Simple Synthesis of Versatile Akaganéite-Silica Core–Shell Rods

Abstract

We present a simple method for preparing large quantities of micrometer-sized core–shell silica rods, via needle-like akaganeite (β-FeOOH) template particles. The preparation of the akaganeite needles by aging ferric chloride solutions at elevated temperature is explored in order to find improved conditions for the formation of well-dispersed high-aspect-ratio needles. The influence of reaction conditions on irreversible bundling of the needles, yield, and the particle size distribution are reported and discussed. Subsequent coating of the template particles with silica leads to core–shell rods with an aspect ratio (A = L/D) that decreases with shell thickness. This facilitates control over the final aspect ratio and is accompanied by a decrease in the polydispersity. The composition of these core–shell particles offers various possibilities in terms of modifying the particle properties, which we demonstrate by preparing fluorescent particles and hollow silica rods while outlining other interesting option...