Inorganic metallodielectric materials fabricated using two single-step methods based on the Tollen's process

Two methods for preparing polycrystalline silver shells on colloidal silica spheres are reported. These do not include the use of organic ligands or metal seeding steps and are based on the Tollen's process for silvering glass. Reaction parameters such as temperature and reactant concentrations are adjusted to slow the reaction kinetics, which we find leads to preferential silver growth on the spheres. The resulting shells are polycrystalline and granular, showing highly uniform sphere coverage. Surface morphologies range from sparsely interconnected grains for shells ∼20 nm thick, to complete (yet porous) shells of interconnected silver clusters which are up to ∼140 nm in thickness. The extinction spectra of the core–shell materials are markedly different from those of smooth continuous shells, showing clear evidence that the granular shell geometry influences the plasmon resonance of the composite system. Spheres coated with shells 20–40 nm thick are also suitable for colloidal crystallization. Monolayers of self-assembled spheres with long-range ordering are demonstrated.

Graphical abstractSilver coated silica spheres are produced using a modified Tollen's process, without utilizing nanoparticle seeding or chemical functionalization. These spheres exhibit geometrically tunable extinction spectra despite the highly granular shell morphologies.Figure optionsDownload full-size imageDownload as PowerPoint slide