Layer-by-Layer synthesis and tunable optical properties of hybrid magnetic–plasmonic nanocomposites using short bifunctional molecular linkers

• Magnetic–plasmonic nanocomposites without polymers or polyelectrolytes.
• Iron oxide and gold or silver nanoparticles as start compounds.
• High quality, variable thickness, partially transparent and high filling fractions.
• Broad and angle-independent plasmon wavelength tunability.
• Ideal samples for magnetoplasmonic research.

Spurred by research in magnetoplasmonics, plasmon-enhanced magneto-optical effects and active plasmonics, the demand for hybrid magnetic–plasmonic nanoparticle-based materials of optical quality is high. Currently used synthesis methods involve possibly interfering polymer media or polyelectrolyte interlayers, grooved supports or non-transparent substrates. To obtain homogeneous, partially transparent and polymer/polyelectrolyte-free magnetic–plasmonic nanocomposites with angle-independent optical properties, we produced hybrid gold–magnetite and silver–magnetite nanocomposites by a novel Layer-by-Layer synthesis using short bifunctional molecular linkers on glass substrates. Resulting nanocomposites had high nanoparticle filling fractions and showed tunability of the plasmon wavelength over a very broad spectral range by changing composite thickness through the number of added nanoparticle layers. The angle-independence of optical properties and the abilities to switch the plasmonic material and to tune the plasmon resonances of the magnetic–plasmonic composites make these materials a unique platform for magnetoplasmonic research.