Controlled Heterogeneous Nucleation for Synthesis of Uniform Mesoporous Silica-Coated Gold Nanorods with Tailorable Rotational Diffusion and 1 nm-Scale Size Tunability

We demonstrate a strategy for the synthesis of discrete and uniform gold nanorod (GNR)@mesoporous silica (mSiO2) core–shell nanoparticles (NPs) with finely tuned shell thickness by significantly suppressing the formation of undesired core-free NPs. We could control the thickness of the mSiO2 shell with high precision, close to 1 nm, and hence the rotational diffusion mode of NPs by simply controlling the silica precursor injection times. The growth of the mSiO2 shell on the GNR seeds and the formation of core-free mSiO2 NPs could be explained by two models based on the modified LaMer's theory. Between these two, we found the most suitable one for the synthesis of GNR@mSiO2 NPs with a precisely controlled shell thickness and negligible core-free NPs as the synthesis mostly occurs via heterogeneous nucleation on GNR seeds. As our results are very simple and highly reproducible, we expect this work to provide profound insights into the synthesis of a variety of heterogeneous nanostructures.