Experiments on recording the ultrafast optical Kerr effect (OKE) in solution of europium(III) β‑diketonate complexes in toluene at a concentration of 10^–2 mol/L showed that the total OKE signal is not a superposition of two contributions, one of which is related to the vibrational–rotational dynamics of toluene molecules, while the other is due to the vibrational–rotational dynamics of the europium(III) complexes. This immediately indicates that the europium(III) complexes essentially change the structure of liquid toluene, which is reflected in the character of an orientational response in picosecond range.

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We report on a method for detection of upconversion nanoparticles (UNPs) in biological preparations by using confocal microscopy technique. Approbation of the method was carried out by monitoring the natural excretion of an injected colloidal solution of YVO4: Yb, Er nanoparticles (0.2 ml, containing 15 mg ANP, dosage 600 mg/kg) with sizes from 10 nm to 700 nm into the snail. The experiments showed that the animal naturally eliminated the nanoparticles from the body within three days, while the excretion rate decreased over time. The threshold of sensitivity in the experiments was equal to one nanoparticle in 1 µl.

The possibility of precise movement of YVO4:Yb,Er nanoparticles was studied in this work. Such nanoparticles exhibit upconversion luminescent properties and can serve as an accurate low-invasive probe of changes in the local parameters of the medium (in particular, temperature). Using an atomic force microscope, the substrate region with upconversion nanoparticles deposited from the solution and accompanying residues of the synthesis products was cleaned. The use of mechanical marks on the substrate made it possible to compare the atomic force and optical confocal images of the surface and to register the luminescence from an individual nanoparticle. Elemental analysis and luminescence spectra unambiguously identify the nanoparticle as YVO4:Yb,Er.