Vapor-Phase Synthesis of Free-Standing and Stable Colloidal Magnetoplasmonic Nanoparticles Encapsulated by an Amorphous Silicon Shell

This chapter presents a novel method to synthesize ternary magnetoplasmonic nanoparticles (NPs) composed of multiple FeAg cores encapsulated by a Si shell as a potential tool for magneto-optical bioapplications. The NPs are prepared using independent targets of Fe, Ag, and Si. These targets are cosputtered under controlled conditions to tune the size, chemical composition, and morphology of the NPs. There are three principal advantages to Si shell encapsulation of multicore NPs: (i) It maintains a fixed spatial configuration between the multiple cores; (ii) it prevents FeAg cores from oxidizing; (iii) it inhibits NP aggregation. Moreover, these hybrid NPs show an enhanced, redshifted, light absorption band due to the strong near-field coupling between the Ag cores and the Si shell. This methodology can be extended to a wide range of materials in addition to those addressed here.