FROM HOLLOWING OF METAL NANOPARTICLES TO "HOLLOWING" OF THIN METAL FILMS

Hollow metallic nanostructure (nanotubes, nanoparticles, etc.) attract great deal of attention due to their possible applications in various fields of nanotechnology (drug delivery, energy production and storage, catalysis, etc.). One of the synthesis methods of hollow nanostructures relies on Kirkendall effect during interdiffusion in the core-shell nanostructures. This method, however, requires high homological temperatures or high concentration of lattice defects ensuring bulk diffusion distances comparable with the nanostructure’s size.

In this study we report on the synthesis of hollow Au nanoparticles (NPs) on various substrates and at low homological temperatures at which only the short-circuit diffusion is operational. Our method provides higher microstructure stability of the hollow structure and allows “sculpturing” of the size and shape of internal pore.

In order to study the formation kinetics of the hollow structures we used the energy filtered transmission electron microscopy (EFTEM) method. Using this method, combined with other microscopy techniques we were able to characterize the mass transfer mechanism at different stage of the hollowing processes and to develop a quantitative model that shows a good agreement with our experimental data.

Applying our method to the nanoparticles of the Ag-Au alloy resulted in partially agglomerated thin Au films with high area density of holes. The decreased thermal stability of the Au film is attributed to the accelerated thermal grooving process. Based on our latter results we concluded that chemical driving forces have to be taken into account in the analysis of thermal stability of multicomponent thin films.