Synthesis and characterization of anisotropic magnetic/plasmonic Fe3O4 NRs@SiO2@Au shell nanocomposites. (a) Schematic illustration of the nanocomposite structure. (b) TEM image of β-FeOOH nanorods. The size of the nanorods is 286 ± 11 nm in length and 45 ± 3 nm in width. (c) TEM image of the magnetic Fe3O4 NRs@SiO2 after forming gas reduction. The thickness of the silica coating is 45 nm. (d) Magnetic hysteresis loop of Fe3O4 NRs@SiO2. (e) TEM image of the gold seed loaded NRs. (f) TEM image of Fe3O4 NRs@SiO2@Au shell after seeded growth to form a complete gold shell coating. The thickness of the gold shell is measured to be 36.5 nm. Scale bars in (b), (c), (e), and (f) are 200 nm.