Magnetic and optical properties of Ag@SiO2-FITC-Fe3O4 hybrid nanoparticles

•New magnetic/fluorescent nanoparticles were synthesized.•The silver core led to a maximum 4-fold enhanced fluorescence of fluorophore.•Maximum enhancement factor was obtained when metal-fluorophore distance is 5 nm.•Magnetism and fluorescence appeared simultaneously for nanoparticles in solution.

Nanoparticles composed of a silver core coated with a silica shell (Ag@SiO2) were prepared. A dye, fluorescein isothiocyanate (FITC), was further encapsulated during the growth of a second silica shell onto Ag@SiO2 nanoparticles. The proximity of silver nanoparticles led to a 4-fold maximal enhancement in the fluorescence of FITC when the first silica shell thickness was set at 5 nm. After amino-functionalization of Ag@SiO2-FITC nanoparticles, iron oxide nanoparticles were bonded to their surface. The magnetic and metal-enhanced fluorescence properties appeared simultaneously when Ag@SiO2-FITC-Fe3O4 hybrid nanoparticles were dispersed in a solution.