Luminescent silicate core-shell nanoparticles: Synthesis, functionalization, optical, and structural properties

SiO2/Zn2SiO4:Mn2+ core-shell nanoparticles with mean diameters in the range of 55-220 nrn were prepared by a modified Pechini sol-gel method followed by lyophilization and annealing at temperatures of 800-1100 degrees C. The as-synthesized nanoparticles were characterized by transmission electron microscopy, X-ray diffraction analysis, and photoluminescence spectroscopy. The results demonstrate that the crystal structure of the shell and the optical properties can be tuned by the annealing temperature and a variation of the concentration of doping ions. Under UV excitation, the samples emit green luminescence with its maximum at 525 nm, typical for the Mn2+ ions in alpha-Zn2SiO4. The resulting nanoparticles were successfully modified with amine and carboxyl functions with respect to a later attachment of biological moieties.