TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The pretreatment comprises shock freezing the coated core, during the first step. The pretreated core is then freeze-dried. The heat treatment is carried out stepwise for the formation of the crystalline shell. In at least the first step of the stepwise heat treatment, a heat treatment is carried out at 50-300 degrees C, preferably 100-120 degrees C. The heat treatment is carried out under mechanical agitation. In at least the second step of the stepwise heat treatment, a heat treatment for the formation of the crystalline shell is carried out at 400-1400 degrees C. The method is carried out with a heating rate of 50-500 degrees C, preferably 300-400 degrees C per hour. The temperature required for the formation of the crystalline shell is maintained for 5 minutes to 1.5 hours, preferably 10-30 minutes. The layer thickness of the crystalline shell is adjusted to 1-100 nm. An additional shell that functions as barrier layer is deposited on the particle. The method comprises surface functionalization of the particle. The surface functionalization is carried out by the coupling of ligands. The core is prepared by wet chemical method, preferably by the Stoeber process or by an emulsion- or aerosol method. The core is prepared from oxidic, organic or hybrid materials. The core is prepared from silicon oxide, polystyrene, zirconium oxide, tin oxide, titanium oxide, iron oxide or from hybrid materials. The coating of the core with an inorganic doped material is carried out by using a wet chemical process, preferably a sol-gel process. A metal salt with acid and/or polyalcohol is added during the coating of the core with an inorganic doped material and by gelatinization effect an atomic distribution of the metal cations are carried out. The dopants comprise transition metals, heavy metals or rare earth elements. The particles are agglomerated and/or aggregated to a maximum of less than 50%, based on the total weight of the particle. Preferred Components: The ligand used for surface functionalization, comprises carboxy-, carbonate-, amine-, maleimide-, imine-, imide-, amide-, aldehyde-, thiol-, isocyanate-, isothiocyanate-, acylazide-hydroxyl-, N-hydroxysuccinimide ester, phosphate-, phosphonic acid-, sulfonic acid-, sulfonic acid chloride, epoxy, CC-double bond containing units including methacrylic group or norbornyl group. EXAMPLE - Zinc acetate (31.2 g) and manganese acetate (1.3 g) were dissolved in a mixture of ethanol (837.6 g) and water (133 g) with the addition of nitric acid (10 mol/l), citric acid (62.6 g) and polyethylene glycol (52 g/l). Silicon dioxide core (6 g) (obtained by mixing ethanol (900 ml) and aqueous ammonia solution (45 ml), adding tetraethoxysilane (45 g) in the prepared solution and centrifuging the mixture to obtain the silicon dioxide core with an average diameter of 73 nm) were provided in the reaction mixture. The mixture was stirred at room temperature for 3 hours. The coated particles were centrifuged, shock-frozen and then freeze-dried. The coated particle was subjected to heat treatment, which included a pre-drying of particle powder for 2-3 hours at 115 degrees C and a 15 minutes of heating the sample at 900 degrees C. The heating process was carried out at a rate of 300 degrees C/hour. Then, the particle was quickly cooled to room temperature. The resulting powder (particle diameter 75 nm) had green luminescence at an excitation wavelength of 254 nm. Then the coated particles was surface functionalized with an aminosilane by redispersing the core-shell nanoparticle (1 g) in ethanol (100 ml), adding aqueous ammonia solution (4.3 ml) and N-(3-(trimethoxysilyl)-propyl)-diethylene triamine (178 mu l) to the obtained mixture, stirring the reaction mixture for 12 hours at room temperature and centrifuging the mixture.