Robust fluorescein-doped silica nanoparticles via dense-liquid treatment

Robust fluorescein-doped silica nanoparticles were synthesized by the conventional Stِber method and following dense-liquid treatment. The as-prepared nanoparticles present stable fluorescence in a wide range of pH value. BET measurements show the dense-liquid process is effective to close the pores of the silica surface and thus effective to prevent the penetration of protons into the particles.