High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects. The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV above the valence band. The thermal activation energies as determined from the temperature dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of the intrinsic defects and the stability of the SI properties were studied up to 1600°C.

Magnetic and structural anomalies of NanC60 (n = 2, 3)

Open Physics ◽  
2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Vladimir Kulbachinskii ◽  
Boris Bulychev ◽  
Vladimir Kytin ◽  
Alexey Krechetov ◽  
Valeriy Tarasov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Fold Increase ◽  
Paramagnetic Susceptibility ◽  
Phase Reaction ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
Face Centered ◽  
Increasing Temperature ◽  
Electron Paramagnetic

AbstractSodium fullerides NanC60 (n = 2, 3) have been synthesized by a liquid phase reaction and investigated with X-ray diffraction (XRD), nuclear magnetic resonance (NMR), electron paramagnetic resonance, and differential thermal analysis. XRD data indicate that the crystal structure of Na2C60 at 300 K is face centered cubic (FCC). A phase transition from primitive cubic to FCC crystal structure has been observed in this work in Na2C60 fulleride at 290 K. The transition is accompanied by the step-like change of paramagnetic susceptibility. The crystal structure of Na3C60 is more complicated than, and different from, what has been reported in the literature. A nearly seven-fold increase of paramagnetic susceptibility with increasing temperature has been observed in the Na3C60 fulleride at 240–260 K. In the same temperature range, a new line at about 255 ppm appears in the 23Na NMR spectrum, indicating a significant increase of electron density near the Na nucleus. The observed effect can be explained by a metal-insulator transition caused by a structural transition.

ELECTRON PARAMAGNETIC RESONANCE STUDIES OF (VO4)+2 IONS DOPED IN REDUCED Pb10-xCax(VO4)1(PO4)5(OH)2 APATITES [x = 0.0, 2.0, 4.0, 6.0, 8.0, AND 10.0]

2009 ◽  
Vol 23 (16) ◽  
pp. 3369-3389
Author(s):  
M. IKRAM ◽  
R. AMBARDAR ◽  
A. M. ROSSI ◽  
J. G. EON
Keyword(s):  
Esr Spectroscopy ◽  
Lattice Relaxation ◽  
Esr Spectra ◽  
Hydrogen Gas ◽  
Spin Lattice Relaxation ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
The Stability ◽  
Calcium Doping ◽  
Electron Paramagnetic

Polycrystalline solid solution of phosphate and vanadate lead calcium apatites Pb 10 -x Ca x( VO 4)1( PO 4)5( OH )2 apatites [x = 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0] was reduced with hydrogen gas at the temperature of 300 and 400°C for 1 h. All these compounds were investigated by XRD and ESR spectroscopy. Only one reduced oxidation state V +4 was detected. Two types of species like isolated vanadium (+4) and clusters of V 4+ had been observed. The stability of the apatites increases and the particle size of the crystal decreases with calcium doping concentrations. As the concentrations of Ca increase the intensity of ESR lines deviates due to the spin–lattice relaxation interactions. The deviation in the intensity of ESR spectra can be attributed as the coexistence of paramagnetic and antiferromagnetic phases in the apatites.

scholarly journals Iron speciation at physiological pH in media containing ascorbate and oxygen

1993 ◽  
Vol 70 (1) ◽  
pp. 157-169 ◽  
Author(s):  
Clare Dorey ◽  
Chris Cooper ◽  
Dominic P. E. Dickson ◽  
John F. Gibson ◽  
Robert J. Simpson ◽  
...  
Keyword(s):  
Mössbauer Spectroscopy ◽  
Mossbauer Spectroscopy ◽  
Gel Filtration ◽  
Relative Molecular Mass ◽  
Paramagnetic Resonance ◽  
Mößbauer Spectroscopy ◽  
High Concentrations ◽  
Uptake Studies ◽  
The Stability ◽  
Electron Paramagnetic

The stability of iron ascorbate solutions was investigated, under both anaerobic and aerobic conditions, with the Fe2+ and Fe3+ indicators, respectively ferrozine and mimosine, at different pH values. The species present under the differing conditions were investigated by electron paramagnetic resonance (EPR) and Mössbauer spectroscopy and by gel-filtration chromatography. At physiological pH (6·8–7·4) iron ascorbate solutions rapidly form mononuclear chelatable Fe3+ species as reflected by indicator studies and EPR. Mössbauer spectroscopy fails to detect any Fe2+ species. EPR studies show a time-dependent decrease in rhombic Fe3+, particularly in oxygenated buffers, consistent with a conversion to polynuclear Fe. O2 uptake studies show that the conversion of Fe2+ to Fe3+ in Fe–ascorbate solutions at pH > 7·0 was accompanied by rapid O2 consumption but preceded depletion of ascorbate. Addition of high concentrations of mannitol (50–200 mM) reduces the O2 consumption and partly stabilizes the rapidly chelatable Fe form. Gel filtration studies show that the oxidation of Fe–ascorbate solutions at pH 7·4 is accompanied by an increase in the apparent relative molecular mass of the Fe, presumably due to Fe polymer formation. These studies indicate the inherent instability of Fe–ascorbate solutions above neutral pH and clearly have important implications in the use of ascorbate in studies of Fe physiology.

Persistent Photoinduced Changes in Charge States of Donors and Acceptors in Hydrothermally Grown ZnO

2006 ◽  
Vol 957 ◽  
Author(s):  
Nancy C. Giles ◽  
Yongquan Jiang ◽  
Xiaocheng Yang ◽  
S. M. Evans ◽  
L. E. Halliburton
Keyword(s):  
Charge Trapping ◽  
Paramagnetic Resonance ◽  
Group Iii ◽  
Device Structures ◽  
State Changes ◽  
Charge States ◽  
The Stability ◽  
Photoinduced Changes ◽  
Electron Paramagnetic ◽  
Dominant Acceptor

ABSTRACTBulk ZnO grown by the hydrothermal technique was investigated using electron paramagnetic resonance (EPR), photoluminescence (PL), and infrared absorption (FTIR) techniques. Isolated subsitutional lithium is the dominant acceptor and could be detected using EPR or PL. A large concentration of neutral Li+-OH− centers were observed using FTIR data. EPR spectra assigned to Mn, Co, Ni, Fe, and Group III (Al, Ga) donors were also observed. Photoinduced changes in the charge states of the different deep and shallow centers were produced using 325 nm light, and the stability of these changes were monitored with EPR during pulsed thermal anneals. The charge-state changes for some defects were persistent and remained up to 300 K. These impurities, when present in device structures, may act as stable charge trapping sites.

scholarly journals Influence of d-Electron Divalent Metal Ions in Complex Formation with L-Tartaric and L-Malic Acids

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5290
Author(s):  
Michał Zabiszak ◽  
Justyna Frymark ◽  
Martyna Nowak ◽  
Jakub Grajewski ◽  
Klaudia Stachowiak ◽  
...  
Keyword(s):  
Metal Ions ◽  
Divalent Metal Ions ◽  
Equilibrium Studies ◽  
Paramagnetic Resonance ◽  
Cobalt Nickel ◽  
Binary Complexes ◽  
Stability Constants Of Complexes ◽  
The Stability ◽  
Electron Paramagnetic

Binary complexes of α-hydroxy acids (L-Tartaric acid and L-Malic acid) with d-electron metal ions (copper, cobalt, nickel) were investigated. Potentiometric measurements have been performed in aqueous solution with computer analysis of the data for determination of the stability constants of complexes formed in the studied systems. The coordination mode of the complexes was defined using spectroscopic methods: electron paramagnetic resonance (EPR), ultraviolet-visible (UV-Vis), circular dichroism (CD), and infrared (IR). Results of the equilibrium studies have provided evidence for the formation of dimers with copper(II) ions and monomers with cobalt(II) and nickel(II) ions.

scholarly journals Mixed-valence cytochrome oxidase-formate complex. A steady-state intermediate

1977 ◽  
Vol 167 (3) ◽  
pp. 531-534 ◽  
Author(s):  
T Brittain ◽  
C Greenwood ◽  
A Johnson
Keyword(s):  
Steady State ◽  
Magnetic Circular Dichroism ◽  
Mixed Valence ◽  
Sodium Dithionite ◽  
Paramagnetic Resonance ◽  
Valence Form ◽  
The Stability ◽  
Electron Paramagnetic ◽  
Mixed Valence Complex

At neutral pH, formate binds to the haem a3 component of cytochrome c oxidase to give a complex that reacts differently from the non-liganded enzyme with reducing agents. Addition of sodium dithionite to the formate complex leads directly to the formation of the fully reduced species, whereas reduction with ascorbate/tetramethylenephenylene-diamine can lead to the production of a mixed-valence species. The stability of this mixed-valence form was studied, and the species appears to represent a ‘steady-state’ situation that is stable only in the presence of an excess of O2 and reducing equivalents. Characterization of the mixed-valence complex by electron paramagnetic resonance and magnetic circular dichroism reveals the presence of reduced low-spin haem a together with reduced detectable copper and high-spin ferric haem a3.

The stoichiometry and stability of the NADP complexes with manganese(II) ions as studied by electron paramagnetic resonance

1979 ◽  
Vol 57 (7) ◽  
pp. 995-999
Author(s):  
M. Kirk Green ◽  
George Kotowycz
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Stability Constant ◽  
Metal Ion ◽  
Metal Ion Binding ◽  
Paramagnetic Resonance ◽  
Ion Concentrations ◽  
Ion Binding Sites ◽  
The Stability ◽  
Electron Paramagnetic ◽  
Apparent Stability

Magnetic resonance techniques have been applied to study the stability of the complexes formed between Mn(II) ions and NADP in aqueous solutions at a pH of 7.5 and 20 °C. The electron paramagnetic resonance (epr) data indicate that at low Mn(II) ion concentrations ([Mn(II)] < 1 mM; [NADP] ~ 5 mM), a 1:1 complex is formed with an apparent stability constant K1 = 370 ± 50 M−1 at an ionic strength of 0.22 in the presence of 0.20 M Cl−. At high Mn(II) ion concentrations, a Mn(II)2 –NADP species, with an apparent stability constant K2 = 54 ± 17 M−1, is present in significant amounts. When the epr data are corrected for the presence of the MnCl+ ion, the analysis of the new Scatchard plot yields stability constants for the two sites of K1 = 640 ± 90 M−1 and K2 = 88 ± 13 M−1 respectively. The presence of two metal ion binding sites on the NADP molecule has not been observed previously, and previous workers have always analyzed their data in terms of the 1:1 Mn(II)–NADP complex. An epr temperature study of K1 yields a value of ΔH equal to 1.3 ± 0.2 kcal/mol (1 cal = 4.187 J).

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