ИСТИНА

Luminescent organo-inorganic hybrid materials (HM) contain nanoclusters of a highly efficient organic phosphor in a stable inorganic matrix. On the base of PbF2-containing matrices HMs were synthesized by different techniques: synthesis in low-melting glasses, solid phase recrystallization and co-precipitation using 8-hydroxyquinolate and ?-diketonate organometallic phosphors as organic constituents. In the PbF2-REF3 system (RE = rare earth element), solid solutions of the Pb1-xRExF2+x cubic phase of the fluorite Fm3m type can be formed. The high capacity of such solutions to RE, suggests the possibility of obtaining HM with high concentrations of organic components. The initial materials were lead, lanthanum, yttrium nitrates, lithium 8-hydroxyquinolate (Liq), and ammonium fluoride was used as a fluorinating agent. When obtaining HM at the first stage of the synthesis, mixing of aqueous solutions of lead nitrate and RE and a solution of 8-hydroxyquinolate lithium in ethanol was carried out. Concentrations of nitrate solutions were 1.43M and 0.8M. At the second stage of the final product was precipitated with ammonium fluoride; direct and reverse precipitation was used. As a result of co-precipitation, powders were obtained containing both the low-temperature ?-PbF2 rhombic phase and solid solutions based on ?-PbF2 cubic phase, depending on the RE concentration and synthesis conditions. It should be noted that during the deposition of nominally pure PbF2 and HM (PbF2+Liq), all powders, regardless of the conditions, corresponded to ?-PbF2. Stable single-phase powders corresponding to the ?-PbF2 structure were obtained at RE concentrations of 20-25 mol% and concentrations of nitrate solutions were 1.43M. The most intense photoluminescence (PL) was possessed by HM obtained by reverse co-precipitation with a nominal LaF3 concentration of 25 mol% and a concentration of the initial fluoride solution of 1.43M. We observed the noticeable shift of HM-PL spectra to shorter (418 nm) wavelengths relative to the initial Liq (448 nm). The short-wavelength component was obviously not associated with the centers of lanthanum or lead 8-hydroxyquinolates, which luminesced in the longer wavelength region than Liq. Also, the center cannot be due to specific bonds in PbF2 cubic phase. Since in HM, obtained by solid-phase synthesis at temperatures above 360 C, and corresponding to the crystalline PbF2 cubic phase, the maximum of the luminescence band is strongly shifted to the long-wavelength region to 511 nm. The PL intensity in this system turned out to be higher than in individual systems with lead or lanthanum fluorides, which, in combination with a very short-wavelength spectrum, seems promising. The research was financially supported by the Ministry of Science and Higher Education of the Russian Federation within the FSSM-2020-0005 project.