Copper K-edge XANES of Cu(I) and Cu(II) oxide mixtures

Gaur, Abhijeet; Shrivastava, B. D.; Joshi, S. K.

doi:10.1088/1742-6596/190/1/012084

Cited by 99 publications

(80 citation statements)

References 20 publications

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“…Notably, the changes in the absorption spectra observed when the gate voltage is increased are similar to those found previously (23)(24)(25)(26)(27) In accordance with experimental evidence, we have generated structures with alternating filled and empty chains consistent with each stoichiometry (28). The computed spectra qualitatively reproduce the experimental trends (Fig.…”

Section: Significancesupporting

confidence: 89%

In operando evidence of deoxygenation in ionic liquid gating of YBa ₂ Cu ₃ O _7-X

Pérez-Muñoz

Schio

Poloni

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Field-effect experiments on cuprates using ionic liquids have enabled the exploration of their rich phase diagrams [Leng X, et al. (2011) Phys Rev Lett 107(2):027001]. Conventional understanding of the electrostatic doping is in terms of modifications of the charge density to screen the electric field generated at the double layer. However, it has been recently reported that the suppression of the metal to insulator transition induced in VO 2 by ionic liquid gating is due to oxygen vacancy formation rather than to electrostatic doping [Jeong J, et al. (2013) Science 339(6126):1402-1405]. These results underscore the debate on the true nature, electrostatic vs. electrochemical, of the doping of cuprates with ionic liquids. Here, we address the doping mechanism of the high-temperature superconductor YBa 2 Cu 3 O 7-X (YBCO) by simultaneous ionic liquid gating and X-ray absorption experiments. Pronounced spectral changes are observed at the Cu K-edge concomitant with the superconductor-to-insulator transition, evidencing modification of the Cu coordination resulting from the deoxygenation of the CuO chains, as confirmed by first-principles density functional theory (DFT) simulations. Beyond providing evidence of the importance of chemical doping in electric double-layer (EDL) gating experiments with superconducting cuprates, our work shows that interfacing correlated oxides with ionic liquids enables a delicate control of oxygen content, paving the way to novel electrochemical concepts in future oxide electronics.electric double-layer techniques | high-temperature superconductivity | near-edge X-ray absorption spectroscopies | first-principles density functional theory | superconductor-insulator transition T he use of an electric field to modulate the charge density of a material in a controlled way is extensively used in metal oxide semiconductor technology and is also a promising technique to manipulate the properties of complex oxides to generate new devices with exciting functionalities. Many correlated oxides exist in the vicinity of a metal to insulator transition and, as such, their rich phase diagrams are critically controlled by the charge density (1). Gating experiments allowing its controlled modification have attracted much attention (2-8), and in recent years, unprecedented changes in the carrier concentration of complex materials have been achieved by using electric double-layer (EDL) techniques that use ionic liquids (ILs) as gate dielectrics (9-11). Superconductivity has been induced in otherwise band-insulating materials such as SrTiO 3 (STO) (12), ZrNCl (13), KTaO 3 (14), or MoS 2 (15), and the superconducting properties of several cuprates have been tuned to the insulating state (16)(17)(18)(19)(20). These results have focused much attention on the EDL technique not only from an applied point of view but also for providing an opportunity to obtain fundamental knowledge about the phase diagrams.Specifically, in the case of high-temperature cuprate superconductors (16-20), a striking similarity betw...

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Section: Significancesupporting

confidence: 89%

In operando evidence of deoxygenation in ionic liquid gating of YBa ₂ Cu ₃ O _7-X

Pérez-Muñoz

Schio

Poloni

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…It may be mentioned here that Figs. 5 and 7 are identical to those reported in our earlier paper [19] which also gives the results of LCF and NDAES methods. These have been repeated here to make the present paper complete in itself and to make available all the methods at one place.…”

Section: Linear Combination Ttingsupporting

confidence: 85%

“…The other X-ray absorption spectroscopic methods in use are residual phase analysis (RPA) [11], target transformation (TT) method [1,4], derivative spectra methods [12], method based on the relative posi- * corresponding author; e-mail: abhijeetgaur9@gmail.com tion of the absorption edge [12] and normalized dierence absorption edge spectra (NDAES) analysis [1318]. In a preliminary report we have shown the usefulness of LCF and NDAES methods for speciation [19]. In the present work using a test case of a heterogeneous mixture of two oxides of copper, i.e., CuO and Cu 2 O, we have tried to compare and evaluate all of the above mentioned methods of speciation.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study of the Methods of Speciation Using X-ray Absorption Fine Structure

Gaur

Shrivastava

2012

Acta Phys. Pol. A

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Determination of the chemical forms along with the relative quantity of the dierent species in a given sample, termed as speciation, can be done by analyzing X-ray absorption ne structure spectra. The dierent methods that can be used for speciation are: principal component analysis, target transformation, methods based on derivative spectra, method based on the relative position of the absorption edge, residual phase analysis, normalized dierence absorption edge spectra analysis and linear combination tting. An attempt has been made to make a comparative study of these dierent methods of speciation by recording the X-ray absorption ne structure at the copper K-edge in a mixture having cuprous oxide and cupric oxide in a specic ratio. The X-ray absorption ne structure spectra of the two oxides have also been recorded separately and the dierent characteristic X-ray absorption near edge structure features have been identied and their origins have been discussed. Speciation of the mixture has been done using these dierent methods and the results obtained have been compared and discussed.

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“…49 XANES post-edge spectra obtained in this study also suggested that Cu(II) may also be present within the cell although this may depend on the Cu-binding ligand present since the edge profile and post-edge regions differ between species. 62,63 The ratio of Cu(I) to Cu(II) was not determined in this study and further investigations are required to identify specific Cu(I) and Cu(II) complexes present in marine microalgae. This could be achieved by identification and preparation of Cu-thiol and Cu-phosphate compounds and comparison of the resultant spectra to those obtained from the microalgae under cryostat conditions (crucial to obtain the sensitivity required to identify individual Cu(I) and Cu(II) complexes).…”

Section: Discussionmentioning

confidence: 92%

Copper Uptake, Intracellular Localization, and Speciation in Marine Microalgae Measured by Synchrotron Radiation X-ray Fluorescence and Absorption Microspectroscopy

Adams

Dillon

Vogt

et al. 2016

Environ. Sci. Technol.

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Metal toxicity to aquatic organisms depends on the speciation of the metal and its binding to the critical receptor site(s) (biotic ligand) of the organism. The intracellular nature of the biotic ligand for Cu in microalgal cells was investigated using the high elemental sensitivity of microprobe synchrotron radiation X-ray fluorescence (SR-XRF) and X-ray absorption near-edge spectroscopy (XANES). The marine microalgae, Ceratoneis closterium, Phaeodactylum tricornutum, and Tetraselmis sp. were selected based on their varying sensitivities to Cu (72-h 50% population growth inhibitions of 8–47 μg Cu/L). Intracellular Cu in control cells was similar for all three species (2.5–3.2 × 10–15 g Cu/cell) and increased 4-fold in C. closterium and Tetraselmis sp. when exposed to copper, but was unchanged in P. tricornutum (72-h exposure to 19, 40, and 40 μg Cu/L, respectively). Whole cell microprobe SR-XRF identified endogenous Cu in the central compartment (cytoplasm) of control (unexposed) cells. After Cu exposure, Cu was colocated with organelles/granules dense in P, S, Ca, and Si and this was clearly evident in thin sections of Tetraselmis sp. XANES indicated coexistence of Cu(I) and Cu(II) in control and Cu-exposed cells, with the Cu ligand (e.g., phytochelatin) in P. tricornutum different from that in C. closterium and Tetraselmis sp. This study supports the hypothesis that Cu(II) is reduced to Cu(I) and that polyphosphate bodies and phytochelatins play a significant role in the internalization and detoxification of Cu in marine microalgae.

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Copper K-edge XANES of Cu(I) and Cu(II) oxide mixtures

Cited by 99 publications

References 20 publications

In operando evidence of deoxygenation in ionic liquid gating of YBa ₂ Cu ₃ O _7-X

In operando evidence of deoxygenation in ionic liquid gating of YBa ₂ Cu ₃ O _7-X

A Comparative Study of the Methods of Speciation Using X-ray Absorption Fine Structure

Copper Uptake, Intracellular Localization, and Speciation in Marine Microalgae Measured by Synchrotron Radiation X-ray Fluorescence and Absorption Microspectroscopy

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Copper K-edge XANES of Cu(I) and Cu(II) oxide mixtures

Cited by 99 publications

References 20 publications

In operando evidence of deoxygenation in ionic liquid gating of YBa 2 Cu 3 O 7-X

In operando evidence of deoxygenation in ionic liquid gating of YBa 2 Cu 3 O 7-X

A Comparative Study of the Methods of Speciation Using X-ray Absorption Fine Structure

Copper Uptake, Intracellular Localization, and Speciation in Marine Microalgae Measured by Synchrotron Radiation X-ray Fluorescence and Absorption Microspectroscopy

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In operando evidence of deoxygenation in ionic liquid gating of YBa ₂ Cu ₃ O _7-X

In operando evidence of deoxygenation in ionic liquid gating of YBa ₂ Cu ₃ O _7-X