S. V. Trubina

A comparative study of the structure of copper and lead xanthates

XPS, PbL3 and CuK EXAFS, solid state NMR, and EPR techniques are used to study insoluble products formed in the interaction of aqueous solutions of lead(II) nitrate and copper (II) sulfate with potassium nbutylxanthate (KX). The XPS spectra of lead xanthates with the composition PbX2 are similar to those of KX, and interatomic distances of 0.279 nm suggest a nearly ionic character of Pb–S bonds. In copper xanthate precipitating together with dixanthogen (approximately 15 wt.%), the Cu(I)–S bond length is smaller (0.229 nm), and copper coordination number of 2.9 in a composite with dixanthogen increases to 3.3 after its removal by washing with acetone. The XPS spectra indicate the covalent character of the bond and non-equivalence of xanthate radicals. Solid state 1H and 13C NMR spectra as well as the actual absence of metal lines under the measurement conditions demonstrate strong disordering of the structure of xanthates, which is stronger for PbX2 and weakest in CuX after the removal of dixanthogen. EPR reveals sulfur-containing radicals and Cu2+ in CuX, however, their amounts are insignificant and decrease after the washing with acetone. The results of the work are significant for the understanding of the reactivity of xanthates, in particular, under the conditions of flotation of base metal ores.

Microstructure of multilayer heterosystems containing molecules of Ge quantum dots in Si on the stages of nucleation and growth as revealed by EXAFS spectroscopy

GeK edge EXAFS (Extended X-Ray Absorption Fine Structure) spectra have been measured for multilayer semiconducting heterosystems containing interacted groups of quantum dots (“molecules from quantum dots”) ordered in rings on different stages of their growth depending on topologic parameters and growth conditions. In accordance with our results obtained previously for the quantum dots of SiGe, for the molecules of quantum dots it was found that deformation at the interface leads to decrease in the interatomic distance of Ge–Ge by ~0.03 Å. Effect of heterosystem topology and temperature at different stages of their growth on interlayer diffusion was investigated. It was found that at the first growth stage (growth of “seeded islands” serving as a basis for obtaining the molecules) at 700°C a concentration of Ge atoms in the system is ~38%. With further growth of the vertically-matched quantum dots groups the concentration of Ge increases up to ~43-47% depending on the growth conditions. Comparable analysis of different modes of EXAFS measurements was performed to determine precisely structural parameters of heterosystem SiGe with different thickness grown on Si(100) surface.

Structural Study of Ni(dpm)2 in Solution by X-Ray Absorption Spectroscopy

The NiK-absorption spectra of Ni(dpm)2 and its adducts in crystal and solution have been studied. X-ray spectra were recorded on a synchrotron radiation station of the Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. It is shown that the fundamental absorption maximum in the compounds is of Rydberg character. The fine structure of the fundamental maximum was used for structure elucidation of the nearest environment of the metal atom of the complex in solutions and adducts. Participation of the highest unoccupied AO of the metal in chemical bonding in the compounds is discussed.