Metal-Insulator transition-induced adsorption-resistant behavior of small au nanoparticles

The size-dependent variation of the electronic and chemical properties of Au nanoparticles formed on native Si oxide surfaces is investigated using synchrotron radiation photoemission spectroscopy and ultraviolet photoelectron spectroscopy. The adsorption reactivity toward butanethiol adsorption initially increases with decreasing particle size; however, the reactivity of Au nanoparticles becomes gradually lower below a size of ∼0.8nm. The photoemission spectral changes suggest a metal-Insulator transition, accompanied by negative charge transfer from the nanoparticles to the support, which may be the source of the chemical Inertness of small Au nanoparticles.