Self-assembly of superparamagnetic magnetite particles into peapod-like structures and their application in optical modulation

Abstract

Superparamagnetic Fe₃O₄/SiO₂/TiO₂ peapod-like nanostructures have been successfully synthesized by using Fe₃O₄/SiO₂ core/shell particles as building blocks and TiO₂ as the adhesive without the need of any hard or soft templates. The fabrication process involves chaining the Fe₃O₄/SiO₂ cores during magnetic stirring and subsequent fixing of the chain structure during TiO₂ coating. The number of Fe₃O₄/SiO₂ cores arranged linearly in the chains could be effectively controlled by tuning the amount of titanium precursor or the magnetic stirring rate. The double layer coating of SiO₂ and TiO₂ enhances thermal and chemical stability of the nanopeapods, and the one-dimensional chain structure produces interesting properties that enable applications not possible with conventional magnetite materials. As a demonstration, we show here the use of these superparamagnetic peapod-like nanostructures for low-frequency optical modulation.