Cobalt Ferrite–Silica–Gold Nanocomposite: Synthesis, Structural Characterization, and Magneto‐Plasmonic Properties

Abstract Cobalt ferrite–silica–gold nanocomposite (CoFe 2 O 4 @SiO 2 @Au) is synthesized using a new method involving: i) the polyol method for cobalt ferrite nanoparticles (CoFe 2 O 4 ), ii) the Stober method for silica coating, iii) surface functionalization with 3‐aminopropyl triethoxysilane (APTES), and iv) decoration with gold nanoparticles via tetrakis hydroxy‐methyl‐phosphonium (THPC) reduction. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirm the morphology of the nanoparticles and coatings for the nanocomposites. Ultraviolet–visible (UV–Vis) absorption spectra exhibit plasmon resonance peaks with tuned shifts, discuss in terms of the difference in dielectric permittivity in the core where gold nanoparticles are anchored. Magnetic hysteresis analysis reveals superparamagnetic behavior with reduced saturation magnetization for the nanocomposites. These findings are useful, as superparamagnetic behavior combined with control of plasmonic emission is highly relevant for several magneto‐plasmonic applications.