ИСТИНА

The modern biology and medicine methods actively research luminescent nanolabels. The main problem of using luminescent agents in biological media is separation of useful signal of markers from the background caused by autoluminescence of biological environment. This problem can be eliminated by using lanthanide-based luminophores revealing intense up-conversion luminescence under NIR excitation. In the given work different suspensions of newly synthesized nanophosphors based on NaYF4:Yb:Tm in dimethyl sulfoxide were studied. The mechanism of up-conversion luminescence is implemented by transferring the energy of exciting radiation from ytterbium (“sensitizer”) to thulium (“activator”). Two series of samples were prepared: for the first one the concentration of the sensitizer was varied while the concentration of the activator kept constant. In the other one the concentration of activator was changed at constant concentration of sensitizer. The dependences of the intensity of the most intense luminescence bands of thulium on the intensity of exciting radiation (980 nm) were revealed. The obtained results allow one to clarify the models of mechanisms of up-conversion luminescence of complexes NaYF4:Yb:Tm and determine the optimal ratio of the sensitizer and activator concentrations.