From functional core/shell nanoparticles prepared via layer-by-layer deposition to empty nanospheres

The adsorption (wrapping) of polyelectrolytes onto (around) oppositely charged nanospheres is a problem in colloid science (stabilization, surface functionalization), biology (DNA-histone complex) and in theoretical physics. Here we report that gold nanoparticles can easily be coated using Layer-by-Layer (LbL) deposition as the sole method. The resulting core/shell nanoparticles are so well stabilized that they can be centrifuged and redispersed without agitation or use of ultrasound. At an average recovery of about 95% of particles per layer, at least 20 layers can be deposited with a minimum of particle aggregation. Thus LbL opens a new and general route for the functionalization of nanoparticles even in aqueous media limiting the risk of ligand exchange reactions. In the case of gold colloids, the core can be gently dissolved resulting in empty (hollow?) nanospheres.