Vìsnik Odesʹkogo Nacìonalʹnogo Unìversitetu: Hìmìâ (Feb 2018)
RESEARCH OF DEGRADATIONS OF NANOSTRUCTURES IN THE SALINE MELT EuF2 – NaCl – KCl BY SPECTROSCOPIC METHODS
Abstract
Methods of luminescent spectroscopy, spectroscopy of diffuse refl ectance and IR transmittance spectroscopy were used for investigation of process of change of nanostructures of Europium (ІІ) fl uoride in stiffened saline melt NaСl – KСl. Europium (ІІ) fluoride was synthesized by high-temperature solid-phase reaction of EuF3 with elemental Germanium ground and pressed into a tablet. The process of synthesis is accompanied by volatizing of GeF2 at hightemperature annealing of the mixture. Prolonged calcinations result in a yellowish powder with a slight gray tint. IR spectrum and spectrum of diffuse refl ectance notify on the nanostructured product. Dissolution of EuF2 in saline melt is regarded as exchange reaction with one of the components, NaCl and complexion with another one, namely KСl. At rapid crystallization of the molten saline solution multiple centers forming and the stabilization of nano-structures of «core-shell» type are occurred. It is established considerable (almost in 2 times for each week) intensity falling 5d-4f photoluminescence with a maximum at ~430 nanometers. At the same time characteristic changes in a spectra of diffuse refl ectance in an UV range of a spectrum with transition from negative values of Kubelka-Munk function to positive ones, with absorption bands observed at 250, 330 and 410 nanometers. Insignifi cant by intensity peaks in a near IR spectrum at 1800-2300 nanometers testify to the small content of Eu3+ ions in the sample that practically does not change eventually. The mechanism of degradation of the nanostructures in stiffened melt and corresponding kinetic equation of the process are proposed. The degradation process is supposed to be caused by environment factors such as moisture and oxygen of an air and results in the destruction of the stabilizing shells of the nanoparticles.
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