Facile one-step synthesis of plasmonic/magnetic core/shell nanostructures and their multifunctionality

A very simple protocol, which involves the chemical reduction of AgNO3 and Fe(NO3)3 with ethylene glycol as reducing agent, has been developed for synthesizing Ag@Fe3O4 core/shell nanostructures in which the silver nanoparticle core was covered by a thicker layer of the Fe3O4 nanoparticle shell. The obtained Ag@Fe3O4 core/shell nanostructures simultaneously possess both strong magnetic responsiveness and tunable plasmonic properties. The plasmonic properties of the composite nanospheres are profoundly influenced by the high dielectric constant of the outer Fe3O4 shell layer and could be conveniently modulated over a broad spectral range spanning from the ultraviolet to near-infrared (NIR) regions (789 nm) by simply altering the thickness of the Fe3O4 shell. The localized surface plasmon resonances of the core/shell nanocomposites red-shifted with increasing thickness of the Fe3O4 shell. The morphology transformation of the Ag/Fe3O4 nanocomposites from core/shell structures with a continuous dense coating to flower-like nanostructures also allows the tuning of their plasmonic properties to be blue-shifted (to 510 nm). Catalytic degradation of rhodamine 6G (R6G) experiments show that the Ag/Fe3O4 composite nanostructures exhibit high catalytic activity by sodium borohydride. Due to the efficient optical response through localized surface plasmon resonances, the catalytic performance from the silver core and external magnetic manipulation from the Fe3O4 shell, such multifunctional nanoparticles will provide an opportunity for simultaneous optical detection and catalytic reduction with the additional benefit of relatively facile recovery and regeneration.