Structural and chemical varieties of dioptase, Cu6[Si6O18] · 6H2O

Breuer, K.; Eysel, W.; Mueller, Ronald L.

doi:10.1524/zkri.1989.187.1-2.15

Cited by 29 publications

(11 citation statements)

References 4 publications

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“…2 in Breuer and Eysel, 1988) is shifted to higher wave numbers from green (13800 cm -1 ) over blue (14100 cm -1 ) to the black (15400 cm" 1 ) dioptase. The major absorption band (Fig.…”

Section: The Structure Of Blue Dioptase and The Mechanism Of Dehydrationmentioning

confidence: 93%

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Structural and chemical varieties of dioptase, Cu₆[Si₆O₁₈]∙6H₂O

Eysel¹,

Müller²

1989

Zeitschrift Für Kristallographie - Crystalline Materials

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Dioptase / Crystal structure / Copper silicate / Polymorphism of dioptase / Composition of dioptaseAbstract. Structural properties of three varieties of dioptase, namely natural green dioptase, Cu 6 Si 6 0 )8 · 6H 2 0, synthetic blue dioptase, Cu 6 Si 6 0 18 •6H 2 0, and synthetic black dioptase, Cu 6 Si 6 0i 8 , are discussed, based on a structure determination of the latter. For blue dioptase a structural model is proposed. All three structures are closely related.The rather sluggish transition green-blue is interpreted as a mobilization of the H 2 0 molecules within the structure. The structural background of the dehydration to black dioptase is discussed.

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“…2 in Breuer and Eysel, 1988) is shifted to higher wave numbers from green (13800 cm -1 ) over blue (14100 cm -1 ) to the black (15400 cm" 1 ) dioptase. The major absorption band (Fig.…”

Section: The Structure Of Blue Dioptase and The Mechanism Of Dehydrationmentioning

confidence: 93%

“…In the first part of this series (Breuer and Eysel, 1988) the thermal properties of dioptase were reported. It was shown that from the natural green dioptase a blue polymorph with deviating lattice parameters can be obtained by annealing just below 400 C. At higher temperatures a dehydration to black Cu 6 [Si 6 0 18 ] takes place.…”

Section: Introductionmentioning

confidence: 99%

Structural and chemical varieties of dioptase, Cu₆[Si₆O₁₈]∙6H₂O

Eysel¹,

Müller²

1989

Zeitschrift Für Kristallographie - Crystalline Materials

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“…Multiple scans (2–5 scans each) were performed at room temperature and were processed using the IFEFFIT Demeter software 0.9.21. 28 FEFF paths for EXAFS fitting were obtained from the copper cyclohexasilicate crystal structure, 29 via Inorganic Crystal Structure Database.…”

Section: Methodsmentioning

confidence: 99%

Model system study of environmentally persistent free radicals formation in a semiconducting polymer modified copper clay system at ambient temperature

et al. 2016

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This paper systematically investigates how environmentally persistent free radicals (EPFRs) are formed in a phenol contaminated model soil. Poly-p-phenylene (PPP) modified and copper-loaded montmorillonite (MMT) clays were developed and used as models of soil organic matter and the clay mineral component, respectively, with phenol being employed as a precursor pollutant. The polymer modification of the clays was carried out via surface-confined Kumada catalyst-transfer chain-growth polymerization. The presence and location of the polymer were confirmed by a combination of thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction data. EPFRs were formed by the Cu(II)-clay (Cu(II)CaMMT) and poly-p-phenylene-Cu(II)clay (PPP-Cu(II)CaMMT) composite systems under environmentally relevant conditions. The g-factor and concentration of EPFRs formed by the Cu(II)CaMMT and PPP-Cu(II)CaMMT systems were found to be 2.0034 and 1.22 × 1017 spins/g and 2.0033 and 1.58 × 1017spins/g, respectively. These g-factors are consistent with the formation of phenoxyl radicals. Extended X-Ray absorption fine structure (EXAFS) analysis shows that there are distinct differences in the local stuctures of the phenoxyl radicals associated with only the Cu(II) redox centers and those formed in the presences of the PPP polymer. X-ray absorption near edge spectroscopy (XANES) results provided evidence for the reduction of Cu(II) to Cu(I) in the EPFR forming process. The 1/e lifetimes of the formed EPFRs revealed a decay time of ~20 h for the Cu(II)CaMMT system and a two-step decay pattern for the PPP-Cu(II)CaMMT system with decay times of ~13.5 h and ~55.6 h. Finally, the generation of reactive oxygen species (hydroxyl radical; •OH) by these clay systems was also investigated, with higher concentrations of •OH detected for the phenol-dosed Cu(II)CaMMT and PPP-Cu(II)CaMMT systems, compared to the non-EPFR containing undosed PPP-Cu(II)CaMMT system.

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“…First results of UV-VIS spectroscopy on Cu 6 (Ge,Si) 6 O 18 ·6H 2 O are given in the doctoral theses of my coworkers Brandt [17] and Meibohm [14], respectively, whereas dioptase itself has been investigated earlier by different researchers [18] [19] [20] [21].…”

Section: Uv-vis Spectroscopic Investigationmentioning

confidence: 99%

Crystal Growth of Cu6(Ge,Si)6O18&#183;6H2O and Assignment of UV-VIS Spectra in Comparison to Dehydrated Dioptase and Selected Cu(II) Oxo-Compounds Including Cuprates

Otto¹

2017

WJCMP

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Low-dimensional quantum spin systems with the Cu 2+ central ion are still in the focus of experimental and theoretical research. Here is reported on growth of mm-sized single-crystals of the low-dimensional S = 1/2 spin compound Cu 6 (Ge,Si) 6 O 18 ·6H 2 O by a diffusion technique in aqueous solution. A route to form Si-rich crystals down to possible dioptase, the pure silicate, is discussed.Motivated by previously reported incorrect assignments of UV-VIS spectra, the assignment of dd excitations from such spectra of the hexahydrate and the fully dehydrated compound is proposed in comparison to dioptase and selected Cu(II) oxo-compounds using bond strength considerations. Non-doped cuprates as layer compounds show higher excitation energies than the title compound. However, when the antiferromagnetic interaction energy as J z ·ln (2)

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Structural and chemical varieties of dioptase, Cu₆[Si₆O₁₈] · 6H₂O

Cited by 29 publications

References 4 publications

Structural and chemical varieties of dioptase, Cu₆[Si₆O₁₈]∙6H₂O

Structural and chemical varieties of dioptase, Cu₆[Si₆O₁₈]∙6H₂O

Model system study of environmentally persistent free radicals formation in a semiconducting polymer modified copper clay system at ambient temperature

Crystal Growth of Cu6(Ge,Si)6O18&#183;6H2O and Assignment of UV-VIS Spectra in Comparison to Dehydrated Dioptase and Selected Cu(II) Oxo-Compounds Including Cuprates

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Structural and chemical varieties of dioptase, Cu6[Si6O18] · 6H2O

Cited by 29 publications

References 4 publications