Abstract: The present invention relates to a surface treatment method for nanoparticles. The present invention particularly relates to a surface treatment method for nanoparticles, which increases the dispersion ability of the nanoparticles in a solvent, and in which a mixture made of a polyvalent acid and a nitrogen-containing base, such as an amine, or a salt of a polyvalent acid and a nitrogen-containing base, such as ammonium salt, or also a corresponding betaine, is used. The present invention also relates to surface-modified nanoparticles, which can be obtained by the inventive method.

Abstract: Methods for the preparation of inorganic nanoparticles capable of fluorescence, wherein the nanoparticles consist of a host material that comprises at least one dopant. The synthesis of the invention in organic solvents allows to gain a considerably higher yield compared to the prior art synthesis in water. All kinds of objects can advantageously be marked and reliably authenticated by using an automated method on the basis of a characteristic emission. Further, the size distribution of the prepared nanoparticles is nartower which renders a subsequent size-selected separation process superfluous.