Natural and Synthetic Copper Phyllosilicates Studied by XPS

Abstract

Abstract--X-ray photoelectron spectroscopy (XPS) has been used to characterize the bonding state of Cu 2 § Si 4+, A13 § and 02 ions in structural (octahedral and interlamellar) or adsorbed position in phyllosilicates. Five smectites, 5 kaolinites, and 1 chrysocolla with Cu(II) in known positions (octahedral, interlamellar, or surface adsorbed) have been investigated. Their spectra were compared with those of pure Cu metal and of pure Cu(I) and Cu(II) oxides.The line for Cu 2p3/2 (binding energy of 935.4 eV) and well-defined shake-up lines (binding energy of about 943 eV) observed after 1 hr of X-ray irradiation are characteristic of Cu(II) in phyllosilicate octahedral sites. But due to the photoreduction effect, they show Cu(I) oxidation states (Cu 2P3/2, binding energy of 933.2 eV and near absence of shake-up lines) for the phyllosilicates with adsorbed Cu or in interlamellar positions. The kinetics of photoreduction distinguishes octahedral from interlamellar positions, and the latter from a surface adsorbed position. The enlargement of the FWHM (full width at half maximum) of XPS lines has been used to describe crystallochemical parameters linked to local ordering around the probe cations. Crystallization produces decreasing O 1 s and Cu 2p (octahedral cation) line widths but has no effect on the Si 2p (tetrahedral cation) line width. The enlargement of FWHM for all ion lines of the lattice is linked to the nature (Cu > Mg > AI) and the number and amount of structural cations in the phyllosilicates.

The interaction of n-octanohydroxamate with chrysocolla and oxide copper surfaces

“…XPS data for a powdered Brazilian chrysocolla have been reported by Mosser et al (1992), but the 4.2 eV Cu 2p 3/2 linewidth would have been too large to enable resolution of a minor component at $932.8 eV. Their Cu 2p 3/2 , O 1s and Si 2p binding energies were reported as 935.8, 532.3, and 102.8 eV, respectively.…”

Migration of Cations in Copper(II)-Exchanged Montmorillonite and Laponite Upon Heating

“…A drop of that dispersion was placed onto a disk of 2-cm refractory vitreous carbon, air-dried and analyzed by XPS spectroscopy. The measurements were carried out after photoreduction times of 15 min, 2 h and 4 h according to the procedure described by Mosser et al (1992). Indeed, it was shown that photoreduction effects can differentiate structural Cu locations in clay minerals.…”

Preparation, Characterization and Electrochemistry of Synthetic Copper Clays

“…It has been proposed that this property of copper is not compatible with a regular clay structure Petit et al 1995). Octahedral sites occupied by Cu(II) in phyllosilicates are distorted, with Cu-O distances of 1.95 ,~ for the 4 in plan oxygens, and 2.32 .~ (in smectites) or 2.41 ,~ (in chrysocolla) for the 2 apical oxygens (Mosser et al 1990(Mosser et al , 1992. The Cu content of natural smectites is limited to about 2% (Mosser et al 1990;.…”