Synthesis and characterization of new barium titanate core–gold shell nanoparticles

A new nanoshell structure composed of a spherical barium titanate (BaTiO3) core and a gold shell is presented. Gold nanoshells were synthesized using the combination of self-assembly method and seed growth technique from colloidal chemistry. (3-aminopropyl) triethoxysilane (APTES) was used to modify the surface of BaTiO3 nanospheres to allow attachment of small gold nanocolloids to their surface (seeding process). In a following step, more gold ions, using sodium borohydride (NaBH4), were further reduced to grow the gold shell on the seeded particles. FTIR, UV–vis and Raman spectroscopy as well as TEM were the characterization methods employed to monitor the assembly process. The results reveal changes in the optical features of the composite nanoparticles corresponding to the coverage density of the core particles by the gold shell. By gradually growing the metal shell, the Surface Plasmon Resonance (SPR) position was shifted from visible to near infrared region of electromagnetic spectrum, a region of particular interest for biology applications.