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.