In situ immobilization of gold nanoparticle dimers in silica nanoshell by microemulsion coalescence

A novel method based on controlled microemulsion coalescence was developed for immobilization of gold nanoparticle dimers in silica nanoshell. Gold nanoparticles were prepared in water-in-oil microemulsion, and then the microemulsion was intentionally fused by ethanol to form gold nanoparticle dimers. Afterward, the gold-containing droplets were vitrified by silica to stabilize the dimers. Transmission electron microscopy and UV-vis spectra were used to study the coalescence process and demonstrated our ability to control the size of gold nanoparticles and the thickness of the silica coating. The encapsulation of gold nanoparticle assemblies into silica particles also prevents further agglomeration and makes additional functionalization possible.