Synthesis and self-assembly of silica-coated anisotropic gold nanoparticle films

Silica-coated anisotropic gold nanoparticles (Au@SiO 2 ), including rod- and ‘dogbone’-like outlines with different aspect ratios, have been prepared using an improved Stöber method. The obtained Au@SiO 2 have a pure silica surface for straightforward and rapid self-assembly onto poly(4-vinylpyridine) (PVP) functionalized quartz substrates. The large-scale assemblies exhibit highly reversible optical changes that can be observed spectroscopically or with the naked eye when repeatedly cycled between a dry and wet process. The relationship among the optical properties of two-dimensional assemblies, the aspect ratio and shape of the gold nanoparticles and the environmental refractive index is also investigated.