Recognition of biomolecular interactions by plasmon resonance shifts in single- and multicomponent magnetic nanoparticles

Composite biomarkers open prospects to combine the targeting advantages of magnetic nanoparticles with direct plasmon-based optical detection of biomolecular interactions. Although nanoparticles from ferromagnetic 3d-transition metals could be suitable for such a task, they are shown to be rather large, thus tending to agglomerate in aqueous suspensions. A superior alternative uses composite nanoparticles consisting of a superparamagnetic core and a noble metal shell. Systematic Mie-theory based calculations of their plasmon peak shifts and sensitivity against biomolecular binding events on their surfaces are presented for this hybrid particle class.