Electrochemical Investigation of Porosity in Core-Shell Magnetoplasmonic Nanoparticles

Porous core-shell nanoparticles (NPs) have emerged as a promising material for broad ranges of applications in catalysts, material chemistry, biology, and optical sensors. Using a typical Ag core-Fe₃O₄ shell NP, a.k.a., magnetoplasmonic (MagPlas) NP, two porous shell models were prepared: i.e., Ag@Fe₃O₄ NPs and its SiO₂-covered NPs (Ag@Fe₃O₄@SiO₂). We suggested using cyclic voltammetry (CV) to provide unprecedented insight into the porosity of the core-shell NPs caused by the applied potential, resulting in the selective redox activities of the core and porous shell components of Ag@Fe₃O₄ NPs and Ag@Fe₃O₄@SiO₂ NPs at different cycles of CV. The porous and nonporous core-shell nanostructures were qualitatively and quantitatively determined by the electrochemical method. The ratio of the oxidation current peak (μA) of Ag to Ag⁺ in the porous shell to that in the SiO₂ coated (nonporous) shell was 400:3.2. The suggested approach and theoretical background could be extended to other types of multicomponent NP complexes.