The position of activator ions in the lattice has a fundamental effect on the luminescent properties of phosphors. In this paper, we describe the normal and defect sites of Eu³⁺ ions in a Y₂O₃ crystal lattice, their interaction and difference in physical properties. Analytically detectable amounts of defect sites reached in Y₂O₃:Eu³⁺ nanopowders with an average size of 40–50 nm were synthesized by a novel combined Pechini-foaming method. The luminescence properties of Eu³⁺ ions in defect sites are most pronounced in highly doped nanocrystalline powders (32 and 40 at%). To explain this phenomenon we suggest the mechanism of irreversible energy transfer from normal to defect sites of Eu³⁺ ions.

Lanthanide-doped nanoparticles characterized by their large Stokes’ shifts, narrow emission bands, long lifetimes and high photostability are promising candidates for luminescent labels in biological research. That is why investigation of lanthanide-doped nanoparticles’ fluorescence in complex biological media (like blood and Intralipid) is of great importance from the standpoint of applicability in medicine and biology. Nanopowder of yttrium aluminum garnet doped with Eu ³⁺ was synthesized by the Pechini method. X-ray diffraction data demonstrated formation of cubic crystalline phase without any impurities. The synthesized sample was found to be well-defined 20–50 nm nanoparticles agglomerated to clusters no bigger than 200 nm in diameter. The emission spectrum of nanocrystalline powder consists of characteristic narrow lines attributed to ⁵ D ₀ – ⁷ F _J transitions. It was found that the long lifetime of ⁵ D ₀ level (4.13 ms) allows using time-resolved techniques to eliminate fluorescence of the biological background. The possibility of the luminescence signal detection of Y ₃ Al ₅ O ₁₂ :Eu ³⁺ nanopowder (0.14 mg per 1 ml) against the background of blood auto-luminescence was demonstrated. Y ₃ Al ₅ O ₁₂ :Eu ³⁺ phosphors luminescence in blood media showed timing stability whereas fluorescein luminescence dropped down by a factor of 3 after 20 min. It was found that the luminescence signal of Y ₃ Al ₅ O ₁₂ :Eu ³⁺ phosphors could be detected through 5 mm of biological tissue. The possibility of independent registration of nanopowders doped with different REI-ions (Eu ³⁺ and Nd ³⁺ ) was investigated.

Damping of coherent optical phonons is investigated by femtosecond time-resolved second-harmonic generation at Gd(0001) and Tb(0001) surfaces. At low temperature the damping rate increases monotonically with temperature, but close to the Curie point the damping rate is strongly reduced. We explain this behavior by phonon-magnon scattering originating from spin-orbit coupling proven by a larger effect for Tb than for Gd. Consideration of phonon-electron and phonon-phonon scattering shows that magnon-mediated damping is dominant almost up to the Curie temperature.

Micro-chips based on organic–inorganic hybrid nanoparticles (NPs) composed of nanoalloys of gold (Au) and silver (Ag) embedded in an amorphous carbonaceous matrix (C–Au–Ag NPs) were prepared directly on a substrate by the laser-induced deposition (for short: LID) method. The C–Au–Ag NPs show a unique plasmon resonance which enhances Raman scattering of analytes, making the μ-chips suitable to detect ultra-low-volumes (10⁻¹² liter) and concentrations (10⁻⁹ M) of bio-agents and a hazardous compound. These micro-chips constitute a novel, flexible solid-state device that can be used for applications in point-of-care diagnostics, consumer electronics, homeland security and environmental monitoring.