Scheme 1.
Synthesis of SPIO@silica-Au nanoshells.17 Silica-coated superparamagnetic iron oxide (SPIO) (γ-Fe2O3) nanoparticles were synthesized using the Stöber process. After the surface of the silica shell was functionalized with 3-aminopropyltrimethoxysilane (APTMS), 2–3 nm gold nanocrystal seeds were attached to the amino groups on the silica sphere by reducing chloroauric acid (HAuCl4) with tetrakis(hydroxymethyl) phosphonium chloride (THPC). Finally, the attached gold nanoseeds were used to nucleate the growth of a gold overlay on the silica surface to form a gold nanoshell.