Biomimetic coating of gold nanoparticles with ultrathin silica layers

Encapsulation of nanoparticles has attracted a great attention as a method for stabilizing nanoparticles and subsequently applying them to various areas of technologies. Especially, the encapsulation of nanoparticles with silica shells has proven advantageous for applications to (nano)biotechnology with the well-established silica chemistry. However, current chemical approaches to the formation of silica shells generally require harsh conditions. In contrast, biological processes are capable of generating silica nano/microstructures under ambient conditions. In this work, we formed ultrathin (∼1.5 nm) silica shell-coated nanomaterials by mimicking the biological processes. The procedure consists of simple two steps: immobilization of a thiol-terminated imidazolium ion onto gold nanoparticles (AuNPs) and biomimetic polycondensation of silicic acids. The resulting AuNP/silica hybrids were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and UV–vis spectroscopy.