Scientists have recently been studying various luminescent materials, in particular, nanocrystalline inorganic phosphors based on compounds of rare-earth elements – they usually use the compound NaYF4, since the material itself practically does not reduce the luminescence of embedded ions.
Researchers from St. Petersburg State University, LAT University in Finland and Sirius University in a new work replaced yttrium (Y) ions with europium (Eu) and gadolinium (Gd) ions, and then studied how the nanoparticle size and luminescent properties of the substance changed.
As a result, it turned out that the optimal concentration of europium in the compound is 30%, this is exactly what is needed to achieve the maximum brightness of the glow. But the intensity can be further increased: it is necessary to additionally replace a small amount of yttrium ions with gadolinium, while leaving the europium concentration unchanged. Despite the fact that gadolinium ions practically do not luminesce, they significantly increase the brightness of the luminescence of the resulting substance.
In order not to distort the proportions, the researchers used an autoclave – a chemical reactor that allows substances to be heated under pressure above atmospheric.
We found that adding only one percent of gadolinium increases the luminescence intensity by 2.5 times. In lanthanides, which include the three rare earth materials used, a decrease in symmetry leads to an increase in luminescence properties.
As a result of the work, the authors found that the replacement of yttrium ions with gadolinium and europium leads to a decrease in the size of the synthesized particles; therefore, nanoparticles will be easier to use for medical purposes.
The authors plan to use their development in photobiology and biomedicine. For example, as markers of various diseases for the study of biological tissues using fluorescence microscopy.
The new phosphor from scientists from St. Petersburg State University can carry out diagnostics using light and a magnetic field: it can be tuned to specific viruses, for example, cancer cells.